Preparation of ultrahigh modulus isotactic polypropylene by means of zone drawing

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Abstract
Highly oriented isotactic polypropylene with ultrahigh modulus was prepared by means of the zone drawing method proposed by Kiho and Asai. This method features heating a limited portion of the sample. The maximum value of modulus attained was 15 GPa, which corresponds to about half the crystal modulus along the molecular axis evaluated by the x‐ray method. Such an ultrahigh modulus was obtained for a sample of medium molecular weight by inducing necking in the heater and subsequently cooling the sample at lower temperature. The loss tangent peak with the initiation of micro‐Brownian motion of amorphous chains became progressively smaller and broadened more at higher temperatures with increasing draw ratio. Orientation function of the crystal c‐axis increased with draw ratio λ in the region below λ = 9, but reached a constant value, 0.995, in the region above λ = 9. The modulus increased with draw ratio in all ranges of the draw ratio.

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