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This study investigates peroxide crosslinking of two low-density polyethylene grades of similar number average molecular weight but differing molecular weight distribution. At gel contents typically associated with dicumyl peroxide (DCP) crosslinked foams, crosslinking and melt tensile properties of the solid matrix, foaming behaviour and foam

Impact cushioning and deformation of flexible open‐cell polyester polyurethane (PU) foams were studied as a function of specimen geometry, including the incorporation of controlled voids. It was shown that cushioning behavior is dependent on sample geometry, which was in trun due to a complex balance of air compression and air flow, which changes with surface area‐to‐volume ratio of the impact specimen. Deformation studies show that impact compression proceeded initially by crushing the surface layers with little or no deformation of the center layers. As bulk compression was increased, deformation progressively propagated for the collapsed layers tending to a more uniform strain distribution at high bulk compression strains. Local asymmetric strain patterns were exaggerated using square cushions, because of cornr effects which complicated air flow paths. It was concluded that cushion curve determination of open‐cell foams would be more accurately performed using circular samples and deflecting air pressure form the top surface of the cushion to more closely simulate practical conditions. When designing at or near the margin, the number of cushions should be kept to a minimum and open surface area to volume ratios minimized by adopting square rather than strip cushions.

The effects of compound formulations and processing conditions on the structure and properties of extruded EPDM and EPDM/NR blends of tube foams were investigated. The foam tubes were prepared by mixing a compound in a two roll mill, extruding the compound through a cold feed extruder and finally vulcanizing the extrudate in a circulating hot air oven. In previous results, the EPDM grade, blowing agent type, composition of EPDM blend and processing conditions were found to affect the cell structure and the physical properties of the resultant EPDM foams. An extended work was carried out using blowing agent blends and NR blending with EPDM as a based rubber. The characteristics of blowing agent blends (ADC/DNPT) were studied using a gas evolution apparatus. Decomposition temperature of ADC decreased with both DNPT and OBSH blending which affected the resultant EPDM foams structure and properties. To promote the use of natural rubber, its various compositions were blended with EPDM to produce the foam tubes. Modified formulations were needed to ease the difficulty of mixing and stabilising the resultant foams. Using a tube mold for an extrudate as an alternative technique to vulcanize the NR/EPDM extrudate in the hot air oven was successfully found to control the expansion and foam dimensions. The NR compositions were also found to affect the foam structure and properties.

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