Effect of temperature on the structure of highly polymerized hydrocarbons

An investigation into the effect of temperature on the structure of polyethylene (polythene) is made over a range extending from the temperature of liquid oxygen to temperatures at which polythene exists in the liquid condition The following main conclusions emerge. As with much lower polymers, the ratio a/b of the two axes increases with temperature, and tends to the value for a pseudo-hexagonal structure, but this value is never attained, since fusion sets in first. A change from a crystalline to an amorphous pattern occurs at temperatures which are below those generally taken as the melting point, but which agree with that for which polythene transforms from a wax-like to a more transparent solid. The transition of structure extends over a number of degrees and in this interval crystalline and amorphous patterns are superimposed Orientation present in crystalline films is retained when the films are heated to temperatures well above the melting point, and subsequently cooled. A preliminary discussion is made on some of the points raised by the observations