Dynamic mechanical and thermal properties of modified poly(propylene) wood fiber composites

Dynamic mechanical and thermal properties of poly(propylene) (PP)/wood fiber composites have been studied using Dynamic Mechanical Analysis (DMA). In order to modify the PP matrix maleated poly(propylene) (PPMA) and poly(butadiene-styrene) rubber were used as compatibilizer and impact modifier, respectively. tan delta peak temperature of the compatibilized systems was found to increase in comparison to that of composites without coupling agent, indicating improved adhesion and interaction between PP. matrix and wood fibers. The storage modulus (E')-temperature (T) relationship of all composites is. characterized by two transition points. The E' of compatibilized composites exhibits higher values than those of the., uncompatibilized ones at low temperatures (up to the beta-relaxation). In the temperature interval from beta-transition to 60degreesC, the composites containing PPMA have lower modulus, and above 60 degreesC the E'-T curves tend to converge. DSC indicates that the wood fibers act as nucleating agent for PP. Maleated poly(propylene) slightly retards the crystallization rate, resulting in a composite structure, composed mainly of large spherulites, with a higher crystallinity index. Fourier Transform Infrared (FT-IR) microscopy was also applied to explore the interface between wood fibers and PP matrix. The strong absorption band at 1738 cm(-1) in the IR spectrum scanned at the interfacial region between the fiber and matrix indicated that PPMA had probably reacted either by formation of ester bonds or hydrogen bonding with hydroxyl groups from cellulose.