Summary: Nascent form of random copolymers of propylene with ethylene, 1-butene, 1-hexene, 1-octene, and 4-methyl-1-pentene was studied by Raman spectroscopy. The most significant spectral alterations with a change in propylene content were observed in two lines at 809 and 841 cm À1. The first line corresponds to vibrations of polypropylene helical chains in the crystalline phase, while the second one is associated with vibrations of polypropylene helical chains having isomeric defects. Raman data confirm that conformational composition and phase state of copolymer macromolecules strongly depend on the comonomer content as well as on the size of the comonomer units.

No abstract

Polypropylene (PP) is one of the most important polymeric materials. At present, this plastic is second only to polyethylene in world volume of consumption [1]. Isotactic polypropylene (IPP) is used in the building industry, in the motor industry, in the aircraft industry, in agriculture, in the textiles industry, in medicine, and so on. There are now about 80 different grades of PP.

We report a Raman structural study of melt-mixed blends of isotactic polypropylene with two grades of polyethylene: linear high-density and branched low-density polyethylenes. Raman methods, which had been suggested for the analysis of neat polyethylene and isotactic polypropylene, were modified in this study for quantitative analysis of polyethylene/ polypropylene blends. We revealed the dependence of the degree of crystallinity and conformational composition of macromolecules in the blends on relative content of the blend components and preparation conditions (quenching or annealing). We suggested a simple Raman method for evaluation of the relative content of the components in polyethylene/ polypropylene blends. The degree of crystallinity of our samples, evaluated by Raman spectroscopy, is in good agreement with the results of analysis by differential scanning calorimetry.