Properties of the Hradened Gypsum Bodies Mixed with Urea-Formalin Resin and Stylen-Butadien Co-Polymer

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The properties of the hardened gypsum bodies mixed with urea-formalin resin and stylen-butadien copolymer were studied. The resin containing plaster is hardened without heating in all treatment. The intermediate polymerization solution of urea-formalin resin contains 50% net polymer, congruently mix with water and in tempering of plaster is used by replacing of same volume for a part of molding water. In addition from three to ten percent for gypsum weight, no influence is observed on the setting time of plaster. It was resulted that after three days tensile strength is same to without resin, after seven days less because of the slow rate of polymerization and after twenty-eight days approximatly equal. The decreasing rate of drying is closely related to the change of tensil strength, and on addition of ten percent net polymer hardened bodies showed a relative large decreasing of the absorbed water as comparison with without resin. The similar procedure is used in the case of stylen-butadien co-polymer emulsion. When emulsion mixed with plaster, in order to keep its stabilities, nonionic surface active agents must sufficiently be added. It was observed that a general properties of the latters is slightly below than the formers. In both experiment, there are no considerable development, of the properties of the hardened gypsum bodies, but the significant reduction of the absorbed water would be a good improvement.
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