Solvent impregnated resins impregnation mechanisms

The three-component cyanate/maleimide/epoxide compositions are mainly used as polymer matrix in copper clad laminates and in carbon fiber composites for engineering purposes. High heat resistance, water and solvent resistance, mechanical and impact strength is claimed. A composition for copper wire enamelling [121] and a resin for electric motor coil windings impregnation were described [107]. 

An impregnated resin prepared from PC-88A and Amberlite XAD7 beads was examined as the stationary column phase for the separation of rare earth [28]. The reagent, PC-88A, is frequently used as an extractant in rare earth separation by solvent extraction. As can be seen in Fig. 27, the distribution ratio at a given pH increases with decreasing ionic radii of lanthanides. The slope analysis for log D versus pH and log D versus concentration of PC-88A indicated that the present extraction mechanism was similar to that of the solvent extraction system. A mutual separation of Y-Gd, La-Pr-Nd, and Ho-Er-Tm was successfully attained with the present resin as the stationary phase and hydrochloric acid as the mobile phase. 

The kinetics of heterogeneous-catalytic epoxidation of cycloh cene (CH) by tert-butyl hydroperoxide (TBHP) was investigated [202]. Catalysts were prepared by impregnating the ion-exchange resin, Amberlite IRS-84 in H-form, with the acidic solution of ammonium molybdate. The concentration of Mo was 0.35 mmole/g resin. The reaction kinetics were studied in the absence of solvent and at high molecular ratios of CH and TBHP. The reaction proceeded by pseudo-zero-order in respect of CH. Reaction selectivity was 90- 95 7o U. the initial rate could be determined from the rate of TBHP consumption. It was found that the reaction order was 1.8 for TBHP and 1 for the catalyst. Analysis of EPR spectra of catalysts before and after the reaction showed partial oxidation of Mo to Mo. The authors supposed a stepwise reaction mechanism in which the interaction between CH and a complex of Mo and TBHP is considered to be the slow and irreversible step. In this complex. Mo was present in the oxidized state. 

Increased wet strength can be achieved for papers by impregnation with substances like neoprene, or phenol formaldehyde and other synthetic resins. However, the impregnation lowers the absorption capacity, and it is more often the case that papers for use as filters are specially treated to make them non-absorbent, to provide maximum mechanical strength and resistance to solvent action. 

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