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The advent of high speed spinning of PET fibers has brought on a higher degree of "frozen-in" orientation in quenched amorphous fibers. Since these fibers are amorphous by x ray, birefringence measurements have constituted, until recently, the only independent characterization method for determining the frozen-in orientation. The amorphous orientation function is then calculated from the well-known equation'

N e w polymers with properties ranging from elastomers to rigids are suitable for high temperature applications. Blends of chlorinated polyethylenes are also evaluated for compatibility. orinated polyethylene is one of the few examples chemical substitution reaction on the backbone chain of the original polymer. The transformation is even more striking because by starting from one specific linear polyethylene a whole new series of polymers results whose properties depend on the degree and randomness of chlorine substitution. The new polymers range in propertics from elastomers to rigids with high glass transition temperatures suitable for high temperature applications. Furthermore, for the same degree of substitution, the polymers can be made to vary in degree of crystallinity allowing further control over mechanical properties. In the present article the broad range of mechanical properties available in this polymer system and the relationships of the properties to the degree of substitution will be discussed. Structure of Chlorinated Polyethylene

An experimental procedure is outlined to examine the potential of thermoplastic sheets in draw forming. Experiments carried out on a variety of materials indicate that the following requirements must be fulfilled for a thermoplastic sheet to be cold formable: (1) The glass transition of polymer should be above ambient temperature and above the temperature of forming, (2) tensile elongation at break should equal or exceed 30%, (3) ratio of tensile to compressive yield stress should equal or exceed 1.6 and (4) sheet must not yield locally (neck) when strained in tension. An experimental method has been developed to determine the compressive, friction and bending forces which oppose the drawing force exerted by the punch. It is shown that the compressive force is, in most cases, largest. A stress analysis is carried out leading to an expression correlating the maximum depth of draw as a function of basic properties of sheets such as tensile strength (St*) and compressive yield stress (Sc). The effect of rolling on drawability is examined and interpreted in terms of the ratio St*/Sc. The cold formed items have a lower heat distortion temperature than their thermoformed counterparts.