Epoxide networks moduli

In this contribution, we report equilibrium modulus and sol fraction measurements on diepoxidet-monoepoxide-diamine networks and polyoxypropylene triol-diisocyanate networks and a comparison with calculated values. A practically zero (epoxides) or low (polyurethanes) Mooney-Rivlin constant C and a low and accounted for wastage of bonds in elastically inactive cycles are the advantages of the systems. Plots of reduced modulus against the gel fraction have been used, because they have been found to minimize the effect of EIC, incompleteness of the reaction, or possible errors in analytical characteristics (16-20). A full account of the work on epoxy and polyurethane networks including the statistical derivation of various structural parameters will be published separately elsewhere. 

Nonstoichiometric systems or incompletely cured stoichiometric systems behave as if they were internally plasticized systems. The modulus variation with cure conversion (x), for a typical stoichiometric epoxide-amine network, is shown in Fig. 11.8. 

A vulcanized sample, obtained from a reference mixture, contained mainly SBR-2 non epoxidized and precipitated silica, presents a value of the storage modulus (G ) at low amplitude of deformation, which is 4 times higher than that value showed by a mixture of SBR-2(ep7)/silica. This reduction of G shows a slightly network, due to the favorable energetically interaction between epoxy groups of the epoxidized rubber and the sUanol groups present onto the silica surface. Because of that, it is possible to have a better dispersion leading to a reduction of the Payne effect (Fig. 20). 

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