Necking of high-density polyethylene

✍ Scribed by Yasaku Wada; Akira Nakayama

• Publisher: John Wiley and Sons
• Year: 1971
• Tongue: English
• Weight: 687 KB
• Volume: 15
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/app.1971.070150116

✦ Synopsis

Necking draw of high-density polyethylene is studied a t draw rates of 2.5 x 10-2 to 25 mm/min and at temperatures of -40' to 8OOC. Effect of temperature and draw rate on necking stress is interpreted in terms of viscoelastic flow of amorphous phase accompanying orientation of crystallites. It is proved that reducibility of draw rate and temperature holds and that the reduction factor obeys approximately the Williams-Landel-Ferry equation. Necking stress at an extremely low draw rate, critical necking stress, is discussed in terms of the phase equilibrium under stress between two states before and after microfracture of crystallites. The theory, with some approximations, leads to the equation by Iida in which the critical necking stress is expressed by fusion parameters. The thermodynamic behavior of isothermal necking is discussed and a phenomenologic criterion for necking is presented.