Effect of natural ageing on the properties of recycled polypropylene/ethylene vinyl acetate/wood flour composites

ABSTRACT Wood flour composites main applications are represented by outdoor furnishing. Therefore, it is important to evaluate their behavior under natural ageing conditions. This work aims to investigate the natural ageing impact on the mechanical, physical, thermal e morphological properties of recycled polypropylene/ethylene vinyl acetate/wood flour composites (PP/EVA/ITA). Samples were exposed to natural ageing for 12 months in Porto Alegre (BR). Mezilaurus itauba (ITA) wood flour was used at 30 % w/w. Results showed that PP filled wood flour retained a higher fraction of the original mechanical properties after natural ageing. Crystallinity degree for composites increased from 30.9 up to 37.5% Climatic conditions affected the colorimetric and morphological characteristics of composites, indicating that there was not only photo-degradation but also thermo-oxidative and hydrolytic degradation. In this way, the use of antioxidant additives and UV photo-absorbers is recommended to avoid stress-cracking, discoloration and loss the mechanical properties.

摘要 木粉复合材料的主要应用领域为户外家具，因此评估其在自然老化条件下的性能表现至关重要。本研究旨在探究自然老化对回收聚丙烯/乙烯-醋酸乙烯酯/木粉复合材料（PP/EVA/ITA）的力学、物理、热学及形貌学性能的影响。试样于巴西阿雷格里港开展为期12个月的自然老化暴露试验，采用质量分数为30%的伊塔巴香樟木粉（Mezilaurus itauba, ITA）作为填料。结果表明，经自然老化后，PP填充木粉复合材料保留了更高比例的初始力学性能；复合材料的结晶度从30.9%提升至37.5%。气候条件对复合材料的色度及形貌特征产生了显著影响，表明其老化过程不仅涉及光降解，还同时存在热氧化降解与水解降解。据此，建议添加抗氧化添加剂与紫外光吸收剂，以避免材料出现应力开裂、色泽劣变以及力学性能损失。