Search Results

Both pellet raw material and resulting extruded insulation samples were obtained from three grades of PVC used to produce automotive insulation and were examined for thermal stability on a Thermogravimetric Analyzer (TGA). The Flynn Wall technique was used to obtain degradation activation energies by plotting ln(heating rate) vs 1/T and using a literature value of 7% weight loss as the point of performance failure. The Arrhenius relationship was used to predict multiple year lifetimes at 100°C from the multiple hour degradation times observed on the TGA at 200°C. The insulation specimens of two of the samples were found to be significantly less thermally stable than the pellets - indicating slight decomposition occurred during extrusion onto the cable core. All cable insulation samples predicted service lifetimes many times the expected auto life. A PVC insulation sample was examined for failure at various oven aging temperatures using ASTM D3032 mandrel wrap testing.

Samples of 33% glass filled and unfilled poly(butylene terephthalate) [PBT] and nylon 66 (PA66) were injection molded into bars,which were immersed in common engine and powertrain fluids: antifreeze, motor oil and automatic transmission fluid for 25 days. Fluid uptake was measured at 1, 7, 18, and 25 days by gravimetry. Both PBT samples absorbed 0.2-0.25% antifreeze and 0.05 - 0.10% motor oil and automatic transmission fluid (ATF). Both DSC and DMA analysis showed no disruption of polymer thermal transitions or storage moduli. The glass filled PA66 sample absorbed 2.5% antifreeze and 0.25-0.3% of motor oil and ATF and showed an 80°C reduction in the tan delta maximum on DMA. The unfilled PA66 sample absorbed 7% antifreeze and 0.2-0.3% of motor oil and ATF also showed a tan delta maximum 80°C less than the unexposed control. Creep analysis was conducted on the unfilled nylon sample and compared to a virgin material.

Poly(butylene terephthalate) stock with 0, 15, and 30% glass fiber filler, used in the housings of electrical connectors on hybrid and electric vehicles, was examined by creep and stress relaxation for viscous deformation and modulus loss at 25, 75, 125, and 150°C. Sets of virgin and aged samples were examined within each set then compared to each other. Both the virgin and aged samples showed little viscous deformation or modulus reduction at 25°C, which was below the Tg of 40°C. Thermoplastic creep and stress relaxation was observed at the temperatures above Tg with, expectedly, more sample distortion and stiffness loss observed at higher test temperatures and lower filler contents both in virgin and unaged samples. Aged samples became stiffer, and more resistant to irrecoverable strain and stress relaxation than virgin samples indicating connectors to have a “self-healing” aspect through in-service use at elevated temperatures.

Twenty plies of low density polyethylene (LDPE) were stacked and irradiated with 200 kGy of 5 MeV electron beam. The plies were analyzed by Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA) for crosslink density using melting point depression and equilibrium storage modulus respectively. Infra-red spectroscopic analysis was conducted to examine the samples for the presence of chemical modification. The thermal stability of the irradiated samples and an unexposed control was investigated using Thermogravimetric Analysis (TGA). Results were utilized in assessing the viability of crosslinking products after the molding process to produce articles with improved resistance to temperature.