Chemical conversion
Hojjatullah Akbari; Fatemeh Ravari; Ghasem Asadpur; Ashraf Sadat ghasemi
Abstract
Background and Objectives: The modification of paper components, such as fibers and chemical additives, through the incorporation of specific chemical agents plays a pivotal role in altering or reinforcing intermolecular bonding within the paper matrix. Such modifications can impart novel characteristics ...
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Background and Objectives: The modification of paper components, such as fibers and chemical additives, through the incorporation of specific chemical agents plays a pivotal role in altering or reinforcing intermolecular bonding within the paper matrix. Such modifications can impart novel characteristics that expand the functional applications of cellulose-based materials. The majority of strength-enhancing additives primarily rely on the formation of multiple hydrogen bonds to ensure their retention and effectiveness. Silk sericin, a natural macromolecule, is recognized as an adhesive-like protein. As a hydrophilic biopolymer, sericin exhibits excellent compatibility with other hydrophilic polymers, including starch, polyvinyl alcohol (PVA), and alginate. Due to its versatility and exceptional physicochemical properties, sericin has been extensively utilized in the fabrication of sponges, films, and hydrogels for diverse biomedical applications. The integration of biodegradable materials as alternatives to forest-based resources holds significant importance in the papermaking industry. Although recycled pulp is widely used, a critical challenge remains the reduction in mechanical strength resulting from repeated recycling cycles. This study aims to modify starch and nanocellulose using sericin to exploit its polymeric properties for enhancing the mechanical performance of recycled paper. The research focuses on improving the physical and mechanical characteristics of paper produced from old corrugated container (OCC) pulp.Material and Methods: This study utilized sericin, nanocellulose, and starch. A nanocellulose-based hydrogel containing sericin was synthesized under controlled laboratory conditions. Functionalization of nanocellulose and starch was achieved via epichlorohydrin (ECH), wherein the hydroxyl groups of these materials reacted with the epoxy groups of ECH. The epoxide-functionalized nanocellulose and starch subsequently reacted with silk sericin, which contains amino acids with active side groups such as amine, carboxyl, and hydroxyl groups, leading to the formation of covalent or hydrogen bonds. The interaction between the amine and amide groups of sericin and the hydroxyl groups of nanocellulose and starch resulted in the establishment of hydrogen bonds, thereby forming the final composite material. The structural modifications of starch and nanocellulose were characterized using instrumental techniques such as Fourier Transform Infrared Spectroscopy (FT-IR), confirming the successful formation of starch-sericin and nanocellulose-sericin compounds. The modified materials were added into recycled pulp at varying ratios to either starch or nancellulose (20/70, 30/70, 40/70, and 50/70), and constant weight of recycled pulp. Handmade paper samples with a grammage of 60 g/m² were produced, and their mechanical properties, including tensile strength index, tear length, burst strength index, tear resistance index, and freeness degree, were evaluated in accordance with relevant standards.Results: The incorporation of starch and nanocellulose modified with sericin resulted in a statistically significant enhancement of tensile strength, burst strength, and tear resistance in the recycled paper samples. The greatest improvement was observed in the samples containing 20/70 modified starch. The addition of these modified materials positively influenced the mechanical properties of the paper. Given that these additives do not intrinsically alter the inherent strength of the cellulose fibers, the observed changes in tensile strength are likely attributable to an increase or decrease in fiber bonding. This enhancement may stem from the penetration of the applied materials into the interfiber voids, thereby reinforcing the fiber network. Conversely, at higher sericin concentrations, a marginal decline in certain mechanical properties was observed in specific ratios. Tear resistance is a crucial parameter in paper evaluation, influenced by factors such as average fiber length, intrinsic fiber strength, fiber bonding, and fiber orientation. In this study, fiber bonding and orientation were identified as the most significant contributors to the observed mechanical behavior. The incorporation of sericin-modified nanocellulose led to increased air resistance and facilitated a more uniform fiber distribution within the paper structure, indirectly indicating improvements in internal bonding and sheet formation quality. Furthermore, the addition of modified starch and nanocellulose resulted in a reduction in pulp freeness across the tested compositions.Conclusion: The findings of this study demonstrate the successful bonding of sericin with starch and nanocellulose, leading to structural modifications that improve their functional properties. The utilization of sericin-modified starch and nanocellulose presents an effective and environmentally sustainable approach to enhancing the mechanical performance of recycled paper. This strategy not only improves the overall quality of paper products but also represents a significant advancement toward sustainable development through the utilization of renewable bio-based materials.
Pulp and paper
Mehrnoosh Tavakoli; Ali Ghasemian; Mohammad Reza Dehghani Firouzabadi; Wojciech Grzeskowiak; Bartłomiej Mazela
Abstract
Background and objectives: The destructive effects of heat increasing in cellulose substrates, which are the basic materials for the packaging industries, high-quality hygiene packaging, and ammunition packaging, are obvious and inevitable. Therefore, it is essential to modify the structure of these ...
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Background and objectives: The destructive effects of heat increasing in cellulose substrates, which are the basic materials for the packaging industries, high-quality hygiene packaging, and ammunition packaging, are obvious and inevitable. Therefore, it is essential to modify the structure of these bio-based products with green and environmentally friendly materials, to increase their durability against heat.Methodology: In the current study, TEMPO-oxidized CNFs and CNCs, were initially and separately retarded using flame retardant mixtures, including dual “ammonium monophosphate+albumin”, “silica+methyltri-methoxysilane”, and quadruple “ammonium monophosphate+albumin+silica+methyltri-methoxysilane”. Using a rod coater, each combination was then coated individually on the produced cellulosic paperboards. Flame retardancy properties were evaluated by three thermal experiments, including a Mini Fire Tube, Limited Oxygen Index, and Mass Loss Calorimeter. Results: Based on the observed results, the role of mono-ammonium phosphate, due to the presence of phosphorus-containing groups as the driving force of the charring during combustion, was more prominent and significant in the dual coating mixture than the quadruple coating mixture, containing silica and phosphorus, both in the paperboards coated based on CNFs and paperboards coated based on CNCs. Comparison of the CNFs and CNCs based-flame retardant, as the main basis of the coating formulation, showed that paperboards coated with CNFs based-flame retardant, due to having amorphous and crystalline regions, had much lower amount of mass loss in the Mini Fire Tube test, almost similar Limited Oxygen Index, and Peak Heat Release Rate (PHRR) and Heat Release Rate (HRR) in the Mass Loss Calorimeter test, compared to those of the paperboard coated with CNCs based-flame retardant. Conclusion: In general, CNFs and CNCs based-flame retardants with mono-ammonium phosphate and albumin, even in low concentrations, can be used as effective retardants and replacements for conventional flame retardants, in high-quality cellulose-based packaging production.
Kobra Dadmohamadi; Mohsen Mohammadi Achachluei; Mohammad taghi Jafari
Abstract
The aim of this study was to evaluate the effect of cellulose nanofiber treatment on discoloration of historical papers. In this study, two types of cellulose nanofiber suspensions with a concentration of 1% by weight with water and ethanol were prepared. After treatment, the prepared samples were subjected ...
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The aim of this study was to evaluate the effect of cellulose nanofiber treatment on discoloration of historical papers. In this study, two types of cellulose nanofiber suspensions with a concentration of 1% by weight with water and ethanol were prepared. After treatment, the prepared samples were subjected to moist-heat aging according to TAPPI T 544 sp-03 standard and colorimetric, pH, ATR-FTIR spectroscopy and SEM microscopy were performed before and after aging. Examination of ATR-FTIR spectra obtained from the samples showed that the application of cellulose nanofiber treatment does not cause damage to the paper structure. After application of two treatments with cellulose nanofibers, the color of the samples became brighter, but after accelerated aging, the brightness of the samples decreased.The darkening of the color of the samples was caused by their exposure to accelerated aging conditions and the treatment of cellulose nanofibers did not cause discoloration. The pH of the samples increased after application of both types of cellulose nanofiber treatments, but after accelerated aging, the pH decreased slightly.
kobra dadmohamadi; Mohsen Mohammadi; Mohammad taghi Jafrai
Abstract
In this study, the effect of cellulose nanofibers on the properties of handmade papers produced from hemp and wood pulp fibers was assessed. Also, the nanofiber application as a strength enhancer for restoration of handmade papers was investigated. Firstly, handmade paper samples were prepared. Cellulose ...
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In this study, the effect of cellulose nanofibers on the properties of handmade papers produced from hemp and wood pulp fibers was assessed. Also, the nanofiber application as a strength enhancer for restoration of handmade papers was investigated. Firstly, handmade paper samples were prepared. Cellulose nanofibers with weight percentages of 0.5, 1 and 2% were prepared as a suspension in water the samples were treated by the suspensions. Blank and treated samples were tolerated accelerated aging process and then pH, colorimetric and tensile strength tests were performed. Comparison of blank and treated samples results showed that the tensile strength of the both groups of hemp (H) and wood pulp (WP) papers were increased after treatment by cellulose nanofibers. Aging process caused to reduction in tensile strength of treated samples but it was increased in comparison with blank samples before and after aging. The pH of the papers in both groups was in the alkaline range after the treatment and aging. Brightness of papers was increased after the treatment and color changes in the samples were due to their accelerated aging conditions.
Jafar Ebrahimpour Kasmani; Ahmad Samariha; Alireza Khakifirooz
Abstract
This study aimed to investigate the use of cellulose nanofibers and starch-nano-cellulose and polyacrylamide-nano-cellulose hybrid systems for the replacement of imported long chemical fibers in the production of these papers. In this study, imported long fiber chemical pulp was added to cotton pulp ...
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This study aimed to investigate the use of cellulose nanofibers and starch-nano-cellulose and polyacrylamide-nano-cellulose hybrid systems for the replacement of imported long chemical fibers in the production of these papers. In this study, imported long fiber chemical pulp was added to cotton pulp at 4 levels. Cellulose nanofibers were added to cotton pulp at a 5% level with 1% starch and 0.1% with polyacrylamide. Three levels of cationic starch and three levels of cationic polyacrylamide were also used. From each of the treatments, 60 gm-2 handsheet were made finally the physical, mechanical and optical properties of the paper made from different pulps were compared. The results showed that with increasing nanocellulose individually, compared to imported long fibers, surface smoothness, tensile strength, bursting, tearing of paper increased and air resistance, folding resistance and opacity decreased. Increasing nanocellulose in combination with cationic polyacrylamide increased the paper air resistance and surface area, tensile, burst, tear, and folding strength of the paper compared to imported long fibers, air resistance and opacity. With the increase of nanocellulose in combination with cationic starch, as compared to imported long fibers, surface smoothness, tensile strength, bursting, folding increased but opacity decreased. FE-SEM results also showed that with increasing percentage of cellulose nanofibers, the pores decreased significantly. As a result of the addition of 5% cellulose nanofibers the surface of the paper became smoother and the pores were filled relatively, confirming the results of surface smoothness and air resistance.
rouzbeh asadi khansari; Mohammadreza Dehghani Firouzabadi; Hossein Resalati
Abstract
The purpose of this research is to evaluate the effect of various paper coatings on initial contact angle and its evolution over time. We investigated nine coatings on two types of 75 g and 125 g printing papers. Seven coating compositions containing 80% clay, 20% ground calcium carbonate, dispersing ...
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The purpose of this research is to evaluate the effect of various paper coatings on initial contact angle and its evolution over time. We investigated nine coatings on two types of 75 g and 125 g printing papers. Seven coating compositions containing 80% clay, 20% ground calcium carbonate, dispersing agent and various levels of polyvinyl acetate and lactic acid as binders were used. In the last two coatings, we used 100% precipitated calcium carbonate pigments, cationic starch, methacrylate, dispersant and two levels of cellulose nanofibers. In these suspensions, the amount of cellulose nanofibers in composition 8 is twice composition 9. After coating using rod method, the papers were dried then coated and control samples were calendered. We then performed contact angle measurements using water droplet and Kit No were performed. We noticed largest contact angle and smallest angle change over time for sample 6 containing 75% binder. Last two coatings contained cellulose nanofibers, which caused presence of hydroxyl group on the surface and lowered the contact angle. Composition eight was the most hydrophilic sample. Best barrier property Kit No and largest droplet volume after 20 seconds was accompanied with the increase of the binder percentage in the formulation. For the control sample and three treatments with highest binders, the contact angle over time remains relatively constant which is a sign of hydrophobicity. The correlation between contact angle and volume of the water droplet was determined to be 0.951 and 0.936 in the 75g and 125g papers relatively. We did not notice a significant difference in contact angle and Kit No between 75g and 125g samples.
Composite wood products
Shoboo Salehpour; Mehdi Jonobi; Masoud Ahmad Zadeh; Fatemeh Rafieian
Abstract
The biodegradability of cellulose nananofiber-PVA nanocomposites were studied under controlled composting conditions and the quality of the compost was evaluated. The nanocomposite based on PVA with 5, 10, 20 and 30 wt % of CNF was prepared by using liquid nitrogen and freeze drying techniques. Specimens ...
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The biodegradability of cellulose nananofiber-PVA nanocomposites were studied under controlled composting conditions and the quality of the compost was evaluated. The nanocomposite based on PVA with 5, 10, 20 and 30 wt % of CNF was prepared by using liquid nitrogen and freeze drying techniques. Specimens were buried in compost obtained from municipal solid waste of a compost Factory, Karaj municipality, Iran, for 150 days. The biodegradability of materials was assessed by calculation the visual observation, weight loss, scanning electron microscopy (SEM) and chemistry and transparency (FTIR). The ecotoxicological impact of compost samples was evaluated via plant growth tests with cress and spinach. Biodegradation studies of the films during municipal solid waste confirmed that the biodegradation time of PVA/CNF films greatly depends on the CNF content. The SEM analysis showed that the biodegradability of the films at surface of the samples (deep pores and cracks) was increased with increased the CNF content. By considering the ecotoxicological test using plants growth, it seems that all nanocomposite and pure PVA did not generate a negative effect on germination or development of the vegetal species.
