Measurement of Polymer-to-Polymer Contact Friction in Thermoforming

P.J. Martin, R. McCool, C. Härter, H.L. Choo

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)
14 Downloads (Pure)


Contact friction plays a critical role in all the major thermoforming processes for polymers. However, these effects are very difficult to measure in practice and, as a result, have received little scientific investigation. In this work, two independently developed test methods for the measurement of elevated temperature polymer-to-polymer contact friction are presented, and their results are compared in detail for the first time. One is based on a modified moving sled friction test, whereas the other uses a rotational rheometer. In each case, friction tests were conducted between two plug and two sheet materials. The results show that broadly similar coefficients of friction were obtained from the two test methods. The measured values were quite low (<0.3) at lower temperatures and typically were higher for polypropylene (PP) sheet than for polystyrene (PS). On approaching the glass transition temperature for PS (95°C) and the crystalline melting point for PP (165°C), the friction coefficients rose very sharply, and both test techniques became increasingly unreliable. It was concluded that despite their physical differences, both test techniques were able to capture the highly temperature sensitive nature of friction between polymer materials used in thermoforming.
Original languageEnglish
Pages (from-to)489-498
Number of pages10
JournalPolymer Engineering and Science
Issue number3
Early online date22 Sep 2011
Publication statusPublished - Mar 2012

ASJC Scopus subject areas

  • Polymers and Plastics
  • Materials Chemistry
  • Chemistry(all)


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