Effect of the cellular structure on thermal conductivity of rigid closed-cell foam polymers during long-term aging

Abstract

The thermal conductivity of rigid closed-ceU polyurethane foams during long-term aging has been studied. The As shown in numerous studies [1][2][3][4][5][6][7][8][9][10][11][12], heat in foams is transferred mainly through thermal conductivity of the gas in cells and of the base polymer, and also through radiation. In particular, in a foam polyurethane (FPU) freshly prepared from freon-ll for heat insulation, about 15% of heat transfer is accounted for by the thermal conductivity of the polymer, 50% by the thermal conductivity of the gas in cells, and 35% by radiation [2]. The component of gas convection in cells can be neglected, since the cell diameter of heat-insulating foam plastics is smaller than 1 mm.Prediction of the long-term thermal conductivity of foamed plastics is usually based on the examination of changes in the gas composition and pressure in closed cells taking into account the gas diffusion in foam materials [1][2][3][4][5][6][7][8][9][10]. It is assumed that their structure does not change during long-term aging.However, in advanced stages of aging, the process mechanism can change, for example, due to the effect of aging on the polymer [13]. Therefore, it is important to predict the thermal conductivity of foam plastics during long-term aging. This problem is of particular interest from the ecological point of view when replacing freon by alternative ecologically safe foaming agents [2,3,[5][6][7][8]14]. In this context, the objective of this study is to estimate the effect of structure on the thermal conductivity of foam polymers during long-term aging.Foam plastics of different brands were examined. Rigid foam polyurethane FPU-331 was obtained by the reaction of polyisocyanate PITS-D and a blend of polyethers P-373 and L-294. FPU-305A was obtained on the basis of polyisocyanate and polyether Laprol-805. Elastic FPU-E-35-0.8 was obtained on the basis of diisocyanate TDI 65/35 and polyester P-2200, while FPU-75

The Influence of Environmentally Friendly Flame Retardants on the Thermal Stability of Phase Change Polyurethane Foams

“…Widely used for sound absorption [1][2][3], furniture [3,4], and insulating materials [5], polyurethane foam (PUF) plays an important role in our daily life. Compared with other insulating materials, PUF has the advantage of low thermal conductivity, high mechanical and chemical stability at both high and low temperatures, and the ability to form sandwich structures with various facer materials [6,7].…”

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

“…The mathematical processing of experimental data was carried out by minimisation using a confi guration method similar to that described in earlier work [17,18].…”

Effects of Aging of Polyurethane Foams in the Context of Furniture Design

“…An ergonomic seat or bed must optimally and evenly support the user's body for sustained periods of time and, hence, it is important to recognize the influence of aging of polyurethane foams used in seats and/or beds on their physical-mechanical properties. However, the available literature on the subject is dominated by articles dealing, primarily, with issues con-nected with the selection, modeling or stiffness analysis of foams for upholstered furniture (Alderson and Alderson, 2007;Scarpa, 2007, 2009 (Ostrogorsky et al, 1986) or foam cell structure (Dementyev et al, 1999). What is missing is a more comprehensive discussion on the effect of aging on stiffness of furniture foams.…”