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Background and objectives: Paper industry in addition to reducing the consumption of various resources such as water, energy, and wood, continues to recycle used paper in different countries due to less pollution. One of the major drawbacks of the old corrugated container (OCC) recycling is its relatively weak strength, which has limited its use in various sections of the packaging industry. In this study, the effect of using some additives to improve the strengths of OCC to make the top liner of cartons in both wet and dry conditions was studied. Methodology: OCC was selected from domestically produced cartons. To determine the performance and optimal amount of additives, corn cationic starch (at 1, 1.4 and, 2%), wet strength resin (at 1, 2 and, 3%), AKD (at 1, 2 and, 3%), and long fiber of imported bulk tea wrapping paper (at 10, 15 and, 20%) based on the dry weight of OCC pulp were separately used as additives. The handsheets were made using laboratory sheet former with the basis weight of 120 g/m² and then tensile, burst, and tear indices were measured both at wet and dry conditions to compare the effect of additives. Also, water absorption was measured by the Cobb test on the test samples. The optimal level of each additive was determined based on the results, and then handsheets data from optimal combination treatment including appropriate levels of all additives, and different properties of handsheets were statistically compared. Results: The water absorption of handsheet was statistically decreased to 90% level compared to the control by adding AKD. This additive was able to reduce the water absorption of handsheet made from OCC to about 20 g/m² as the appropriate range. The greatest increase of wet tensile strength of the handsheet was achieved using 3% wet strength resin compared to the control. The resin maintained the wet tensile, burst, and tear indices of the residual strength of handsheet by 25, 46, and 58%, respectively, compared to dry strengths which indicates its good performance. The results showed that by adding cationic corn starch and recycled long fiber paper, all the dry strengths of handsheet independently increased compared to the control. The optimal combination treatment was determined according to the results independent use of additives in OCC pulp, including 1% cationic starch, 1% AKD, and 3% wet strength resin based on technical-economic considerations. There is no significant difference between dry tensile and burst strength of handsheet using this treatment and 20% recycled long fiber of wrapping paper, which both means ranked statistically in the same group. Conclusion: The use of 20% recycled long fiber of wrapping paper significantly improved the dry strength of OCC pulp, but adding 1% cationic corn starch to OCC pulp caused limit increase in dry strength. The wet strength of handsheet was significantly improved by adding 3% wet strength resin whereas 1% AKD significantly decreased the water absorption of the OCC pulp to 14 g/m². The optimal combination treatment of chemical additives including 1% cationic corn starch, 1% AKD, and 3% wet strength resin improved the wet and dry strength of handsheet made from OCC pulp that could be used for packaging products which need to be kept in refrigerator and freezer. [ABSTRACT FROM AUTHOR]

There is current interest in replacing petroleum-based additives in consumer paper products with abundantly available, renewable and sustainable biopolymers such as lignin-containing cellulose nanofibers (LCNFs) and cottonseed protein. This research characterized the performance of cottonseed protein isolate with/without LCNFs to increase the dry strength of filter paper. The application of 10% protein solution with 2% LCNFs as an additive improved the elongation at break, tensile strength and modulus of treated paper products compared to the improved performance of cottonseed protein alone. Improvements in tensile modulus and tensile strength were greatest for samples containing larger amounts of lignin and a greater degree of polymerization than for those with less lignin from the same biomass sources. [ABSTRACT FROM AUTHOR]

Abstract The dry strength properties of hot-pressed moist paper improved as stiff high-yield pulp fibers soften and the sheet density increased. Very high wet strength was also achieved without adding strengthening agents. This research focuses on a new hot-pressing methodology based on a steel belt-based pilot cylinder press with infrared heating. The heated steel belt transports the moist paper into the cylinder nip with two adjacent steel rollers with adjustable nip pressure. The temperature ranges up to 300 °C, maximum speed is 5 m/min, maximum pulling force from the steel belt is 70 kN and the line load in the two press nips is 15 kN/m each. High peak pressures are possible due to the hard press nip between steel rolls and steel belt, allowing a good heat transfer to the paper. The long dwell time allows strained drying of the paper which results to high density and high wet strength. Paper samples from high-yield pulps were tested at different nip pressures, temperatures and machine speeds while the dry content was kept constant at about 63%. High nip pressure showed the largest effect on densification and dry strength. While high temperature and long dwell time seem to be most important in achieving high wet strength.

There is current interest in replacing petroleum-based additives in consumer paper products with abundantly available, renewable and sustainable biopolymers such as lignin-containing cellulose nanofibers (LCNFs) and cottonseed protein. This research characterized the performance of cottonseed protein isolate with/without LCNFs to increase the dry strength of filter paper. The application of 10% protein solution with 2% LCNFs as an additive improved the elongation at break, tensile strength and modulus of treated paper products compared to the improved performance of cottonseed protein alone. Improvements in tensile modulus and tensile strength were greatest for samples containing larger amounts of lignin and a greater degree of polymerization than for those with less lignin from the same biomass sources.

Currently, there is an increasing interest in the use of biopolymers in industrial applications to replace petroleum-based additives, since they are abundantly available, renewable and sustainable. Cottonseed protein is a biopolymer that, when used as a modifier, has shown improved performance for wood adhesives and paper products. Thus, it would be useful to explore the feasibility of using cellulose nanomaterials to further improve the performance of cottonseed protein as a paper strength agent. This research characterized the performance of cottonseed protein isolate with/without cellulose nanofibers (CNFs) and cellulose nanocrystals (CNCs) to increase the dry strength of filter paper. An application of 10% protein solution with CNCs (10:1) or CNFs (50:1) improved the elongation at break, tensile strength and modulus of treated paper products compared to the improved performance of cottonseed protein alone. Further analysis using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) indicated that the cottonseed protein/nanocellulose composites interacted with the filter paper fibers, imparting an increased dry strength.

Nonwoven fabrics have grown in popularity in recent years due to their overwhelming usage in a wide range of consumer products. Cotton-based nonwovens are of particular interest because of their ability to be recycled and reused, resulting in a more environmentally friendly product compared to their petroleum-based counterparts. The current research characterized the use of cottonseed protein as an additive to increase the dry strength of cotton-based nonwovens. The tensile strength of nonwovens was found to increase as the concentration of protein applied was increased. At 11% protein concentration, the tear strength and burst strength increased significantly (relative to the nonwoven by itself) by 288% (machine direction) and 295%, respectively. Further characterization by thermogravimetric analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy suggested that cottonseed protein interacted with the cotton fiber in the nonwoven fabric to produce the increased dry strength. [ABSTRACT FROM AUTHOR]

Spent cooking liquor from kraft pulping, known as black liquor, was applied to linerboard (corrugated medium) by surface sizing in order to increase strength properties. The influence of alum in black liquor on linerboard properties was also investigated. The surface application of black liquor improved the dry strength of linerboard. A slight addition of alum into black liquor (2.5% on black liquor solids) significantly improved strength properties such as tensile strength, TEA, compressive strength, and bursting strength. The results implied that black liquor with alum can be used for industrial grade papers that require high strength properties. The air permeability of corrugated medium increased after 5 g/m2 of dry pick-up. Black liquor appeared to penetrate the paper pores, and aggregates of lignin and carbohydrates in the black liquor increased bonds between fibers, which improved strength. The surface sizing of black liquor and alum addition also affected the hydrophobicity of linerboard.

Amphoteric polyacrylamide (AmPAM) is a linear water-soluble polymer that has been applied in papermaking as an agent for flocculation, retention, filtration, and dry-strength improvement. However, AmPAM with different ranges of molecular weight (MW) have different properties in these processes. In this study, a series of AmPAMs were constructed with an anionic monomer, itaconic acid (IA), a cationic monomer, methacryloxyethyl-trimethyl ammonium chloride (DMC), and a main backbone of acrylamide (AM). Four factors influencing free radical polymerization, i.e., reaction temperature, pH, initiator load, and the concentration of monomers, were systematically investigated via an orthogonal test to determine their effects on the MW of AmPAM. Spectroscopy and isoelectric point assays were used to characterize the structure of the produced AmPAM, and the MW was assessed by calculating the viscosity. The reaction temperature had the greatest influence on the MW of AmPAM, followed by the solution pH and the initiator load. To determine the dry strength of papersheets containing AmPAM, the breaking length of handsheets was assessed after adding 0.5% AmPAM (based on fiber) with different MWs. The maximum value, 4.05 km, was 15.0% higher than the control and was obtained using AmPAM with a MW of 330 kDa.

This study aimed to identify the performance properties that drive the shelf price of kitchen paper towels and evaluate whether sustainability is an important driver for pricing. Nineteen products were compared according to their performance (softness, absorbency, and strength), technology, and fiber morphology. Metrics to rank the products in different grades (economy, premium, and ultra) according to their performance were provided. A multiple linear regression showed that absorbency and softness are the most significant properties used to predict the price. Market data indicates that there is a segment of consumers willing to pay a premium price for products marketed as "sustainable", even though their performance is comparatively inferior to the majority of the samples. Sustainable products are up to 85% more expensive than regular products. The metrics obtained in this work can contribute to improvement in market transparency, and aid companies in deciding strategies for product development and new investments. [ABSTRACT FROM AUTHOR]

There is current interest in using agro-based biopolymers in industrial applications. Because cottonseed protein is abundantly available, it would be useful to explore its feasibility as a polymeric additive and possible substitute for petroleum-based materials. In this work, we studied cottonseed protein isolate as a paper additive and observed its effects on the paper’s dry and wet strength. The tensile strength of paper was found to vary with the amount of the protein applied. By application of an 11% protein solution to the paper, the dry and wet strength increased by 33 and 16% compared with the paper by itself, respectively. The combined use of cottonseed protein and an acid (acetic, adipic, aspartic, and citric acids) to promote adhesion resulted in even greater dry paper strength but not in greater wet paper strength. Thermogravimetric analysis, infrared spectroscopy, and scanning electron microscopic studies suggested that the protein interacted with acid and that both components interacted with paper fibers to produce increased strength. [ABSTRACT FROM AUTHOR]

Cellulose materials have poor wet strength and are susceptible to acidic or basic environments. Herein, we developed a facile strategy to modify bacterial cellulose (BC) with a genetically engineered Family 3 Carbohydrate-Binding Module (CBM3). To assess the effect of BC films, water adsorption rate (WAR), water holding capacity (WHC), water contact angle (WCA), and mechanical and barrier properties were determined. The results showed that CBM3-modified BC film exhibited significant strength and ductility improvement, reflecting improved mechanical properties of the film. The excellent wet strength (both in the acidic and basic environment), bursting strength, and folding endurance of CBM3-BC films were due to the strong interaction between CBM3 and fiber. The toughness of CBM3-BC films reached 7.9, 28.0, 13.3, and 13.6 MJ/m3, which were 6.1, 1.3, 1.4, and 3.0 folds over the control for conditions of dry, wet, acidic, and basic, respectively. In addition, its gas permeability was reduced by 74.3 %, and folding times increased by 56.8 % compared with the control. The synthesized CBM3-BC films may hold promise for future applications in food packaging, paper straw, battery separator, and other fields. Finally, the in situ modification strategy used to BC can be successfully applied in other functional modifications for BC materials. • Family 3 carbohydrate-binding module was obtained through genetic engineering. • Bacterial cellulose film was in situ modified by adding CBM3 in broth. • Improved mechanical properties in toughness and strength of tensile, folding and burst • BC films demonstrated high oxygen and water vapor barrier. [ABSTRACT FROM AUTHOR]

Paper production requires large amounts of cellulosic fiber, whereas the world’s forested lands and croplands have a finite capacity to supply such resources. To deal with likely future pressure on forest resources, as well as to hold down costs of materials, publications examined in the preparation of this review suggest that the paper industry will need to implement several concurrent strategies. In particular, the industry can be expected to view recycling as a central part of its activities. Basis weights of various paper-based products can be expected to decrease over the coming decades, and more of the fiber content will be replaced with fillers such as calcium carbonate. Such trends will place intense demands upon chemical-based strategies to enhance the bonding within paper and paperboard. Based on the literature, further progress in reducing the amount of new forest resources used to meet a given set of paper product requirements will require a combined approach, taking into account various fiber attributes, nanostructures, novel concepts in bond formation, and advances in the unit operations of papermaking.

Biocide programs have become necessary in most fine paper manufacturing circuits, as drastic reduction of fresh water consumption in the industry enhances microbial development. Depending on their chemical nature, biocides may interfere with typical wet-end chemistry additives and furnish. A reference wet-end chemistry was set (including fixing aid, dry strength aid, sizing agent, and retention system), then biocides were added to the furnish (bleached virgin fibres + mineral filler) prior to handsheet making. Four of the tested biocides (organo-sulfur, dibromonitrilopropionamide, isothiazoline, and glutaraldehyde) were not found to interact with wet-end chemistry. On the other hand, the tested quaternary ammonium salt biocide showed very detrimental effects: it reduced filler retention in the sheet, decreased sheet strength, and destroyed sizing (sheet hydrophobicity).

Considering the mild degradation strength and the fact that it may be an organic matter reserve for the soil, in the past years lignocellulosic materials have been used as fibrous raw materials in the manufacture of biodegradable nutritive pots for the seedling in vegetable containerized production. This paper analyses the behavior of the nutritive pots made from biodegradable composites for the vegetable seedling production process, focusing on their mechanical strength properties and biodegradability. It was found that the biodegradability of composite materials obtained from a mixture of secondary cellulosic fibers, peat, and additives, is strongly influenced by the presence or absence of the rhizosphere effect and the synergistic relations set in the culture substrate between the plant roots and microorganisms, which develop permanently the recycling and solubilization of mineral nutrients. The results showed that the presence in the substrate of some complex populations made by heterotrophic bacteria favors full degradation of the pulp and lignin contained in the substrate and pots composition. Therefore, unlike the reference sample (plant-free), cultivated versions exhibited an intense biodegradation on the account of rhizosphere effect.

Various hydrophilic polyelectrolytes, including cationic starch products, are used by papermakers to promote inter-fiber bonding and increase paper’s dry-strength. Thus, papermakers can meet customer require-ments with a lower net cost of materials, more recycled fibers, or higher mineral content. In the absence of polymeric additives, key mechanisms governing bond development between cellulosic fibers include capillary action, three-dimensional mixing of macromolecules on facing surfaces, conformability of the materials, and hydrogen bonding. Dry-strength additives need to adsorb efficiently onto fibers, have a hydrophilic character, and have a sufficiently high molecular mass. Though it is possible to achieve significant strength gains by optimal usage of individual polyelectrolytes, greater strength gains can be achieved by sequential addition of oppositely charged polyelectrolytes. Superior strength can be achieved by in-situ formation of polyelectrolyte com-plexes, followed by deposition of those complexes onto fiber surfaces. Polyampholytes also hold promise as efficient dry-strength additives. Opportunities for further increases in performance of dry-strength agents may involve fiber surface modification, self-assembled layers, and optimization of the dry film characteristics of dry-strength polymers or systems of polymers.

The hypothesis has been tested that a carboxymethyl hemicellulose improves more effectively the dry strength of papers than a native hemicellulose. To that end, β- d-glucan from oat was treated with an alkaline ethanolic solution of sodium chloroacetate for different times to obtain a range of carboxymethylated β- d-glucan (CM-glucan) samples. The derivatization was confirmed by Fourier transform infrared spectroscopy and elemental analysis. The physical properties of paper concerning burst and tensile strength as well as folding endurance were essentially improved if CM-glucan was added to unbleached kraft fiber suspension from pine before papermaking. The effects could be maximized by a proper selection of carboxymethylation time and the amount of CM-glucan added to the suspension. The effect was also beneficial in the case of recycled fibers. [ABSTRACT FROM AUTHOR]

Paper production requires large amounts of cellulosic fiber, whereas the world's forested lands and croplands have a finite capacity to supply such resources. To deal with likely future pressure on forest resources, as well as to hold down costs of materials, publications examined in the preparation of this review suggest that the paper industry will need to implement several concurrent strategies. In particular, the industry can be expected to view recycling as a central part of its activities. Basis weights of various paper-based products can be expected to decrease over the coming decades, and more of the fiber content will be replaced with fillers such as calcium carbonate. Such trends will place intense demands upon chemical-based strategies to enhance the bonding within paper and paperboard. Based on the literature, further progress in reducing the amount of new forest resources used to meet a given set of paper product requirements will require a combined approach, taking into account various fiber attributes, nanostructures, novel concepts in bond formation, and advances in the unit operations of papermaking. [ABSTRACT FROM AUTHOR]

Highlights: [•] Bonding agents can improve the strength of paper products. [•] Beta-d-glucan, an oat byproduct, is shown to be an effective bonding agent. [•] The performance of beta-d-glucan is greatly improved by oxidation. [•] Strength benefits of oxidation were observed even after recycling of the fibers. [ABSTRACT FROM AUTHOR]

Abstract: Paper is a versatile material with obvious advantages in being both inexpensive and environment friendly. However, a major drawback compared with many other materials, such as plastics, is that it is sensitive to both liquid water and moist air. Traditionally paper is protected from liquid water by sizing. The present work presents a new way to make paper water resistant by combining the layer-by-layer (LbL) technique with the adsorption of a colloidal wax onto the multilayer structure. After the adsorption of five layers of poly(allylamine hydrochloride) and poly(acrylic acid) followed by the adsorption of 8mg paraffin wax per gram fibre, the contact angle measured 60s after a drop of water was applied to the sheet was about 138°. If the sheets were cured for 30min at 160°C after sheet making, the contact angle was ca. 150°. The heat treatment of sheets prepared from LbL-modified fibres without the addition of wax gave a contact angle of about 113°. To decouple structural effects from changes in surface energy upon heat treatment of PAH/PAA LbL films, model experiments were carried out where LbL assemblies were prepared on silicon oxide and cellulose model surfaces. The contact angle increased when these films were heat treated but it did not exceed 90°. The reason for this is due to the lack of structure of the model surfaces on a micrometre scale. The adsorption of wax impaired the mechanical properties of paper sheets made from modified fibres compared to sheets from the LbL-modified fibres. However, at an adsorption of 8mg paraffin wax per gram fibre there was still an increase by 37±1% in tensile strength index compared to the untreated reference pulp (33.8±0.7 and 24.7±0.6kNm/kg respectively). [Copyright &y& Elsevier]

Cationic polyelectrolytes (polyallylamine and polyvinylamine with different molecular masses) were adsorbed onto lignocellulosic fibres from unbleached and unbeaten spruce chemical fibres with different kappa numbers to investigate the effects on the mechanical properties of the final paper materials. Adsorption isotherms were first established to determine the maximum quantity of polymer that could be adsorbed onto each type of fibre. Paper sheets were then made with different amounts of added polyelectrolyte, and the structural and mechanical properties of the sheets were investigated, as well as the effect of an extra heating. The use of fibres with different kappa numbers led to different responses in terms of adsorption, and thus to differences in the mechanical properties of the resulting sheets. The tensile strength index was significantly increased (almost 50 % improvement in the best case) as a consequence of this polyelectrolyte adsorption onto the fibres, even at as low an adsorption level as 2 mg/g. The heating of paper sheets for 10 min at 160 °C was also shown to improve the tensile strength index by about 10 % for pulps with high kappa number. [ABSTRACT FROM AUTHOR]

Scots pine micro-veneers were subjected to hydrolysis with sulphuric acid or delignification with acidic sodium chlorite and a combination of both treatments. The tensile strength of untreated and treated veneers was determined at finite span (f-strength) and zero span (z-strength) under both dry (20°C, 65% relative humidity) and water-saturated conditions. Acidic hydrolysis resulted in significant strength losses in both testing modes and both moisture conditions, with the greatest strength reduction found for f-strength tested dry. After delignification, only f-strength under wet conditions was substantially reduced; dry f-strength and both dry and wet z-strength hardly changed. A combined treatment of prehydrolysis and delignification resulted in disintegration of the veneers, which made strength determination impossible. It was concluded that, in addition to cellulose, the hemicelluloses determine the f-strength under dry conditions, while lignin confers wet strength but appears not to contribute to interfibre adhesion and f-strength under dry conditions. [ABSTRACT FROM AUTHOR]

The function of water in the adhesion between wet cellulose fibers both in the assembly of papers and the establishment of the properties is discussed. The contributions of friction and hydrogen bonds are reviewed, together with the new concept of interfiber ordered water structure created by the hydrophilic surfaces of the fibers. Procedures for the enhancement of interfiber adhesion are summarized in terms of the accessibility, the stereotopochemistry and the enthalpies of the interacting moieties on contiguous surfaces. [ABSTRACT FROM AUTHOR]

High-yield pulp (HYP) is gaining increasing interest in wood-free papers, because it can improve the bulk, formation, and opacity of papers. However, one of the challenges for the papermakers is the strength of papers when a large amount of HYP is replaced with hardwood kraft pulp. In this work, we explored the potential of using cationic-modified polyvinyl alcohol (C-PVA) in increasing the strength properties of HYP. Also, C-PVA was applied to the paper-sheets made of softwood/hardwood bleached kraft pulps (SBKP/HBKP) and HYP under various conditions, and the corresponding paper properties were evaluated. It was observed that C-PVA increased the strength properties of these paper-sheets, and the results obtained from using C-PVA were only slightly less effective than those obtained from using cationic starch (C-starch). Furthermore, the addition of C-PVA to HYP, and subsequently mixing with the blend of SBKP/HBKP (option no. 1) improved the tensile and burst indices, light scattering coefficient and apparent density of paper-sheets more significantly than did the addition of C-PVA directly to the mixed furnish of SBKP/HBKP/HYP (option no. 2). Additionally, atomic force microscope (AFM) analysis showed that the attraction force, developed between the AFM-tip and the fiber surface, was changed by the C-PVA modification. The tensile and burst indices of paper-sheets were improved by adding 10 mg g-1 C-PVA and substituting 30% of HYP for HBKP, whereas the tear index, apparent density, PPS-roughness, and brightness decreased. [ABSTRACT FROM AUTHOR]

Considering the mild degradation strength and the fact that it may be an organic matter reserve for the soil, in the past years lignocellulosic materials have been used as fibrous raw materials in the manufacture of biodegradable nutritive pots for the seedling in vegetable containerized production. This paper analyses the behavior of the nutritive pots made from biodegradable composites for the vegetable seedling production process, focusing on their mechanical strength properties and biodegradability. It was found that the biodegradability of composite materials obtained from a mixture of secondary cellulosic fibers, peat, and additives, is strongly influenced by the presence or absence of the rhizosphere effect and the synergistic relations set in the culture substrate between the plant roots and microorganisms, which develop permanently the recycling and solubilization of mineral nutrients. The results showed that the presence in the substrate of some complex populations made by heterotrophic bacteria favors full degradation of the pulp and lignin contained in the substrate and pots composition. Therefore, unlike the reference sample (plant-free), cultivated versions exhibited an intense biodegradation on the account of rhizosphere effect. [ABSTRACT FROM AUTHOR]

Abstract: Results reported in Part 1 of this series showed that paper strength improvements could be optimized by varying pH and the overall content of ionic groups in random terpolymers containing a fixed molar ratio of acidic and basic monomeric groups. Further treatment of kraft fiber slurries with polyaluminum chloride (PAC), after polyampholyte addition, yielded significant strength benefits. The present paper shows how these results can be explained in terms of the streaming potential (SP) of glass fibers, which were used as a model substrate. The data suggest that aluminum ions interact both with the anionic carboxyl groups of the polyampholytes and with anionic silanol groups at fiber surfaces. The streaming potential of the treated surfaces could be changed by varying the pH, the overall density of charged groups of the polyampholytes, the ratio of cationic to anionic groups on the polymer and by post-treatment with polyaluminum chloride. [Copyright &y& Elsevier]

Abstract: Polyampholytes, which are macromolecules that contain both positive and negative ionizable groups, can provide superior strength improvements for paper manufacture, compared to the addition of simple polyelectrolytes. Colloidal effects, which were measured in solution and in fiber suspensions, were consistent with observed bonding effects. The same colloidal effects were found to correlate with the effects of pH and of the density of the ionizable groups on the polyampholytes. Tests were carried out with a series of polyampholytes having a constant ratio of cationic to anionic monomeric groups and molecular mass. Their charge density varied in the ratio 1:2:4:8. The greatest strength gains were obtained at intermediate charge density and under conditions of pH favoring instability of the aqueous polymer mixtures. Colloidal phenomena were elucidated by turbidimetric tests, sediment volumes of treated fiber suspensions, flocculation tendencies of treated fiber suspensions, and zeta potentials of probe particles. [Copyright &y& Elsevier]

Polyacrylamides have wide range of industrial applications as well as paper industry. They are applied mainly as clarifiers, retention and paper strengthening agents. In this research we synthesized a series of wet strength resins based on glyoxalated polyacryamide (GPAM) under different reaction conditions using acrylamide, ethylenediamine and glyoxal as the main materials and their effects on wet and dry-strength papers was investigated. The properties of the polymers were compared with the commercially available polyamideamine-epichlorohydrin (PAE) wet-strength resin. During the synthesis, the obtained products were characterized by Fourier transform infra-red spectroscopy. The tests showed that a water soluble aminated polyacrylamide (PAa) with desired storage stability could be obtained by reaction between polyacrylamide and ethylenediamine (ETD) under the conditions of 50-60°C for 24-25 h. In the next step, the synthesized GPAM under the condition of 25-30°C, 6% concentration of basic polymer containing 2.3 mmol of amine per gram of polymer with the ratio of 0.2 of glyoxal to base polymer showed a good strengthening ability. The obtained GPAM significantly enhanced both the dry- and wet-strength of papers. At similar application level (0.2% of dry mass of the pulp), synthesized GPAM provided superior wet tensile strength, dry tensile strength, burst strength and effective energy adsorption by 16%, 10%, 5% and 23%, respectively, compared to those that were achieved by commercial PAE. The combined results supported that the synthesized GPAM under suitable condition was environmentally preferred as an adsorbable organic halide (AOX) free wet-strength resin and its superior strengthening properties ensured the production of higher quality wet-strength papers.

Currently, there is an increasing interest in the use of biopolymers in industrial applications to replace petroleum-based additives, since they are abundantly available, renewable and sustainable. Cottonseed protein is a biopolymer that, when used as a modifier, has shown improved performance for wood adhesives and paper products. Thus, it would be useful to explore the feasibility of using cellulose nanomaterials to further improve the performance of cottonseed protein as a paper strength agent. This research characterized the performance of cottonseed protein isolate with/without cellulose nanofibers (CNFs) and cellulose nanocrystals (CNCs) to increase the dry strength of filter paper. An application of 10% protein solution with CNCs (10:1) or CNFs (50:1) improved the elongation at break, tensile strength and modulus of treated paper products compared to the improved performance of cottonseed protein alone. Further analysis using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) indicated that the cottonseed protein/nanocellulose composites interacted with the filter paper fibers, imparting an increased dry strength. [ABSTRACT FROM AUTHOR]