Thermodeformation effects at the initial stages of orientation of polyethylene

Temperature changes during repeated loading-unloading cycles were studied a t the initial stages of LDPE orientation. It was shown that the degree of o rientation increases by increasing the number of cycles. The strong effect of the initial stage of orientation on the "solidlike" cooling phenomenon o bserved upon tension of LDPE was revealed and analyzed. Taking into account the value of residual heating, the mechanism of inner friction upon plasti c shears was found to play an important role in the above phenomenon. The r esults of thermal studies are compared with the corresponding data on the s tructural changes in LDPE and the stress-strain recovery curves.