PA6/PA66/talc composite: Effect of reprocessing on the structure and properties

• Published in: Journal of applied polymer science 2022-04, Vol.139 (13), p.n/a
• Main Authors: Domingo, Gustavo D., Souza, Adriana M. C.
• Format: Article
• Language: English
• Subjects: composites; Crack propagation; Degree of crystallinity; Differential scanning calorimetry; Fatigue failure; Fatigue life; Fatigue tests; Flexural strength; Fourier transforms; Impact strength; Injection molding; Materials science; Mechanical properties; Melt flow index; Modulus of rupture in bending; Photomicrographs; Polyamide resins; Polymers; recycling; Reduction; Reprocessing; structure‐property relationships; Talc; thermal properties; Thermodynamic properties; Thermogravimetric analysis
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.51869

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. The effect of reprocessing cycles on polymer properties must be known in advance since, during mechanical recycling, the polymers can undergo thermal and/or mechanical degradation. In this study the effect of injection molding reprocessing on the mechanical, thermal, structural and morphological properties of PA6/PA66/talc composite was assessed. The composite can be subjected to up to four reprocessing cycles without changes in the investigated properties, except for fatigue life.