Epoxy glass workers

Very accurate PCS measurements for different T and P conditions were carried out on different molecular glass-forming systems by Patkowski and co-workers, including epoxy oligomers [129-131], and the van der waals liquids PDE [132,133], BMPC [134], and BMMPC [135], In most of the investigated systems, master curves are obtained for kww(T,P) of the a-relaxation plotted versus xa(T,P), with the value decreasing (broader dispersion) as the dynamics slow (longer xa(T,P).). This is another evidence that the a-dispersion is directly related to the relaxation time. 

Lin and co-workers [51] observed that cnring phenolic resins with epoxies instead of with hexamethylene tetramine yields polymers which have almost the same flame retardance as polymers produced with hexamethylene tetramine curing. They also have toughness, stiffness, good thermal stability, excellent flame retardance and low glass transition temperature (Tg). 

The in-plane mechanical, viscoelastic and thermal properties of a satin weave carbon fabric impregnated with an amine cured epoxy resin were studied by Abot and co-workers [74]. The in-plane quasi-static behaviour including the failure modes under tension, compression and shear and all the mechanical properties including elastic moduli and strengths were determined. The viscoelastic properties including the glass transition temperature were also measured as well as the coefficients of thermal expansion. These measured properties for the fabric composites were also compared with their corresponding ones for a unidirectional composite with the same fibre and matrix. 

Following the work of Mishra and co-workers (53), Dean and co-workers (54,55) investigated the SIN syntheses of dimethacrylate- and epoxy-based materials by near-infrared and other methods. The rates and order of the polymerizations were systematically altered. The final conversion of the dimethacrylate was limited by the vitrification or topological restraint of the SIN. Whether one or two glass transitions are observed depends on the relative rates and order of the polymerizations. 

Figure 2.72 graphically illustrates the relationship between the glass transition temperature and conversion measured from the residual exotherm of the DSC curves of the epoxy-amine system shown in Fig. 2.70. Several workers have shown that for most thermoset systems there is indeed a unique relationship between the chemical conversion of a thermoset and its glass transition temperature, independent of the cure temperature and thermal history [see, e.g., Pascault and Williams (1990), Hale et al. (1991), Venditti and Gillham (1997), and, for a general overview. Prime (1997)]. It is good practice to establish the Tg-conversion relationship as part of a cure study. Conversion can be difficult or impossible to measure directly, for example, for systems where mass loss accompanies cure. In these cases this relationship may be invoked in order to use Tg as a measure of cure. As Fig. 2.72 suggests, may be preferred as a measure of cure for the final 5-10% of cure where it is usually more sensitive than the residual heat of reaction.

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