Investigations of the processing-structure-property relationships of isotactic poly(4-methyl-1-pentene) tubular extruded films

An investigation was undertaken of the processing-structure-property relationships of two linear poly(4-methyl-1-pentene) resins (PMP) which differed in molecular weight (Mw). This was done by characterizing tubular films (BUR = 1) extruded at two processing conditions, with specific attention being focused upon the morphological results and the crystal orientation as a function of Mw. Carreau-Yasuda analysis of oscillatory shear data was utilized to evaluate the melt-flow behavior of the two resins. Atomic force microscopy and wide-angle X-ray scattering were utilized to the study the morphology of the final films, which was shown to be a stacked lamellar structure for both resins. The Mw and melt-extrusion conditions affected the orientation state and the nature of the stacking, planar or twisted. It was concluded that both extrusion stress and the relaxation behavior of the polymer melt are critical in determining the orientation/structural features of the extruded PMP films.