Natural rubber (NR) is sensitive to oxidative degradation, which needs to add commercial antioxidant for NR compounding to improve its aging properties.The aim of this study is to apply natural antioxidant obtained from extracted rambutan peel powder (RE) by methanol compared to commercial antioxidants for NR compounding in a conventional vulcanization (CV system). Two types of commercial antioxidants were N-(1,3-dimethylbutyl)-N'phenyl-pphenylenediamine (6PPD) and 2,2,4-Trimethyl-1,2dihydroquinoline (TMQ).The main phenolic compounds in RE were geraniin, corilagin, ellagic acid and gallic acid which had greater antioxidant activity based on all methods, especially for 2,2-Diphenyl-2-picrlhydrazyl radical-scavenging assay (DPPH) and had a similar antioxidant activity to 6PPD. The antioxidants were applied in NR vulcanizates at 1 phr and 2 phr to study their physical and mechanical properties. The decomposition temperature of RE was higher than for 6PPD but similar to TMQ. The decomposition temperature of the rubber vulcanizates containing RE was higher than for the commercial antioxidants. Rubber vulcanizates with RE retained similar tensile strength and modulus at 100% strain as the commercial antioxidants. Furthermore, the addition of RE in rubber vulcanizates helped to resist thermal aging at 70 C and ozone aging, particularly at 1 phr at least as well as in the commercial antioxidants. Therefore, RE can be used as an alternative natural antioxidant in natural rubber to replace commercial antioxidants.

In-situ silica nanoparticles with ammonium laurate surfactant in natural rubber latex composites were characterized to describe the reinforcement mechanism in enhanced mechanical properties. In-situ sol-gel method was introduced to generate silica nanoparticles in natural rubber latex using a mole ratio of water-to-TEOS of 28.9 stirring at room temperature for 24 hours. The addition and effect of adding ammonium laurate surfactant for enhancing dispersion and compatibility between silica nanoparticles and rubber matrix was also studied. The natural rubber latex was then vulcanized by electron beam radiation at 200 kGy. The silica content in rubber composites made in-situ, was analyzed by TGA, showed an increase from 3.08 phr to 8.92 phr, corresponding to addition of TEOS amounts of 10 phr to 30 phr, respectively. The dispersion of silica nanoparticles in rubber matrix with ammonium laurate surfactant was improved and exhibited less aggregation than rubber composites absent of ammonium laurate surfactant as evidenced by SEM-EDX. The increase of silica content in rubber composites exhibited lower swelling ratio and higher crosslink density when compared with neat natural rubber. Also, the modulus at 100% and 300% strain also increased with increasing silica nanoparticles incorporation in contrast to tensile strength.

Silica nanoparticles were synthesized by rice husk ash (RHA) produced from jasmine rice husk and riceberry rice husk via sol-gel method for the use as reinforcing fillers in natural rubber (NR). The obtained silica nanoparticles are spherical in shape and the particle sizes were observed to be in the 10-20 nm range with uniformly size distribution. The surface of silica nanoparticles was treated with a silane coupling agent confirmed by FTIR. The treated silica nanoparticles were then incorporated into NR and vulcanized with electron beam irradiation. The rubber nanocomposites with silica nanoparticles, produced from jasmine rice husk and riceberry rice husk, resulted in higher mechanical properties (tensile strength and modulus) than neat rubber vulcanizate. The modified rubber vulcanizates revealed rougher surface with tear lines as compared to the neat rubber vulcanizates, indicating the improved strength. Interestingly, the rubber nanocomposites with silica nanoparticles from jasmine rice husk showed higher tensile strength and modulus than silica nanoparticles produced from riceberry rice husk. The micrographs indicated better dispersion of NR composites with jasmine rice husk which leads to a strong interaction between silica nanoparticles and rubber matrix, thereby improving the strength.

Diglycidyl ether of bisphenol A (DGEBA) epoxy resin with cycloaliphatic polyamine curing agent was modified with lignin to improve thermal and mechanical properties of of polymer composite. A systematic study of lignin loading, between 5 and 20 phr (per hundred parts resin) as compared to neat epoxy, was conducted for the reinforcement effect of epoxy resin composites. With the as-received lignin having spherical particles of 80 to 100 microns in diameter, the Tg of the epoxy-filler composites increased with a small addition of lignin up to 10 phr. Likewise, the yield stress and stiffness (Young’s modulus) of the epoxy resin-lignin composites significantly increased to a maximum value of 49.32 MPa and 2.75 GPa, respectively, with 10 phr lignin, due to the higher modulus of the filler compared to the bulk epoxy resin. Correspondingly, the storage moduli of the lignin-containing composites also increased upon filler addition up to 10 phr due to the impact of lignin. Conversely, however, the tanδ decreased in intensity with increasing lignin filler content, which reflects the dampening effect due to restricted chain mobility in thepresence of lignin particlesin epoxy systems.