Studies on the durability of plastics filled with filler reinforcements. IV. Unrecovered deformation due to cyclic creep in polypropylenes filled with talc and without talc

The unrecovered deformation due to cyclic creep under cycles from 30 s to 606 min and stresses from 10 to 110 kgf/cm exp 2 , for variable ratios of unloading time to loading time at 22-60 deg C, were investigated in polypropylenes filled with talc and without talc. The following results were obtained. (1) The unrecovered deformation of polypropylene was decreased about 30-70% by filling with talc in 20-30 wt.%. The variation of the unrecovered deformation with time was greatly affected by loading stress; above a critical stress of 50-60 dgf/cm exp 2 , the variation changed from linear to nonlinear. (2) The unrecovered deformation of polypropylene increased about three times as the cycle duration shortened to less than 1 min, and the difference of the unrecovered deformation between polypropylene filled with talc and that unfilled became smaller as the cycle duration was lengthened beyond 10 min. (3) As unloading time lengthened beyond 30 min, the unrecovered deformation decreased to less than 1 mm, and the differences of the unrecovered deformation between polypropylene filled with talc and that unfilled became smaller. The properties of creep recovery of polypropylene filled with talc were less than those for unfilled samples under some stress or at some temperature. 13 ref.--AA