For the grade of a polymer whose creep curves are given in Figure 1, confirm that the strain may be predicted by a relation of the form &t) = At" where A and n are constants for any particular stress level. A small component made from this material is subjected to a constant stress of 2.3 MN/m for 30 days at which time the stress is completely removed. Estimate the strain in the material after a further 30 days. Creep curves for a polymer at 45C 12 11 9 8 7 6 5 10 3.0 2 3 2.5 4 5 2.0 3 6 7 Strain (%) 1.5 8 N 2 9 1.0 10 0.5 11 12 0.0 1.00E+03 1.00E+04 1.00E+07 1.00E+08 1.00E+05 1.00E+06 Time (s) Figure 1: Creep curves for polypropylene at 45C