Modifications of the Ideal Rubber Model

Besides the assumption of ideality inherent in Equation 9.61, several approximations were made in obtaining the force-extension relation of Equation 9.70. These assumptions are as follows  

Individual chains between cross-links (strands) obey Gaussian statistics. 

The cross-links are fixed in space and deform affinely. 

The chains are all independent and do not interact with one another (phantom chain approximation). 

Several theoretical and empirical modifications of Equation 9.70 have been developed to improve the agreement between predictions and experimental results [24-26], Some of these modifications will now be discussed  

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