MORPHOLOGICAL-CHANGES IN ANNEALED ULTRAHIGH MOLECULAR-WEIGHT POLYETHYLENE (UHMWPE) GEL-FILMS

X-ray diffraction of the UHMWPE gel-films has shown that high heating rate annealing of the films causes deformation of the crystallites. Th e apparent crystal sizes change with the annealing temperature (T-a). With T-a below 110 degrees C, the dimensions of the crystallites in c- axis (L(c)) increase associated with the decreasing in a-axis (L(a)) a nd b-axis (L(b)), but the changes are small because of the higher ener gy barrier. When T-a is raised to 138 degrees C, L(c) is nearly double d its value at 60 degrees C whereas L(b) increases and L(a) remains un changed. IR spectral subtraction was applied to reveal the morphologic al changes of the gel-films upon annealing. It has been found that ban ds of the same type of conformation have different sensitivities subje ct to the thermal treatment at different annealing temperatures. The r esults can be understood by assuming the changing process being comple ted through chain segments sliding along the (020) sectors. (C) 1995 J ohn Wiley and Sons, Inc.