Study On Synthesis Of Silane Modified Styrene-Acrylate Emulsion And Effect Of Composite Mineral Materials For Waterproof Performance Of Desulfurized Gypsum

In this thesis,the self-made silane modified styrene-acrylic emulsion was combined with silicate clinker and silica fume to modify desulfurization gypsum to improve its water resistance,and the mechanism was discussed.The following results were obtained:(1)This experiment used silane-modified styrene-acrylic emulsion as an organic polymer additive for desulfurization gypsum.The parameters such as synthesis temperature,stirring rate,amount and ratio of complex emulsifier,amount of initiator,amount and ratio of complex silane,and reaction time were studied,the results showed that the polymerization temperature was 75~80 ?,the stirring rate was 250r/min,the amount of composite emulsifier was controlled at 4%,and the ratio of OP-10 to SDS was 3:1,and the amount of initiator ammonium persulfate was 0.6%,the amount of the composite silane is 6%,the mass ratio of G-570 to YDH-171 is 1:2,and the silane-modified styrene-acrylic emulsion obtained by the reaction for 3 hours has the best performance.The water absorption of the coating film of the silane-modified styrene-acrylic emulsion obtained at this time was 5.6%,and the water absorption rate was reduced by 78.8% as compared with that before the modification,the solid content was 48.8%,which was 5.6% higher than that before the modification.(2)In the case of single-doped modified emulsion,as the amount of modified emulsion increases,the water consumption of the standard consistency of the desulfurized gypsum was decreased,and the setting time was increased.When the silane-modified styrene-acrylic emulsion was added 0.1% or less,the strength and softening coefficient of the desulfurized gypsum become larger as the amount of the water-repellent emulsion is increased,and the water absorption rate gradually decreases.When the dosage of the emulsion is 0.1%,the softening coefficient of the desulfurized gypsum block reaches 0.72,the compressive strength is 9.0 MPa,and the water absorption rate was 36%,compared with the blank sample,the softening coefficient and compressive strength increased by 148% and 18%,respectively,andthe water absorption rate decreased by 33%.(3)Used silicate clinker and silica fume can extend the setting time of the desulfurized gypsum sample,however,the silicate clinker can reduce the water consumption of the standard consistency of the desulfurized gypsum,and the addition of the silica fume increases the standard consistency water consumption of the desulfurized gypsum sample.Both silicate clinker and silica fume can enhance the strength and water resistance of desulfurized gypsum,whether it is single or complex.The composite of 6% silicate clinker and 9% silica fume makes the compressive strength and flexural strength of the desulfurized gypsum reach 12.9 MPa and 5.5MPa,the compressive softening coefficient and the flexural softening coefficient reached 0.57 and 0.66,and the water absorption rate decreased to 23.7% in 24 hours.(4)The combination of the modified emulsion and the inorganic mineral material can reduce the water consumption of the standard consistency of the desulfurized gypsum within a certain dosage range,and increase the time of initial setting and final setting.The optimum dosage is: 0.15% modified emulsion,6% silicate clinker and9% silica fume,at this time,the compressive strength and flexural strength of the desulfurized gypsum are 13.4 MPa and 6.5 MPa,and the compressive softening coefficient and the flexural softening coefficient are 0.79 and 0.87,compared with pure desulfurized gypsum,which increased by 36.7%,91.2%,146.9% and 128.9%,respectively,and the water absorption rate of 24.h was 15.3%,which was reduced by55.4%.(5)Through microscopic analysis,the modified emulsion and inorganic mineral material were combined can improve the strength and water resistance of the desulfurized gypsum.Mainly because the modified emulsion can form a good hydrophobic film layer inside the desulfurized gypsum crystal,the hydrated products ettringite and CSH gel of silicate clinker and silica fume with esulfurized gypsum slurry were filled in the desulfurization gypsum,they have prevented the entry of external moisture.Thereby,the defects of desulfurization gypsum,low water resistance and low strength are improved,and it will promote the development of desulfurized gypsum in the future.