Effects of shearing conditions on crystalline orientation and relaxation in polyethylene

The effects of shearing conditions (i.e., shear temperature and shear rate) on the degree of orientation of polyethylene (Marlex 6006) and to what extent the induced orientation could be relaxed were examined in this study. Two types of samples were prepared: namely, SIC (shear‐induced crystallization) and non‐SIC samples. The SIC samples show induction times and possess a high degree of c ‐axis orientation along the shear direction. The induced orientation of SIC samples can be relaxed to a small extent but does not reach a steady value. Non‐SIC samples do not show induction times and they show low degrees of c ‐axis orientation. The induced orientation of non‐SIC samples can be relaxed to a steady state value with an activation energy of 90 kJ/mole. Our results also indicate that, when the shear temperature is at and above 145°C, polyethylene can be sheared up to 200X without introducing any significant molecular orientation even at very high shear rates.