Influence of repeated processing on the change in properties of polypropylene

Zámorský, Z.; Muras, J.

doi:10.1016/0141-3910(86)90020-0

Cited by 10 publications

(4 citation statements)

References 5 publications

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“…As opposed to degradation mechanisms such as chain scission, oxidation, or cross-linking due to formation of free radicals leading to quite different changes in the viscoelastic behavior (28,29) and to changes in molecular weight distribution (30)(31)(32)(33), shear modification implies only physical changes in the interactions of the polymer chains to one another and, consequently, the molecular weights and their distribution should not be altered. The initial, highly entangled structure of the polymer network and, hence, initial material behavior can be recovered by special treatment of the shear-worked materials.…”

Section: Introductionmentioning

confidence: 99%

Effect of shear modification on the rheological behavior of two low‐density polyethylene (LDPE) grades

Ritzau

Ram

Izrailov

1989

Polymer Engineering & Sci

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Shear modification treatment represents a special shearing history affecting mainly the elastic behavior of polymer melts. This process has been attributed to reversible physical changes in the entanglement structure of the polymer chain network. Shear modification studies were performed for two well-characterized low-density polyethylene (LDPE) grades differing in molecular weight distribution and degree of long chain branching. The shear working of the material was carried out using a specially designed shearing unit producing definable amounts of pure shear in a continuous process. Measurements of the dynamic storage modulus, G ', steady-state shear compliance; J,, extrudate swell, melt flow index, and the extensional behavior (Rheotens test) indicate that primarily properties associated with the elasticity of the melt are reduced in value. The observed reduction is found to correlate with the mean specific energy dissipated during sample preparation. Comparing the two LDPE grades showed that higher degrees of modification can be obtained at lower energy input levels for the more highly branched grade. Reversibility tests were performed and complete recovery of the initial material behavior was observed. Comparison of measurement results for samples prepared using the shearing unit presented here and a Brabender Plasticorder indicates that the degree of modification depends not only on the molecular structure of the polymer but also on the manner in which the shearing history is imposed upon the material.

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Section: Introductionmentioning

confidence: 99%

Effect of shear modification on the rheological behavior of two low‐density polyethylene (LDPE) grades

Ritzau

Ram

Izrailov

1989

Polymer Engineering & Sci

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“…nature o f t h e chemistry has n o t been determined, b u t the r e s u l t i s d e f i n i t e improvements i n such p r o p e r t i e s as impact strength, f l e x u r a l modulus, and The p r e c i s e heat deflection." The above phenomena might also be related to results reported by Zamorsky and Muras (20) when PP was repeatedly extruded and the melt viscosity only decreased by 4.4%, while the carbonyl index during weathering was re1 atively unchanged.…”

Section: The Capsmentioning

confidence: 62%

A ten year review of plastics recycling

Howell

1992

Journal of Hazardous Materials

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“…It has been shown (14)(15)(16)(17) that the recycling process is always accompanied by thermo-oxidative and mechano-chemical degradation phenomena, which bring about a reduction of the average molecular mass of the material and a widening of the molecular mass distribution. These effects produce a general worsening of the mechanical performances of the material.…”

Section: Resultsmentioning

confidence: 99%

Recycling of Polypropylene Based Car Bumpers: Mechanical and Morphological Analysis

Ragosta

Musto

Russo

et al. 2003

Progress in Rubber, Plastics and Recycling Technology

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The recycling of new and ten years old bumpers either painted or unpainted have been investigated. They were made by a polypropylene matrix and an ethylene-propylene rubber copolymer as dispersed phase. Mechanical testing carried out before reprocessing showed a dramatic loss in the tensile and impact properties of aged bumpers with respect to the new items. The recycling further reduces the mechanical performances of these items while it has only a little effect on the properties of new bumpers. The addition of appropriate stabilising agents, during the recycling process of aged bumpers, produced an enhancement of the whole mechanical parameters. In particular the impact strength reached values typical of very tough materials and close to those of new items. Scanning electron microscopy of the fracture surfaces showed a considerable enhancement of matrix plasticity when stabilisers were used.

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Influence of repeated processing on the change in properties of polypropylene

Cited by 10 publications

References 5 publications

Effect of shear modification on the rheological behavior of two low‐density polyethylene (LDPE) grades

Effect of shear modification on the rheological behavior of two low‐density polyethylene (LDPE) grades

A ten year review of plastics recycling

Recycling of Polypropylene Based Car Bumpers: Mechanical and Morphological Analysis

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