Title: A study on the role of wetting parameters on friction in injection moulding

Authors: Gerald R. Berger; Clemens Steffel; Walter Friesenbichler

Addresses: Institute for Injection Moulding of Polymers, Department Polymer Engineering and Science, Montanuniversitaet Leoben, Otto-Gloeckl-Strasse 2, 8700 Leoben, Austria ' Institute for Injection Moulding of Polymers, Department Polymer Engineering and Science, Montanuniversitaet Leoben, Otto-Gloeckl-Strasse 2, 8700 Leoben, Austria ' Institute for Injection Moulding of Polymers, Department Polymer Engineering and Science, Montanuniversitaet Leoben, Otto-Gloeckl-Strasse 2, 8700 Leoben, Austria

Abstract: In the injection moulding of thermoplastics, hot polymer melt wets a cold mould surface during filling. In contrast, ejecting can be considered as de-wetting a solid polymer from a solid mould surface. In ongoing research, we suggest that the interfacial tension γ₁₂ predicts the resistance of a solid polymer being separated from a solid mould, i.e. low γ₁₂ indicates elevated ejection friction and vice versa. The aim of this study was to validate this assumption for polymer PA6 and the mould surfaces M333_IP, M268_VMR, MoN, and CrC/a-C:H. To calculate γ₁₂, we determined the five solids surface energies at 90°C. Therefore, we conducted contact angle measurements using bromonaphtalene and ethylencarbonate and applied the OWRK method. In succeeding friction experiments, we used a friction-test injection mould to determine the ejection friction of the same material combinations at 90°C. To conclude, the four mould coatings ranked in friction to PA6 as γ₁₂ suggested.

Keywords: demoulding forces prediction; wetting behaviour; contact angle; surface energy; interfacial tension; friction tests; injection moulding; temperature impact; plastics; ejection forces; thermoplastics; ejection friction.

DOI: 10.1504/IJMPT.2016.073632

International Journal of Materials and Product Technology, 2016 Vol.52 No.1/2, pp.193 - 211

Received: 18 Nov 2014
Accepted: 14 Jul 2015
Published online: 14 Dec 2015 *

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