Physical Properties of Foams

In practically all our food products we have depended on the practical application of foam stability to solve our problems. The answer to many of our problems lies in the theoretical aspects of the stability and formation of foams. As yet, little time has been spent on the chemical and physical properties of foam. 

To illustrate MCD-regression, we analyze a data set obtained from Shell s polymer laboratory in Ottignies, Belgium, by courtesy of Prof. Christian Ritter. The data set consists of n = 217 observations, with p = 4 predictor variables and q = 3 response variables. The predictor variables describe the chemical characteristics of a piece of foam, whereas the response variables measure its physical properties such as tensile strength. The physical properties of foam are determined by the chemical composition used in the production process. Therefore, multivariate regression is used to establish a relationship between the chemical inputs and the resulting physical properties of foam. After an initial exploratory study of the variables, a robust multivariate MCD-regression was used. The breakdown value was set equal to 25%. 

This survey deals with the fundamental morphological parameters of foamed polymers including size, shape and number of cells, closeness of cells, cellular structure anisotropy, cell size distribution, surface area etc. The methods of measurement and calculation of these parameters are discussed. Attempts are made to evaluate the effect and the contribution of each of these parameters to the main physical properties of foamed polymers namely apparent density, strength and thermoconductivity. The cellular structure of foamed polymers is considered as a particular case of porous statistical systems. Future trends and tasks in the study of the morphology and cellular structure-properties relations are discussed. 

The volximetric weight, a parameter characteristic for the relative contents of both the solid and gas phase in a material, is the fundamental morphological parameter of foamed polymers and is related to all relevant physical properties of foamed plastics such as strength, thermophysical and electric properties. 

Foam Properties and Testing Methods. In general, most physical properties of foams, both flexible and rigid, are proportional to the foam density. Therefore, at all times, the first physical property to be determined is foam density. Foam density can be calculated fi om the following equation ... 

The physical properties of foams are changed by both the fluctuations in the surface rates of components and the temperature and pressure gradients the foam experiences as it travels down the wellbore and into the formation. Bottomhole treating pressures (BHTP) can be calculated as follows ... 

Dement ev,A.G., Khlystalova, T.K., Demina, A.I., Zinger, P.A., 1991. Structural-physical properties of foam polyurethanes with various foaming agents. Polymer Science U.S.S.R. 33, 2125-2134. 

Comparison of flavor and physical properties of foam spray-dried whole milks prepared from concentrates foamed with air and with nitrogen. J. Dairy Sci. 56(2) 161-163. 

Keywords Polyolefin foams Polyethylene foams Crosslinking Foaming agents Physical properties of foams... 

Blending is one of the easiest ways to modify the properties of CPOF. The physical properties of foams manufactured from blends of LDPE and EVA have been studied as a function of the LDPE content in the blends [15,16]. The properties of the blends usually lie between the Umits of the foamed constituents, although the relationship is not always Unear, which mainly depends on the blend morphology. 

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