Crystalline forms of isotactic polypropylene

Wiley - Tập 75 Số 1 - Trang 134-158 - 1964
Alan Jones1, Jean M. Aizlewood1, D. R. Beckett1
1From the Imperial Chemical Industries Limited, Welwyn Garden City, Herts., England

Tóm tắt

AbstractThe X‐ray diffraction patterns of two crystalline forms of isotactic polypropylene, the β‐ and γ‐forms distinct from the α‐form described by NATTA1, have been recorded. The β‐form, previously observed only as single spherulites6 has now been obtained in a well crystalline polymer, practically free of α‐form. The γ‐form is obtained, free of α‐form, in stereoblock fractions taken over the range 35–70°C. from normal commercial polypropylenes; the γ‐form is formed after cooling from the melt. The conditions for the production of the two forms and their melting behaviour, have been investigated by X‐rays.Oriented fibres were not obtained in either form as conversion to α‐form took place on drawing. Both forms have a ternary helical chain configuration. The derivation of the unit cells of the β‐ and γ‐forms from X‐ray photographs of unoriented specimens has been attempted and speculations have been made as to the packing of the helices in both forms. There are at least six and possibly twelve helical chains in the pseudohexagonal unit cell of the β‐form; the unit cell of the γ‐form is triclinic.

Từ khóa


Tài liệu tham khảo

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Thông tin
Thông tin xuất bản

Wiley

Tập 75 Số 1

134-158

Thông tin tác giả