Microdomain structure and chain orientation in polypropylene/polyethylene blends investigated by micro-Raman confocal imaging spectroscopy

Compositional domain structure of blends of isotactic polypropylene with linear polyethylene and chain orientation of neat polymers and of the blends were assessed by micro-Raman confocal imaging spectroscopy and FT Raman spectroscopy. The results were correlated with polarised photoacoustic FTIR and with DSC. The surface and inner parts of compression-moulded, injection-moulded and drawn specimens were compared. Polymer domains in the blends and domains of different orientation were identified. The larger size of the polymer domains and lower chain orientation in the core of the specimens prepared by injection-moulding were explained by different cooling conditions of the melt. Possibilities and limitations of the micro-Raman confocal spectroscopy method were discussed.