In order to study possible changes in the mechanical properties of wood plastic composites produced from thermally modified wood fibers as reinforcement material (60%) and polypropylene (40%) after long-term storage under constant conditions, tensile and flexural specimens were tested in the years 2004 and 2009 after storage at 20°C and 65% humidity. Increased tensile strength, Young’s modulus (tensile test) as well as modulus of elasticity (flexural test) were observed for the long-term stored samples indicating a positive effect of the storage conditions on the mechanical properties of the samples.
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