Herman Gerard Dikland

Effect of Third Monomer Type and Content on Peroxide Crosslinking Efficiency of EPDM

Abstract Peroxide crosslinking of EPDM is commonly applied in rubber practice. Although the presence of a diene termonomer is not a prerequisite for peroxide crosslinking, it does provide a significant increase of the peroxide crosslinking efficiency. Different explanations for the effect of the type and the amount of the third monomer on the peroxide curing efficiency have been put forward; but, a comprehensive overview and an acceptable explanation of all the effects observed are still lacking. In the present paper, this gap is filled by combining results from low-molecular-weight model studies and rheometer experiments with information from the literature. It is shown that peroxide crosslinking of EPDM proceeds via the combination of two EPDM macro-radicals and the addition of an EPDM macro-radical to the residual EPDM unsaturation. The extent to which the latter radical addition occurs, is governed by the amount of the third monomer and by the steric hindrance of the residual unsaturation of the EPDM,...

Miscibility of EPM-EPDM blends

Abstract Blends of elastomers are often used as a basis for compound formulations. For instance, tire tread formulations may contain NR, BR and SBR in order to provide cost-effective products with good mechanical properties, dynamic properties and abrasion resistance. Blends of dissimilar EPDM grades are often used when formulating EPDM compounds. In many cases such EPDM-EPDM blends are used to obtain synergy, i.e. properties of the parent EPDM grades are not averaged, but favorable properties of the blend components are combined or unfavorable properties suppressed. In the present paper the miscibility regime for gum stock EPDM-EPDM blends has been calculated based on elementary thermodynamic considerations. Results of calculations have been validated by experiments, and excellent agreement was found. It was found that the chemical composition of EPDM grades has a major influence on miscibility. It is concluded that, as a rule of thumb, two EPDM grades are thermodynamically miscible if the difference bet...