In view of the formulation changes induced by the use of alternative physical blowing agents, the understanding of the main parameters determining the dimensional stability performance was an important issue for the rigid laminate industry. So far, the influence of formulation and processing variables on dimensional stability has mainly been described qualitatively, and new evaluation techniques have been proposed in several publications. This paper describes how the application of the so-called dimvac test has led to a better quantification of the formulation and processing parameters influencing the long-term dimensional stability performance. A series of pentane blown laminates based on different formulations and processed on a variety of equipment were evaluated at the most severe condition in the dimvac test. We found that a set of formulation and processing requirements had to be fulfilled in order to ensure the dimensional stability of the laminates in service. The requirements were different for each formulation, production line and product. To quantify the influence of polyether polyol composition and type of non-reactive liquid fire retardant, a systematic laboratory study was carried out. For foams without fire retardant, a clear model was obtained predicting the dimvac performance in terms of foam density and polymer network parameters. For formulations including fire retardants, deviations from the model were observed, and differentiation between dilution and plasticization could be made.

Abstract. A mathematical model describing the main physical processes occurring during thermal processing of cable thermocouples (CT) during their production is presented. The polymerization of the insulating layer is taken into account in the conditions of its intense heating. The developed mathematical model allows to carry out calculations of heat transfer processes under the conditions of substantial heterogeneity of cable thermocouple structure. The computational experiments carried out have established significant differences in the characteristics of heat transfer in CT in the presence of thermoelectrodes with differing thermophysical characteristics.