The influence of supermolecular structure on linear polyethylene drawing

This study focuses on the structure, morphology, and properties of linear polyethylene (PE) profiles manufactured by continuous extrusion. High level of chain orientation was achieved using specific flow and processing conditions. An extrusion die with semihyperbolic convergency was used to generate high percentage of elongational flow and chain extension. Simultaneously, high extrusion pressure and relatively low melt temperature led to flow-induced crystallization of PE extended chains. The structure of PE tapes consists of crystal aggregates with different level of orientation and crystallinity.

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“…[1][2][3][4] Unfortunately, it cannot be used for large volume profiles. There are several orientation types and procedures.…”

Section: Introductionmentioning

confidence: 99%

Structure and morphology of linear polyethylene extrudates induced by elongational flow

Rybnikář

Kaszonyiova

Čermák

et al. 2012

J of Applied Polymer Sci

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Orientational crystallization and orientational drawing as strengthening methods for polyethylene

Elyashevich

Karpov

Rosova

et al. 1993

Polymer Engineering & Sci

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St. Petersburg 199004, Russia and V. A. MARIKHIN and L. P. MYASNIKOVA A. F. lo8e Physical Technical Institute Russian Academy of Sciences St. Petersburg 194021, RussiaThis paper reports on the theoretical and experimental studies of structure formation and strengthening (stiffening) of flexible-chain polymers. Two techniques of strengthening relying on the melt extrusion, i.e., orientational crystallization (crystallization initiated by melt extension) and drawing (uniaxial stretching of a crystallized polymer) are analyzed by theory. The experiments involved preparation and study of melt extruded films and film fibers of linear polyethylene formed by the two techniques mentioned above. The effect of the degree of orientation and other parameters of the formation processes on the mechanical characteristics and the factors limiting the ultimate values of these characteristics are discussed. It is shown that multistage drawing succeeds in achieving a higher tensile strength and elastic modulus (1.2 and 35 GPa, respectively) than the orientational crystallization, which gives 0.8 and 15 GPa. The strengthening by drawing is accompanied by microcrack formation. In contrast, no discontinuities are observed in orientationally crystallized samples up to their ultimate extension.

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Mechanochemical syntheses

Simionescu¹,

Oprea²,

Negulianu³

1978

J. polym. sci., C Polym. symp.

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In the present paper some main directions in mechanochemical synthesis are developed, based on the mechano‐destructive process induced under different conditions in homo‐ and heterochain solid polymers (polyethylene, cellulose and derivatives, polyesters and polyamides). The fact is known that the elastic energy conferred to crystalline amorphous polymers focuses on structural and composition defects distributed statistically, causing molecular ruptures of the homolytic type which generate nascent microcracks propagating and increasing within the solid leading finally to a fracture. The nascent microcrack represents in fact the existence within small volumes of a number of active macroradicals (or of a number of reactive functional groups after the stabilization of the destruction fragments) capable of reacting with appropriate chemical reagents existing in the working medium. On this basis became possible the initiation of graft polymerization, block copolymerization, polycondensation, and complexing reactions. The concentration of the elastic energy not on molecular underlayers but on metallic surfaces, even when these are the reaction vessel walls, leads to the formation of active centers of a particular type, capable of initiating homo‐ or copolymerization reactions.

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The influence of supermolecular structure on linear polyethylene drawing

Cited by 7 publications

References 1 publication

Structure and morphology of linear polyethylene extrudates induced by elongational flow

Structure and morphology of linear polyethylene extrudates induced by elongational flow

Orientational crystallization and orientational drawing as strengthening methods for polyethylene

Mechanochemical syntheses

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