Silk sericin (SS) from the Bombyx mori silk cocoons has received much attention from biomedical scientists due to its outstanding properties, such as antioxidant, antibacterial, UV-resistant, and ability to release moisturizing factors. Unmodified SS does not self-assemble strongly enough to be used as a hydrogel wound dressing. Therefore, there is a need for suitable stabilization techniques to interlink the SS peptide chains or strengthen their structural cohesion. Here, we reported a method to form a silk semi-interpenetrating network (semi-IPN) structure through reacting with the short-chain poly(ethylene glycol) diacrylate (PEGDA) in the presence of a redox pair. Various hydrogels were prepared in aqueous media at the final SS/PEGDA weight percentages of 8/92, 15/85, and 20/80. Results indicated that all semi-IPN samples underwent a sol-gel transition within 70 min. The equilibrium water content (EWC) for all samples was found to be in the range of 70-80%, depending on the PEGDA content. Both the gelation time and the sol fraction decreased with the increased PEGDA content. This was due to the tightened network structure formed within the hydrogel matrices. Among all hydrogel samples, the 15/85 (SS/PEGDA) hydrogel displayed the maximum compressive strength (0.66 MPa) and strain (7.15%), higher than those of pure PEGDA. This implied a well-balanced molecular interaction within the SS/PEGDA/water systems. Based on the direct and indirect MTS assay, the 15/85 hydrogel showed excellent in vitro biocompatibility towards human dermal fibroblasts, representing a promising material for biomedical wound dressing in the future. A formation of a semi-IPN structure has thus proved to be one of the best strategies to extend a practical limit of using SS hydrogels for wound healing treatment or other biomedical hydrogel matrices in the future.

Molded pulp is an eco-friendly packaging product popularly chosen nowadays. It is mostly used to replace plastic containers such as polypropylene (PP), polystyrene (PS) and polyethylene (PE). Besides, the non-wood pulps from agricultural crops and residues have been increasingly studied as alternative materials in pulp production. Therefore, this study aimed to investigate the possibility of utilizing rice straw (R), pineapple leaf (P) and banana stem (B) as raw materials to prepare pulps by using a soda-anthraquinone (AQ) pulping process. The pulping was carried out with 4-7% sodium hydroxide solution and 0.1% AQ, a liquid-solid ratio of 10:1, and pulping time of 15-30 min at 98 ± 2°C. Next, the obtained pulps unscreened (u-) were sieved into screened (s-) portions, and the molded sheets from both u-and s-portions were formed using compression molding technique under pressure of 0.6 MPa at 130°C for 5 min. The molded sheets from R pulp showed higher tensile strength and tensile index (62 MPa and 63.28 Nm/g, respectively) when compared to the sheets from P and B pulps. From SEM images, the cross-sections of the R pulp sheets revealed less voids between fiber layers and, hence, better fiber-packing and bonding. Based on their mechanical properties compared to commercial molded pulp products, it suggested that these agricultural residues and their pulps can be considered promising alternative sources for pulp and molded pulp production.

Due to poor barrier properties and high sensitivity to moisture, the applications of paper‐based food packaging remain limited. While gaining high barrier performance and surface durability, laminating papers with binders and other materials often leads to reduced recyclability and sustainability. Herein, we present a promising approach to improve the barrier properties and surface oil resistance of bagasse moulded pulp while preserving its green profile. A bio‐nanocomposite layer, combining nanocellulose and shellac (natural polyester), was coated on the surface of moulded pulp. This nanocomposite coating layer provides excellent gas barrier and water barrier performance simultaneously, thanks to the ester modification of nanocellulose to improve its hydrophobicity. With a good compatibility and dispersion in the shellac matrix phase, the modified nanofibrillated cellulose demonstrated an improved barrier performance compared with the unmodified nanofibrillated cellulose. Oxygen transmission rate and water vapour transmission rate of the coated pulps were in the range 60–300 cm3 m−2 day−1 and 10–30 g m−2 day−1, respectively, comparable to those of conventional food packaging materials. The surface resistance of the coated pulps was also greatly improved, indicated by the water contact angle, oil contact angle, Kit test and oil resistance test in a bowl model. The nanocomposite was able to enhance the tensile strength of the moulded pulp by 23%. In summary, the current sustainable nanocomposite coating layer demonstrated great potential in converting paper‐based materials to high barrier and sustainable food packaging. © 2022 Society of Industrial Chemistry.

The nanofibrillated celluloses (NFC) from different sources (i.e. bacterial cellulose (BC), pineapple leaf (PA) and banana pseudostem (BA)) were prepared using microfluidization. TEM and XRD results revealed diverse characteristics of the NFCs from different sources. Then, 0.1wt% of the prepared NFCs were integrated into the bagasse (BG) paper sheets. SEM images showed the densest surface of BG/NFC-BA sheet which also exhibited the highest sheet rigidity. Furthermore, the tensile tests indicated that the BG sheet reinforced with NFC-BC, possessing the highest fiber aspect ratio (L/D of 336) and crystallinity (80%), offered the highest strength and toughness. All tensile properties of the BG sheets were impressively enhanced with very low content (0.1wt%) of NFC addition. This confirmed that NFC is a highly effective reinforcement and suitable for use in paper making industry. However, suitable sources of NFCs for a particular paper product or application should be considered in advance.

Nanofibrillated cellulose (NFC) was systematically tailored by ultrasonic-assisted esterification with lactic acid at different amplitudes and times, which led to modified NFC (mNFC) with different degrees of substitution (DS), between 0.21 and 0.55, as confirmed by titration, FTIR, and C 13 NMR. A partial fragmentation and decrease in crystallinity of mNFC were revealed by TEM and XRD. To form molded pulp sheets, 5 wt% mNFC was added into a bagasse (BG) pulp slurry, then partially dewatered before hot-pressed. mNFC worked effectively as selfretention aid, partly solving the issue of drainage during sheet forming as commonly observed from unmodified NFC. The BG/mNFC (DS 0.55) sheet exhibited an enhancement in tensile properties. Water resistance and barrier performance of the current sheets were also evidently increased. The results suggested that the higher DS on mNFC can improve water resistance and mechanical properties, simultaneously overcoming drainage challenges in processing of molded pulp products.