AbstractWe have studied the mechanical moduli of oriented linear polyethylene with crystallinitiesXvarying from 0.44 to 0.63 and draw ratios λ = 1–9 by using a dynamic tensile method at 10 Hz and an ultrasonic technique at 10 MHz. Wide‐angle X‐ray diffraction and birefringence measurements reveal that the chains in the crystalline regions are fully aligned at λ>4, but the degree of amorphous orientation increases steadily up to the highest draw ratio. From −180°C to the β relaxation region (near 0°C at 10 Hz) the mechanical behavior at all crystallinities is controlled by three factors: molecular orientation, weak c‐shear deformation and stiffening effect of taut tie molecules. At low temperature the chain alignment in an oriented sample gives rise to an axial Young's modulusE0which is much larger than the transverse Young's modulusE90, with the modulus for the undrawn material lying in‐between. However, the results thatE45展开▼
