Effect of different chemical treatments and loadings of Arundo donax L. fibers on the dynamic mechanical, thermal, and morphological properties of bisphenol A aniline based polybenzoxazine composites

In this research paper, bisphenol A aniline based benzoxazine (BA-a) was reinforced with natural, inexpensive, and largely distributed cellulosic plant, namely Arundo donax L. (AD) at various loadings of 5, 15, and 25 wt%. AD fibers were initially subjected to three different chemical surface modifications using alkaline, silane, and combined alkali-silane solutions. The main purpose of this work was to investigate the dynamic mechanical properties, morphological stability, and thermal stability of the as-prepared composites by pointing out the effects of natural reinforcements treated in different ways at different loadings. Dynamic mechanical analysis of the prepared composites revealed an enhancement in storage modulus ( E ′) and loss modulus ( E ″) to higher values, especially for composites reinforced by alkali- or combined-treated fibers due to the strong effect of alkaline solution to remove noncellulosic matters. Composite loaded at 25% of alkali-silane treated AD exhibited a glass transition temperature ( T g ) of 217°C, while pure polymer had a T g of 188°C. The enhanced properties are a great indicator of the high fiber–matrix adhesion and compatibility. This conclusion is strengthened by scanning electron microscopy images. The thermal stability and degradation of the different biocomposites are also investigated by thermogravimetric analysis, revealing that the nature of the employed chemical treatment affected considerably the thermal behavior and the char yield of the composites.