Reaction-induced vitrification

The potential of MTDSC for the real-time monitoring of reaction-induced phase separation is demonstrated with the cure of an epoxy— aniline-polyethersulphone (PES) mixture [80,104], The epoxy-aniline system allows following the isothermal cure accurately above and below goo (94°C), Choosing an isothermal cure temperature below will provoke a combination of phase separation of a PES-rich phase and vitrification of the epoxy-aniline matrix. Figure 2,17 shows the quasi-isothermal cure at 80°C for both modified and unmodified epoxy-aniline systems. The effect of primary and secondary amine reactions is seen as a positive A Cp,react- In the unmodified system, vitrification is seen after 91% conversion as a stepwise... 

Figure 2.115. Reaction-induced phase separation (RIPS) occurs when a homogeneous mixture of epoxy (bifunctional sticks ), amine (tetrafunctional sticks ), and polymeric modifier (dashed line) is heated and the epoxy-amine network formation induces phase separation. The position of Tcure to the glass transition of the modifier Tgniod determines whether vitrification of a phase rich in this component will occur during cure.

Isothermal detection of the cure exotherm and heat capacity changes, reflecting effects such as the reaction heat capacity, vitrification, and reaction-induced phase separation... 

The crosslinking of these polyoxiranes with aromatic diamines using the standard procedures applied to epoxy resins was then studied by DMTA. Reactions proceeded normally, except for the fact that early vitrification, arising from the high aromatic content of these compositions, induced a considerable slowdown of the late curing stages. 

The ef-CNT/BP/DDS system has developed for this application (Chen et al. 2011 Hsu et al. 2012b). The incorporation of ef-CNT in the LCER system induces the formation of crystalline phase in the composite, thus greatly enhances the thermal and mechanical properties of the composite as compared with the pristine LCER system (Table 19.6). Besides, the incorporation of thermal conductive CNT has accelerated the curing reaction of ER. However, the excessive amount of ef-CNT in matrix results in reaching vitrification stage quickly and lowering the degree of conversion. The mechanical properties are decreased when the amount of CNT is >2.00 wt%. 

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