The critical molecular weight for resisting slow crack growth in a polyethylene

✍ Scribed by Xici Lu; Narumi Ishikawa; Norman Brown

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 316 KB
• Volume: 34
• Category: Article
• ISSN: 0887-6266
• DOI: 10.1002/(sici)1099-0488(19960730)34:10<1809::aid-polb12>3.0.co;2-f

✦ Synopsis

An ethylene-hexene copolymer was fractionated into five fractions and the density of shortchain branches was measured for each fraction. The slow crack growth behavior was measured on each fraction by sandwiching the small amount of fractionated resin of about 0.2 g between polyethylene grips. The resistance to slow crack growth was negligible for the three fractions whose M w was less than 1.5 X lo5. For the fourth fraction with M w greater than 1.5 X lo5, the resistance to slow crack growth was very high, being greater than that for the whole resin even though its density of short-chain branches was less than that of the whole resin. It is concluded that a molecular weight greater than 1.5 X lo6 is required to create the number of tie molecules that is necessary to produce a high resistance to slow crack growth in this particular copolymer. 0 1996 John Wiley & Sons, Inc.