Development of Highly Oriented Polymers with Improved Mechanical Properties
Final rept. Jun 1973-Jun 1975
AKRON UNIV OH INST OF POLYMER SCIENCE
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Highly oriented crystalline polymer films were prepared in several different ways. Mechanical properties of the film were examined experimentally and related to the theoretical expectations of strengths and moduli. The first general method adopted for producing oriented polymer films involves the crystallization of polyethylenes in dilute solutions under shear. The data indicate a trend towards greater orientation with increased shear rate however, the films lack good physical integrity. Consequently the mechanical properties are low compared to theoretical expectations. The second general method adopted involves the simultaneous application of a shear field and high pressure on dilute solutions of polyethylene in a top-stirred high pressure reactor kept at constant stirring rates. The pressure varied from atmospheric to 400 C psi, and the stirring rate ranged from 110 to 380 rpm. The films had greater physical integrity than in the first method, but the dependence of the mechanical properties on the pressure and stirring rate is not clear. A third general method of obtaining highly oriented polymer film uses a very rigid polymer backbone structure. Semi-rigid cellulosic polymers and very stiff poly-n-alkyl isocyanate and poly- -benzyl L-glutanate films are described. The films are prepared using both ultra-thin film casting and melt extrusion. The orientation of these very stiff chains, particularly poly-n-hexyl isocyanate, is found to be extremely high. Only small amounts of these polymers are available. However, the high crystallite orientation of these polymers suggests that they are more likely to produce desirable mechanical properties.