Chemical conversion
hojjatullah akbari; fatemeh ravari; ghasem asadpur; Ashraf Sadat ghasemi
Abstract
AbstractBackground and Objectives:The modification of paper components, including cellulose 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 ...
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AbstractBackground and Objectives:The modification of paper components, including cellulose 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 (Figure 1). 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-derived 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 incorporated into recycled pulp at varying ratios (20/70, 30/70, 40/70, and 50/70), with 70% of the composition consisting 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.
Khashayar Vaezi; ghasem asadpour
Abstract
Concerns about environmental pollution caused by petroleum-based packaging materials waste have increased the motivation to research and study on biodegradable packaging materials. In this study, in order to make added value and reprocess of the recycled papers, cellulose nanocrystals were produced from ...
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Concerns about environmental pollution caused by petroleum-based packaging materials waste have increased the motivation to research and study on biodegradable packaging materials. In this study, in order to make added value and reprocess of the recycled papers, cellulose nanocrystals were produced from them and added to the hydroxypropyl methyl cellulose / cationic starch nanocomposite in amounts of (3%, 5%, 7%, 9% and 11%) and their structural, strength and barrier properties were investigated. The yield of crystalline cellulose nanoparticles produced from this alpha cellulose was about 65% and according to the (TEM) test results, the obtained nanoparticles were rod-shaped and had a length of 100 to 150 nm and a diameter of 15 to 30 nm. Also, their degree of crystallinity was 79.6% according to the X-ray diffraction test. According to the results, with the addition of cellulose nanocrystals to the nanocomposites, the tensile strength, moisture absorption resistance, and oxygen permeability resistance were increased and only the strain to the breaking point (Flexibility) was decreased and the best strength properties and barrier properties of the nanocomposites were obtained in the presence of 9% cellulose nanocrystals from recycled papers.
