Flow instability in capillary extrusion of plasticized poly(vinyl chloride)

Yamaguchi, Masayuki

doi:10.1002/app.1961

Cited by 20 publications

(10 citation statements)

References 23 publications

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“…4 and Table 2, which allows us to find resemblances between the rheological response of our triblock copolymers and the well-studied extrusion rheology of PVC samples. It is known [34][35][36][37][38][39] that PVC behaves rather like a filled polymer, owed to the systematic presence of crystallites at the test temperatures. A significant difference, in favor of the copolymers, is that, owing to the viscosity reduction associated with the copolymerization with PBA, temperatures considerably lower than with PVC can be used in capillary extrusion experiments.…”

Section: Resultsmentioning

confidence: 99%

The effect of crystallites on the rheological properties of microphase‐separated PVC‐PBA‐PVC triblock copolymers obtained by single electron transfer‐degenerative chain transfer living radical polymerization

Calafel

Muñoz

Santamarı́a

et al. 2014

Vinyl Additive Technology

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Linear and nonlinear rheological properties of poly(vinyl chloride) (PVC)-poly(n-butyl acrylate)-PVC triblocks of different compositions, obtained by single electron transfer-degenerative chain transfer living radical polymerization, are investigated, focusing on the effect of crystallites. Dynamic mechanical thermal analysis results show the existence of two glass transition temperatures, denoting microphase segregation. However, rather than phase separation, it is the presence of two types of crystals that melt at T m1 5 127 6 0.8 C and T m2 5 185 6 2 C, respectively, the factor that determines the rheological response of the copolymers. To the difference with PVC homopolymers, extrusion flow measurements at very low temperatures (T 5 100 C) are possible with the copolymers. A change in the viscositytemperature dependence is observed below and above the lowest melting temperature. Notwithstanding the microphase separation and the presence of crystallites, experiments carried out in conditions similar to industrial processing reveal a remarkable viscosity reduction for our copolymers with respect to PVC obtained by single electron transfer-degenerative chain transfer living radical polymerization, conventional PVC, and PVC/ [diethyl-(2-ethylhexyl)

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Section: Resultsmentioning

confidence: 99%

The effect of crystallites on the rheological properties of microphase‐separated PVC‐PBA‐PVC triblock copolymers obtained by single electron transfer‐degenerative chain transfer living radical polymerization

Calafel

Muñoz

Santamarı́a

et al. 2014

Vinyl Additive Technology

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“…The onset of gross melt fracture, originating at the capillary entrance, is attributed to the marked melt elasticity, 11,12 which is also responsible for the high level of drawdown force. Surface minute irregularity, so-called shark-skin failure, however, still appears on the strand extrudated by type (a) configuration.…”

Section: Processing By Continuous Twin-screw Extrudermentioning

confidence: 99%

“…Figure 6 shows the strands obtained at the third extrusion at 151 • C. It is obvious that the strand processed by kneading blocks exhibits gross volumetric melt fracture, whereas that obtained by conveying screws does not. The onset of gross melt fracture, originating at the capillary entrance, is attributed to the marked melt elasticity, 11,12 which is also responsible for the high level of drawdown force. Surface minute irregularity, so-called shark-skin failure, however, still appears on the strand extrudated by type (a) configuration.…”

Section: Processing By Continuous Twin-screw Extrudermentioning

confidence: 99%

Rheological properties of LDPE processed by conventional processing machines

2003

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ABSTRACT:The impact of applied processing history and the postprocessing annealing on the rheological properties of low-density polyethylene (LDPE) have been studied employing various kinds of conventional processing machines. Processing by a corotating twin-screw extruder (Co-TSE) and an internal batch mixer depressed the drawdown force, one of the elastic properties of a melt, to a great extent, even though molecular weight and the polydispersity did not change. On the other hand, the sample processed by a two-roll mill exhibited the drawdown force as high as the original pellets, which is owing to the intermittent stress history instead of the relentless one in the Co-TSE and the internal batch mixer. Furthermore, the effect of screw configuration in the Co-TSE has also been investigated. It was found that the processing by conveying screws depressed the drawdown force and melt fracture more than that by kneading blocks as long as the torque and the residence time are the same. The large, abrupt, and frequent RHEOLOGICAL PROPERTIES OF LDPE PROCESSED BY CONVENTIONAL PROCESSING MACHINESchange in flow direction in the Co-TSE with kneading blocks prohibits the molecular orientation, which leads to disentanglement associated with long-chain branches.

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“…Since it is generally accepted that a high viscous polymer melt slips on the wall, the slippage can be the origin of surface instability [35,43,44]. Gross melt fracture is attributed to the flow instability at a die entrance, and associated with long time relaxation mechanism [38,[45][46][47][48][49][50][51]. Yamaguchi et al found that gross melt fracture of LDPE can be avoided by applying intense shear history, which weakens the relaxation mechanism associated with long-chain branches, by shear modification [51].…”

Section: Introductionmentioning

confidence: 99%