The Permanence Properties of Flexible Urethan Foams

Abstract

The acceptance of urethan foam as a commercial product has hinged to an important extent on its permanence as a foam under all conditions of actual end use. Customer experience with commercial flexible urethan foams has confirmed the satisfactory service life of these materials. However, in the development of this industry, it was necessary to be able to predict the performance of experimental systems which later were to become fully commercial. Most often, this prediction had to be made very early, long before the materials were allowed to be put into end service. The common way to do this is by accelerated testing, wherein the time axis is condensed by stepping up the aging process well beyond any normal conditions. Considerable time and expense are saved in this kind of test; however, there is always the question that such an accelerated step-up of test conditions is not representative of actual use, and/or causes reactions in the sample which do not occur in normal use. It is important that these questionable features be reconciled before the intercomparability of accelerated and shelf-life testing is accepted.

Natural weathering, artificial photo‐oxidation, and thermal aging of low density polyethylene: Grafting of acrylic acid onto aged polyethylene films

“…It is worth noting that the carbonyl bands of the polymer photo‐oxidized by sunlight form more carboxylic groups, but less ester and vinyl alkene 16. Thus, the enrichment of the aged films with carboxylic groups may themselves accelerate further the degradation process,17 producing an autocatalytic effect. Furthermore, there is some evidence that the carboxylic groupsmay promote microbiological growth within the system.…”

Ageing of Flexible Polyurethane Foams and Determination of their Service Life under Different Climatic Conditions

“…The noted differences in the behaviour of PPU-E-35-0.8 and PPU-75 during climatic ageing are due primarily to the difference in their structure and to the effect of hydrolytic degradation of polyurethanes, fragments of which have different stability [19][20][21][22][23][24][25]. In particular, in terms of susceptibility to hydrolytic degradation, the main fragments of polyurethane foam macromolecules can be placed in the following order: ester > allophanate > biuret > urea > urethane > ether.…”

Physical Property Relationships and Chemical Factors Affecting Flex Fatigue Characteristics of Flexible Urethane Foam

“…In many instances the determination of the «actual&dquo; or &dquo;true&dquo; physical properties of the foam itself presents a problem. It has been found in many cases (5,6) that simple laboratory tests show agreement with actual &dquo;in use&dquo; tests. These accelerated laboratory aging tests indicate performance which is consistent with the aging process of the material under normal conditions.…”