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The prevalence of diabetes has increased over the past years. Therefore, developing minimally invasive, user-friendly and cost-effective glucose biosensors is necessary especially in low-income and developing countries. Cellulose paper-based analytical devices have attracted the attention of many researchers due to affordability, not requiring trained personnel, and complex equipment. This paper describes a microfluidic paper-based analytical device for the detection of glucose in tear with the naked eye. The paper-based biosensor fabricated by laser CO2, and GOx/HRP enzymatic solution coupled with TMB was utilized as reagents. A sample volume of 10 µl was needed for the biosensor operation and the results were observable within 5 minutes. To evaluate the device performance, color intensity-based and distance-based results were analyzed by ImageJ and Tracker. Distance-based results showed a linear behavior in the range of 0.1–0.6 mM with an R2 = 0.967 and LOD of 0.2 mM. The results could be perceived by the naked eye without any need to further equipment or trained personnel in a relatively short time (3–5 minutes). Moreover, glucose concentration could be obtained non-invasively by tears collected by this µPAD.

Access to medical care is a significant challenge facing developing countries. The World Health Organization developed the ASSURED criteria, which specifies requirements for the ideal diagnostic. ASSURED stands for Affordable, Sensitive, Specific, Rapid/Robust, Equipment-free and Deliverable. Traditional microfluidic diagnostics (comprised of glass/PDMS) require expensive fabrication procedures and user-intervention to manipulate fluids on the device. For those reasons, paper shows great promise as a substrate for an ASSURED microfluidic diagnostic. It is affordable and does not require external pumping to move fluids. Initially, microfluidic paper-based analytical devices (μPADs) performed simple, colorimetric assays. However, the field has evolved rapidly. Modern μPADs have been developed for a plethora of applications such as nucleic acid amplification. Wider adaptation of μPADs relies on the incorporation of more complicated assays (i.e. involving multiple fluids), which would allow μPADs to replace more expensive benchtop equipment. This requires more robust fluid control. Typically, fluid control on μPADs has been achieved by slowing fluid down to create delays between different channels. However, adding delays increases overall assay time and creates other complications such as fluid loss due to evaporation. Instead, creating ‘delays’ by accelerating wicking (relative to native paper) is being investigated. Previous approaches include sandwiching the paper between polymer films or creating ‘macro capillaries’ within the paper for the liquid to flow through. Of particular interest is the etching of grooves onto paper channels using either a plotter or a CO2 laser. These grooves create hollow regions in the paper which lead to faster wicking speeds. This study aims to characterize the behavior of grooved channels in paper and assess their performance as ‘delay’ mechanisms for a multi-fluid paper-based sensor.Typically, μPAD designs evolve in a trial-and-error basis, where devices are fabricated, tested and updated. Having accurate models that characterize the imbibition process could streamline development by allowing direct translation of in-silico designs to fully-functioning paper-based tools. Current imbibition models do not adequately describe the complex transport phenomena occurring within the paper matrix. This study also aims to develop an in-silico simulation that can reliably predict imbibition in both native paper and grooved channels.

The flexibility and insulating nature of polymeric dielectric materials are widely used in robotic and wearable electronic devices like electrical insulation, capacitive sensors, and electromechanical actuators. When combined with a phase transition-induced shape memory property, the resultant bistable electroactive polymer (BSEP) opens up new applications due to the rigid-to-rigid actuation of BSEP tremendously reducing the energy consumption for device operation while providing desirable strength for external loads. This dissertation focuses on investigating insulating, electroactive, and phase transition properties of BSEP, and adapting each aspect of the properties in the pursuit of innovative devices, such as rewritable photonic paper, smart windows with whole solar spectrum modulation, and wearable pressure sensors. An ink-free rewritable photonic paper has been invented through the interdisciplinary combination of photonic crystals, shape memory and electroactive properties of BSEP. The rewritable paper consists of a ferroferric oxide-carbon (Fe3O4@C) core–shell nanoparticle (NP)-based photonic crystal embedded in a BSEP. The nanocomposite can be repeatedly triggered to change into different shapes and colors due to the z-directional deformation that is induced by an electric field. The actuated shape and color can be maintained for a long term without energy input, and the stored images can then be rewritten over 500 times without noticeable degradation. Low energy consumption and simple erasing/rewriting are features that match the benefits of conventional paper as a zero-energy and long term data storage medium, but provide the additional advantage of rewritability. With pixelated electrode arrays, user-defined information can be actuated and erased at will which has been demonstrated through a seven-segment numerical display. A smart window with wide-band light modulation is designed solely based on the phase transition property of BSEP. One component of BSEP can be switched between semicrystalline and amorphous states through cooling below or heating above its melting temperature, leading to a reversible opaque-to-transparent transition. The opacity switching property of BSEP was further improved by mixing a more hydrophilic component to induce micro-scale phase separation, which is responsible for the whole solar spectrum light modulation due to Mie scattering. The resultant smart window achieves both high solar transmittance modulation of 70.2% and high luminous transmittance modulation of 80.4% which rivals the best reported smart windows and commercial privacy glasses with the highest privacy levels. This flexible smart window can also be mounted on curved surfaces for the need of windows with arbitrary shapes. This work is the first one to report an all-solid thermochromic smart window film without the inclusion of any metal/metal oxides or liquid crystals to enable a large light modulation over the whole solar spectrum.A flexible fiber-based pressure sensor is realized by applying a dielectric layer on the outside of a TEMPO-oxidized bacterial cellulose (TOBC)/silver nanowire (AgNW) conducting fiber. The pressure sensor can detect pressures up to 134 MPa with sensitivity of 101 � 10-4 kPa-1 due to its hierarchical structure and high conductivity. The porous structure of TOBC/AgNW helps increase the thickness deformation of the sensor with applied pressure, improving the sensing ability. Small pressures of human pulse and voice vibration can be detected with this sensitive pressure sensor. A machine learning classification model was implemented to recognize human’s speech where the prediction accuracy on a test dataset is > 90%. The ultrathin fibrous sensor (53 �m) is capable of high-resolution detection, and suitable as a comfortable and fashionable thread substitute for real wearable devices.The combined properties of BSEP with the proof-of-concept developments of rewritable paper, smart windows and wearable sensors demonstrate its potential for real-world applications. And an outlook for future research and suggested improvements for commercialization are discussed in the conclusion.

Paper sheets represent one of the infection risk sources inside educational and administrative institutions under biological pandemics. So, the present study aimed to validate the efficiency of gamma radiation or dry heat techniques to sterilize contaminated paper sheets with different indicator pathogens while retaining their structure. The results showed that gamma radiation at 6, 12, or 24 kGy can successfully kill Gram-positive bacteria such as Bacillus cereus and Staphylococcus aureus, Gram-negative bacteria such as Escherichia coli and Salmonella typhi, and fungi such as Candida albicans. Moreover, dry heating at 100 °C for 60 min, 150 °C for 30 min, or 200 °C for 15 min can be successful in paper decontamination of all tested species. Surprisingly, scanning electron microscopy (SEM) micrographs proved that gamma radiation at 6 kGy, dry heat at 100 °C for 60 min or 150 °C for 30 min or 200 °C for 15 min, is suitable for paper sheet sterilization while maintaining their structure. Ultimately, dry heat is a simple, effective, fast, safe, and inexpensive technique for paper sterilization. It may be used as a precautionary step inside educational institutions, especially during written examination periods, to ensure a safe life for academic members during biological pandemics such as COVID-19.

This manuscript aimed to enhance the mechanical, thermal, and ignition properties of bagasse paper when coated with different coatings synthesized from hydroxyethyl cellulose, 1,3-di-p-toluidine-2,2,2,4,4,4-hexachlorocyclodiphosph(V)azane, Talc powder, NaHCO3, cellulose nanocrystal. The effect of these coatings on the mechanical properties was studied by measuring elongation, tensile strength, and burst strength. The stages of degradation and ash residue of the measuring specimens were determined using thermal gravimetric analysis (TGA), behind that, the ignition properties as the flame chamber (UL/94), and limiting oxygen index (LOI) was measured according to standards. These tests proved that 1,3-di-p-toluidine-2,2,2,4,4,4-hexachlorocyclodiphosph(V)azane has a direct effect on improving the mechanical characteristics and enhancing the ignition properties of the coated specimens compared to uncoated. In this study the physical, mechanical, thermal, and ignition properties of the bagasse paper sheets were enhanced by easy and low-cost method via synthesis of new coatings based on commercially available chemicals in a reasonable cost.

Paper has been widely employed as cheap material for the development of a great number of sensors such as pregnancy tests, strips to measure blood sugar, and COVID-19 rapid tests. The need for new low-cost analytical devices is growing, and consequently the use of these platforms will be extended to different assays, both for the final consumer and within laboratories. This work describes a paper-based electrochemical sensing platform that uses a paper disc conveniently modified with recognition molecules and a screen-printed carbon electrode (SPCE) to achieve the detection of gluten in a deep eutectic solvent (DES). This is the first method coupling a paper biosensor based on aptamers and antibodies with the DES ethaline. Ethaline proved to be an excellent extraction medium allowing the determination of very low gluten concentrations. The biosensor is appropriate for the determination of gluten with a limit of detection (LOD) of 0.2 mg L−1 of sample; it can detect gluten extracted in DES with a dynamic range between 0.2 and 20 mg L−1 and an intra-assay coefficient of 10.69%. This approach can be of great interest for highly gluten-sensitive people, who suffer from ingestion of gluten quantities well below the legal limit, which is 20 parts per million in foods labeled gluten-free and for which highly sensitive devices are essential. Graphical abstract

Biodegradable paper cups coated with rice bran wax and whey protein isolate were designed to package popcorn. Coatings with different concentrations of whey protein isolate (5.5, 7.75, and 10% w/v) and rice bran wax (0.2, 0.4, and 0.6% w/v) were applied on the outer surface of the paper cups. Thickness, color changes, Young's modulus and tensile strength, water vapor transmission rate (WVTR) of the coated and uncoated cups, and also popcorns properties (pH, texture, and sensory properties) were evaluated. Water vapor transmission rate, Young's modulus, thickness, total color change index, and tensile strength of coated cups with the optimal coating formulation was 19.785 (g/m2 day), 11.810 (MPa), 276.583 (µm), 1.839, and 11.222 (MPa), respectively. The results showed that paper cup coating increased thickness and yellowness and reduced the brightness, Young's modulus, and WVTR. Coating had a positive effect on the pH and texture of popcorns packaged in coated cups than samples packed in uncoated cups (p, Biodegradable packaging is one of the best types of packaging that wishes not to harm the environment. Paper packaging coated with materials, such as rice bran wax and whey protein isolate, both of which are food waste, can improve paper color and resistance, and provide a good moisture barrier. This type of coating can be used in paper packaging of food such as snacks, noodle packaging, semi‐prepared foods, etc. This type of packaging can also maintain the physicochemical and sensory properties of food for a long time. Also, due to the edible nature of this type of coating, this coating can be used inside the package so that the printability of the packaging surface is not affected.

An innovative consolidation strategy for degraded paper is presented based on the reversible application of cellulose nanocrystals as sustainable fillers to reinforce mechanical properties and resistance to further degradation. The compatibility and efficacy of the proposed consolidation treatment are assessed first on pure cellulose paper, used as a model, by reliable techniques such as field emission scanning electron microscopy, atomic force microscopy, tensile tests, X-ray powder diffraction, and Fourier transform infrared spectroscopy, evidencing the influence of the surface functionalization of nanocellulose on the consolidation and protection effects. Then, the consolidation technique is applied to real aged paper samples from Breviarium romanum ad usum Fratrum Minorum S.P. (1738), demonstrating the promising potential of the suggested approach. Amperometric measurements, carried out with a smart electrochemical tool developed in our laboratory, demonstrate the reversibility of the proposed treatment by removal of the nanocrystalline cellulose from the paper surface with a suitable cleaning hydrogel. This completely new feature of the consolidation treatment proposed here satisfies a pivotal requisite in cultural heritage conservation because the methodological requirement for the ″reversibility″ of any conservation measure is a fundamental goal for restorers. A paper artifact, in fact, is subject to a number of natural and man-made hazards, inducing continuous degradation. With time, monitoring and consolidation actions need to be often performed to ensure conservation, and this tends to modify the status quo and compromise the artifact integrity. Removable treatments can potentially avoid erosion of the artifact integrity.

Paper manufacturing on a global scale is a highly competitive market which requires to constantly improve the manufacturing process to be competitive. To decrease production cost paper manufactures, add filler material prior to sheet forming to replace costly wood fiber based raw material. This research project investigates the use of in-situ precipitated calcium carbonate produced in the presence of eucalyptus fiber material at a 41.0% filler level prior to beating. The in-situ filler containing eucalyptus fiber suspension was used on a 12’ (304mm) wide Laboratory Fourdrinier Paper Machine together with non-filler containing eucalyptus fiber material, and a commercial precipitated calcium carbonate filler material. The manufactured in-situ fiber suspension resulted in a higher ash retention compared to the addition of the powdered commercial PCC filler material. In addition to commercial filler material retention is improved at higher filler addition above 30%. The increased ash retention is linked to the increased micro fibrillation fiber material of the in-situ filler-fiber suspension forming neckless like particles on the fibers microfibrils. Mechanical paper properties showed an improvement for in-situ precipitated filler material compared to commercial filler material addition. Optical properties could be improved in comparison to the eucalyptus fiber without filler addition for in-situ precipitated filler material and a combination of in-situ and commercial filler material.

Laser-induced graphene (LIG) technology featuring low-cost, high-efficiency and scalability has presented great advantages in micro-supercapacitors (MSCs) fabrication. However, the limited capacitance of LIG based MSCs is still hindering their further development. Herein, we introduce joule heating as a critical in-situ treatment merged with the assembly of laser-induced graphene paper based MSCs (LIGP-MSCs) toward capacitive enhancement. By increasing heating-treatment temperature from ∼20 to 500 °C, the number of nanopores in LIGP continuously increases, attributed to the gradual decomposition of amorphous carbon components. The resulting joule-heated LIGP (J-LIGP) with improved specific surface area (160.97–533.49 m2/g) and pore volume (0.179–0.553 cm3/g) as well as superhydrophilic surface is highly suitable to be employed as J-LIGP-MSCs microelectrodes. By investigating process dependent performance, the J-LIGP-MSCs heated at 500 °C for 60 min delivers a significantly improved specific areal capacitance (CA) of 13.71 mF/cm2 at 10 mV/s, which is approximately six-fold higher than that of unheated LIGP-MSCs. By further exploring and optimizing the process efficiency, J-LIGP-MSCs with a CA of 12.61 mF/cm2 has been achieved by 550 °C heating for only 5 min. Along with superior mechanical flexibility, cyclability and structural modularity, the proposed in-situ joule heating treatment is finally proved to be a universal approach for consistently enhancing the CA of LIG based MSCs processed under various chemical modifications.

Million tons of cellulosic paper have been used for insulating coils in oil-filled electrical power transformers, thereby assuring the electricity supply for our societies. The high working temperatures in transformers constantly degrade paper insulators throughout their service life of up to 40 years. We approached the structural changes in oil-immersed cellulosic paper samples upon thermal stress in a study that compared unbleached softwood Kraft paper used as insulator paper with pure cotton cellulose paper. The model experiments used a thermal treatment in transformer oil at 170 °C for up to 14 days. The samples were characterized by means of 13C CP/MAS NMR spectroscopy, mainly based on deconvolution of the C4 resonance. An automated, fast, and reproducible C4 resonance deconvolution employing the “Peak Analyzer” tool of OriginPro 2020 (OriginLab Corporation, USA) was developed and used to exploit 13C CP/MAS NMR spectroscopy for the characterization of thermally stressed paper samples. Our results show that thermally induced structural changes depend heavily on the composition of paper, that hornification and coalescence of fibrils take place, and that the allomorph composition of cellulose crystallites is altered under the given conditions. Graphical abstract

To explore the reinforcement effects of different reinforcement methods, kraft paper was used as reinforcement material, and shear tests were carried out in sand to study the reinforcement effects of kraft paper perpendicular and parallel to the shear plane. The test results show that the two reinforcement methods can effectively improve the strength of sand and the orthogonal reinforcement form is more superior. The existence of reinforced materials greatly improves the cohesion of sand, but does not significantly improve the internal friction angle. The width of reinforcement material has little effect on the reinforcement effect and shows different variation laws under different reinforcement forms.

Mechanical properties are crucial in assessing the paper quality. Deformation and strength properties of paper are determined by the strength and stiffness of the interfiber and intermolecular hydrogen bonds. The contribution ratio of interfiber and intermolecular hydrogen bonds to the strength of paper can be changed by adjusting the degree of its anisotropy. The article presents the results on a study of the deformation properties of laboratory anisotropic paper samples from kraft bleached softwood pulp with a beating degree of 30 °SR. The samples had basic weight of 90 g/m2 and the degree of stiffness anisotropy TSIMD/CD of 1.75–4.08. They were made by using Techpap SAS automatic dynamic handsheet former (Grenoble, France), with varying forming parameters – diameter of the nozzle, motion speed of the forming wire, and injecting speed of pulp. Deformation properties were determined by tensile test and processing of the stress-strain dependence (σ−ε). The outcomes have shown that, an increase of the fiber orientation degree in paper structure by changing the forming parameters caused a change in the nature of the paper deformation under tension. Increasing the fiber orientation degree in the structure of paper made it possible to increase the strength by 55 %, tensile stiffness by 63 % in the machine direction, while reducing the extensibility by 10 %. In the cross direction, it was possible to decrease tensile stiffness by 33 %, strength by 55 %, and increase the extensibility by 5 %. Anisotropy of tensile strength was 1.73–6.00. The greatest effect was obtained for the elasticity modulus in the pre-failure zone E2 (2.8–38.6). It means that, fiber orientation had a key importance when large deformations in the samples took place. The established quantitative regularities allowed optimizing the values of the deformation and strength properties of paper, and their ratio in the machine direction and cross direction due to the variation of the forming parameters. For citation: Rech D., Potasheva A.N., Kazakov Ya.V. Regulating the Deformation Properties of Paper by Varying the Degree of Its Anisotropy. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 5, pp. 174–184. DOI: 10.37482/0536-1036-2021-5-174-184

Cellulosic insulating paper is the essential component of the insulation in power transformers. Under the thermal stress inside the transformer, the cellulosic insulating paper degrades and generates formic acid. Meanwhile, the presence of formic acid further accelerates the aging process of cellulosic insulating paper. This study takes the cellulose molecule composed of D-glucose as the research object. The ReaxFF reactive force field is applied to simulate the high-temperature thermal aging process of cellulosic insulating paper. During pyrolysis process, the number of formic acid molecules presents short-term fluctuations and continuous increases. Though simulation, the main reaction pathways of cellulose pyrolysis to generate formic acid are obtained. In addition, an accelerated thermal aging experiment of oil-paper insulation is designed. The formic acid in the experimental samples is detected by the silanization derivatization method. Through the combination of simulation and experimental results, the feasibility of formic acid as an aging indicator for cellulosic insulating paper is further demonstrated.

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.

In the present approach, a Cr2O3-TiO2-modified, portable, and biomimetic nanosensor was designed to meet the requirement of a robust and colorimetric sensing of hydrogen peroxide. Cr2O3-TiO2 nanocomposites prepared via the hydrothermal method were fabricated as a transducer surface on the filter paper using the sol-gel matrix. The color on the filter paper sensor changed from green to blue upon the addition of hydrogen peroxide in the presence of TMB. This change in the color intensity was linear with the concentration of H2O2. RGB software was used as a color analyzing model to evaluate the optical signals. This paper-based colorimetric platform provided us with an improved analytical figure of merit with a linear range of 0.005-100 μM with 0.003 μM limit of detection. The real sample analysis and excellent anti-interference potential results proved the good analytical performance of the proposed design, providing a more promising tool for colorimetric H2O2 detection. Introducing Cr2O3-TiO2 nanocomposite-based paper sensors, being a novel method for optical and colorimetric detection, can pave the way for the development of other sensing devices for the detection of different analytes.

Cellulose paper, a material that is naturally derived, low cost, lightweight, eco-friendly, and mechanically deformable, plays important roles in producing next-generation flexible electronics. Following the booms in the development of functional electronics, the soft actuators built from cellulose paper have attracted great attention. In this focused review, the milestones and recent achievements of cellulose paper-based actuators are summarized. Electro-, thermal, moisture and magnetic actuation mechanisms are utilized to acquire energy from external stimuli. Corresponding functional materials and available fabrication techniques like film assembly and layer deposition are described. Programmable actions for the emerging applications in bionics, paper grippers and robots are realized by pursuing different strategies to control the responding deformation. Along with a conclusion, the existing challenges and possible solutions in evaluating and improving the performance of cellulose paper are summarized in the final section.

Paper mulch has the advantages of simple process, low production cost and strong degradability, but it is still a great challenge to prepare paper mulch with excellent water resistance and light transmittance. In this paper, through a simple physical brushing method, Zinc oxide (ZnO) solution and silica (SiO2) solution were brushed on the surface of paper mulch film respectively, and ZnO/SiO2 composite superhydrophobic paper mulch film (CSPMF) with micro-nano rough structure was constructed. The microstructure of original paper mulch film (OPMF) and ZnO/SiO2 CSPMF was studied by scanning electron microscope (SEM), and the superhydrophobic surface elements were analyzed by energy dispersive spectrometer (EDS). The contact angle (CA) and rolling angle (RA) of two kinds of sample surfaces are measured by contact angle meter. The static CA and RA of ZnO/SiO2 CSPMF were 160 ± 0.4° and 3 ± 0.3°, respectively. The self-cleaning behavior of soil simulated dust environment was tested on the surface of OPMF and ZnO/SiO2 CSPMF respectively. The horizontal bounce performance and tilt bounce performance of the superhydrophobic surface were tested by high-speed camera. In addition, frost experiments and delayed icing experiments were carried out. The results show that ZnO/SiO2 CSPMF has good self-cleaning performance, bouncing performance and delayed icing performance.

Today, recycling is becoming increasingly important. In recycling process, the product performance should also be considered. In this study, manufacturing insulation fiberboard, as a practical wood product from recycled fibers, was investigated. For this purpose, two types of waste (MDF wastes and waste paper) were recycled to fibers and used for producing insulation fiberboards. The target fiberboard density was 0.3 g/cm3. The ratio of waste paper to MDF waste recycled fibers (WP/RF) was considered at two levels of 70/30 and 50/50. Polyvinyl acetate adhesive was used as a variable in the board manufacturing process. The mechanical properties, dimensional stability, thermal conductivity, and fire resistance of the boards were evaluated. Besides, the thermal stability of fiberboards was studied using thermal analysis including thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The results showed that the insulation fiberboards had admissible mechanical properties and dimensional stability. The manufactured boards displayed low thermal conductivity, which proved to be well competitive with other insulation materials. The fiberboards manufactured with PVAc adhesive and WP/RF ratio of 50/50 had higher fire resistance compared to other treatments. Additionally, results of thermal analysis showed that the use of PVAc adhesive and WP/RF ratio of 50/50 leads to improved thermal stability. Overall, the recycled fibers from MDF and paper wastes appear to be appropriate raw materials for manufacturing thermal insulation panels, and use of PVAc adhesive can significantly improve thermal and practical properties of insulation fiberboards., Danas recikliranje postaje sve važnije, a u tom postupku treba uzeti u obzir i svojstva proizvoda koji se recikliranjem dobivaju. U ovom je radu istražena proizvodnja izolacijske ploče vlaknatice kao praktičnoga drvnog proizvoda od recikliranih vlakana. Za tu su namjenu u vlakna reciklirane dvije vrste otpada (MDF otpad i papirni otpad), koje su iskorištene za proizvodnju izolacijskih ploča vlaknatica. Ciljana gustoća ploče vlaknatice bila je 0,3 g/cm3. Planirani je omjer vlakana recikliranih od otpadnog papira i MDF otpada (WP/RF) iznosio 70 : 30 i 50 : 50. U procesu proizvodnje ploča upotrijebljeno je polivinilacetatno ljepilo. Eksperimentom su određena ova mehanička svojstva ploča: dimenzijska stabilnost, toplinska vodljivost i vatrootpornost. Osim toga, uz pomoć toplinske analize koja je podrazumijevala termogravimetrijsku analizu (TGA) i diferencijalnu toplinsku analizu (DTA) istražena je toplinska stabilnost ploča vlaknatica. Rezultati su pokazali da izolacijske ploče vlaknatice imaju odgovarajuća mehanička svojstva i dimenzijsku stabilnost. Usto, proizvedene su ploče imale nisku toplinsku vodljivost, što potvrđuje njihovu konkurentnost s ostalim izolacijskim materijalima. Ploče vlaknatice proizvedene s PVAc ljepilom i uz omjer WP/RF od 50 : 50 imale su veću vatrootpornost od ploča proizvedenih ostalim postupcima (omjerima sastojaka). Usto, rezultati toplinske analize pokazali su da upotreba PVAc ljepila i omjer WP/RF od 50 : 50 pridonose poboljšanoj toplinskoj stabilnosti. Zaključno, reciklirana vlakna od MDF otpada i otpadnog papira čine se prikladnom sirovinom za proizvodnju termoizolacijskih ploča, a uporaba PVAc ljepila može znatno poboljšati toplinska i uporabna svojstva takvih izolacijskih ploča vlaknatica.

An increase in the environmental and health concerns over fluorochemical‐based, wax‐based, and extrusion‐based paper coatings has led to a growing interest in bio‐based, biodegradable, and repulpable alternatives to obtain water‐ and oil‐repellent coatings. Reported herein is a fluorine‐free, plastic‐free, and cost‐effective water and grease resistant paper coating approach that utilizes blends of corn‐starch (S) and a novel chitosan‐graft‐polydimethylsiloxane (CP) copolymer. The hydrophobic and oleophobic performance of the S/CP‐coated paper was evaluated by varying the ratio of S and CP in the overall blend. The S/CP‐coated papers were observed to have low cobb60 values (water absorptivity) of 13 ± 0.9 g m−2 and an excellent kit rating (oil resistance) of 12/12. The S/CP‐coated paper substrate surface profile was analyzed via scanning electron microscopy (SEM). The repulpability of the coated paper is also demonstrated by washing the coating materials from the paper and recovering the pulp.

Despite previous efforts, the fabrication of superhydrophobic substrate via an environment friendly and easy approach remains a great challenge. In this study, a low cost, simple, and green procedure was developed to prepare a superhydrophobic paper surface that is acceptable for the papermaking industry. First, a wax mixture (beeswax & carnauba wax) was emulsified and coated on the filter paper surface. Then, the coated paper was annealed at different temperatures. The further heat-treatment-rendered wax-coated paper hydrophobic or superhydrophobic because submicrometer or micrometer wax structures were present on the paper surface. The water contact angle of the annealed filter paper sample reached 151.5° at 60 °C, and the sliding angle was under 10°. Further, the relationship between surface composition and the hydrophobic properties of the coated paper samples was discussed. The obtained paper samples showed great potential in water/oil separation, as they had an efficiency over 99%. This work proposed a new simple and mild approach to fabricate superhydrophobic filter papers and explored the hydrophobicity and water/oil separation properties.

Cellulose based nanomaterials have the great potential to be applied to paper as bulk additive or coating material to improve overall final properties, especially in secondary fiber. In the present work, the effect of applying different kinds of cellulose nanofibrils (CNF) to papers obtained from recycled fibers using size press on physical, mechanical and barrier properties was investigated and compared with the sole use of starch as coating material. The coating process of CNF was carried out by the addition of size press grade starch to coating suspension. As a cellulose source, wheat straw was evaluated and CNF was obtained through oxidative and enzymatic pretreatments. Results indicate that starch/CNF suspension improves the overall paper properties. As a result of the deposition of coating suspension contains of 4 % wt. periodate-oxidized CNF onto paper surface, tensile and burst indices of papersheets increased as 52.2 % and 194.4 %. Significant decreases were observed in air permeability as 69.8 %. Compression tests also have been conducted to evaluate papersheets end-use properties. In comparison to the other pretreated CNF, due to is lower viscosity, applying periodate-oxidized CNF as size press significantly increased the mechanical properties of the papers fabricated from the recycled pulps. TUBITAK-TEYDEBTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [1505]; Scientific and Technological Research Council of Turkey, Technology and Innovation Funding Programs Directorate [1505, 5180044] This work was supported by TUBITAK-TEYDEB 1505 (The Scientific and Technological Research Council of Turkey, Technology and Innovation Funding Programs Directorate 1505), Project No. 5180044. WOS:000703585400013 2-s2.0-85108063350

Surface characteristics of printing substrates are of the utmost importance to all types of paper that interact with ink. During all types of printing processes, the behaviour of the liquid phase (ink or dye) on the paper is directly defined by the paper cellulose-based surface. The printed ink spreads and penetrates more into paper fibres when the paper surface is rougher and more permeable. Contact angle measurements by sessile drop method are considered the most appropriate for determining the paper sheet surface energy. Paper as hydrophilic material has a high absorption rate resulting in a low contact angle. The objective of this study was to evaluate the surface free energy of laboratory-made papers containing straw pulp obtained from residues after the harvest of the most cultivated cereals in Croatia (wheat, barley and triticale). The obtained surface free energy results are promising for straw pulp usage in the manufacture of printing paper.

This study was aimed to examine the effects of basic properties, fiber morphological properties, strength properties, wettability and optical properties on offset printing of office papers. Widely used office papers with different brands were obtained from Istanbul-Turkey. Technical characteristics of papers; basic properties, strength properties including tensile, burst, tear, and Z direction tensile strength and optical properties such as gloss, whiteness, opacity, and wettability tests were determined according to TAPPI and ISO standards. The results obtained by the tests are as follows; i) there is a great difference in water resistance between the top and the lowest values (207 %), ii) there is little difference between the highest and the lowest brightness value (3.8 %), other papers values have close to each other, iii) in the printing process there is a little difference between the highest, and the lowest gloss values (36.7 %), although the others are close iv) the highest and lowest values in CIE C* showed that it ranged from the narrowest color gamut to the widest color gamut. By applying the widely used offset printing process to commercially produced office papers, the quality levels were evaluated to raise awareness of consumers and sellers.

In order to study the feasibility of kraft paper as watercolor paper, the wetting properties, mechanical properties and friction properties of kraft paper and watercolor paper were compared before and after aging. The aging test was carried out on kraft paper and the watercolor paper by aging chamber, the wetting properties of distilled water and three watercolor solutions before and after aging of kraft paper and watercolor paper were compared, tensile tear test of paper on the tensile testing machine, the fracture changes of paper were analyzed by scanning electron microscope, the friction tester performs the paper friction test. The results show that both kinds of paper are amorphous, watercolor paper was showed hydrophobicity before and after the aging, the contact angle was maintained at about 119,09° ± 5° in four different solutions, unaged kraft paper exhibited hydrophilicity, the aged kraft paper showed hydrophobicity with a contact angle of 92,52° ± 1°，the aged kraft paper shows better performance in both tensile and tearing aspects and tensile strength is 20 MPa higher than watercolor paper, the surface roughness of kraft paper is higher than watercolor paper. The experiment is helpful for the market to consider whether the cheaper kraft paper replaces the more expensive watercolor paper in some aspects and provides some scientific reference value for future research.

Hydrothermal Carbonization an emerging technology for the conversion of biomass into carbon rich materials called as hydrochar. In this study, the paper board mill ETP sludge has been used for the production of hydrochar. The characterization of point of zero charge, Heavy metals, proximate and ultimate constituents, structural morphology (SEM), and molecular surface functionalities (FTIR) were also analysed. The results of Hydrochar showed slightly acidic pH (6.40), EC (1.33), and the pHPZC (point of zero charge) of 7.8 and the heavy metals content were found to be below detectable limit. FTIR analysis revealed that, the produced hydrochar have oxygen containing functional groups (-OH, C-O-C, -C=O). SEM analysis has the morphological features such as spongy, fuzzy and fluffy porous network on surfaces. These results of hydrochar can be act as an active adsorbent with further activation.

High strength concrete (HSC) is an amazing breakthrough in the history of construction material. Due to its high strength, durability, and economic value, it has been used in large-scale construction with a unique structure design not achievable by conventional concrete. However, HSC uses a high amount of cement powder which contributes to its overall strength. However, it will require high cement consumption and increases carbon dioxide emission. Waste paper sludge ash (WPSA) is utilised in cement and has improved concrete properties. Nano engineered WPSA might further enhance HSC capabilities. This research focused on the physical and fresh properties of HSC with partial replacement of nano-engineered WPSA to cement through experimental investigation. The HSC produced in this research has a targeted strength of more than 40MPa with a fixed water-cement ratio of 0.2. The WPSA was oven-dried and was sieved to a particle size of 212 micrometers. Then, it was milled until a nano-size particle is obtained. The nano WPSA is used to replace cement in the HSC mix with a replacement percentage of 1%, 3%, 5%, 7%, and 10%. The new properties of the concrete were measured by conducting the flow table test, and the physical property was determined by conducting the compressive test. Compressive tests were conducted for 1, 3, 7, 14, and 28 days with a cube sample size of 50mm x 50mm x 50mm. This research shows that 1% of nano WPSA replacement tends to improve the compressive strength of the HSC concrete by 10.7% compared to the control sample. On the other hand, the 1% replacement of nano WPSA in HSC did not affect the concrete's workability compared to the control sample. The conventional HSC properties were improved with less usage of cement with the use of WPSA.

The sorption properties of organomineral composite sorbents have been investigated by ICP-MS method. The diatomite of the Jradzor deposit and bentonite of the Sarigyuh deposit (Armenia) were used as inorganic constituents. Diatomite serves as a structure-forming component and provides mass transfer due to its high porosity (V = 2.0 cm3/g) and large pore sizes (150–200 nm). Bentonite is responsible for the functionality of the sorbents. The organic component is also responsible for the functionality of the obtained sorbents. Paper pretreated with acids (nitric and phosphoric) was used as an organic component. A synthetic solution containing cations of heavy metals was used as an object of study. The experiments were carried out in static mode on a Jar-Test device.

Polymeric felts are commonly used in the papermaking process on the paper machine wet end, in the press section, and in the dryer section. They provide an important function during paper manufacturing, including as a carrier or support; as a filter media assisting with water removal on the paper machine; in retention of fibers, fines, and fillers; and in some applications, such as tissue and towel, to impart key structural features to the web. These felts can have highly interwoven complex internal structures comprised of machine direction and cross-machine direction yarns of varying sizes and chemical compositions. Here, we present a non-intrusive three-dimensional (3D) image visualization method using advanced X-ray computed tomography (XRCT). This method was used to characterize the complex 3D felt structure and determine the water removal characteristics of some commonly used paper machine felts. The structural features analyzed include porosity; specific pore-yarn interfacial surface area; 3D pore size distribution; 3D fiber or yarn-size distribution; and their variations through the thickness direction. The top, middle, and bottom layers of the felt have very different structures to assist with water removal and impart paper properties. The size distribution of the yarns, as well as the pores in the different layers of the felt, are also inherently different. These structural features were non-intrusively quantified. In addition, variation in the structural characteristics through the thickness of the felts and its potential role in papermaking is explored. In addition to the 3D structural characteristics, permeability characteristics and water removal characteristics, including rewetting of select felt samples, have also been experimentally determined. It is interesting to observe the relationship between key structural features and permeability and water removal characteristics. These relationships can provide additional insights into press felt design, as well as ways to improve product properties and the dewatering efficiency and productivity of the paper machine.

Sandwich-structured nanocomposites have the potential to improve the mechanical and electrical properties of materials simultaneously. Nanofibrillated cellulose (NFC) modified paper sheet (denominated as N) and softwood paper sheet (denominated as P) are used to prepare insulating paper. Different kinds of insulating paper with the structures of PPP, NNN, NPN and PNP are prepared. Tensile strength, DC conductivity, dielectric response, space charge and breakdown strength are measured. The activation energies of prepared materials are calculated through DC conductivity at 30, 50, 70, and 90 °C. The mechanism for sandwich structure regulating the mechanical and breakdown properties of insulating paper is discussed. Oil impregnated N/P/N paper has a remarkable improvement on tensile strength, conductivity, and DC breakdown strength, which provides a promising scheme to obtain the insulating paper with outstanding tensile and breakdown strength.

Rice straw waste is a lignocellulosic waste produced by farmers in large quantities. In this study, regenerated cellulose (RC) from rice straw was prepared by dissolving rice straw holocellulose (HC) in NaOH/Urea/Thiourea/Water solution by the freeze-thawing process. The crystallinity index of RC was calculated at 31%, which is out of the crystallinity range of 39%–69% that has been previously suggested. The study indicated that the RC is amorphous with a low degree of polymerization (638) and higher hydroxyl group content as compared to HC. The fiber length of RC was found to be 26.7% shorter; however, the width of RC was 21.2% higher as compared to HC. Reduced kinked fiber content was observed in the fraction of RC (18.3%) as compared with HC (39.1%), and a higher curl index of fiber was observed more so in HC (10.5%) than RC (5.6%). Because of the regeneration process, the fiber length was reduced and a fines element content of about 96% was observed in RC compared to the initial fines content of HC (56.9%). Irrespective of the high fines element content of RC, the composite paper of rice straw bleached pulp and RC fibers was developed with an increase in the tensile index from 41.4 N.m/g to 71.2 N.m/g and an increase in the burst index from 4.7 kPa.m2/g to 5.3 kPa.m2/g with the addition of 5% and 15% RC, respectively. However, enhanced tear index of paper was observed up to 5% and then it declined upon further addition of RC. The study revealed that regenerated cellulose can be used as a strength additive to overcome the shortcomings of low mechanical properties in paper products.

An approach of green in situ synthesis single-step method was applied to produce antibacterial paper. The objective was to investigate the effect of precursor addition on the formation of zinc oxide particles using an in situ single-step method. Zinc chloride concentrations of 0.1, 0.3, 0.5, and 0.7 M were prepared and added into a solution of algae extract and bamboo pulp. The prepared pulps were tested and made into handsheets using a papermaking machine based on TAPPI T205 (2006). Morphological observation of treated papers was conducted using a field emission scanning electron microscope (FESEM). An average of 400 to 570 nm zinc oxide spherical-shaped particle was observed on the fibers of paper. The percentage of element composition of the treated paper were 15.08% to 34.08% of zinc and 17.45% to 32.59% of oxygen captured via scanning electron microscopy with energy dispersive X-ray (SEM-EDX) analysis. The crystallinity test was performed using X-ray dispersion (XRD). A higher percentage of precursors exhibited a more amorphous structure. A measurement of more than 30% increment of inhibition zone was obtained from 10.00 to 25.00 mm against S. aureus, S. choleraesuis, and E. coli. Precursors addition of more than 0.3 M would have the most potential to enhance the growth of zinc oxide via in situ preparation, hence providing better antibacterial properties of the prepared papers.

In this work, we fabricated a novel origami paper-based analytical device (oPAD) assisted by the nanostructuring effect of in situ Pd decoration of Cu/Co-doped CeO2 (CuCo-CeO2-Pd) nanospheres, functionalized with their strongly enhanced electrocatalytic properties to realize an electrochemical and visual signal readout system in oPAD, for highly sensitive detection of amyloid-β (Aβ). The CuCo-CeO2-Pd nanospheres were introduced as an enhanced "signal transducer layer" on account of the electron transfer acceleration caused by catalyzing glucose to produce H2O2 for differential pulse voltammetry signal readout and further 3,3'5,5'-tetramethylbenzidine (TMB) oxidation for colorimetric analysis. Meanwhile, for achieving superior performance of the proposed oPAD, in situ growth of urchin-like gold nanoparticles (Au NPs) onto cellulose fibers was adopted to improve "the recognition layer" in favor of immobilizing antibodies for targeting Aβ through specific antigen-antibody interactions. Combined with the delicate design of oPAD, exhibiting actuation of the conversion procedure between hydrophobicity and hydrophilicity on paper tabs in the assay process, the oPAD successfully enabled sensitive diagnosis of Aβ in a linear range from 1.0 pM to 100 nM with a limit of detection of 0.05 pM (S/N = 3) for electrochemical detection, providing a reliable strategy for quantifying the Aβ protein in clinical applications. Ministry of Education (MOE) This work was financially supported by the Science and Technology Projects of University of Jinan (XKY2002), the Natural Science Foundation of Shandong Province (ZR2020MB057), the Singapore Ministry of Education (MOE AcRF Tier 1 RG176/16), the Taishan Scholars Program, the Case-by-Case Project for Top Outstanding Talents of Jinan, and the project of "20 Items of University" of Jinan (2018GXRC001).

Commercial Chinese ink was employed to disperse pristine vapor-grown carbon nanofibers (VGCNFs) in aqueous suspensions via horizontal ball milling. The obtained suspension was used to fabricate conductive paper-based composites through filtration-deposition onto filter paper. It was found that the carbon black particles from the Chinese ink helped separate VGCNFs and acted as connection points between the VGCNFs, while the glue reinforced the conduction network. Thus, the VGCNF-ink/paper ternary composite showed sufficiently low sheet resistance. With merely 2.5 mg·cm−2 VGCNFs, the sheet resistance could be reduced to 4.5 Ω·sq−1. As a proof of concept, these paper-based composites were directly used as electrodes of solid-state symmetric electronic double-layer capacitors (EDLCs) and the substrate for the electrodeposition of MnO2 to achieve higher electrochemical performances. The EDLCs fabricated with 2.5 mg·cm−2 VGCNFs showed a specific capacitance of 224 mF·cm−2 at a current density of 1 mA·cm−2, which was retained by 86.4% after 10,000 charge-discharge cycles. Moreover, thanks to the high electrical conductivity and the porous structure, the MnO2 decorated paper-based composites exhibited dramatically enhanced specific capacitance. It is believed that our finding offers an idea to directly utilize commercial Chinese ink for the fabrication of electrode materials.

Natural yellow plant dyes and traditional medicines were used widely on historical papers in ancient China for religious reasons and conservation considerations. This study aims to evaluate some traditional yellow botanical sources of dyes that contain different chemical colorant compositions in order to understand their effects on the properties of traditional handmade paper. The physical and chemical changes in paper specimens treated with plant dyes were studied by examining properties such as the color, pH, thermogravimetric (TG) characteristics, tensile strength, folding endurance and microstructure by scanning electron microscopy (SEM). The results indicated that different colorants had different toning effects and that the main components, including carboxyl and ketone groups, could affect the paper stability at high temperatures. The results also revealed that the mechanical properties of paper specimens were improved after treatment with plant dyes. The significant improvements in the tensile strength and folding endurance and the slightly higher decomposition temperature of Amur cork tree-dyed paper could be ascribed to the strong interaction between the colorants’ main components and the fibers. The scientific evaluation of the property changes is therefore valuable information for weighing the advantages and disadvantages of the various yellow toning materials for paper conservation treatment.

Purpose: The study aims to manufacture paper mulberry-added formulations to improve hair quality, apply it to damaged hair, and examine the effect of the formulations in improving hair quality. Methods: Formulations were manufactured by varying the contents of paper mulberry extract at 0, 2, 4, and 6 g. Then, the formulations were applied to discolored sample hairs, which were treated with heat and left in nature. Then, the conditions of the sample hairs before and after application of the formulations were compared. To examine the effect of the formulations on hair quality, the study measured tensile strength, optical absorption using methylene blue, and luster. Results: For all samples, the average values for tensile strength increased after application of the formulations, especially for samples 7L(1), 7L(2), 7L(3), and 9L(3). The analysis of optical absorption using methylene blue demonstrated that the average values for optical absorption decreased for all samples except in the case of healthy hair. Such decreases were noted for samples 7L(1), 7L(2), 7L(3), and 9L(3). Finally, the average values for luster increased samples 7L(3) and 9L(3). Conclusion: The study found that paper mulberry extract is effective for improving tensile strength, optical absorption, and luster of damaged hair. However, the study only verified the results on a limited number of hair characteristics and used one ingredient. Thus, further research using various measurement methods and other ingredients is necessary.

The research aims to evaluate the efficiency of some consolidation materials for tracing paper; hydroxypropyl cellulose (Klucel-E), zinc oxide nanoparticles and nanocellulose. The consolidated materials were used independently, and as hybrid mixtures to improve their properties. The prepared nanomaterials were examined with an Atomic Force Microscope (AFM), and the materials used to consolidate the tracing paper samples after artificial aging were evaluated. Evaluation methods included investigation of the surface morphology by Scanning Electron Microscope (SEM), measurement of mechanical properties (tensile strength and elongation), and detection of chemical changes of the treated samples before and after thermal ageing at 80°C and 65% relative humidity by Fourier transform infrared spectroscopy (FTIR) analysis. Based on the results of the examinations, consolidation by the hybrid mixture consisting of hydroxylpropyl cellulose and nanocellulose proved to be successful; giving the best results when this hybrid mixture was applied on tracing paper samples. This mixture was distinguished by its ability to spread easily inside the paper, giving greater strength to the binding, without forming a film on the surface of the paper and causing stiffness or opacity to treated tracing paper. Therefore, this hybrid mixture was used to consolidate an archaeological tracing map at the Egyptian Geographical Society dating back to (1807 AD).

A new coating method was developed, based on cellulose regenerated from an N-methylmorpholine N-oxide (NMMO) solution applied to paper. In particular, the purpose of this study was to compare the effectiveness of the “deep coating” method using cellulose regenerated from NMMO solution and the classic pulp refining process as methods to improve paper mechanical properties and overall quality. The “deep coating” name comes from the fact that the coating process is combined with subsequent heating of the coating before its final solidification. As a result of this operation, deep penetration of the cellulosic solution into the paper structure occurs. This increases the contact surface of the solution with the cellulosic fibers, which increases the strength properties of the paper structure. It was found that the cellulosic coating increased the apparent density of the paper, the tensile strength, the elongation, the resistance to bursting, and the double fold number. However, the coating also decreased the air permeability and the tear resistance of the paper samples. Despite some technological difficulties, this method could be an attractive solution in the case of a need for additional functionalization of a paper structure.

Excellent mechanical and electrical properties of graphene-based paper-like materials are essential for applications in flexible conductors, energy-storage devices, etc. The graphene oxide (GO) supernatant separated by centrifugation and ultrasonication has been used to prepare graphene oxide paper and reduced graphene oxide paper (rGOP) with high strength and conductivity. However, this method has cumbersome steps and low supernatant concentration, which greatly increases time and energy consumption, and is not suitable for rapid batch preparation of high-strength and high-thickness rGOP. Herein, a high-speed mechanical shearing method has been used to efficiently exfoliate graphite oxide suspension into high-concentration GO slurry with large lateral size, and rGOP has been further prepared by blade coating and HI acid chemical reduction. Compared with the product prepared by ultrasonic exfoliation method, the average area of GO sheets obtained via the mechanical shear exfoliation method can reach around 16.31 μm2. As a result, the mechanical properties and conductivity of the prepared rGOP have been increased by 30% and 23.5%, respectively, with the tensile strength and electrical conductivity of 478.2 MPa and 208.4 S/cm being obtained. The developed method is of great significance for the large-scale production and emerging applications of lightweight and high-performance rGOP.

Funding Information: The financial support of the Austrian Federal Ministry of Digital and Economic Affairs and the National Foundation for Research, Technology and Development , Austria, is gratefully acknowledged. We also thank the industrial partners Mondi, Canon Production Printing, Kelheim Fibres, and SIG Combibloc for their support. Publisher Copyright: © 2021 Copyright: Copyright 2021 Elsevier B.V., All rights reserved. Hydrophobization of cellulosic materials and particularly paper products is a commonly used procedure to render papers more resistant to water and moisture. Here, we explore the hydrophobization of unsized paper sheets via the gas phase. We employed three different compounds, namely palmitoyl chloride (PCl), trifluoroacetic anhydride/acetic anhydride (TFAA/Ac2O)) and hexamethyldisilazane (HMDS) which were vaporized and allowed to react with the paper sheets via the gas phase. All routes yielded hydrophobic papers with static water contact angles far above 90° and indicated the formation of covalent bonds. The PCl and TFAA approach negatively impacted the mechanical and optical properties of the paper leading to a decrease in tensile strength and yellowing of the sheets. The HMDS modified papers did not exhibit any differences regarding relevant paper technological parameters (mechanical properties, optical properties, porosity) compared to the non-modified sheets. XPS studies revealed that the HMDS modified samples have a rather low silicon content, pointing at the formation of submonolayers of trimethylsilyl groups on the fiber surfaces in the paper network. This was further investigated by penetration dynamic analysis using ultrasonication, which revealed that the whole fiber network has been homogeneously modified with the silyl groups and not only the very outer surface as for the PCl and the TFAA modified papers. This procedure yields a possibility to study the influence of hydrophobicity on paper sheets and their network properties without changing structural and mechanical paper parameters.

Due to great advantages, such as simple operation, high porosity, and good fiber continuity, the working principle and research progress of electrospinning technology was studied and polyvinyl alcohol (PVOH) nanofibers were prepared via this process. Air filter paper was used as the receiving substrate to prepare electrospun nano air filter paper (NAFP). The PVOH concentration, static voltage, and receiving distance, were tested to explore the influence of spinning parameters on the filtration performance. Further, the microfiber morphology of the electrospun NAFP was observed. The performance of filter paper, including air permeability, pore size, initial resistance, filtration efficiency, and dust retention, were tested. The results showed that the electrospun NAFP had better filtration performance compared to the air filter paper, and simultaneously they had lower initial resistance and higher precision filtration efficiency. The nanofiber influenced the surface of the air filter paper, as it sharply reduced the pore size. When the spinning condition was 10%, 21 kV, and 15 cm, the pore size decreased approximately 0.6 times of the original, which meant the electrospun NAFP could capture particles ≥ 0.2 μm in size. Finally, after three repeated uses, the good filtration performance was maintained.