Effect of Compound Formulation and Processing Conditions on Properties of Extruded EPDM and NR/EPDM Foams

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.