Balkis Fatomer A. Bakar

Vitrimers have emerged as an innovative class of polymeric materials that combine the robustness of thermosets with the reprocessability of thermoplastics through dynamic covalent bond exchange. While extensive research has focussed on their mechanical performance and processing conditions, the fundamental role of stoichiometric balance in vitrimer formulations remains underexplored. This review explores the influence of stoichiometry on vitrimer network formation, with a particular emphasis on bio-based epoxy vitrimer systems incorporating epoxidized vegetable oil (EVO). The impact of different epoxy-to-EVO and curing agent-to-EVO ratios on crosslinking density, thermal stability and self-healing characteristics are discussed in detail. The discussion includes the selection of curing agents, namely those with carboxyl (-COOH) and amine (-NH) functional groups, regarding their influence on vitrimer reactivity and recyclability. Notably, findings indicate that EVO-based vitrimer require lower catalyst loading compared to conventional epoxy-based vitrimer, contributing to more sustainable and cost-effective formulations. Understanding the stoichiometric interplay in vitrimer formulations is crucial for optimizing material performance, minimizing catalyst requirements and enhancing long-term durability. Resolving these stoichiometric problems is crucial for the growth of vitrimer applications in biodegradable composites and other high-performance industries.

Bamboo is suitable to be a material for the production of new products that can be used indoors and outdoors. Five-, seven- and nine-ply laminated woven bamboo mat boards from semantan bamboo, Gigantochloa scortechinii, were fabricated in this study. G. scortechinii has been used commercially in a structural application and is easily available in Malaysia. The present work investigated the physico-mechanical properties and flammability of the laminated bamboo mat boards as a function of the number of ply. Phenol-formaldehyde resin was used as a binder. The panels’ density, physical, mechanical properties, formaldehyde emission and flammability were evaluated. As the number of ply increased, the density of the laminated boards decreased. Similarly, the highest modulus of elasticity was found in 5-ply laminated boards. However, the lowest modulus of rupture was also measured in 5-ply laminated boards. Regarding shear strength, 5-ply and 7-ply laminated boards outperformed 9-ply laminated boards. Meanwhile, 7-ply laminated boards exhibited the highest dimensional stability, as evidenced by the lowest water absorption and thickness swelling. In terms of flammability, all composites are classified as V-0 because the burning stops within 10 s and no flaming drips are observed.

The main objective of this study was to investigate the properties of polymer composites reinforced with grape cane fibers. The fibers were subjected to a sodium hydroxide (NaOH) treatment at two treatment concentrations to extract the fibers as well as fiber surface treatment. Panels were fabricated by hand lay-up and compression molding according to different fiber types, namely outer bark (OB) and whole (W) fibers. The whole fiber was a mixture of OB and inner bark (IB) fibers. Grape cane fibers were used as the reinforcement material for unsaturated polyester (UPE) resin panels. Acrylated epoxidized soybean oil (AESO) was used as a reactive diluent material with the UPE resin, and the results were compared with panels prepared with commercial styrene–UPE. There were inconsistent alkali treatment concentration effects on the mechanical properties and water absorption. However, panels fabricated with the whole bark fibers that have been treated with 1 wt % NaOH and had AESO–UPE resin resulted in the best tensile and flexural strength.

The objective of this study was to investigate tensile properties of two grape cane fibers, namely, outer bark (OB) and inner bark (IB). The cane is a necessary annual by-product from vineyards and is produced at approximately 36 million tons yearly around the world, which currently has no substantial commercial utilization. Grape cane fibers were subjected to an alkali treatment, at different concentrations, to separate the fibers from the cane. Moreover, two displacement methods such as system compliance (C_s) and digital image correlation (DIC) were performed to determine Young’s modulus of the samples, and the results were compared. The OB fibers had better overall properties than IB fibers. The effect of the treatment concentrations (1, 3, 5, and 7 wt% of sodium hydroxide) and gage lengths (10, 25, and 40 mm) on the tensile properties was not consistent for both fiber types. The DIC method consistently yielded greater tensile modulus of the samples than the C_s method for OB fibers.

The objective of this study was to investigate the moisture content (MC), density, and amount of extractives along the height of a 32-year-old oil palm stem. The extractives were removed following TAPPI standards T-207 and T-280 for water solubility and acetone extractives. The results showed that the MC of the palm stem increased from the outer towards the inner section, while the density decreased. Along the tree height, the MC was found to increase from the bottom to the middle part, but slightly decreased towards the top. An inverse trend was obtained for the density distribution along the tree height. The results of the extractive separation showed that the middle and center sections of the oil palm stem contained the highest amount of extractives irrespective of the types of solvent. The highest amount of extractives was obtained from hot water extraction, followed by cold water and acetone extractions. The lowest amount of extractives was located at the bottom outer section of the oil palm stem which ranging from 2.0 to 9.2%, whereas the middle and center sections contained a greater amount of extractives ranged from 4.6 to 32.8% regardless of the type of solvent used.