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

A study of the mechanical properties in an accelerated service-related environment of recycled glass-fiber-reinforced polyamide 66 is report ed. 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 showe d no significant differences in behavior pattern. In addition to mecha nical testing, the fiber length measured directly and the matrix stabi lity measured by differential scanning calorimetry (DSC) were used to determine the influence of process-induced degradation on the durabili ty of recycled samples compared with that of virgin samples. The resul ts indicate that fiber length controls the initial properties. The dif ferences in tensile strength and modulus between recycled and virgin s amples were similar within the examined times of aging and could be ex plained by process-induced fiber shortening. The onset of embrittlemen t during both aging conditions is revealed first in a decrease in tens ile elongation at break. Because of a lower degree of fiber reinforcem ent, the elongation at break of recycled samples was always as good as that of virgin reference samples. However, increasing the number of m olding operations up to four to five times resulted in a faster deteri oration rate in elongation at break of recycled samples. Further proce ssing had less effect on the deterioration rate. The oxidative stabili ty of the matrix as determined by USC decreased as a result of repeate d processing. The results suggest that matrix stability is related to changes occurring in elongation at break during accelerated aging of s amples remolded. up to about four times. (C) 1997 John Wiley & Sons, I nc.