Resin isotherms

Attenuation i.s due to scattering of ultrasonic waves by the fibers and by absorption into isothermal resin. However, attenuation is reduced with the through-transmission method and by the use of low frequencies. Defects such as voids, resin rich or resin starved... 

Maier, R. S., Rohaly, T. R, Advani, S. G. and Rickie, K. D., A fast numerical method for isothermal resin transfer mold filling , International Journal of Numerical Methods in Engineering, 39, 1405-1422, 1996. 

The 2eohte and the resin adsorbents show different adsorption isotherm characteristics, particularly at higher concentration (51). The resin adsorbent isotherm is slightly concave upward, whereas the 2eohte isotherm is linear, or even slightly concave downward. Resins, therefore, have an advantage in a UOP Sarex operation that involves high feed-soHds concentration. 

McCabe-Thiele diagrams for nonlinear and more practical systems with pertinent inequaUty constraints are illustrated in Figures 11 and 12. The convex isotherms are generally observed for 2eohtic adsorbents, particularly in hydrocarbon separation systems, whereas the concave isotherms are observed for ion-exchange resins used in sugar separations. 

Softening and cure is examined with the help of a torsional pendulum modified with a braid (65), which supports thermosets such as phenoHcs and epoxies that change from a Hquid to a soHd on curing. Another method uses vibrating arms coupled to a scrim-supported sample to measure storage and loss moduH as a function of time and temperature. An isothermal analytical method for phenoHc resins provides data regarding rate constants and activation energies and allows prediction of cure characteristics under conditions of commercial use (47). 

Adsorption beds of activated carbon for the purification of citric acid, and adsorption of organic chemicals by charcoal or porous polymers, are good examples of ion-exchange adsorption systems. Synthetic resins such as styrene, divinylbenzene, acrylamide polymers activated carbon are porous media with total surface area of 450-1800 m2-g h There are a few well-known adsorption systems such as isothermal adsorption systems. The best known adsorption model is Langmuir isotherm adsorption. 

Fig. 7. Isotherms of the epoxy resins as a function of curing temperature, percent water vs P/Po. (Moy and Karasz (16))...

The ion exchange particles may be regarded as isothermal, and the effective diffusivity of isobutylene within the particles may be taken as 2.0 x 10 5 cm2/sec. The resin particles may be considered as spheres with radii equal to 0.0213 cm. The density of the swollen resin is assumed to be equal to 1.0 g/cm3. 

Char Preparatioa Chars were prepared both by isothermal pyrolysis of 5 g samples of resin in a quartz boat heated in an atmosphere of flowing (0.5 SCFM) N2 in a quartz tube oven (N2 pyrolysis chars) and by open combustion of 1 g samples of resin exposed to 2.8 watts/cm2 of radiant energy from an electric heating panel (4-5) (combustion or burn chars). All chars were finely ground with a glass mortar and pestle prior to analysis. 

A similar study was carried out with vinyl ether based resins which were UV-cured isothermally at 25°C and at70°C, in the presence of a triarylsulfonium... 

Toteja RSD, Jangida BL, Sundaresan M, Venkataramani B (1997) Water sorption isotherms and cation hydration in dowex 50w and amberlyst-15 ion exchange resins. Langmuir 13 2980-2982... 

The fluorine content, density, critical surface energy, glass transitions, thermal expansion coefficient above and below the glass transition, and 300°C isothermal thermogravimetric stabilities of the fluoromethylene cyanate ester resin system with n = 3, 4, 6, 8, 10 are summarized Table 2.2. Also included for the purpose of comparison are the corresponding data for the aromatic cyanate ester resin based on the dicyanate of 6F bisphenol A (AroCy F, Ciba Geigy). 

Figure 12.9 illustrates the influence of temperature on iodate removal. In the case of desorption at 25°C, iodate will remain on the resin particles. Flowever, desorption is fully completed at 50°C. Figure 12.10 provides an example of an adsorption isotherm of the iodate ion. 

It is theoretically possible that equilibrium between liquid and resin will be maintained at all points of contact. Liquid and solid concentrations are then related by the sorption isotherm. It is usual, however, that pellet or film diffusion will dominate or control the rate of exchange. It is also possible that control will be mixed, or will change as the ion exchange proceeds. In the latter case, the initial film-diffusion control will give way to pellet-diffusion control at a later stage. 

The isothermal cure kinetics of a series of TGMDA/DDS resin formulations were investigated over the temperature range 121°-187°C. Figure 4 illustrates data obtained for the resin TGMDA/DDS(25%) at 177°C. During the early stage of cure prior to the onset of... 

Isothermal cure of the B-stage neat resin to the C-stage cure. 

---