Glass transition temperature of epoxy resins

Table 13. On-line prediction method for glass transition temperature of epoxy resin curing system ...

Table 2. Glass Transition Temperature of Epoxy Resin Toughened with E-30 ( C)...

Fig. 4.5 Relationship between equilibrium moisture concentration and glass transition temperature of epoxy resins (Delasi and Whiteside 1978)...

Figure 14.2 Schematic showing the degree of cure of an epoxy at glass transition g as afunction of dimensionless temperature T /T, where denotes the glass transition temperature, gO denotes the glass transition temperature of uncured resin, denotes the temperature at which gelation and vitrification cross each other, and the solid line is the best fit to Eiq. (14.6). (Reprinted from Enns and Gillham, Journal of Applied Polymer Science 28 2567. Copyright 1983, with permission from John WUey Sons.)...

The most noticeable property change is a decrease in the glass transition temperature of the epoxy resin as a function of absorbed dose. The decrease in Tg is due to plasticization by degradation products and free chain ends from chain scission. 

The addition of microspheres lowers the glass transition temperature of the epoxy binder (Fig. 13). This seems to be because the filler causes defects in the matrix network. Equal diffusion coefficients of filled and unfilled epoxy binder indicates, therefore, that the diffusion processes are insensitive to binder changes. The sorption of water by epoxy resins is in fact known to depend mainly on their polarity and only slightly on the three-dimensional compactness of the network. 

Table 9 Code names, compositions and glass transition temperatures of pure and antiplasticised epoxy resins...

The resin processed at 200°C reaches 100% cure because the glass transition temperature of fully cured epoxy is 190°C, less than the processing temperature. On the other hand, the sample processed at 180°C reaches 97% cure and the one processed at 160°C only reaches 87% cure. Figures 2.26 and 2.27 also illustrate how the curing reaction is accelerated as the processing temperature is increased. The curing reaction of thermally cured thermoset... 

Curing of epoxy resins is a typical example where overall diffusion control can become operative. During curing, the glass transition temperature of the system increases and may reach or exceed the reaction temperature. This phenomenon is dealt with in several reviews of this volume, particularly in those by J. K. Gillham and E. F. Oleinik. 

The relation between the epoxy content of various epoxy resins based on Bisphenol-A diglycidylether and AH and the glass transition temperatures of linear and cured resins is given in Table 3. 

Hydantoin epoxy resins having glycidyl groups in the 1- and 3-positions and one or two alkyl groups in the 5-position were prepared by the Bucherer reaction, followed by treatment with epichlorohydrin. These resins were crosslinked with hexahydrophthalic anhydride to examine the effect of alkyl substituents on the glass transition temperatures of the cured systems. 

Microwave-assisted curing of epoxy resin systems was one of the first applications of MW in polymer chemistry and is the most widely studied area in polymer chemistry under both continuous and pulse microwave conditions. The structure, dielectric properties, toughness, mechanical strength, percentage of cure, and glass transition temperature of the epoxy formulations have been investigated [1]. 

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