The mechanical and structural properties of novel melt processed poly-ethylene terephthalate (PET)-hemp fiber composites for engineering applications were investigated. First, four reinforcement formulations were compared with the PET modified with poly-epsilon-caprolactone: hemp, Clay/hemp, pyromellitic dianhydride/hemp and glycidyl methacrylate/hemp. Next, the effect of hemp fibers concentration as well as the effect of heat treatment was analyzed. A significant difference was observed in the mechanical and structural properties of the composites. Moreover, we observed a good fiber–matrix interface without the use of a coupling agent, particularly in the absence of additives. Our data suggest that a careful trade-off between the additives, the hemp fiber concentration and the desired engineering applications is key requirement for the applications of high melting polymers-reinforced with natural fibers.

The thermal stability of poly(ethylene terephthalate) reinforced with 1, 5, 10, 15, and 20% hemp fibers was investigated with the aim of extending the applications of biocomposites to high-melting thermoplastics. The material was injection-molded following compounding with a torque-based Rheomix at 240, 250, and 2608C. A combination of thermogravimetric methods at 5, 10, and 208C/min, Liu and Yu's collecting temperature method, and Friedman's kinetic method were used for testing and analysis. A significant thermostability for all formulations was observed below 3008C; this demonstrated their potential for successful melt processing. Moreover, two degradation steps were observed in the temperature ranges 313-390 and 390-4908C. The associated apparent activation energies within the temperature ranges were determined as 150-262 and 182-242 kJ/mol, respectively. We found that the thermostability was significantly affected by the heating rates; however, the effect of the temperature of the mixing chamber was negligible. These findings suggest that the successful melt processing of high-melting thermoplastics reinforced with natural fibers is possible with limited fiber thermodegradation.