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EFFECT OF THERMAL ANNEALING ON THE MECHANICAL AND THERMAL PROPERTIES OF WOOD FIBER REINFORCED BIOCOMPOSITES BASED ON POLYLACTIC ACID
Pine wood reinforced biocomposites based on polylactic acid (PLA) were produced by a combination of extrusion and injection molding with contents of 10, 20, and 30% of pine fibers. In particular, some samples were subjected to thermal annealing (105 °C for 1 h) to modify the crystallinity of the materials. In all cases, morphological (scanning electron microscopy) and thermal (differential scanning calorimetry, dynamical mechanical thermal analysis) characterizations were related to the mechanical properties (Charpy impact, tensile and flexural tests). The results showed that annealing increased the crystallinity of the materials produced, but different mechanical behaviors were observed depending on the content of pine fiber. For example, annealing increased the impact strength and flexural modulus of PLA and PLA biocomposites, while decreasing their flexural strength. But the main conclusion is that pine fiber addition combined with thermal annealing can substantially increase the thermal stability of the studied materials. To compare the effect of processing conditions on the biocomposites properties, a further study will take place comparing rotational molding and compression molding using PLA as the biopolymeric matrix with different wood fiber reinforcements. Additionally, the biocomposites will be characterized after accelerated weathering as well as their biodegradation process.