ポリプロピレンの延伸配向機構と力学的性質との関連性に関する研究

第1報逐次溶媒抽出によるポリプロピレンの分別とフラクションの抑制

抄録

Atactic and isotactic polypropylenes were fractionated by means of successive solvent extraction method using saturated hydrocarbons at their boiling point. Physical properties of each fraction were evaluated in terms of isotacticity, viscosity average molecular weight, density, melting point, tensile stress-strain curve, infrared spectrum, x-ray diffraction and tensile storage and loss moduli.
The tacticity of lower temperature fractions increases with extracting temperature, while the viscosity average molecular weight stays almost constant.
The stereoregularity of each fraction was estimated qualitatively by using Fiory-Coleman's theory on sequence propagation probability and isotacticity, and it is concluded that each fraction is of block polymer nature composing of isotactic and atactic sequences.
The drastic change of tensile storage modulus was observed at about 70% crystallinity and is explained in term of Fujino's theory of simple mechanical mixture of island-matrix mixing. It is concluded that the change could be explained in term of phase conversion from crystalline islands in amorphous matrix to amorphous islands in crystalline matrix due to hexagonal close-packing of crystalline phase at about 70% crystallsinity.
Tensile stress-strain bahavior of each fraction shows that the higher tho isotacticity the larger the yield stress, initial tensile modulus add ultimate energy resistance, even if the viscosity average molecular weight bo same.