Epoxy processing data

FIGURE 17.2 Equipment and process for solid epoxy resin. (Data from Hutz, C. E. in W. M. Smith (ed.), Manufacture of Plastics, Reinhold, New York, 507, 1964.)... 

Due to the chemical structure, fimctionality and composition of their constituents, ordinary variations of the processing conditions as well as the quality of the raw materials have been observed to lead to changes of the fine structure which are often responsible of lower ageing resistence of the polymer. The data reported here correlate the morphology of some widely utilized epoxy matrices to the informations that can be obtained from the study of the sorption behaviours. 

Results are presented of experiments undertaken by Gaiker in the manufacture of sandwich panels containing foam cores based on PETP recycled by a solid state polyaddition process developed by M G Ricerche. Panels were produced with glass fibre-reinforced unsaturated polyester and epoxy resin skins, and allthermoplastic panels with PE, PP, PS and glass fibre-reinforced PETP skins were also produced. EVA hot melt adhesives and thermoset adhesives were evaluated in bonding glass fibre-reinforced PETP skins to the foam cores. Data are presented for the mechanical properties of the structures studied. 

EGA. The overall ion profiles for the semiconductor grade epoxy compounds are presented in Figures 9 and 10 for samples F(FR) and G(no-FR), respectively. Very little outgasslng is observed from these samples below 200 C, in marked contrast to the results obtained for the electrical grade epoxy samples. These data clearly reflect the effects of the more stringent processing controls employed in the production of the semiconductor grade materials. Also, because of the lower out-... 

Probably the first major publication of a process model for the autoclave curing process is one by Springer and Loos [14]. Their model is still the basis, in structure if not in detail, for many autoclave cure models. There is little information about results obtained by the use of this model only instructions on how to use it for trial and error cure cycle development. Lee [16], however, used a very similar model, modified to run on a personal computer, to do a parametric study on variables affecting the autoclave cure. A cure model developed by Pursley was used by Kays in parametric studies for thick graphite epoxy laminates [18]. Quantitative data on the reduction in cure cycle time obtained by Kays was not available, but he did achieve about a 25 percent reduction in cycle time for thick laminates based on historical experience. A model developed by Dave et al. [17] was used to do parametric studies and develop general rules for the prevention of voids in composites. Although the value of this sort of information is difficult to assess, especially without production trials, there is a potential impact on rejection rates. 

Although the simple rate expressions, Eqs. (2-6) and (2-9), may serve as first approximations they are inadequate for the complete description of the kinetics of many epoxy resin curing reactions. Complex parallel or sequential reactions requiring more than one rate constant may be involved. For example these reactions are often auto-catalytic in nature and the rate may become diffusion-controlled as the viscosity of the system increases. If processes of differing heat of reaction are involved, then the deconvolution of the DSC data is difficult and may require information from other analytical techniques. Some approaches to the interpretation of data using more complex kinetic models are discussed in Chapter 4. 

Figure 26 shows the thermal expansion behavior of requenched epoxies. Upon reaging, the densification process was again measurable. Data shown in Figure 26, therefore, supports the notion that physical aging processes are thermoreversible. 

The model was also applied to the reaction of a tetrafunctional amine with a trifunctional epoxy, denoted A4 + 4/3Bj, and was compared with available data (Fig. 18). An approximate value of k was obtained from the times to gelation. This model appears to provide a reasonable framework within which the vitrification process for nonlinear systems can be discussed. 

DSC, middle IR and near IR data suggest that the crosslinking reaction of an epoxy resin with phthalic anhydride is a stepwise process as follows. 

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