DURABILITY STUDY OF RECYCLED GLASS-FIBER-REINFORCED POLYAMIDE 66 IN A SERVICE-RELATED ENVIRONMENT

摘要

A study of the mechanical properties in an accelerated service-related environment of recycled glass-fiber-reinforced polyamide 66 is reported. Material reinforced with 30 wt % of short fibers was reground and remolded up to seven times. Thermal aging in air at 140 degrees C for up to 3000 h and coolant aging at 100 degrees C for up to 1000 h showed no significant differences in behavior pattern. In addition to mechanical testing, the fiber length measured directly and the matrix stability measured by differential scanning calorimetry (DSC) were used to determine the influence of process-induced degradation on the durability of recycled samples compared with that of virgin samples. The results indicate that fiber length controls the initial properties. The differences in tensile strength and modulus between recycled and virgin samples were similar within the examined times of aging and could be explained by process-induced fiber shortening. The onset of embrittlement during both aging conditions is revealed first in a decrease in tensile elongation at break. Because of a lower degree of fiber reinforcement, the elongation at break of recycled samples was always as good as that of virgin reference samples. However, increasing the number of molding operations up to four to five times resulted in a faster deterioration rate in elongation at break of recycled samples. Further processing had less effect on the deterioration rate. The oxidative stability of the matrix as determined by USC decreased as a result of repeated processing. The results suggest that matrix stability is related to changes occurring in elongation at break during accelerated aging of samples remolded. up to about four times. (C) 1997 John Wiley & Sons, Inc. [References: 30]