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Accelerated weathering tests were conducted to evaluate the weathering resistance of poly(lactic acid) (PLA) based biocomposites without and with epoxidized natural rubber (ENR), that were reinforced with unmodified wood pulp fiber (WP) and silanized wood pulp fiber (modified WP). Changes in mechanical and thermal properties and morphology were observed, and structural and chemical degradation were analyzed. The addition of ENR improved the impact strength of the biocomposites before weathering, acting as an impact modifier. After the weathering test, the flexural properties of PLA-based biocomposite with ENR and silanized wood pulp fiber (ENR-modified WP) was better than the flexural properties of a biocomposite without ENR. The biodegradability of the biocomposites largely depended on the PLA matrix. The modified fibers have lower UV absorbance and can protect composites from UV light better than unmodified fibers. ENR and modified WP helped prevented the degradation of PLA. While weathering reduced the molecular weight of the WP and modified WP biocomposites by 78% and 61%, respectively, the molecular weight of the same biocomposites with ENR decreased by 51% and 50%, respectively. The accelerated weathering test produced cracks and increased surface roughness in the biocomposites and the glass transition temperature was reduced as a result of crystallization and chain shortening. These indicated that the biocomposite based containing ENR and silanized wood pulp fiber had better weathering resistance due to lowest absorption of UV radiation which was more suitable for applications in construction, furniture, and exterior and interior decoration. • ENR mostly compatible to modified pulp leading maximal impact strength of composite. • PLA/ENR/modified pulp mostly resisting to weathering acceleration for 30 days. • Silanization of pulp leading the reduction of UVB absorbance and water uptake. [ABSTRACT FROM AUTHOR]

The aim of this work was to improve mechanical properties of a biocomposite of polylactic acid (PLA) reinforcing with fibrillated methacrylate-silanized hemp fibre. The effect of hemp fibre on photo-oxidation and hydrolytic degradation of PLA was evaluated through a QUV accelerated weathering test. Incorporation of 20 mass% fibre filler into neat PLA matrix resulted in increased tensile and flexural modulus for 150% and 200%, respectively. The outdoor degradation of neat PLA and PLA biocomposites was simulated in a 30 days of QUV accelerated weathering test in accordance with ISO 11507 method B. Glass transition temperature (Tg) was periodically recorded to measure the rate of degradation. Differential scanning calorimetry (DSC) analysis indicated that the degradation rate of the PLA matrix of the biocomposites tended to decrease proportionally to exposure time. The statistical regression method revealed a linear relationship between ln(Mn) and lnTg (R2 = 0.96). The 20 mass% hemp/PLA biocomposite was mostly destroyed over neat PLA after 30 days. The rate of degradation tended to have a linear proportion with hemp content. The results of FTIR 13C-NMR analysis confirmed that the substantial degradation of hemp/PLA biocomposites was due to the lignin content of the hemp fibre. The sensitivity of the PLA biocomposite to UVB light and moisture absorption accelerated photo-oxidation and hydrolytic degradation to the lowest molecular weight of PLA. [ABSTRACT FROM AUTHOR]