Re: Humidity's Effects on Cured Photopolymer Resin Epoxy Tensile Strength

From: John Male (
Date: Tue Oct 14 1997 - 12:38:05 EEST


A paper was published at the second national conference on Developments
in Rapid Prototyping and Tooling, titled 'Effect of humidity on the
properties of stereolithography parts manufactured from SL5180 epoxy
resin' by T S Peng, D I Wimpenny and S Windsor.

They found that at 95% humidity the tensile strength fell from 57MPa to
36MPa after one week, then to 18MPa after 2 weeks, and to 14MPa after 4
weeks. I've taken these values from a graph, so they may be out by
1-2MPa. They also have information on parts swelling when exposed to
high humidity for long periods of time.

This paper was published anout a year ago, so they may have more recent
results, so it may be worth contacting them directly. They are based at
the Advanced Manufacturing Centre, which is part of the Warwick
Manufacturing Group, at Warwick University. Their web site is


John Male
Research Student
Centre for Rapid Design and Manufacture
Buckinghamshire University College
Queen Alexandra Road
High Wycombe
HP11 2JZ

Tel 01494 605085 Fax 01494 538593

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