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This work studied the properties of poly(lactic acid) (PLA) and chemically crosslinked poly(lactic acid) (CrPLA) in the presence of different types of silica (SiO2): SiO2 from rice husk ash (RhSiO2) and commercially available SiO2 (CoSiO2). A mixture of triallyl isocyanate and dicumyl peroxide was used as a chemical crosslinking agent. The rice husk was burnt in a furnace to extract RhSiO2. The thermal and mechanical properties of the PLA and CrPLA composites were investigated as a function of the SiO2 content. The presence of C–H functional groups supports the compatibility of stearic acid and RhSiO2, thereby facilitating the esterification reaction observed in the Fourier transform infrared-attenuated total reflectance spectra. This played an important role in changing the properties of the PLA-based composites. The concave fracture surfaces were consistent with the tensile results, the thermal properties, and the degree of swelling, which suggested that there was a better reaction between stearic acid and RhSiO2. However, the heat deflection temperatures of both the PLA and the CrPLA composites were not significantly affected by blending with either CoSiO2 or RhSiO2.

Polylactic acid (PLA) is a biodegradable polymer which has a wide range of applications; in this work, all PLA based composites formulations were compounded by twin screw extruder and testing specimens were produced. This article focuses on determinations of mechanical, antibacterial, thermal and barrier properties of PLA composites. It was found that only the tensile modulus of PLA composites increased while the others decreased when 10% wood was loaded. The effect of Triclosan and Cloisite® 30B compounding did not change the mechanical properties and glass transition temperature. However, by the presence of wood and Cloisite® 30B, Tm values of the composites exhibited double peak characteristic which was related to an increase in crystallinity level. Antibacterial activity of the PLA composites was improved with the Cloisite® 30B content, and this was attributed to cationic bactericide quaternary ammonium group between the silicates layers. Hydrophobic material Triclosan obviously changed water vapor permeability (WVP) of the PLA from 8.24 × 10−11 to at 7.26 × 10−11 g.mm/mm2.h.Pa for triclosan/PLA specimens. All PLA composites samples with 0.5% clay content showed a significant increase in oxygen barrier property.

Anti-bacterial and biodegradation activities of Poly (lactic acid) (PLA) and wood flour/PLA composites (WPLA) were investigated for the effect of anti-bacterial agent addition. Silver substituted Zeolite (commercially designated as Zeomic) was used as anti-bacterial agent in this study. Anti-bacterial activities were investigated through dynamic shake flask method accompanying with plate count agar (PCA) technique, against Staphylococcus aureus as testing bacteria. The results of anti-bacterial activity were reported by viable cell count. For biodegradation test, the degree and rate of biodegradations were evaluated from percentage of carbon conversion, the test being carried out under laboratory controlled-aerobic degradation environment at a temperature of 58±2°C. The results found that addition of Zeomic did not perform anti-bacterial activities for both the neat PLA and WPLA due to non-diffusivity of silver in Zeomic. For biodegradation test, both PLA and WPLA samples during incubation times of 21-60 days had shown considerable biodegradation rates as a result of chain scission by hydrolysis reaction and subsequent enzymatic-biodegradation by microorganism of PLA molecules. Regarding the effect of wood and Zeomic addition, it was found that introducing wood and Zeomic in PLA matrix tended to markedly increase the degree and rate of biodegradation of PLA and WPLA materials, whereby the PLA having 10%wt of wood with 1.5%wt of Zeomic had the most satisfactory biodegradation level and rate as a consequence of accelerated hydrolysis degradation from moisture in wood and Zeomic.