Temperature dependence of the elastic modulus of crystalline regions of isotactic poly(4-methyl-1-pentene)

Abstract

Abstract The elastic modulus E 1 of crystalline regions of isotactic poly(4-methyl-1-pentene) (P4M1P) in the direction parallel to the chain axis and its temperature dependence were investigated by x-ray diffraction. E 1 values for the (001) and (007) planes of P4M1P agreed well at 4.1 GPa at room temperature. This small E value could be attributed both to the contracted helical conformation (7/2 helix) and to a large cross-sectional area of P4M1P in the crystalline regions. Though the lattice distortion of the first kind increased and partial destruction of crystallites occurred with increasing stress, the stress-strain curve for the crystal lattice was linear up to 80 MPa. However, the E1 value remained unchanged up to 150°C. The lattice spacing for the (007) plane increased monotonously with increasing temperature, with a thermal expansion coefficient of 0.9 × 10−4 K−1. These phenomena were in contrast with the temperature dependence of E 1 values of various polymers previously reported, in which E 1 d...