Ultrasound Assisted Preparation And Characterization Of MAA_AN Copolymer And Thermal Decomposition Kinetic

Ultrasonic chemistry has become one of the frontiers discipline of chemical researchfield. The effect of cavitation, violent stir can be producted by ultrasonic in liquid system, andwidely used in polymer synthesis and the mechanism of polymer reaction. On the cavitationbubble phase interface, high temperature of 5000K, high pressure of 66.24kPa can be got, andhave been verified by sonochemical theoretical calculation and experiments. Under theextreme environment of high temperature and high pressure, free radicals can be producedfrom the decomposition of solvent, monomer or polymer chain, and the more free radical, theeasier initiated reaction was. In addition, effective mixing action of ultrasonic helps reaction.In this work, copolymer of MAA/AN was synthetised through ultrasonically inducedfree radical polymerization of methacrylic acid(MAA) and acrylonitrile (AN). The influenceon polymerization, which was caused by monomer ratio, initiator amount, ultrasonicfrequency, reaction temperature, etc, was studied and the reactivity ratio between MAA andAN was calculated. The result shows that, higher molecular weight can be got andpolymerization rate was easied to control, when monomer concentration was 1:1, initiatorconcentration 0.2%, ultrasonic frequency 20kHz, and ultrasonic field temperature was 55～60℃. The reactivity ratio between MAA and AN was 0.04 and 0.50.The themal degradation kinetics was studied through DTG. Themal degradation reactionactivation energy of MAA/AN copolymer synthesized at 50℃, 120℃, 140℃, 160℃wascalculated, the corresponding value was 61.24kJ/mol, 101.59kJ/mol, 147.46kJ/mol, 185.14kJ/mol and the pre exponential factors lgA0 4.40, 7.70, 10.35, 14.69, respectively. Thestructures and properties of copolymers was analysised through infrared spectroscopicanalysis(FTIR), thermogravimetic analysis(TG), dynamic thermomec- hanical analysis(DMA). Through mechanics performance testing, the flexural strength of the copolymer synthesized at50℃, 120℃, 140℃, 160℃was 93.8MPa, 192.5MPa, 55MPa, 168.4MPa, flexural modulus4.06GPa, 4.79GPa, 0.75GPa, 6.74Gpa, and impact strength 7.5kJ/m2, 13.2kJ/m2, 23.4 kJ/m2,18.4kJ/m2. The carbon residue rate of the copolymer at 800℃was 40%, showed wonderfulthermalstability. The glass transition temperature (Tg) of copolymer synthesized at 50℃, 120℃, 140℃, 160℃, achieved from DMA, was 92.92℃, 154.64℃, 187.66℃, 203.93℃,respectively.