Structural degradation of polyurethane-based elastomeric modules

Abstract

Degradative characteristics were studied using specimens of three polyurethane-based elastomeric modules that were treated in solutions of varying acidity, oxygen content and temperature. After periods of 10 and 100 days, molecular weight distribution changes, mechanical property changes and elemental chemistry changes were studied using gel permeation chromatography (GPC), stress-relaxation testing and X-ray photoelectron spectroscopy (XPS), respectively. As determined through analyses of the molecular, mechanical, and elemental changes after treatment, the degradative mechanism was influenced by whether the polyurethane was polyester-based or polyether-based, and the degree of structural degradation was influenced by the type and duration of conditioning treatment. Degradation of the polyester-based materials after treatment was dominated by a chain scission mechanism; conversely, the degradation of the polyether-based material was dominated by a crosslinking mechanism. Among the conditioning treatments, the combined effects of an increase in acidity, oxygen content and temperature most influenced the degree of degradation with time, with the increase in temperature having the greatest effect of any of the single variables investigated.

Colour changes of orthodontic elastomeric module materials exposed toin vitrodietary media

“…6,9 Structural conformation and degradation have also been examined. [11][12][13][14][15] Although the modules have been reported to be susceptible to staining in the oral environment, to the best of our knowledge, no systematic studies on colour stability of these modules have been reported previously. 16 The ability to prevent intrinsic and extrinsic stains of the polyurethanes modules has become an important challenge, as the oral environment is exposed to a variety of media on a daily basis, many of which may stain or alter the surface of modules causing aesthetic degradation.…”

Effect of different γ‐irradiation doses on cytotoxicity and material properties of porous polyether‐urethane polymer

“…Polyether‐urethanes are generally considered to be resistant to the effects of high‐energy radiation. At very high doses (>25 kGy), irradiation can cause progressive degradation to the polymer 14–18. Recent work has indicated that γ‐radiation may result in the release of methylene dianiline (MDA).…”

XPS study of the changes during the service life of polyester powder coatings

“…1 It has been used to study the degradation of polymers, 2,3 brought about by radiation in a vacuum, 4,5 photooxidation, 6 simulated low earth orbit environments, 7,8 degradation in solution 9,10 , ageing after plasma treatment 11 and in natural weathering situations. 12,13 The aim of this study was to determine if XPS is a useful technique for detecting the early stages of powder coating deterioration, specifically polyester coatings, which can lead to a lack of corrosion protection.…”