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L.A. Rishina, E.I. Vizen, L.S. Shibryaeva, L.N. Sosnovskaya, A.J. Veretennikova, T.A. Lodygina, A.B. Gilman



The modification of polypropylene structure by low-frequency glow discharge (in English)

Polimery 1998, No 1, 34


DOI: dx.doi.org/10.14314/polimery.1998.034


Summary

PP prepared (a) over a δ-TiCl3—AlEt2Cl heterogeneous catalytic system in the presence of hydrogen and (b) rac-Et(Ind)2ZrCl2—methylalumoxane homogeneous system, was modified by low-frequency glow discharges in air. Functional groups containing oxygen were found to appear in a thin surface layer. Under some conditions changes of the whole structure of PP were determined, evident in a great increase in the molecular mass (M) and melting temperature (Tm). The structural modification is especially considerable for the PP synthesized with the metallocene system b. M rose by a factor of ~10, the melting temperature rose from 130°C to 164°C, stereoregularity parameters enhanced and the fractional composition changed. The boiling ≪-heptane-soluble fraction increased from 7 to 96% (PP became highly isotactic). The crystalline structure of this PP was found to consist of the α- and the γ-modifications, the latter passing into the former when exposed to plasma. The UV-component of the plasma is believed to be responsible for the modifications observed.


Keywords: PP, modification by low-frequency glow discharge, stereoregularity, crystal structure


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