Study on Preparation and Modification of Azodicarbonamide
|School||Hebei University of Technology|
|Course||Hebei University of Technology|
|Keywords||Hydrazine hydrate Biurea Azodicarbonamide PVC resin Inorganic nanopowder Complex foaming agent|
Azodicarbonamide (trade name : foaming agent ADC) is a non-toxic , tasteless , non-polluting , orange - yellow azo blowing agents , its biggest feature is a molecule containing -N = N- structure , Heating may release large amounts of N2 gas evolution up to 200 ~ 250 ml / g, a widely used chemical foaming agent . Currently, the synthesis process of the azodicarbonamide is mainly synthesized by the condensation of hydrazine hydrate by the acid method biurea , biurea synthesized by oxidizing agent azodicarbonamide . Acid prepared biurea to adding large quantities of sulfuric acid in the reaction system to adjust the pH value is acidic , severe corrosion of the equipment , are difficult to recover and dispose of ammonium sulfate generated . With hydrochloric acid to adjust a pH of the hydrazine hydrate solution weakly alkaline , rather than adjusting the pH value of the reaction system , and reduces the amount of hydrochloric acid . Also studied using high concentrations of hydrazine hydrate and the direct synthesis of Urea biurea process , this process does not use an acid , the corrosion of the equipment smaller , friendly to the environment . Orthogonal experimental method to study the optimum conditions for the synthesis azodicarbonamide , under optimum conditions , the auxiliary ultrasound, to improve the the azodicarbonamide the gas evolution . Azodicarbonamide decomposition temperature of 195 to 220 ° C , far exceed the plasticizing temperature of the PVC resin (about 170 to 175 ° C ) , therefore need to be added in the azodicarbonamide activators, reducing azodicarbonamide decomposition temperature, in order to meet the processing requirements of the PVC resin . Zinc oxide zinc ions having the acceptance of the ability of a lone pair of electrons that can accept the azodicarbonamide the nitrogen atom and the carbonyl oxygen atom lone pair of electrons , reduce the decomposition temperature of the azodicarbonamide , is a relatively excellent activators. In this paper, the sol - gel method to prepare nano ZnO -SiO 2 < / sub > powders , nano ZnO-SiO 2 powder was added to the azodicarbonamide , preparation mixed blowing agents. Mixed blowing agent decomposition temperature , gas evolution , and is conducive to the processing of PVC resin foam , so it has a certain application prospects .