| Desulfurization gypsum is a kind of solid waste. Desulfurization gypsum contains a lot of pores with poor water resistance and low mechanical strength. Increasing the desulphurization gypsum density degree and reducing the pores can improve the performance of desulfurization gypsum. MDF(Macro-defect Free) cement which using the process of pressure molding, create far higher performance than that of conventional cement products.This paper has researched MDF phenolic resin- desulfurization gypsum composites which drawing lessons from the production of MDF cement process with desulfurization gypsum modified by phenolic resin. Mechanical properties and water resistance have been explored, the results shows that: at the condition of 160℃, 5 MPa, 120 s, the best dosages for mechanical properties is phenolic resin 1%, silane coupling agent 0.1% and expansive agent 3%, at which tensile strength is 23.1 MPa improved by 234.8% and compressive strength is 49.5 MPa improved by 38.7%. The best dosages for water resistance is phenolic resin 1%, silane coupling agent 0.3% and expansive agent 3%, at which water absorption(2h) is 0.58% and water absorption(24h) is 1.07%.Influence of the hot-pressing process parameter on MDF phenolic resin-desulfurization gypsum mechanical properties has been studied. The result show that: the hot-pressing process had important influence on the mechanical properties of MDF phenolic resin- desulfurization gypsum. The order of factor impacting on mechanical properties form small to greatly is hot-pressing pressure, hot-pressing temperature, hot-pressing time. The optimum hot pressing parameters are hot-pressing pressure 5Mpa, hot-pressing temperature 160℃ and hot- pressing time 120 s.Microstructure and mechanism of the MDF phenolic resin- desulfurization gypsum have been explored. The results showed that: the mainly hydration products of MDF phenolic resin- desulfurization gypsum are dihydrate calcium sulphate, and the system still contain small amounts of hemidrate calcium sulfate. Microstructure of dihydrate calcium sulphate crystal in MDF phenolic resin- desulfurization gypsum is mainly thick plate, needle bar and mainly existing in the form of plate-like. New chemical bonds have not been fond. Phenolic resin incomplete covers on surface of desulfurization gypsum particles, which impacting crystal morphology of dihydrate calcium sulphate. |
