The effect of teflon™ coatings in polyethylene capillary extrusion

Hatzikiriakos, Savvas G.; Hong, Peter; Ho, Wally; Stewart, Charles W.

doi:10.1002/app.1995.070550406

Cited by 62 publications

(65 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This mechanism is independent of the material constituting the walls. Experiments, however, indicate that in general, the onset of slip does depend on the wall composition (Ramamurthy 1986, HD, Denn 1992, Hatzikiriakos et al 1995. This work indicates that, at least in some cases, slip is a result of adhesive, rather than cohesive failure.…”

Section: Introductionmentioning

confidence: 77%

Wall slip and the nonlinear dynamics of large amplitude oscillatory shear flows

Graham¹

1995

Journal of Rheology

102

View full text Add to dashboard Cite

SynopsisLarge amplitude oscillatory shear flows of polymer melts between parallel plates may exhibit complicated nonperiodic responses characteristic of quasiperiodicity or chaos. This complex time dependence is related to the wall slip exhibited by these materials. We use simple models for the fluid elasticity and slip to theoretically and computationally study the nonlinear dynamics of melts in oscillatory shear. The results indicate that both fluid elasticity and a dynamic (e.g. memory-slip) model for the wall slip are necessary for nonperiodic dynamics to occur. Furthermore, when elasticity and a dynamic slip model are coupled, many qualitative features of the dynamics observed in the experiments can be reproduced. In particular, asymmetric periodic responses exhibiting even harmonics are found, as well as quasiperiodic and chaotic motions. Particularly interesting is the prediction of multiple stable periodic motions for a given set of parameters, depending on initial conditions. As a special case, the model reduces to the classical Duffing equation of nonlinear vibration theory. The existence of complex dynamics is robust with respect to changes in both the constitutive model chosen and the details of the wall slip model. 0 1995 Society of Rheology.

show abstract

Section: Introductionmentioning

confidence: 77%

Wall slip and the nonlinear dynamics of large amplitude oscillatory shear flows

Graham¹

1995

Journal of Rheology

102

View full text Add to dashboard Cite

show abstract

“…Such behavior has been observed previously in the capillary extrusion of LLDPE when a small amount of fluoropolymer is included as a processing aid. 20 The gradual decrease of the load in these experiments was associated with gradual coverage of the wall with the processing aid and the gradual increase of slippage of the polymer melt over fluoropolymer layer on the die wall surface.…”

Section: The Rheological Properties Of Mlldpe/bpa Blends With Varied mentioning

confidence: 78%

Effect of diatomite/polyethylene glycol binary processing aids on the rheology of a metallocene linear low‐density polyethylene

Liu

2004

J of Applied Polymer Sci

View full text Add to dashboard Cite

Flow performance of metallocene linear lowdensity polyethylene (mLLDPE) containing small amounts of polyethylene glycol (PEG) diatomite and diatomite/PEG binary processing aids respectively was investigated. The mLLDPE melt viscosity is increased by the addition of diatomite, but is decreased by addition of PEG or the diatomite/ PEG binary processing aids. It was also found that the viscosity reduction of mLLDPE with the addition of diatomite/PEG binary processing aid was significantly greater than that obtained with the addition of only PEG. The flow curves of mLLDPE containing diatomite/PEG binary processing aid show extremely lower value and stronger dependence on shear rate than the others. It is suggested that the rheological improvement of mLLDPE with diatomite/ PEG binary processing aids resulted not entirely from the wall slip promoted by PEG; the intrinsic structure may have changed under the application of shear flow.

show abstract

“…In the second case, the percentage of fiIl represents the fraction of the plate covered with flow marks. Conditions 1 and 2 (Dowlex 2 (49) clearly show that the wall shear stress, and even more so the wall shear rate, are higher in the ca<;e where fiow marks appear. The same conclusion can be drawn for Exxon 6706 (conditions 3 and 4)…”

Section: Critical Conditions For the Occurrence Of Flow Marksmentioning

confidence: 95%

The Occurrence of Flow Marks during Injection Molding of Linear Polyethylene

Heuzey

Dealy

Gao

et al. 1997

International Polymer Processing

View full text Add to dashboard Cite

Injection molded parts often show several types of surface defect. It has been hypothesized that wall slip is associated with some of these defects. Wall slip of molten plastics has been observed above a certain critical shear stress in rheological measurements. The objectives of the proposed research were to analyze the occurrence of flow marks during the injection molding of linear polyethylene and evaluate its possible relation to wall slip. Various variables were studied in terms of their influence on flow mark formation: mold thickness, mold temperature, melt temperature, gate, injection speed and TeflonTM and silicone oil coatings. It was found that injection speed is the controlling factor for the generation of flow marks during injection molding of the linear polyethylenes studied. Since one of the resin studied had shown no tendency to slip in capillary flow experiments, and since a Teflon TM coating on the mold walls did not affect the occurrence of flow marks, we conclude that there is no relationship between wall slip and the generation of flow marks. Microscopic observation of molded surfaces suggests instead that flow marks result from the filamentaton and stretching of semi-solidified material in the neighborhood of the three-phase contact line.

show abstract

The effect of teflon™ coatings in polyethylene capillary extrusion

Cited by 62 publications

References 18 publications

Wall slip and the nonlinear dynamics of large amplitude oscillatory shear flows

Wall slip and the nonlinear dynamics of large amplitude oscillatory shear flows

Effect of diatomite/polyethylene glycol binary processing aids on the rheology of a metallocene linear low‐density polyethylene

The Occurrence of Flow Marks during Injection Molding of Linear Polyethylene

Contact Info

Product

Resources

About