Summary
The work reported in this memo is the initial stages of an investigation
of the time-dependent behaviour of certain anisotropic polymers. In the
first instance low density polyethylene with a transversely isotropic
symmetry is being examined. Different degrees of anisotropy have been
induced by cold drawing and the time dependent material parameters
necessary to describe the stiffness of the anisotropic polyethylene have
been determined. This involved the measurement of uniaxial tensile
creep: lateral contraction creep, and torsional creep under conditions
of constant load at 20°C ± 0.5°C.
The tensile creep and contraction creep apparatus has been described
elsewhere (Darlington (a) 1968) and only the principle of the apparatus
is discussed here. The torsional creep apparatus is described in detail.
Analysis of the experimental data is not yet complete. The data is
tabulated in section 5 and a preliminary analysis is presented in section G.
Details of proposed future work are discussed in section 7
