Density model derivative, defined

GB-like approximations [41, 71, 119, 161, 187, 189, 230-233] may be derived from eq (1) by using the concept of dielectric energy density, as in the work of Bucher and Porter [130], Ehrenson [131], and Schaefer and Froemmel [234], As the GB methodology has been extensively reviewed in the recent past [81, 83, 213], we confine our presentation to a very brief discussion of the key aspects of the theory. The polarization free energy in the GB model is defined as... 

An equation was derived based on such a model. It defines the critical current density as... 

Therefore, a different approach was followed in the present paper in order to improve the understanding of the relationship between the structure and the behavior of crosslinked polymers. A series of directly comparable model polymers were prepared with crosslink densities varying from high (thermoset) to zero (thermoplastic). Five polymers with well defined crosslink densities [11] were tested at various levels of deformation. This approach produced a small but assessable and fairly consistant body of results. Basic relationships derived from these results were related to corresponding results from the literature. 

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