Several samples of xps, foam with CFC-12 were selected from different applications (roofs, walls and ceilings). Plates were prepared at different times between 1972 and 1989 one of the famous manufacturers of xps. Samples have different densities (32-36 kg / m 3) and thickness (25-100 mm). The concentration of ba was measured twice (1997 and 2003), Plates, foamed with HCFC-142b, were manufactured in 1989 and stored in a warehouse of the manufacturer. By theory, the higher the concentration of ba, the lower the thermal conductivity of plates xps. The experimental curves (Fig.
2) confirm this. Reducing the concentration of ba is not a linear function of time (age XPS). Immediately after production rate of loss of va is very high, but over time it decreases and stabilizes. Loss rate of ia in accordance with the laws of physics depends on the thickness of the material and the transport properties of the va. For example, the thinner the material, or (ii) higher permeability blowing agent, the faster the loss of ba plates xps. At the end of 1980. National Research Council Canada (NRC) has developed a methodology to assess long-term thermal characteristics of the foam insulation. The aim of the project – development of laboratory rapid procedure, which resulted in it would be possible to predict the long-term thermal engineering performance of the polymer insulation, in particular, made from xps, using any va.
Such a laboratory procedure would help to greatly reduce development time and cost of new foam products. Draft used to test computer models of a continuum with distributed parameters, which was used to estimate a rigid roof insulation. The test structures were assembled with the participation of the samples various foam products that are exposed to the basic natural factors for 2,5 years. Samples were taken periodically from the roof to measure the thermal resistance under laboratory conditions. In follows a series of samples was measured and the thermal resistance under field conditions. To develop a methodology for assessing long-term thermal performance, which could be applied to all types of xps, regardless of their operating conditions, the type of va should consider the following aspects of evaluation: Systematic variation of the physical properties of cellular plastics produced industrially. Because of these characteristics of the material, obtained on small samples may be incorrect to characterize the product; Systematic differences in the characteristics of the material, measured on samples taken from the surface or "in depth" of the material. Because heterogeneous structure of the material characteristics are defined on a sample taken in the "core" of the material, may not adequately represent the product as a whole; Possible impacts of environmental factors on the aging process foam insulation. Because of this effect, thermal performance, measured in isothermal conditions, may misrepresent the actual characteristics of the material in the field. More information is housed here: Castle Harlan. So way, environmental factors can cause an even greater difference between the thermal technical indicators xps, projected computer model, and the value measured during the field tests. Results studies have shown that environmental factors do not exert significant influence on the aging process plates xps.