MOLECULAR-MODEL FOR THE MECHANICAL-PROPERTIES OF ELASTOMERS .4. INTERPENETRATING NETWORKS

The ultimate mechanical properties of simultaneous and sequential interpenetrating networks (IPNs) have been studied theoretically. Results for bimodal networks made through interpenetration of long by very short PDMS chains show no synergism in mechanical properties. Tensile strength and toughness values for IPNs are usually lower than those for the corresponding interconnected networks. Based on our model results, a new type of IPN is proposed in which the long chains form macrocycles which are threaded by the short-chain component. Those novel IPNs show very high toughness values which are comparable to those of the interconnected bimodal networks. Finally, our study indicates that network dominance in a sequential IPN is due to the lower extensibility of the earlier polymerized network and not, as previously anticipated, to segregation of the later polymerized monomer.