Time and temperature effects on the tensile yield properties of polypropylene

✍ Scribed by T. C. Uzomah; S.C.O. Ugbolue

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 202 KB
• Volume: 65
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/(sici)1097-4628(19970725)65:4<625::aid-app1>3.0.co;2-m

✦ Synopsis

Tensile tests were made on polypropylene films as a function of aging temperature from 80 to 130ЊC at a strain rate of 5 cm min 01 . Polypropylene films aged at 60 and 100ЊC and at time intervals up to 180 min were also stretched at the same strain rate. The yield stress and initial modulus were found to be linear functions of temperature, extrapolating to a zero value close to the thermodynamic melting point of the polymer (170ЊC). The work of yield, the plastic and yield strains also decreased with increase in aging temperature but the elastic strain increased. The plastic strain, yield strain, yield stress, and initial modulus for the 60ЊC aged film had larger values than the corresponding values for the 100ЊC aged film at equivalent time intervals and all properties decreased with increasing log time of aging. These decreases in properties were explained in terms of decrease in the density (crystallinity) of aged PP films.