Various properties of a series of uni-and biaxially oriented polypropylene film have been determined in seven different laboratories participating in a collaborative IUPAC Working Party programme. Small strain (visco-) elastic properties, viz. Young's modulus, sonic modulus, dynamic storage and loss compliances, were found to be mainly dependent on molecular orientation in the non-crystalline phase and may be described, in a first approximation, with the aid of a simple two-phase "lower bound" model. The highly non-linear behaviour observed at larger strains, characterised by yielding and/or ultimate rupture, was also found to be strongly dependent on the initial state and degree of molecular orientation but it was, in general, not possible to conclude definitely about respective contributions from crystalline and non-crystalline phases. Characteristic differences in the structure of uni-and biaxially oriented films, reported in Part 1, were also revealed by technologically important properties such as impact resistance, tear strength, thermal shrinkage, gas permeability, etc. I •
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