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Digitale Medien

Designing high-modulus polyethylene with lamellar structures (1984)

Odell, J. A. ; Keller, A. ; Miles, M. J.

Springer

Colloid & polymer science 262 (1984), S. 683-690

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Details

ISSN: 1435-1536

Schlagwort(e): High-modulus ; polyethylene ; shish-kebab ; melt extrusion ; self-stiffening

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie , Maschinenbau

Notizen: Abstract In a preceding work we described a method whereby ultra high modulus filaments of polyethylene of essentially lamellar structure could be produced from the melt by a combination of capillary flow and pressure quenching [1]. Here the lamellae are nucleated by flow induced fibrous crystals formed during the extrusion but present in too small amounts to influence the properties themselves. Yet these microfibrils ensure the particular parallel and mutually interlocking arrangement of lamellae which is the source of the ultra high modulus. In the present work we set out to engineer this interlocking parallel lamellar morphology by utilizing preexisting fibrous crystals, as opposed to relying on their coincidental formation during the extrusion. By a judicious choice of the initial starting material and heat treatment conditions our objective was achieved, illustrating that lamellar self-composites with desirable properties can be achieved by planned design of the micro-morphology. As an additional feature these samples displayed ageing effects which have led to improved properties. Analogous phenomena, termed ‘self stiffening’ have been observed previously in drawn fibre products [8]. The presently arising example has now allowed its morphological origin to be identified: this is the delayed crystallization by which the interlocking lamellae fill in the residual interstices, the stage at which the corresponding sample acquires its final modulus.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01451539

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Digitale Medien

The deep drawing of thermoplastics (1977)

Miles, M. J. ; Mills, N. J.

Stamford, Conn. [u.a.] : Wiley-Blackwell

Polymer Engineering and Science 17 (1977), S. 101-110

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ISSN: 0032-3888

Schlagwort(e): Chemistry ; Chemical Engineering

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Maschinenbau , Physik

Notizen: The theory of deep drawing, which has been developed for metals, is examined critically for thermoplastics. Two special characteristics of thermoplastics, the strong orientation hardening after initial yielding and the ease of crack formation and growth, are shown to vitiate the usual correlation between the drawability of the sheet and the low strain plastic behavior of the material. Attempts to improve the limiting draw ratio of thermoplastics, by biaxially rolling sheet prior to forming, are shown to be effective only if the polymer does not craze easily under tensile stresses.

Zusätzliches Material: 16 Ill.