| Abstract: | The rheological properties of molten LDPE and mPE foams have been measured for small‐amplitude oscillatory shear flow. The foam samples were prepared by injection molding, and the effect of injection conditions on the resultant cell structure is discussed. In all cases cellular foams with closed cells were obtained with cell densities in the range of 4 × 105 ? 7 × 106 cells/cm3 and cell diameters in the range of 30–110 μm. The viscoelastic behavior of the foams is shown to be well described by the emulsion model proposed by Palierne (1) without using any fitting parameter. The linear viscoelastic properties of LDPE and mPE foams depend only on the properties of the polymer matrix and of the gas volume fraction. The Palierne model is also used to predict the linear properties of microcellular foams. Polym. Eng. Sci. 44:2158–2164, 2004. © 2004 Society of Plastics Engineers. |
