Back SearchTitle: SUPERCRITICAL FLUIDS IN THERMOPLASTICS FOAMING: FACTS OR FALLACIES?
Page Range: p.199-220
Author(s): Gendron R; Champagne M F; Reignier J
File size: 496K
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Issue Year: cp
Volume: 25
Issue No: No. 4
Abstract
The specific nature of some supercritical fluids dissolved in thermoplastics for foaming purposes is discussed in relation to several key observations. Experimental facts are presented which support the idea that lack of homogeneous dissolution at a molecular level of the foaming agent may prevail when it is processed close to or over its critical point. Particular attention is paid to extrusion foaming of PS with hydrofluorocarbons(HFCs), the latter being identified as potential replacement for the ozone-depleting hydrochlorofluorocarbon actually under their phasing-out stage. The addition of co-foaming agents to hard-to-process HFCs is considered. This latter method is shown to be a convenient method of circumventing the negative issues related to physical foaming agent supercritical state in the extrusion-foaming process. 36 refs.
Title: GAS DIFFUSION IN POLYOLEFIN FOAMS DURING CREEP TESTS. EFFECT ON IMPACT BEHAVIOUR AND RECOVERY AFTER CREEP
Page Range: p.221-236
Author(s): Rodriguez-Perez M A; Ruiz-Herrero J L; Solorzano E; de Saja J A
File size: 338K
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Issue Year: cp
Volume: 25
Issue No: No. 4
Abstract
A method for obtaining the effective diffusion coefficient of the gas contained in closed-cell polyolefin foams under static loading is presented. This property is obtained from pressure decrease with time using an analytical solution of the diffusion equation. The effect of density, type of base polymer, crosslinking and sample size on the diffusion coefficient is analysed. It is shown that the impact behaviour of low-density closed-cell PE-based foams deteriorates after compressive creep periods and that this reduction of the cushion capabilities is directly related to the diffusion coefficient of the foams. Moreover, the recovery of the foams after creep shows a peculiar non-homogeneous behaviour, which is analysed. Gas diffusion during creep is the main factor responsible for this particular behaviour. 20 refs.
Title: INVESTIGATING THE SOLUBILITY OF CO"2 IN POLYPROPYLENE USING VARIOUS EOS MODELS
Page Range: p.237-248
Author(s): Li G; Li H; Wang J; Park C B
File size: 220K
Download the pdf (subscribers only) Buy the pdf (non-subscribers)Journal: Cellular Polymers
Issue Year: cp
Volume: 25
Issue No: No. 4
Abstract
The swollen volume of a polymer with dissolved gas generally needs to be determined in order to obtain reliable gas solubility data in a polymer melt. The swollen volume is typically estimated by an equation of state(EOS). This paper reports on the application of three different EOSs (the Sanchez-Lacombe(SL) EOS, the Simha-Somcynsky(SS) EOS, and the Perturbed Chain Statistical Associating Fluid Theory(PC-SAFT) EOS) to a polymer/gas mixture system for the study of phase equilibria and gas solubility determination. The apparent solubility was obtained using a magnetic suspension balance. Approaches based on the SL, SS and PC-SAFT EOSs are proposed for predicting the swelling behaviour of polymer/gas mixtures and correlating the swollen volume to the apparent solubility. 21 refs.