Comparative Analysis of the Effect of Organoclay, Boron Nitride, and Fluoropolymer on the Rheology and Instabilities in the Extrusion of High Density Polyethylene

I A Hussein,A A Adesina,M S Nasser

doi:10.1155/2015/190537

Abstract

The effect of different processing additives on the extrusion instabilities of high density polyethylene (HDPE) was investigated. The concentration of each processing additive was fixed at 0.05 wt%. Organoclay, boron nitride, and fluoropolymer reduced transient shear and extensional viscosities of HDPE melt. Drop in extrusion pressure occurred during the extrusion experiment. The initial loss of glossiness in HDPE was restored with the addition of these additives. However, the fluoropolymer did not succeed in eliminating the stick-slip fracture. Despite the inclusion of the processing additives, gross-melt fracture in HDPE reappeared at apparent shear rate of 141 s−1. Both moment and distortion factor methods of analyses were employed and their findings support the observed visual trends of the extrudate surface. The quantifying tools indicated that combined organoclay and fluoropolymer reduced the pressure fluctuations and its performance surpassed that of the individual additives.

Highlights

The major challenge during extrusion is the onset of melt instabilities that hinder high productivity [1,2,3,4]
Processing aids are often added to polyolefins during their extrusion to make the processes economically viable
Stearates [15], silicon-based additives, hyperbranched polymers [16, 17], and blends of polymers [18, 19] are other forms of conventional processing aids. Another processing aid found useful in the elimination of gross-melt fracture is boron nitride [5, 20,21,22]

Summary

Introduction

The major challenge during extrusion is the onset of melt instabilities that hinder high productivity [1,2,3,4]. Stearates [15], silicon-based additives, hyperbranched polymers [16, 17], and blends of polymers [18, 19] are other forms of conventional processing aids Another processing aid found useful in the elimination of gross-melt fracture is boron nitride [5, 20,21,22]. Boron nitride was suggested to eliminate surface melt fracture and postpone gross-melt fracture at high shear rates in metallocene polyethylenes [20] and HDPE [37]. Boron nitride was reported to eliminate the gross-melt fracture in polypropylene by making the discontinuous streamlines in the polymer bulk flow smoother at the die entry [21]. To the best knowledge of the authors, such fluctuations were for first time quantified using moment and Fourier transform methods of analyses

Experimental

Results and Discussion

Conclusions