Search

Innovative and cost-effective paper sheets with superior fire safety and reinforcement properties have been developed. The paper sheets were fabricated via valorization of agricultural waste to paper and then coated with nanoparticles. Paper attained from rice straw was used to create the sheets. Afterward, bentonite sheets were incorporated in these sheets, and finally, PbO nanoparticles were coated on prepared paper nanocomposites. The mass ratio of bentonite sheets was altered. The flammability and mechanical properties of the developed paper nanocomposites were studied. The flame retardancy of developed paper nanocomposite was significantly improved achieving LOI value of 24% compared to 20% for bentonite and PbO nanoparticle-free sample. Additionally, the tensile strength was improved recording 44% enhancement compared to unmodified sample. Furthermore, the flame retardancy mechanism was proposed and studied. [ABSTRACT FROM AUTHOR]

The pulp and paper industry generates vast quantities of paper sludge, posing significant environmental challenges due to its disposal in landfills or incineration. This study explores the potential of valorizing paper sludge by incorporating it into particleboard production. It aims to optimize sludge content and particle size to enhance board properties—a novel approach to waste management in the wood composites industry. Through systematic variation of sludge content (0–25%) and particle size (< 0.5 to > 2 mm), we assessed the mechanical and physical properties such as internal bond strength (IB), modulus of rupture (MOR), modulus of elasticity (MOE), water absorption (WA), and thickness swelling (TS). The findings indicate that incorporating paper sludge at moderate levels (5–15%) with optimized particle sizes (< 1 mm) significantly improves the mechanical properties of the particleboard, including increased IB, MOR, and MOE while reducing WA and TS. Principal Component Analysis (PCA) further supported these results, revealing that higher-density boards with enhanced mechanical properties absorb less water, highlighting the interrelationship between structural integrity and moisture resistance. The PCA also identified thickness swelling as an independent factor, suggesting that while mechanical properties can be optimized, additional strategies are needed to control swelling. In conclusion, this study demonstrates that up to 15% paper sludge can be effectively used in particleboard production without compromising quality, provided particle size is carefully controlled. This approach not only offers a sustainable solution for managing paper sludge but also contributes to the development of eco-friendly composite materials, aligning with circular economy principles. [ABSTRACT FROM AUTHOR]

Nowadays, a high percentage (> 50%) of the paper produced in Europe uses recovered paper (secondary fibers) as raw material. In order to improve the mechanical properties of the paper produced, different kinds of additives are usually incorporated into the paper. Emerging renewable materials based on agricultural or forest residues, such as cellulose nanomaterials, have recently proved good capacities as reinforcing agents for different applications. In this work, pulp from wheat straw with a content of cellulose nanomaterial has been produced and tested as a mechanical reinforcing agent for paper production. A soda semi-chemical process was applied for the delignification of straw, to produce pulp with high cellulose content. Posteriorly, pulps with cellulose nanofibers were obtained in a high-pressure homogenizer, applying three different pretreatments to the cellulose pulp (acid hydrolysis, enzymatic hydrolysis and thermal treatment with glycerol) in order to facilitate the obtention of cellulose nanomaterial. Handsheets of paper were prepared from two sources of secondary fiber (fluting paper and old corrugated containers), adding different percentages of wheat straw derivatives (0, 3.5, 5 and 7%). The fibers' morphology and the papers' mechanical properties were investigated. Noticeable improvement rates (up to 25%) were observed for some mechanical properties of paper containing nanocellulose produced after the enzymatic and acid pretreatments. The quality of the secondary fibers source also affected the improvement rates achieved, with higher percentage changes for the lower-quality recycled paper. [ABSTRACT FROM AUTHOR]

Waste to energy conversion routes can contribute to solving energy poverty and waste disposal problems while improving farmers' incomes by creating tradable value-added products. This study explored compositing waste paper and biogas digestate-derived char to produce fuel briquettes as a waste to energy conversion route. The objective was to optimize fuel and mechanical properties of derived briquettes. Response surface methodology was employed with independent variables of waste-paper mass, compression force, and drying time while ash content, higher heating value (HHV), density, compressive strength, and moisture content were the response variables. Linear models best fit the responses of HHV, compressive strength, and moisture content. Quadratic models best fit ash content and bulk density responses. Waste-paper mass had the most significant influence on briquettes' ash content, HHV, moisture content, and bulk density. Waste paper to digestate mass ratio of 0.3, compression force 1531 N, and drying time 11 days were found to be the optimum production conditions resulting into ash content of 22.7% db, HHV 14.7 MJ/kg, bulk density 562.7 kgm−3, compressive strength 9.9 N mm−2, and moisture content 5.5% wet basis (wb). Briquettes developed at optimum conditions exhibited drop test strength of 93%. Formulated briquettes had thermal efficiency of 52% compared to eucalyptus wood 31% and eucalyptus charcoal 36%, as well as a lower specific fuel consumption of 47 g/l compared to digestate char briquette and eucalyptus wood with 162 and 80 g/l respectively. If these briquettes replaced wood and its derived charcoal, cost savings of US$328.5 and US$216.23 would be realized per ton of the respective fuel foregone. [ABSTRACT FROM AUTHOR]

In this work, cellulose nanofiber was prepared from water hyacinth (WH) using a simple domestic blender and employed as reinforcement in recycled paper. There are various sources to prepare cellulose nanofiber. However, water hyacinth was used as a source to synthesize cellulose in this study to decrease its devastating effect on the water body. Pure cellulose was isolated from water hyacinth with chemical treatments including dilute alkali swelling and bleaching. The chemical composition of water hyacinth was gravimetrically determined and the result demonstrated that cellulose is the largest constituent of the plant (55%), followed by hemicelluloses (19%) and lignin (14%). The remaining 12% was related to other extracts like fat, oil, pectin, etc. As the FTIR data revealed, the functional groups corresponding to lignin and hemicelluloses were absent in the FTIR spectra of extracted cellulose. To increase its functionality, the prepared cellulose was disintegrated into nanofibers using a simple mechanical treatment. To learn more about cellulose fibrillation, UV–Vis spectroscopy was used to analyze the light transmittance of 1 wt% water dispersed, mechanically treated cellulose. The dispersion showed high light transparency, particularly at a higher wavelength. As a result of the cellulose dispersion's reasonable light transmittance value, it can be deduced that the aggregated cellulose chains were efficiently transformed into nanofibers. The inclusion of cellulose nanofibers as reinforcement significantly improved recycled paper's moisture resistance, thermal stability, and mechanical strength. [ABSTRACT FROM AUTHOR]

Free-standing reduced graphene oxide (rGO) papers were prepared by chemical reduction, thermal reduction and combined chemical-thermal reduction, respectively. Four-point probe and nanoindentation experiments were conducted to investigate the electrical and mechanical properties of rGO papers. The rGO paper prepared by soaking in L-ascorbic acid and thermal annealing in argon at 1000 °C (labeled rGO-AsA-T) showed superior electrical and mechanical properties when compared with rGO papers prepared merely by chemical reduction or thermal reduction. The as-prepared rGO-AsA-T paper exhibited an electrical conductivity of 5.7 × 104 S/m, showing an increase of 90% compared to that in the thermally annealed rGO paper and nearly 40 times that of rGO paper reduced by L-ascorbic acid. It was also found that the rGO-AsA-T paper had the lowest elastic modulus of 288 MPa, showing enhanced flexibility. The nearly free voids in rGO-AsA-T paper proved by scanning electron microscopy (SEM) were due to the capillary action in chemical reduction and were significant in improving the electrical conductivity and flexibility of the paper. The rGO-AsA-T paper with high conductivity and flexibility has a promising application in flexible electronics. [ABSTRACT FROM AUTHOR]

Nano-modified insulating paper, due to its outstanding performance, is regarded as a promising material in power system. Accordingly, in this study, three different kinds of polysilsesquioxane (POSS) nanoparticles were prepared from silsesquioxane monomers with octaaminophenyl, octaphenyl, or octamethyl substituents and used to prepare modified cellulose insulating paper. Doping with the POSS nanoparticles effectively improved the tensile strength of the insulating paper and reduced its relative dielectric constant. Specifically, doping with octaaminophenyl-POSS (OAPS) nanoparticles at 10 wt% showed the optimal modification effect. Accelerated thermal aging was carried out on this OAPS-modified insulating paper. Compared with those of the unmodified sample, the tensile strength of the modified sample was 16.87% higher and the relative dielectric constant was 24.63% lower after aging at 130 °C for 31 days. Molecular dynamics simulation was used to study the mechanism by which OAPS improves the tensile strength, dielectric properties, and thermal stability of cellulose insulating paper, and the results indicated that it forms hydrogen bonds with the cellulose chains, inhibiting their movement and inhibiting system polarizability. [ABSTRACT FROM AUTHOR]

Mechanical properties of paper coating layers are very important in converting and printing operations. Kaolin is commonly used in paper coating as cheap pigment in addition to its superior properties. In this study, a new approach for improving coated paper mechanical properties using doped kaolin with ammonium molybdate was presented. Kaolin and modified kaolin were characterized using several analyses tools (e.g., XRD, SEM, and EDX), and then they were applied in paper coating mixture. The results revealed that the dopant was found in the kaolin as MoOx; this oxide form with its needle shapes led to change in the kaolin crystals, and its presence in high concentrations led to exfoliation of kaolin. Also, at high concentration it was found that MoOx reacted with γ-alumina that is found in kaolin after its heating at 300°C to form aluminum molybdate. It can be observed that modified kaolin increased the coated paper porosity and consequently the opacity; also bulk and thickness were increased. Significant improvement in coated paper tensile strength, bursting strength, tensile energy absorption, and bending stiffness was also noticed. Thermal study also showed that increasing the concentration of ammonium molybdate increased the heat stability of the coated paper. [ABSTRACT FROM AUTHOR]

The pursuit for sustainability in the papermaking industry calls for the elimination or reduction of synthetic additives and the exploration of renewable and biodegradable alternatives. Cellulose nanofibrils (CNFs), due to their inherent morphological and biochemical properties, are an excellent alternative to synthetic additives. These properties enable CNFs to improve the mechanical, functional, and barrier properties of different types of paper. The nanosize diameter, micrometre length, semicrystalline structure, high strength, and modulus of CNFs have a direct influence on the mechanical properties of paper, such as tensile index, burst index, Scott index, breaking length, tear index, Z-strength, E-modulus, strain at break, and tensile stiffness. This review details the role played by CNFs as an additive to improve strength properties of paper and the factors affecting the improvement in paper quality when CNFs are added as additives. The paper also includes techno-economic aspects of the process and identifies areas that need further research. [ABSTRACT FROM AUTHOR]

This research uses WP to investigate the effect of two types of Shredded Waste Paper (SWP) comprising Shredded Copier Waste Paper (SCPWP) and Shredded Cardboard Waste Paper (SCBWP) as additives on the properties of concrete and the structural behaviour of Reinforced Concrete Beam (RCB). The slump, compressive, flexural, and splitting tensile strengths increase by 4–13% for 5–10% addition of SCPWP and decrease by 16–23% for 15% addition of SCPWP compared to 0% addition. For SCBWP, the slump, compressive, flexural and splitting tensile strengths increase by 10–23% for 5–10% addition and decrease by 15–21% for 15% addition compared to 0% addition. 15% of SCPWP and SCBWP addition records the highest effect in water absorption and efflorescence, showing 11% and 10.28% increases with 15% addition of SCBWP and SCPWP. Scanning electron microscope (SEM) analysis reveals that the crack is repaired, and the presence of calcium hydroxide (Ca(OH)2) and calcium–silicate–hydrate (C–S–H) links enhances the concrete strength. The addition of 10% SCPWP and 10% SCBWP in the concrete mixtures improves the structural behaviour of RCB with stirrup spacing (SS) = 100 mm (full), 150 mm and 200 mm (reduced) by increasing the load and reducing the deflection. Apart from that, the concrete bending and shear strains also increase by 44.17% and 34.9%. The failure mode of the RCB changes from shear to bending. This study indicates that SCPWP and SCBWP can be used as additives in concrete at 5% and 10%, and 10% for RCB with significant strength and structural improvement. [ABSTRACT FROM AUTHOR]

Coated papers have an excessive impact on the appearance and utility of printed materials with respect to the increase in mechanical strength, print gloss and print density. Styrene–butyl acrylate copolymers were synthesized utilizing different emulsifier systems and modified with acrylamide. These lattices were evaluated as paper coats in the presence of kaolin, calcium carbonate and a mixture of both as pigments. The evaluation aimed at employing these lattices on recycled white and brown paper substrates with respect to their mechanical properties and their printability. The tensile strength of coated papers was upgraded by ~ 20–30% in CD compared with that of uncoated papers. The improvement ratio was ~ 12–16% in bursting strength compared with that of the uncoated paper. The maximum gloss values (39 and 48) and the maximum print density values (2.51 and 2.44) were obtained for ground calcium carbonate "GCC" composites on white and brown bases, respectively. Formulas containing GCC had a uniform printed surface with high-quality ink distribution without any picking up of coated surface. This work is a promising one as efficient synthesized binders and a local pigment were employed besides achieving offset printing on recycled brown papers for the first time. [ABSTRACT FROM AUTHOR]

Aminoalkylalkoxysilane copolymers (co-AAAS) have the ability to simultaneously deacidify and strengthen paper documents. Nevertheless, despite enhancing the tensile strength, they generally fail to improve the folding endurance of the degraded groundwood pulp-rich papers. Focusing on that specific type of papers, several ways to overcome their lack of reinforcement were investigated. Promoting the polymerization of AAAS using catalysts and thermal steps was one of them. A monitoring with FTIR spectroscopy showed that the thermal step was the most efficient in speeding up the hydrolysis and polycondensation of 3-aminopropylmethyldiethoxysilane (AM) monomer in aqueous solutions. The progress of the two-steps reaction in terms of degree of polymerization of AAAS polymers was then studied in-situ after heating the paper, using Cross Polarization—Magic Angle Spinning 29Si solid-state NMR, and was shown to be enhanced as well. The other optimization route explored was to stabilize the paper before treatment. Our previous research had shown that the presence of oxidized groups in paper hampered the strengthening. Sodium borohydride, a known bleaching agent in paper conservation, was used prior to the AAASs treatment to decrease the amount of carbonyls in paper. The reduction and the thermal step were compared in terms of the mechanical properties (folding endurance and tensile strength) upon AAASs treatment of several lignocellulosic papers, including three newsprints dated 1911–1923. The use of sodium borohydride led to a significant improvement of the folding endurance of the samples, an unprecedented result. It enabled at the same time to counteract the yellowing induced by the AAAS and to build a larger alkaline reserve. [ABSTRACT FROM AUTHOR]

The growing demand for sustainable products has spurred research into renewable materials, with cellulose-based materials emerging as prominent candidates due to their exceptional properties, abundance, and wide-ranging applications. In this context, there is a need to develop a better fundamental understanding of cellulose interactions such that we can continue to design and improve sustainable materials. Individual interactions can be difficult to assess in bulk fibre-based materials and therefore cellulose model materials have become indispensable tools for researchers as they can facilitate the study of cellulose interactions at a molecular level enabling the design of sustainable materials with enhanced properties. This study presents a new methodology for studying the effects of surface treatments on the individual fibre–fibre joint strength using wet-spun cellulose nanofiber (CNF) filaments as model materials. The Layer-by-Layer assembly technique is used to modify the surface chemistry of the model materials as well as bleached and unbleached hardwood Kraft fibres, demonstrating its potential to enhance adhesive properties and overall mechanical performance of papers made from these fibres. The study further explores the impact of increasing network density through wet-pressing during paper preparation, showcasing a comprehensive approach to molecularly tailor fibre-based materials to achieve superior mechanical properties. The proposed methodology provides a time-efficient evaluation of chemical additives in paper preparation. [ABSTRACT FROM AUTHOR]

Purpose: The study examines the potential of Mauritian hemp (Furcraea foetida L.), a lignocellulosic non-wood biomass, as a more environmental friendly substitute to virgin wood for printing paper production. Methods: The best pulping method for Mauritian hemp was first investigated. A4 sized papers were then produced using 100% Mauritian hemp fibres and mixtures of Mauritian hemp fibres with Elephant grass fibres and wastepaper. Using Standard tests, the physical (thickness, grammage, apparent density, water absorbency) and mechanical (tensile strength, burst strength, crease recovery, abrasion resistance) properties of the papers produced were evaluated and compared with those of an 80 gsm A4 commercial printing paper used as control. Lastly, internal sizing was done by adding different proportions of starch to the paper whose properties were closest to the control (judged most printable) to investigate any property enhancement. Results: Soda cooking with 12% Wt/V NaOH solution at a temperature of 90 °C for 90 min was found best for pulping Mauritian hemp. The 100% Mauritian hemp paper had characteristics closest to the control, with apparent density 141.54 kg/m3, water absorbency time 1.436 s, burst strength 0.323 kPa m2/g, tensile strength 10.97 Nm/g, abrasion resistance 37.5 cycles before rupture and crease recovery angle 34.8°. Increasing the starch content from 10 to 40% caused the 100% Mauritian hemp paper's characteristics to increasingly approach those of the control, thus showing printability improvement. Conclusion: The methodologies adopted for papermaking and testing demonstrated that Mauritian hemp is a suitable alternative to wood to produce good quality printing paper. [ABSTRACT FROM AUTHOR]

Waste paper pulp (WP) is considered an eco-friendly alternative to petrochemical plastic. However, certain properties of WP limit its application in packaging. Starch–acid cross-linking reportedly improves the physical and barrier properties of cellulose-based materials. Therefore, this study aims to investigate the effect of starch–citric acid (CA) cross-linking on the physical and barrier properties of WP. Herein, WP/starch–CA-cross-linked composite sheets (WPSAs) were fabricated, and their physical, barrier, and thermal properties and morphology were investigated. The results indicated that introducing CA into WP/starch (WPS) reduced water absorption up to 39.5% compared to that of the control. Additionally, the surface and cross-section morphology, tensile strength, contact angle, and thermal properties improved as the concentration of CA increased. The highest tensile strength was obtained for WPSA with 5% of CA, providing 1445% and 26% values higher than that of the control and WPS, respectively. Moreover, the contact angle of this WPSA was superior at 116.83°. The thermal stability was also improved by increasing the glass transition temperature and decreasing the weight loss and decomposition rate. Furthermore, the addition of CA into WPS increased the system R-values up to 38% compared to that of the control, indicating improvement in the thermal-insulation property. However, introducing more than 5% of CA negatively affected the morphology, tensile strength, and contact angle. Thus, adding 5% of CA improves the physical and barrier properties of WPSA, which can be utilised for biodegradable packaging. [ABSTRACT FROM AUTHOR]

The aim of the study was to investigate the impact of three types of polysiloxane microspheres on the barrier properties, structure and mechanical properties of paper. An influence of new silicon filler on properties of cellulose paper sheet was analyzed. Polysiloxane microspheres were used as an additive introduced into the network of cellulosic fibers in order to obtain new functional properties of the paper. The following types of microspheres were used in the research: M1 hydrophilic of average diameter 23.5 µm, M2 hydrophobic of average diameter 3.1 µm and M3 hydrophobic of average diameter 23.5 µm. The obtained handsheets were analyzed for changes in apparent density, roughness, tensile strength, bursting strength, and tear resistance. Wettability and resistance to liquid were characterized by contact angle measurement, penetration dynamics analysis and uniformity of liquid penetration measured using an extended liquid penetration analyser. It was found that the presence of M2 (small diameter) microspheres improved significantly the paper's hydrophobicity without changing the mechanical properties. The addition of M1 and M3 (large diameter) microspheres decreased the mechanical properties of the paper samples and did not improve their hydrophobicity. However, M1 microspheres resulted in increased uniformity of liquid penetration through the paper structure. The presented studies also show that it is possible to obtain paper with high hydrophobic properties only through the filling application when polysiloxane microspheres are used for this purpose. The results also indicate that it is not necessary to hydrophobize the entire material structure in order to achieve its high hydrophobicity. [ABSTRACT FROM AUTHOR]

Recent progress towards the development of lightweight, flexible, wearable, and foldable portable electronics has promoted the increasing demand for high-performance substrates. However, eco-friendly materials with low cost and remarkable performance are still under investigation. In this study, a kind of lightweight, flexible, and electrically conductive multi-walled nanotube (MWCNT) and a few layered graphene (GR) reinforced hybrid recycled papers were obtained by a facile and scalable papermaking process. The influence of nanofiller type and concentration on the mechanical, electrical, thermal performance of the nanocomposite paper were investigated. Fourier transform infrared spectroscopy and Raman spectroscopy revealed the formation of molecular interactions between the MWCNTs, GR, and the cellulose fibers. Scanning electron microscopy proved the continuous network of nanofiller phase within the cellulose matrix. Tensile tests revealed that the tensile strength of MWCNTs reinforced recycled paper increased about 276%, while the GR reinforced recycled paper exhibited the highest Young modulus with 425% increase compared to the neat waste paper. The highest electrical conductivity was measured around 0.219 S/cm for the GR/CNT10 hybrid recycled paper. A positive synergetic effect of the MWCNTs and GR nanofillers was observed in the case of hybrid nanocomposite papers. More importantly, adjusting the microstructure of the waste paper with the introduction of carbon-based 1D/2D nanofillers led to higher improvement in the mechanical properties, electrical conductivity, thermal conductivity. These regenerated properties made the hybrid nanocomposite paper a promising substrate material with considerable potential applications for various flexible and portable electronic devices. [ABSTRACT FROM AUTHOR]

Abstract: The objective of the presented research was to determine the influence of cellulose coating, obtained from the cellulose solution in N-Methylmorpholine N-oxide (NMMO), on the structural and mechanical properties of paper. The effect of heating time of paper samples coated with cellulose dissolved in NMMO was also investigated. Depending on the heating time of the coating, a continuous or porous layer was obtained. Coating without any heating stage yielded a continuous cellulose layer of hydrophobic properties (higher contact angle in comparison to base paper), and paper of higher smoothness and increased tear resistance. Analysis of the paper samples showed that cellulose coating not only changed the surface properties of paper, but also significantly improved paper strength properties, such as the tensile index, elongation, bursting strength index and double folds number. Despite the process’ limitations (e.g. necessity of removing the NMMO), this method can be considered as a novel approach for paper property modification.Graphical Abstract: [ABSTRACT FROM AUTHOR]

This study sustainably developed natural fiber composites from extracted nano-cellulose (ENC) from waste paper egg trays and incorporated them into vinyl ester/kenaf fiber (ENCVK) composites using a vacuum-assisted resin transfer molding (VARTM) process. Overhead stirring, three-roll milling, and ultrasonication were used to uniformly mix the ENC into the resin. The surface morphology exhibited a homogeneous distribution of ENC in the composites, and change in the % of transmittance of spectral peaks refers to the chemical interaction of ENC with the VK composites. ENC significantly improved tensile (32 MPa), flexural (77 MPa) and impact (0.0197 J/mm2) properties of the VK composites (18 MPa, 61 MPa and 0.009 J/mm2) by approximately 73%, 25% and 110%, respectively. Further, ENC inclusion enhanced the storage modulus of VK composites owing to the addition of rigid ENC particles, which enhances the bearing capacity of the composite and is reflected in its high performance. The loss modulus indicates that the interfacial interaction of ENCVK is more vital than VK. The tan Δ value indicates that the filler has strong adhesion, and the polymer cohesion damping is reduced, thus reflecting its high performance. [ABSTRACT FROM AUTHOR]

In this work, the mechanical properties of Kraft paper (KP) coated with a coating formulated with recycled polystyrene dissolved in the solvent lime limonene (rEPS/LL) are investigated. These mechanical properties are compared with those of KP coated with three different commercial coatings: oil-based alkyd coating (ALKY), oil-based phenolic coating (PHEN) and water-based acrylic coating (ACRY). The morphology characterization via scanning electron microscopy showed the KP coated with rEPS/LL resembles a layered structure, in which, part of the coating remained on the surface and part of the coating was absorbed by the KP. The KP coated with rEPS/LL exhibited the highest tensile stiffness and compression strength when compared to the uncoated KP and KP coated with commercial coatings. The remarkable compression properties of the KP coated with rEPS/LL coating may be explained by the bending and crushing mechanisms observed during the ring crush test. The excellent mechanical performance of rEPS/LL combined with an environmentally friendly process to obtain recycled EPS using a bio-based solvent presents several advantages for coating applications. These results warrant further research to fully understand the properties of KP coated with rEPS/LL. [ABSTRACT FROM AUTHOR]

This paper reports the temperature-dependence of methanol generation and the tensile index under ageing conditions for two paper/oil systems: one consisting of a standard wood Kraft paper and the other of a thermally-upgraded Kraft paper (TUK). A linear correlation between methanol and the tensile index for these paper/oil systems was observed in a previous study at 170 °C. In the current study, the correlation was extended to a large range of temperatures (150-190 °C). The experimental data were fitted with a modified Calvini's kinetic model, while the Arrhenius equation was used to model the kinetic of changes of the paper's mechanical properties during ageing. Good agreement with the temperature ( lnk vs. 1/ T) was observed for the rate constants of the chain-end group production, methanol formation, and the decrease of mechanical properties. The Arrhenius equation applied to this data grouping showed activation energy of 130 ± 29 kJ/mol for the decrease in mechanical strength of the standard Kraft paper, while the value was 118 ± 55 kJ/mol for the TUK paper. These values are of the same order of magnitude as those obtained in this study and in the literature for the depolymerization of cellulose and the generation of methanol that was reported. This confirmed the close relationship between cellulose depolymerization, methanol generation and the reduction of the paper's mechanical strength during ageing, dominated by the acid hydrolysis mechanism. The results, which can be seen as a benchmark and pave the way to further research, provide an opportunity for applying the proposed correlations to estimate the insulation condition in operating transformers. [ABSTRACT FROM AUTHOR]

Nano-TiO pigments in pure crystallographic anatase and rutile phases have been successfully prepared by hydrothermal at 120°C and hydrolysis methods, respectively. The laboratory-prepared pigments were characterized parallel to two commercial pigments of the same crystal structure. All pigments were applied in paper coating mixtures, and their influence on coated paper properties was systematically investigated. X-ray diffraction investigation showed that the laboratory-prepared pigments using the hydrothermal method at 120°C were pure anatase, whereas hydrolysis method produced pure rutile phase pigment. The application of the prepared nanopigments and the corresponding commercial TiO phases in paper coating revealed that clay/rutile nano-TiO pigments in paper coating mixture decreased coated paper roughness more than blending clay with anatase nano-TiO pigments. Commercial nano-TiO pigments increased porosity of coated paper at both the 30% and 50% addition of nano-TiO pigments to clay, while laboratory-prepared nano-TiO pigments highly decreased it at 30% addition of nano-TiO to clay, compared to clay only. Blending of clay/nano-TiO pigments improved both brightness and opacity of the coated paper where commercial pigments are more effective. Burst, tensile strength, stretching, and TEA were improved in the case of all pigments. The 50% addition of the prepared and commercial nanopigments in conjunction with clay improved the mechanical coated paper properties more than 30% addition (except the cases of stretching and TEA of the commercial pigments). The coated paper samples were offset printed. It was found that blending of clay/nano-TiO pigments improved print density. Commercial nano-TiO pigments improved print gloss more than the laboratory-prepared ones. This result was found consistent with the results of coated paper roughness. [ABSTRACT FROM AUTHOR]

In this work, the effect of using Ag-doped TiO2 nanopigments on optical, mechanical and antimicrobial properties of coated paper was explored. Furthermore, the long-term antimicrobial activity of the coated paper was examined for up to 25 years. Titanium dioxide (TiO2) nanoparticles have been synthesized and doped with different percentages of Ag nanoparticles (Ag NPs) using a simple wet chemical approach. The Ag@TiO2 modified nanopigments were in the form of nanorods with an average size of about 20 nm as observed from TEM images. Increasing Ag content from 0.01 to 1.0% showed an increase in the mechanical properties of coated paper in terms of tensile, stretching, tensile energy absorption and burst while preserving the optical properties. Moreover, the antimicrobial inhibition activity increased with increasing the Ag content. The 1% Ag@TiO2 showed a long-lasting antimicrobial effect against Staphylococcus aureus (S. aureus) Gram-positive bacteria even after 25 years of ageing (93.4% inhibition). Investigation of reactive oxygen species (ROS) generation and reaction mechanism of antimicrobial activity over Ag/TiO2 under visible light is proposed. These results suggest that Ag/TiO2 NPs can be potentially used as a disinfection coating for paper and improving its mechanical properties. [ABSTRACT FROM AUTHOR]

There is a continuing demand for bio-sustainable and readily recyclable polymers for hot food packaging and hot beverage containers. An important candidate for these applications is poly(lactic acid), PLA, which possesses insufficient heat deflection temperature (HDT) performance, short of being fully crystallized. In order to address this issue, correlations were established for the observed enhancement in HDT with PLA resin after annealing with both thermal properties and the crystallinity of PLA (Ingeo™ 4032D) and extrusion melt blends thereof. The kinetic parameters of crystallization (reaction order, n and rate constant, k (s)) were obtained after fitting the Avrami equation. The reaction order for all of the systems had an n of approximately 3. Models derived from the Avrami equation with n ~ 3 are consistent with systems that undergo heterogeneous nucleation and subsequent spherulitic crystal growth. The addition of paper and talc did not change the model but did change the rate of crystallization. An increased quantity of cellulosic filler led to an increased rate of crystallization. The smaller particle sized fillers offered the greatest improvement in the rate of crystallization. However, the smaller-sized inorganic fillers did not appear to further improve HDT above that of the annealed blends of PLA/paper. The melting temperature for the PLA and all of the blends thereof formed containing paper from different sources of talc had identical melting temperatures ( T ). The variations in the HDTs of the composites were not found to be mirrored in the T . Annealing typically raised the crystallinity from approximately 10-15 to 30-40%. In situ determinations of enhanced moduli via annealing were performed using solid torsion bar dynamic mechanical spectroscopy, the results of which support the findings obtained via DSC. The annealed PLA/paper blends were found to be superior overall to the PLA/talc blends and are, importantly, sustainable. [ABSTRACT FROM AUTHOR]

An innovative approach of using a laboratory embossing prototype was carried out to develop and optimize tissue papers, to quantify the influence of "deco" and "micro" embossing. A comparison between non-embossed and embossed tissue papers was conducted to investigate the effect of this process, on industrial and laboratory-made structures, evaluated by mechanical and softness properties. To identify the influence of the embossing patterns, the fiber composition and the creping process, a creped industrial base tissue paper, a disintegrated fibrous suspension obtained from this one, and an industrial never-dried bleached eucalyptus kraft pulp, were used as samples. These last two materials were used to produce similar industrial base tissue paper, in other words, handsheets with a grammage of 17 g/m2 and unpressed. The end-use tissue properties were evaluated on the non-embossed and embossed structures. The results indicated that the embossing process produced bulkier and more porous structures, at the expense of reduced mechanical and softness properties, more intensified in the "micro" embossing than in the "deco" embossing. The effect of fiber composition shows that the mechanical properties were increased with an adverse effect on the structures' TSA-softness. Furthermore, these properties are enhanced for the structures where creping process effects are presents. The performance of structures with and without embossing allowed to quantify the functional properties of softness and strength, combining ISO experimental methods and computational approaches that benefit from modeling strategies considering its structural hierarchy at the fiber and structure levels, and the shape pattern used in the embossing process. Finite Element Model (FEM) analysis enabled a better understanding of how the embossing patterns affect the mechanical properties during the embossing process. The experimental results were validated using FEM simulation, which proved that "micro" pattern has a higher stress field value, and consequently a lower mechanical strength. Overall, the results indicate that the embossing prototype can be used as an opportunity to investigate the embossing process at laboratory scale and to optimize the final end-use tissue properties due to the controlled process parameters implemented in this methodology. [ABSTRACT FROM AUTHOR]

Oil-immersed transformers use paper and oil as insulation system which degrades slowly during the operation of these machines. Cellulose materials are used generally as insulation solid in power transformers. The degree of polymerization (DP), defined as number of repeating β-glucose residues in the cellulose molecule, is a critical property of cellulosic insulation material used in transformers, since it provides information about paper ageing and its mechanical strength. The fast-developing electric power industry demanding superior performance of electrical insulation materials has led to the development of new materials, as well as different drying techniques performed during transformer manufacturing and service when required. Both developments have caused some practical difficulties in the DP measurement. Moreover, the increasing interest in synthetic dielectric materials replacing cellulose materials requires measuring alternative properties to the DP to quantify the degradation of insulation solids over time. In this sense, this paper proposes the possibility of analyzing paper degradation through fracture toughness. This approach is different from the study of mechanical properties such as tensile strength or strain because it provides a tool for solving most practical problems in engineering mechanics, such as safety and life expectancy estimation of cracked structures and components which cannot to be considered through the traditional assessment of the mechanical resistance of the material. An accelerated thermal ageing of Kraft paper in mineral oil was carried out at 130 °C during different periods of time, to obtain information on the kinetics of the ageing degradation of the paper. Double-edged notched specimens were tested in tension to study their fracture toughness. The evolution of the load–displacement curves obtained for different ageing times at the ageing temperature of 130 °C was utilized to the determination of the stress intensity factor. Furthermore, different kinetic models based on this stress intensity factor were applied to relate its evolution over time as a function of the temperature. Finally, the correlation between the DP and stress intensity factor, which depends on the fiber angle, was also defined. [ABSTRACT FROM AUTHOR]

Background: As a result of use of library and archival documents, defined as reading with handling in the context of general access, mechanical degradation (wear and tear) accumulates. In contrast to chemical degradation of paper, the accumulation of wear and tear is less well studied. Previous work explored the threshold of mechanical degradation at which a paper document is no longer considered to be fit for the purpose of use by a reader, while in this paper we explore the rate of accumulation of such damage in the context of object handling. Results: The degree of polymerisation (DP) of historic paper of European origin from mid-19th-mid-20th Century was shown to affect the rate of accumulation of wear and tear. While at DP > 800, this accumulation no longer depends on the number of handlings (the process is random), a wear-out function could be developed for documents with DP between 300 and 800. For objects with DP < 300, one large missing piece (i.e. such that contains text) developed on average with each instance of handling, which is why we propose this DP value as a threshold value for safe handling. Conclusions: The developed model of accumulation of large missing pieces per number of handlings of a document depending on DP, enables us to calculate the time required for an object to become unfit for use by readers in the context of general access. In the context of the average frequency of document use at The UK National Archives (Kew), this period is 60 years for the category of papers with DP 300, and 450 years for papers with DP 500. At higher DP values, this period of time increases beyond the long-term planning horizon of 500 years, leading to the conclusion that for such papers, accumulation of wear and tear is not a significant collection management concern. [ABSTRACT FROM AUTHOR]

Transparent paper with high transmission haze has garnered great attention due to its potential applications in light management of optoelectronics as a bulk optical material. Herein, we investigated the transmission haze and mechanical properties of transparent paper with different fiber species. The morphological dimensions of cellulose fibers (Northwood, Eucalyptus wood, Manila hemp) before and after 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) treatment were investigated in detail. The effect of fiber morphology and preparation methods on transmission haze and mechanical properties (tensile strength, Young’s modulus, bursting strength) of the resultant paper was then analyzed. The results showed that transparent paper with TEMPO-treated northern fibers possessed highest optical transmittance and transmission haze, as well as strongest mechanical strength compared to two other transparent paper. Furthermore, transparent paper prepared by solution casting exhibited higher mechanical strength, but lower transmission haze compared to paper prepared by vacuum filtration. It’s worth noting that sub-micro and nanofiber partially contributed to the transparency and mechanical properties of the resulting transparent paper. This work sheds light on the preparation of highly transparent and strong paper with excellent light scattering behavior for manipulating light behavior of optoelectronics as a bulk optical material. [ABSTRACT FROM AUTHOR]

Single-use packaging materials, such as those used in food and beverage packaging, have become a significant concern due to their negative impact on the environment. With its eco-friendly attributes, recycled paper (RP) holds great potential as a sustainable replacement for petroleum-based plastics, particularly in the realm of single-use packaging materials. However, to fully realize its potential, it is crucial to enhance the mechanical strength and barrier properties of RP. One particularly promising approach to achieve this enhancement involves the use of starch-citric acid (CA)-crosslinking. While laboratory-scale experiments often result in RP products that fall short of the required specifications, this study aims to explore the feasibility of improving these properties on an industrial-scale. The physical and thermal properties, morphology, and biodegradability of the RP/starch-CA-crosslinking composite sheets (RPSAs) were evaluated and compared to those of a commercial product containing a waterproof agent (CPW). The results indicate that the starch-CA-crosslinking process leads to the formation of a compact and foam-like structure, resulting in improved mechanical strength, thermal insulation, water resistance, and thermal stability. The burst and tensile strengths of RPSA with 50% starch (w/w of RP) were found to be 66.32 and 123.63% higher than those of the control, respectively. Additionally, the thermal-insulation property exhibited a higher R-value, up to 15% higher than the control. Furthermore, the water resistance and thermal stability of RPSAs with an appropriate level of starch-CA-crosslinking were comparable to, or even exceeded, those of CPW. However, it was observed that starch-CA-crosslinking reduced the biodegradability of the RPSAs. This study demonstrates the efficacy of starch-CA-crosslinking techniques in improving RP products and the feasibility of scaling up production. The findings can serve as a valuable reference for future commercial-scale studies, indicating the potential for utilizing starch-CA-crosslinking to enhance the properties of RP-based products and facilitate their widespread adoption as an eco-friendly alternative to petroleum-based plastics. [ABSTRACT FROM AUTHOR]

Background: Cellulose extraction from gloss art paper (GAP) waste is a recycling strategy for the abundance of gloss art paper waste. Here, a study was conducted on the impact of ultrasonic homogenization for cellulose extraction from GAP waste to improve the particle size, crystallinity, and thermal stability. Results: At treatment temperature of 75.8 °C, ultrasonic power level of 70.3% and 1.4 h duration, cellulose with properties of 516.4 nm particle size, 71.5% crystallinity, and thermal stability of 355.2 °C were extracted. Surface modification of cellulose GAP waste with H3PO4 hydrolysis and 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) oxidation was done followed by starch reinforcement. Surface hydrophobicity and mechanical strength were increased for H3PO4 hydrolysis and TEMPO oxidation starch–cellulose. No reduction of thermal properties observed during the treatment, while increment of crystallinity index up to 47.65–59.6% was shown. Neat starch film was more transparent, followed by starch–TEMPO film and starch–H3PO4 film, due to better homogeneity. Conclusions: The cellulose GAP reinforced starch film shows potential in developing packaging materials and simultaneously provide an alternative solution of GAP waste recycling. [ABSTRACT FROM AUTHOR]

This study aims to decrease the dielectric constant of cellulose insulating paper by octa(aminophenyl)silsesquioxane (OAPS) grafting. OAPS was grafted onto the primary hydroxyl group of cellulose molecules via amino groups and epichlorohydrin. The dielectric constant and dielectric loss of insulating paper before and after modification were investigated. Relative to the unmodified paper, the dielectric constant of 15 wt% OAPS-grafted paper decreased from 5.27 to 4.28, and the dielectric loss decreased by 37.5% at 50 Hz. The movement and orientation polarization of the cellulose chains could be restricted due to the porous macromolecular structure and nano quantum interface effect produced by OAPS, thereby resulting in the reduction of cellulose polarizability. Moreover, the OAPS grafting modification does not degrade the other properties of cellulose insulation, i.e., its thermal stability, mechanical performance, fire-resistant properties, and electrical strength. OAPS grafting has promising potential application for preparing low dielectric constant insulating paper. [ABSTRACT FROM AUTHOR]

In this study, TiO2 nanoparticle (TiO2NP)-coated film was produced to protect manuscripts against microorganisms using ecofriendly benign materials. As a result, a simple method was created that uses poultice biofilm made of carboxymethyl cellulose (CMC) and Phytagel plant cell (PGP) loaded with TiO2NPs to preserve manuscripts against microbes in an environmentally responsible way. Three volumes (1, 2, 4 mL) of TiO2NPs were put into a biofilm combination to produce the poultices known as CMC/PGP/TiO2-1, CMC/PGP/TiO2-2, and CMC/PGP/TiO2-3. The synthesized TiO2NPs were nearly spherical in shape, small in size (98 nm), and stable (zeta potential value − 33 mV). The results showed that the unique deposition of TiO2NPs on the biofilm surface gave the produced films loaded with TiO2NPs a rough structure. The highest values of mechanical characteristics were determined to be in CMC/PGP/TiO2-1 with values of 25.4 g, 6.6 MPa, and 11.4%, for tensile strength, elongation at break, and tear strength, respectively. Based on molecular identification, the fungus Aspergillus sydowii and the bacterium Nevskia terrae, with accession numbers MG991624 and AB806800, respectively, were isolated and identified from an antiquated manuscript formed from cellulosic fibers. Before the experiments, the produced cotton paper samples were aged, and then, one group was infected for 6 months by A. sydowii and the second group with N. terrae. Following the preparation of a CMC/PGP biofilm loaded with various volumes of TiO2NPs, poultices were applied to infected cotton paper in order to clean it. The infected cotton paper was placed inside the sandwich-like poultices that were created. The poultice CMC/PGP/TiO2-2 demonstrated potential for preventing the growth of A. sydowii and N. terrae-infected cotton paper, when the fibers were saved, cleaned, and coated with CMC/PGP/TiO2-2 after absorbing the fungus and the bacterium and exhibiting exceptional antimicrobial activities. Finally, the novel biofilms have demonstrated their capacity to lessen microbial contamination of cotton paper. In order to generalize the usage of these poultices, it is also advised that they be produced on a large scale and tested on a variety of organic materials in the future. [ABSTRACT FROM AUTHOR]

This article contributes to the understanding of biobased and biodegradable polyhydroxybutyrate (PHB) bionanocomposites melt processed by pre-industrial methods such as extrusion and injection molding and reinforced by weight contents of 1 and 3 wt% of cellulose nanocrystals (CNC) derived from waste streams of the paper industry. Ultrasonic treatment was used for dispersion of the CNC, which was followed by transmission electron microscopy. The thermal properties and the crystallization behavior of bionanocomposites were studied by thermogravimetric analysis, differential scanning analysis, X-ray diffraction and polarized optical microscopy. Investigations on the bending properties were carried out in conjunction with the analysis of their dynamic mechanical behavior. Scanning electron microscopy was used to characterize the fracture surface. All these analyses give a deep insight into their structure-property relationship. The moisture absorption measurements and gas barrier properties analysis made to the processed bionanocomposites have provided an insight into their behavior under environmental conditions. The PHB bionanocomposites with a low content of 1 wt% CNC were found to have the best dispersion quality, which had a positive effect on almost all mechanical and thermal properties. The increase in crystallinity with the incorporation of CNC also contributed to an improvement in mechanical properties. In addition, the bionanocomposites show a slightly lower tendency to absorb moisture and better barrier properties to oxygen and water vapor. These findings showed that these bionanocomposites are suitable for use in the packaging industry. [ABSTRACT FROM AUTHOR]

Fiber agglomeration and poor interfacial combination with the matrix restrict the performance of composites. Herein, soybean meal-based adhesives were fabricated via the addition of dialdehyde cellulose (DAC) obtained from waste paper dissolved in an alkali–urea system and oxidized with sodium periodate. Due to the dissolution by the alkali–urea system, DAC dispersed well in the solution and did not aggregate in the adhesive matrix. Because of the oxidation treatment, DAC was crosslinked with the adhesive matrix via a Schiff base reaction. Meanwhile, hydrogen bonds were formed at the interface between the DAC and the adhesive matrix. Plywood with the SM/DAC/PTGE adhesive reached its highest wet bonding strength of 1.27 MPa (4 wt% DAC addition), a 95% increase compared to that with the unmodified SM/PTGE adhesive. Fine DAC-to-SM interfacial bonding and a dense crosslinking network were constructed in the SM/DAC/PTGE adhesive systems. The cycle of reuse for the alkali–urea system in the experiments demonstrated that the preparation method of the cellulose solution was scalable and sustainable. [ABSTRACT FROM AUTHOR]

Demand for particleboards keeps increasing and as such more trees are fell for its production, engendering deforestation. For the purpose of reducing falling of trees, this study, focused on recycling of waste paper in the development of paperboard as alternative to particleboards used for furniture and interior household applications. Kenaf fiber (KF) was blended at varying proportions of 0, 1, 2, 3, 4, and 5 wt.% with 20 wt.% constant cement and 20 wt.% constant coconut shell powder while the remaining was paper pulp. Board specimen developed were cured for 14, 28, and 90 days and mechanical properties were examined. Results obtained showed that fiber dosage improved bond strength and screw holding strengths as compared with the control mix. Similarly, modulus of rupture was enhanced with KF loading as compared with control mix while 1 to 3 wt.% KF spawned enhancement of modulus of elasticity. However, 4 and 5 wt.% KF led to a reduction in the modulus. Infusion of the fiber enhanced tensile strength from 1 to 3 wt.% content. 14-day and 28-day curing periods were observed to improve properties while the 90-day curing period is detrimental to all properties. Optimization via signal-to-noise ratio revealed an optimum mix of 2 wt.% obtained for fiber and an optimum curing duration of 28 days. [ABSTRACT FROM AUTHOR]

The reutilization of paper mill sludge as filler/reinforcement of polypropylene composites has been evaluated. The results show that the increasing content of sludge in composites resulted in materials with higher Young's modulus, although with lower tensile strength and deformation at break. Thus, in composites submitted to tensile stress paper mill sludge behaved mainly as filler. On the contrary, when materials were submitted to flexural stresses sludge worked partially as reinforcement. The addition of a coupling agent enhanced the fiber-matrix interface. As a result, composite materials with improved mechanical properties, either to tensile, flexural and impact tests were obtained. Considering the mechanical properties of the materials obtained, the substitution of traditional mineral fillers by paper mill sludge is a feasible alternative for composites used in low mechanical demand applications. [ABSTRACT FROM AUTHOR]

Deinking paper sludge (DPS)/high density polyethylene (HDPE) composites with and without coupling agent (3 % of maleated polyethylene (MAPE)) were manufactured by twin-screw extrusion followed by injection molding with high percentages of DPS (0, 20, 30 and 40 %). The effects of DPS content and MAPE on the mechanical, thermal, and morphological properties of the DPS/HDPE composites were investigated. Increasing DPS content in composites increased the tensile and flexural modulus (E; MOE), tensile and flexural strength (Rm; MOR), while decreased elongation at break and Un-notched impact resistance due to a poor adhesion between the DPS and HDPE. The addition of DPS also improved the thermal stability and increased the composites crystallinity. High content of DPS (40 %) and 3 % MAPE achieved good interfacial adhesion between fibres of DPS and HDPE. Therefore, an increase is observed for Rm, MOR, ductility, and impact toughness. [ABSTRACT FROM AUTHOR]

Cellulose nanofibers (CNF) have been proposed by several authors as a reinforcing additive for papermaking pulps; their use allows one to avoid mechanical refining of pulp fibers, which damages the fibers and reduces their lifespan and consequently recycling cycles. In the present work, use of CNF obtained through enzymatic pretreatment as a bulk pulp additive is studied versus traditional (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO)-oxidized CNF. Results indicate that enzymatic CNF improves the overall paper properties in a similar way to TEMPO-oxidized CNF; however, the enzymatic pretreatment is supposed to be significantly cheaper and environmentally friendly compared with the chemical treatment. Paper reinforced with enzymatic CNF was later surface-coated with solution containing TEMPO nanofibers oxidized with 15 mmol NaClO to further promote the mechanical strength. The results indicate that the combination of bulk addition of enzymatic CNF to the papermaking pulp followed by surface application of TEMPO-oxidized CNF induced significant improvement in the mechanical properties of the paper at lower cost than sole use of TEMPO-oxidized CNF as bulk additive. To the best of our knowledge, this is the first work in which enzymatic and TEMPO-oxidized CNF are combined as paper additives for bulk and surface application to improve overall paper properties. [ABSTRACT FROM AUTHOR]

We report on a simple approach to fabricate mechanically robust magnetic cellulose papers containing M-type barium hexaferrite (BaFeO) nanoplates. BaFeO nanoplates were synthesized by a hydrothermal method and then chemically functionalized by using a silane coupling agent. The magnetic cellulose papers prepared with the silane-treated BaFeO nanoplates exhibited improved mechanical properties with tensile strength of 58.5 MPa and Young's modulus of 2.95 GPa. [ABSTRACT FROM AUTHOR]

In the present work the evolution of physical and mechanical properties of papers and nanopapers is studied. Handsheets made of eucalyptus fibres reinforced with 0, 25, 50, 75 and 100 wt% of nanofibrillated cellulose (NFC) content were fabricated using a Rapid Köthen-like equipment. The obtained papers and nanopapers were physical- and mechanically-characterized. The results showed a significant increase in density and a reduction of porosity in the samples during their transition from paper to nanopaper; besides, nanopapers were more transparent and smoother than normal papers. These physical changes where more evident with increasing amounts of NFC. Regarding mechanical properties, nanopapers with a 100 wt% content of NFC improved their strength and rigidity in 228 and 317 %, respectively, in comparison with normal papers. The evolution of strength and rigidity from paper to nanopaper was linear in relation to the amount of NFC, which means that the ultimate tensile strength was mainly dependant on nanofibril failure. [ABSTRACT FROM AUTHOR]

Wet cleaning of ancient papers is a common treatment performed for the removal of degradation products, external contaminants and salts, which can promote the degradation of cellulose (i.e., hydrolysis, oxidation). In this research, the effects on the mechanical properties of paper samples caused by wet cleaning treatments were evaluated by considering the changes induced in the ultimate tensile strength, deformation at break and flexibility. For this purpose, samples were subjected to different aqueous cleaning treatments such as immersion in deionised water and the application of rigid gels of agar and gellan gum at different concentrations was carried out. Tensile tests were run, and morphological observations of paper by means of light microscopy and scanning electron microscopy were recorded. Contrary to the significant changes in the mechanical properties of paper samples after immersion treatment (an increase in flexibility as the elongation at break), the use of gelled systems caused slight improvement in the mechanical properties of paper (in both the ultimate tensile strength as well as in the breaking strain). Changes in the mechanical properties of paper were also correlated with slight changes in the diameter of the cellulose fibres as a consequence of the swelling action of water molecules, especially in the case of immersion treatment. Finally, the tensile tests performed on the paper samples after thermo-hygrometric accelerated artificial ageing (70 °C and 65 % RH) demonstrated that cleaning treatments by rigid gels did not seem to accelerate any sort of paper degradation in the mid to long term. [ABSTRACT FROM AUTHOR]

Hybrid inorganic-organic treatments, based on amide-amine polymers (PAAs), against thermal oxidation have been prepared on paper dating back to eighteenth century. The polymeric sols are obtained by step-growth Michael addition polymerization and functionalized with siloxane network by sol-gel method. Five types of samples have been prepared changing the molar ratios among the reagents and their concentration. The treated paper samples were subjected to morphological and structural characterization, by using Scanning Electron Microscopy and vibrational spectroscopies (FTIR and Raman), respectively. Static mechanical tests have been carried out on the samples for measuring elastic modulus, ultimate strength, ultimate deformation and energy loss, whereas dynamic-mechanical measurements have been recorded at increasing temperatures to evaluate E′, E″ and tan δ. Finally, Thermo-Gravimetry and Differential Scanning Calorimetry have been carried out in order to study the behaviour of treated samples in temperature with respect the plain paper. The main result is that the siloxane-modified PAA treatment can improve significantly both mechanical and dynamic-mechanical properties, as well as the thermal resistance, without altering the aspect and texture of the original material. In general, the thicker the impregnation, the better the performances of treated paper: the thickest treatment is able to prevent the combustion of paper samples until 500 °C. The treatment is very promising to preserve ancient manuscripts during accidental fire and against the embrittlement due to natural ageing. [ABSTRACT FROM AUTHOR]

Abstract: In this study, SiO2 nanoparticles were in situ grown onto the surfaces of polyimide fibers via sol-gel synthesis and the corresponding paper-based composites were fabricated by wet-forming process using the as-obtained fibers as the starting materials. A simultaneous enhancement of the tensile and tearing index as well as the interlayer bonding strength of paper-based composites could be achieved with an increment of 17.7%, 17.2% and 50%, respectively. What is more, the dielectric strength of the resultant composites increased by 127% compared with the pristine paper-based composites. The results indicated that the SiO2 nanoparticles could be used as an excellent interfacial linker between the fibers and polymer matrix, and a smart cushion to release interior and exterior applied forces. Besides, satisfactory results on thermal stability of paper-based composites were attained after coated with SiO2 nanoparticles.In this graphical abstract, carboxylated PI@SiO2 fibers were successfully fabricated via a facile approach that SiO2 nanoparticles were in-situ grown onto the surfaces of carboxylated PI fibers via sol-gel synthesis. Moreover, the modified paper-based composites consisting of carboxylated PI@SiO2 fibers possess more excellent dielectric strength compared with the pristine paper. A dense and uniform SiO2 nanoparticles layer can be in situ synthesized onto the PI fibers via sol-gel synthesis after activating the surface of PI fibers.SiO2 nanoparticles could be used as an excellent interfacial linker between the fibers, and the interlayer bonding strength and dielectric strength of modified PI paper-based composites was significantly enhanced with an increment of 50 and 127%, respectively. [ABSTRACT FROM AUTHOR]

In this study, self-reinforcing composites (SRCs) were produced via the partial dissolution route with a NaOH/urea solvent from paper made of softwood sulphite dissolving and abaca pulp. Solvent welding leads to increased tensile strength due to gluing the fibres together with the dissolved portion of cellulose but does not densify the material completely. The resulting porosity makes it difficult to compare the obtained materials with other composites and gives the potential for optimizing the SRCs. Calendering, however, is a well-known and easy method to reduce the thickness of paper and therefore reduce the porosity, but the influence of calendering on the mechanical properties has not been widely studied for paper or for SRCs at this stage. The change of morphology and mechanical properties was investigated by calendering the untreated paper and the SRCs with nip pressures from 10 up to 200 kN/m and then comparing scanning electron microscopy (SEM), X-ray diffraction, tensile strength and short-crush resistance. The SEM imaging indicated that calendering indeed densifies the paper and the SRCs by increasing the nip pressures, but tensile strength measurements showed that the strength of paper and SRCs increases for low nip pressures but significantly decreases for high nip pressures despite better densification. Furthermore, it was found that the elastic modulus can be increased by calendering, and short-crush resistance is not influenced by calendering at all. [ABSTRACT FROM AUTHOR]

Colloidal suspensions of glutaraldehyde (GA) crosslinked or grafted graphene oxide (GO) sheets were fabricated by simply tailoring the feed sequence. The different structures were confirmed by Fourier transform infrared spectra and X-ray diffraction. As demonstration of the utilities, the different colloidal suspensions were used to prepare free-standing papers by flow-directed filtration and poly(vinyl alcohol) (PVA)-based nanocomposite films by casting. Free-standing papers from GA crosslinked GO sheets exhibited better mechanical properties than unmodified GO paper, while nanocomposite films from GA grafted GO exhibit higher tensile strength and Young's modulus. [ABSTRACT FROM AUTHOR]

Cellulose-binding domains have been isolated from various cellulases, and proteins, which lack hydrolytic activity. The hypothesis that a cellulose-binding domain can be used to alter surface and mechanical properties of paper was tested. Two cellulose-binding domains from Clostriium cellulovorans were fused to form a cellulose crosslinking protein (CCP). The recombinant bifunctional cellulose-binding protein was expressed in E. coli, appliedby immersion onto Whatman cellulose filter paper, and its mechanical properties were tested. The purified protein improved the treated paper's mechanical properties (tensile strength, brittleness, Young's modulus and energy to break). In addition, cellulose crosslinking protein treatment was shown to transform filter paper into a more water-repellent paper. The binding of cellulose-binding domains to cellulose under a wide range of envi-ronmentalconditions, without the need for chemical reactions, and its biodegradability make them attractive moieties for the design of a new class of paper-modification materials.p> [ABSTRACT FROM AUTHOR]

Due to the high potential of cellulose nanoparticles in composite materials and for both fundamental and technological considerations, we investigated the interaction between microfibrillar cellulose and fibers. The contribution to the paper properties of fines added to a pulp suspension was determined. The impact of various proportions of fines added to a softwood kraft pulp on the paper strength and how they affected porosity and density was evaluated. The respective effects of dried fines (dead fines), originating from paper or board degradation, and the newly formed secondary fines (fresh fines) generated during refining were examined. The nature of the bonding between the fines and the fibers versus physical retention was characterized in the pulp suspension. For the first time the respective parts in the interaction of hydrogen bonds and mechanical associations were demonstrated and quantified. The amount of H-bonded fresh fines exceeded that of dead fines by more than 30 %. The results revealed that, for both types, the amount of H-bonded fines reached a threshold, independently of the proportion of fines added to the fibers. Addition of fines significantly affected the porosity of papers, fresh fines decreasing porosity more readily than dead fines. All the results are convergent to indicate that fresh fines penetrate more evenly and more deeply into the fiber network and induce better bonding that produces a closure of the fiber mat structure. They also demonstrate that incorporating an optimal proportion of fresh cellulose fines in fiber networks can bring significant improvement to the final composite material. [ABSTRACT FROM AUTHOR]

Applicability of super-insulating silica aerogel materials for thermal insulation is still restricted by limited mechanical strength. We report on a systematic improvement of silica aerogels in respect to shrinkage, density and thermal conductivity by varying sol-gel parameters as the molar ratios of TEOS:EtOH:HO or the hydrolysis time. The received silica aerogels can be combined with paper-based honeycomb structures to improve the mechanical strength. We successfully manufactured such silica aerogel paper honeycomb composites. The challenges in the preparation are the must to prevent shrinkage of the silica aerogels during synthesis, to avoid cracks by supercritical drying, and to get a perfect bonding at the paper-silica interface. The composite materials are characterized with respect to their compression modulus, thermal conductivity, and flammability. Graphical abstract: [ABSTRACT FROM AUTHOR]

During cocoa processing, a considerable residue of biomass with high economic potential is generated. The purpose of this research was to evaluate whether cocoa husk residue after cocoa harvesting has the potential to be used as a fibre source in papermaking applications for packaging. Cocoa husk was collected, and pulp was produced chemically from the obtained biomass. Lignocellulosic components, ash and extractive content were established using standard or well-established methods. The results were in line with previous literature studies and demonstrated that agricultural residual biomass from cocoa husk contains 34.6% cellulose which is similar to wood fibre, but with higher lignin (30.7%) and ash content (9.0%). Chemical pulping and screening delivered a very low fibre yield of 19.6% which was further reduced to 11% after bleaching. Morphological properties of the obtained pulp were also measured. The obtained fibres after bleaching were very short (0.348 mm) and coarse (43.4 µm) when compared to softwood fibres. Laboratory handsheets with different blends of cocoa husk and commercial softwood fibres were prepared. The impact on handsheet properties were studied. The unbleached and bleached cocoa husk pulps were not suitable for papermaking as individual fibre sources, due to poor bonding characteristics and very slow drainage, respectively. When unbleached cocoa husk pulp was blended with softwood pulp, the strength properties of the sheets were negatively impacted. As cocoa husk fibre content was increased to 30% and 50%, tensile decreased by 10–34%, tear by 13–37%, burst by 22–39% and bending stiffness by 13–21%, respectively, making such addition undesirable for lightweight paper packaging applications. The addition of 30% bleached cocoa husk fibre to softwood, however, showed an improvement of 39% in tensile strength and 11% in burst, while tearing resistance and bending stiffness were compromised by 16% and 15%, respectively. [ABSTRACT FROM AUTHOR]

Microindentation as a method for determining important material properties of paper coating materials is studied experimentally and numerically. The bulk of the investigation is concentrated upon the short-lived elastic part of a spherical indentation test, but determination of the failure stress of the coating is also discussed. The results indicate that microindentation can be a powerful tool for material characterization of these materials, but only if careful efforts are made to account for the influence from plasticity as well as from boundary effects. [ABSTRACT FROM AUTHOR]