Wall detachment and high rate surface defects during extrusion of clay

Kulikov, O. L.; Hornung, Klaus

doi:10.1016/s0377-0257(02)00145-3

Cited by 14 publications

(6 citation statements)

References 7 publications

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“…areas with some gap between the die wall and the polymer flow. Such wall detachments have been observed earlier for the case of clay mixtures [24]. Microscope images of the die near its exit are presented in Fig.…”

Section: Glass Diessupporting

confidence: 80%

A simple way to suppress surface defects in the processing of polyethylene

Kulikov

Hornung

2004

Journal of Non-Newtonian Fluid Mechanics

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Section: Glass Diessupporting

confidence: 80%

A simple way to suppress surface defects in the processing of polyethylene

Kulikov

Hornung

2004

Journal of Non-Newtonian Fluid Mechanics

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“…from a leading edge of a glass lens to its trailing edge. Similar structures we observed during slip of clay [50] and molten LLDPE [46] in transparent dies. These waves of macroscopic detachment or ''surface cavitation'' propagate in the direction of melt flow.…”

Section: Mechanisms Of Lubrication and Sharkskin Eliminationsupporting

confidence: 83%

Low viscous hydrophilic processing additives for extrusion of polyethylene at reduced temperatures

Kulikov

Hornung

Wagner

2010

Polymer Engineering & Sci

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Industry is using fluorinated polymer processing additives (PPA) to delay the onset of sharkskin to higher rates of extrusion of PE resins. Yet it is necessary to keep elevated temperatures during extrusion to reduce apparent melt viscosity. We propose to use low viscous PPA made from reacting mixtures of polyethylene glycol with organic polyacids, phosphoric acid, and polyesters of oxiacids of Phosphorus. Surprisingly, extrusion pressures and apparent viscosity with the novel PPA at reduced temperatures are less, than at elevated temperatures. In total, extrusion pressures can be reduced 2-5 times for concentrations of PPA from 0.1 to 0.5 wt%, while sharkskin melt fracture can be eliminated for concentrations of PPA above 0.02 wt%. Extrusion with the novel PPA at reduced temperatures potentially increases productivity, reduces production cost, and allows processing of PE resins of higher MW and highly filled polymer composites.The use of novel PPA is a challenging opportunity to simplify processing of PO resins. The use of low viscous PEG in the composition of PPA with existing machinery has to be combined with changes in the die design for film blowing, blow molding, and pipe extrusion to extract

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“…self-healing shear cracks) along the boundary. We observed quickly fluctuating voids during extrusion of a clay paste with slip inside a transparent die [37]. From this, we might consider the traveling voids of detachment as a plausible mechanism of the slip for polymer melts.…”

Section: Tentative Explanation Of the Empirical Resultsmentioning

confidence: 73%

Novel processing aid based on modified Silly Putty®

Kulikov¹,

Hornung²

2006

Vinyl Additive Technology

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A viscoelastic material based on low-molecular-weight silanols cured by boric acid, i.e., having a composition similar to that of the well-known Silly Putty®, was used to delay sharkskin and stick-slip instabilities in the extrusion of linear low-density polyethylene (LLDPE). The use of sodium hydroxide and phosphoric acid in the composition helped to improve adhesion of the material to metal and to extend its efficiency above 200°C. Adding powders of metal oxides, e.g., borax, silica, and especially silicates, further helped to delay the flow instabilities. A delay of the sharkskin instability to 25-35 times higher extrusion rates was achieved, and about 45% less pressure was observed in a screw extruder at the same throughput when this material was used as an additive to LLDPE (ϳ0.1%) or as a coating of the extrusion die. Tentative explanations of the sharkskin origin and for the delay of the instability are proposed. J. VINYL ADDIT. TECHNOL., 12:131-142, 2006.

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Wall detachment and high rate surface defects during extrusion of clay

Cited by 14 publications

References 7 publications

A simple way to suppress surface defects in the processing of polyethylene

A simple way to suppress surface defects in the processing of polyethylene

Low viscous hydrophilic processing additives for extrusion of polyethylene at reduced temperatures

Novel processing aid based on modified Silly Putty®

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