Study On Grafting Modification Of Phenolic Resin

Phenolic resin has been widely used for refractories as binder, because of its some excellent properties such as easy mixing at room temperature, high strength and carbon residue as well as less pollution, however, there are a few weakness, especially, the water component could be lost from the phenolic resin in heating process because the phenolic hydroxyl groups and methylene existe in the structure of the phenolic resin, and would react with the component of basic refractories to form hydroxide. It will cause the damage of the basic refractories. Basic above reasons, the phenolic resin was grafted and modified for decreasing the generation of water component in the carbonization of the resin. The obtained results are as follows.(1) The amount of molecular weight, softening temperature, polymerization rate, solid content and carbon residue of the phenolic resin could increase with the increasing of the molar ratio of formaldehyde to phenolic and the amount of catalyst, and the prolonging of the synthesis reaction time, however, the fluidity and the free phenol content could decrease. The optimum condition for the synthsis of the phenolic resin was as follows. That was the molar ratio of formaldehyde to phenol was0.85, the reaction time was3.5h, and the amount of catalyst is1.5%. The structure of synthezed phenolic resin was mainly ortho-substituted and para-substituted, and a small amount of2,4,6-substituted.(2) With the increasing of the amount of allyl chloride, the limiting viscosity number of allyl phenolic resin increased, the molecular weight increased and the yield decreased. The curing of allyl phenolic resin was achieved by the addition reaction of the carbon-carbon double bond, the curing temperature was higher about100℃than ordinary phenolic resin, and the curing window was wider. The curing process parameters could be obtained that curing for at180℃, the temperature was raised to225℃and cured4h. The surface of cured resin was flat, continuous phase structure and nonporous. The carbon residue rate of allyl phenolic resin was31.34%, lower than that of the thermoplastic phenolic resin, but it had lower moisture content, and could reduce the hydration of the calcium oxide. The curing activation energy Ea of thermoplastic phenolic resin and allyl phenolic resin was separately calculated by Kissinger and Ozawa methods, and the curing kinetics model was eatablished, the model with experimental data were in good agreement. The activation energy of allyl phenolic resin was lower than phenolic resin at curing initial stage, and the curing reaction of the two resins was controlled by diffusion, the activation energy was increased with the curing temperature increased.(3) Compared with the phenol resin modified by boric acid, the phenol resin modified by organic boron showed lower limiting viscosity, polymerization rate and higher solid content, however the softening point was same as each other. The curing temperature of phenolic resin modified by boric acid was lower, and the hydroxyl groups were still involved in the reaction during curing process. The curing process parameters of two kinds of resins could be obtained that the phenolic resin modified by boric acid, was cured for2h at126℃, the temperature was raised to144℃and cured4h, and the phenolic resin modified by organic boron, was cured for2h at135℃, the temperature was raised to142℃and cured4h. The phenolic resin modified by boric acid, had unreacted borate fibers after curing, and the surface of phenolic resin modified by organic boron was smooth, nonporous and no phase separation. Two kinds of phenolic resins had the same residual carbon ratio, increasing the boron element content, the residual carbon ratio of the resin could be improved. The water flowage of the phenolic resin modified by organic boron was low, and it could reduce the hydration of the calcium oxide. The curing activation energy Ea of two kinds of resins were separately calculated by Kissinger and Ozawa methods, the curing activation energy of the phenolic resin modified by boric acid was large, it was361.33KJ/mol, and the curing kinetics model was eatablished.(4) The solid content of SKPF was90.73%, its interior structure was looked like a net, and the softened phenomenon would not take place in the heating process. The solid content of BKPF was87.04%, and both of the molecular weight and the intrinsic viscosity number were high. When the BKPF cured, the polycondensation reaction was processing. Compared with the thermoplastic phenolic resin, the difference on the curing temperature was small. There was no hole on the surface of substrate after the curing of the two resins. The carbon residue of BKPF was higher than that of SKPF. The amount of TEOS made little effect on the carbon residue rate of SKPF. The carbon residue rate of BKPF increased with the increase of the amount of boric acid. The water released during the decomposition of BKPF was less, which would reduce the hydration of calcium oxide.