ISSN: 0090-3973
Page Count: 5

A New Scale of Microtension Test for Polymers
Groves, DJ
Senior research physicist, senior research chemist, and physicist, Imperial Chemial Industries PLC., Hertfordshire

Sang, RD
Postdoctoral fellow and reader, University of Southampton, Hampshire

Scott, JT
Senior research physicist, senior research chemist, and physicist, Imperial Chemial Industries PLC., Hertfordshire

Scrutton, IN
Senior research physicist, senior research chemist, and physicist, Imperial Chemial Industries PLC., Hertfordshire

Millie, RP
Undergraduate student and senior lecturer, University of Southampton, Hampshire

Wigley, DA
Undergraduate student and senior lecturer, University of Southampton, Hampshire

Hendra, PJ
Postdoctoral fellow and reader, University of Southampton, Hampshire

Abstract

Microtension tests on polyethylene, polypropylene, and polyethylene terephthalate are reported for grip separations typically around 10 mm and as little as 4 mm. A waist geometry of uniform radius is used and particular attention to grips and jaw facings is necessary. The results show these microtension specimens to behave in accordance with predictable sources of stress concentration, giving yield and draw processes free from grip influence. There is a small though significant decrease of around 2% when the mean values of yield or draw stress from the microtest are compared with conventional test data, although the testing errors are similar. The mean value of break strength is unaffected whether the microtest or conventional test is used, but the scatter about it is larger with the microtest. For many purposes the differences are small, and the material sample needed is considerably reduced.

Keywords:
tension tests, stress concentration, yield strength, microtension tests, specimen shape, grip facings, draw stress, fracture stress, polypropylene, polyethylene terephthalate, plastics testing, statistical analysis

Paper ID: JTE10241J
DOI: 10.1520/JTE10241J
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