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Recycled HDPE maintains film quality.

Popular wisdom has it that HDPE post-consumer reclaim (PCR) has no place in high-quality blown film. But Occidental Chemical Corp. of Dallas has challenged that notion with recent tests of its HDPE PCR resin, Cyclathon R1000, on Reifenhauser Film System's new lab line in Peabody, Mass.

Half-mil film made of 30% Cyclathon and 70% virgin Alathon L5005 HMW-HDPE showed only a slight drop in physical properties (see table) when compared with product made entirely from the virgin resin. "The drops were minimal in terms of functionality," said OxyChem product manager James Clark.

From a production standpoint, using PCR imposed no compromises at all, according to Reifenhauser v.p. Matthew Bangert. The company produced the 30%-PCR film at 660 lb/hr, the same rate as 100% virgin Alathon and an intermediate blend with 15% PCR. Reifenhauser ran all the films on an 80-mm, 30:1 L/D extruder equipped with a 225-mm oscillating die.

CLEAN RESIN IS QUALITY RESIN

Introduced just a year ago, OxyChem's PCR resin has typically found a home in blow molding or other "thickwalled" applications (see PT, June '91, p. 165). Made from milk and juice bottles, Cyclathon has a melt index of 0.7 g/10 min and density of 0.960 g/cc.

Clark credits recent quality improvements for allowing the Cyclathon to go into a functional blown film. "We've made tremendous strides in the quality of the resin," he said.

Since January, OxyChem has had a new source for Cyclathon. EnviroPlastics of Auburn, Mass., produces it on a reclaim line from John Brown Recycling of Providence, R.I., dedicated solely to HDPE reclaim. The company makes roughly 15 million lb/yr of clear and colored HDPE from PCR, according to Tom Whitcomb, one of the principal partners.

Whitcomb credits a proprietary waste-water treatment system that has been added to the John Brown system as one key contributor to the quality improvements. And a new blackflushing screenchanger from Beringer Inc., a division of John Brown in Marblehead, Mass., allows EnviroPlastics to use a fine, 150-mesh screen without frequent changes, Whitcomb explained.

Clark said EnviroPlastics has "vastly improved" Cyclathon by lowering its contaminant and gel levels. Indeed, both the virgin film and two PCR films showed zero count of gels above 1/64 in. when tested in OxyChem's laboratory. He did note, however, that the number of smaller gels was slightly higher in the PCR film. (CIRCLE 18)

'PCR-FRIENDLY' EXTRUSION

Reifenhauser made no special changes in processing conditions to accommodate the PCR, according to Bangert. He attributed the ease of processing instead to the company's "PCR-friendly" equipment design philosophy. "Our goal here is to elevate the level of confidence in using PCR," he told PLASTICS TECHNOLOGY. "You can maintain physical properties without sacrificing output rates."
PHYSICAL PROPERTIES OF 0.5-MIL HDPE FILM WITH PCR
% Virgin(a) 100 85 70
% PCR(b) 0 15 30
Elmendorf Tear,
 g/mil
 MD 12.6 10.4 9.6
 TD 130 168 126
Dart Impact
 Strength, g 390 290 260
Gel level/sq ft(c) 0 0 0
Yield Strength, psi
 MD 5550 5330 5540
 TD 4180 4090 4280
Break Strength, psi
 MD 11,240 9350 9170
 TD 6570 5140 4690
Elongation, %
 MD 300 315 285
 TD 480 450 445
Secant Modulus,
 Mpsi(d)
 MD 126 131 132
 TD 143 155 170
aAlathon L5005. bCyclathon R1000. cCounts gels greater than
1/64 in. d1% strain.


Accordingly, Reifenhauser now favors 30:1 extruders with proportionately longer low-shear mixing sections. The design reportedly helps protect shear-sensitive materials like PCR from degradation while fostering thorough mixing. And both Bangert and Clark emphasized that mixing is another important factor in the zero gel count. (CIRCLE 19)
COPYRIGHT 1992 Gardner Publications, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1992, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

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Title Annotation:Blown Film; Technology News; polyethylene
Author:Ogando, Joseph
Publication:Plastics Technology
Date:May 1, 1992
Words:613
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