▎ 摘　　要

NOVELTY - Preparing graphene-modified aqueous polyurethane composite material involves preparing prepolymer by adding toluene-2,4-diisocyanate (TDI) to a four-necked flask, under a nitrogen atmosphere, slowly dropping the dehydrated polypropylene glycol (PPG, number average molecular weight: 2000), and the mixture is stirred at a temperature of 60 to 70 degrees C for 2 hours to obtain a prepolymer. The prepolymer is added with dimethylolpropionic acid (DMPA) and reacted at 80 degrees C for 1 to 2 hours. USE - Method for preparing graphene-modified aqueous polyurethane composite material (claimed) for coating buildings. ADVANTAGE - The method enables to prepare graphene-modified aqueous polyurethane composite material in simple, low-cost and efficient manner, is suitable for large-scale production, and provides anti-static protection. DETAILED DESCRIPTION - Preparing graphene-modified aqueous polyurethane composite material involves preparing prepolymer by adding toluene-2,4-diisocyanate (TDI) to a four-necked flask, under a nitrogen atmosphere, slowly dropping the dehydrated polypropylene glycol (PPG, number average molecular weight: 2000), and the mixture is stirred at a temperature of 60 to 70 degrees C for 2 hours to obtain a prepolymer. The prepolymer is added with dimethylolpropionic acid (DMPA) and reacted at 80 degrees C for 1 to 2 hours. The temperature is reduced to 40 degrees C followed by adding acetone to reduce the viscosity, then adding a diethylene glycol and reacting for 1 hour. The temperature is decreased to 10 degrees C, then adding triethylamine (TEA) and reacting for 40min ~ 1h. The reaction product is added to deionized water, stirred at a high speed in an ice water bath for 1 to 3 hours to obtain an aqueous polyurethane emulsion. 300 mesh flake graphite, sodium nitrate are added in 98% concentrated sulfuric acid, placed in ice bath for cooling to 4 ~ 5 degrees C, slowly adding potassium permanganate, and stirring reaction for 3 to 4 hours. The mass ratio of the flake graphite, sodium nitrate and potassium permanganate is 1: 0.4 to 0.7: 2.5 to 4. Concentrated sulfuric acid and graphite ratio is 20 ~ 35ml: 1g. The stirring is performed at 35 degrees C in warm water bath for 30 ~ 40min, then slowly adding 40 ~ 60ml deionized water. The temperature is controlled at 45 ~ 50 degrees C, gradually heated to 90 degrees C and then adding water and slowly adding hydrogen peroxide to obtain bright yellow liquid. The bright yellow liquid is added with dilute hydrochloric acid and deionized water for repeated centrifugal cleaning to neutral, ultrasonic treatment for 2 to 3 hours after freeze drying to obtain brown solid form of graphene oxide. The vitamin C reduced graphene I is prepared by taking prepared graphene and dissolving in water, then adding a certain percentage of vitamin C and adjusting the pH with ammonia to 9 ~ 10 and placing at 95 degrees C in water bath for 30 ~ 40min. The product is washed with deionized water to neutral, freeze-dried to obtain vitamin C reduction after the graphene solid. The preparation of graphene aqueous solution according to a certain proportion prepared graphene solid and dispersant diphenylamine sulfonate, adding deionized water, ultrasonic treatment for 30min ~ 5h to obtain stable dispersion of graphene aqueous solution. The aqueous polyurethane emulsion is added in an amount of 0.5 wt.% (graphene-containing water-based polyurethane solid content of 0.5 wt.%) in terms of the solid content of the aqueous polyurethane, performing ultrasonic treatment for 1 to 4 hours to obtain a mixture. The mixture is poured on the polytetrafluoroethylene plate and air dried to obtain film. The obtained film is placed into a vacuum oven and dried at 50 degrees C. The film is cooled to room temperature to obtain graphene modified water-based polyurethane composite materials.