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In the present investigation, the tensile mechanical properties of the isotactic polypropylene (PP) biocomposite material reinforced with randomly oriented short bamboo fiber bundles were determined. Samples of the material with different reinforcement contents (20, 30 and 40%) were prepared, using polypropylene with grafts of maleic anhydride molecules (MAPP) as coupling agent. A group of these samples were subjected to an accelerated thermal aging treatment to evaluate the effect of said treatment on the tensile properties of the biocomposite. Tensile tests were carried out at different deformation rates (10 and 50 mm/min) and an increase in tensile strength (29 to 45 MPa) and elastic modulus (1 to 3 GPa) of the PP with the fiber content was obtained. For different stretching speeds, better resistance at high speeds was obtained. Thermal aging for 24 hours at 100 °C increased the resistance of pure PP. For the biocomposites, a low resistance was obtained in the samples aged in greater time (98 °C, 10 days). Through scanning electron microscopy, a microstructural characterization was carried out that allowed explaining the improvement of the resistance of the fiber reinforced PP, and in some cases, the loss of resistance due to heat treatment. [ABSTRACT FROM AUTHOR]

An analysis of combined effect of temperature and load frequency on the fatigue crack growth rate and cracking velocity for Chlorinated Polyvinyl Chloride (CPVC) is presented in this paper. CPVC is a thermoplastic material used for piping systems where higher temperature and chemical resistance are important, becoming a good alternative to metals. The Dual Boundary Element Method (DBEM) is used to determine three dimensional states of stresses and strains at each increment of crack. Stress intensity factors at the crack tip are determined using the J-integral, and the crack growth direction is defined by the maximum principal stress criteria. A mathematical model proposed by Kim & Wang in 1994 based on experimental results is applied to predict cracking velocity. In this work, a specimen with lateral crack using temperature values between 23 and 70 °C and frequencies between 0.1 and 10 Hz is evaluated. The results show that cracking velocity increases with temperature increase and with frequency decrease. These results are compared to Paris & Erdogan model showing good agreement which reveals that DBEM could be an accurate tool to investigate the prediction of crack growth in polymers. [ABSTRACT FROM AUTHOR]