| Abstract Scope |
Premature cracking during fastener installation of injection molded, thermoplastic polyethylene terephthalate (PET) glass-reinforced receptacles was investigated. Testing of cracked “defective” and non-cracked “functioning” receptacles was conducted to investigate potential compositional or processing deficiencies, and to determine mechanical property differences. Material samples were cut from both defective and functioning receptacles and subjected to thermal/chemical analytical and mechanical materials tests to include TGA, DSC, FTIR, DMA, liquid NMR, mechanical bend, drop ball impact, and microhardness. Preliminary fractographic images were taken of both defective samples at cracked locations and functioning sample bulk material. The defective receptacles exhibit lower thermal stability, increased crystallinity and lower glass transition temperature compared to the functioning receptacles, though compositional differences were not detected. Preliminary test results point to discrepancies in the injection molding process and possible moisture contamination leading to thermal degradation, and/or possible differences in starting resin quality/glass fiber loading. |