Rice straw fiber can be considered as important potential reinforcing filler for thermoplastic composite because of its lignocellulosic characteristics. It is thus of practical significance to understand and predict the thermal decomposition process of rice straw fibers. A method proposed by Málek, Šesták, and co-workers was used to investigate and model thermal decomposition process of common natural fibers with detailed analysis on rice straw system. Assuming a global model occurring within the entire degradation of natural fibers with consideration of fiber as one pseudo-component, model can be used to describe both isothermal and non-isothermal degradation process of most selected fibers within acceptable error limits of 3 and 5%, respectively. The parameters of kinetic model were given in this dissertation. The model obtained has practical significance for introducing straw fiber into some engineering plastics with comparatively lower melting temperature.

Influences of different rice straw components, and compatibilizers on various properties of rice-straw based polymer composites were also investigated. Rice straw fibers can work well with both VHDPE and RHDPE as reinforcing filler. Also, different components of rice straw had no significant influence on mechanical properties of composites. The PE-g-MA/EPR ratio affected mechanical properties of composites modified by combined compatibilizers. The optimum PE-g-MA/EPR ratio was considered to be 2:1 and 1:1 for PE-g-MA/uEPR and PE-g-MA/EPR-g-MA modified composites, respectively. At the optimum ratio, composites modified by combined compatibilizers showed better strength and impact toughness, and acceptable modulus compared to those modified by either EPR or EPR-g-MA.

It was found that 13% weight loss seemed to be the limit for rice straw to maintain its strength in a composite system. High-temperature one-step extrusion was feasible for manufacturing HDPE/nylon-6/rice-straw composites without significant strength loss caused by thermal degradation of fiber. The two-step method failed to exhibit better performance than the one-step method.