Abstract. In this study, polyamide 6 containing 30wt% talc was reprocessed via injection molding up to eight processing cycles. The effects of reprocessing on the mechanical properties and on the melt viscosity were analyzed by flexural and impact tests and by melt flow index (MFI) tests, respectively. Flexural strength and modulus remained unchanged up to the 5th processing cycle. From the 6th processing cycle, flexural strength and modulus decrease with increasing processing cycles. Similar trend was observed for impact strength, however, the decrease observed in this property was much lower. From the 6th processing cycle, MFI increases with increasing processing cycles, indicating a possible reduction in PA6 molar mass.
In this study the effect of repeated injection molding cycles on the structure and properties of polyamide 6/polyamide 66/talc (PA6/PA66/talc -35/35/30) composite was investigated for samples subjected to one, four, and seven processing cycles. Their morphology (scanning electron microscopy), structure (Fourier transform infrared spectroscopy), melt viscosity (melt flow index [MFI]), mechanical (tensile, flexural, impact, and fatigue tests), and thermal properties (differential scanning calorimetry and thermogravimetric analysis tests) were analyzed. The increase in MFI value and the decrease in the maximum decomposition temperature of PA6, observed by TG analysis, for samples subjected to seven processing cycles, indicated a possible reduction in molar mass of the PA6/PA66 matrix. These samples presented a decrease in degree of crystallinity of PA6 and PA66, which was more pronounced for PA6. The reprocessing of the composite did not present changes in the mechanical properties up to the fourth processing cycle, except for fatigue life which presented a 59% reduction. Samples subjected to seven processing cycles presented a decrease in tensile and flexural strength as well as in tensile and flexural modulus. Charpy impact strength of the samples did not significantly change upon reprocessing. The micrographs of the fatigue fractured surfaces indicated that the weak talc-matrix interaction and talc-matrix debonding became more evident with increasing processing cycles.
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