A study of the phase behaviour of polyethylene blends using micro-Raman imaging

The origin of morphological phase structures in blends of a linear deuterat ed polyethylene and a hydrogenous branched polyethylene has been investigat ed using Raman imaging. Blends were crystallized to produce samples with la rge domains that are rich in linear material surrounded by a matrix that is rich in blanched polymer. The samples were then remelted for a range of ho lding times and quenched to examine the rt mixing of the separated domains in the melt. The micro-Raman images show that the samples remixed to a homo geneous distribution by branch content within the expected time scale, as e stimated from the diffusion constants. However, micro-Raman imaging was als o used to detect crystallinity variations and it reveals a biphasic structu re in quenched blends that display a morphological phase structure when exa mined in the transmission electron microscope. Raman images of the same sam ples are uniform when constructed by branch content. Possible causes for th is phenomenon are briefly discussed. (C) 2000 Elsevier Science Ltd. All rig hts reserved.