Study On Aqueous Deposited Polymerization Of Polyacrylonitrile And Voscosity Of Spin Solution

Aqueous deposited polymerization was adopted to prepare PAN, with aqueous as solvent, ammonium persulphate (APS) as initiator. The weight ratio of monomers and aqueous was 22/78, and APS as initiator was lwt% to monomers. The polymerization was carried out 60℃under nitrogen atmosphere, and stopped after 2 hours. Polyacrylonitrile (PAN) homopolymers, bipolymers with itaconic acid (IA) and methyl acrylate (MA) as comonomer respectively, and terpolymers with MA and IA under 4 various monomer ratios.The conversions of the seven polymerizations were caculated and compared. It was found that the ones of copolymerizations was higher than homopolyerization, but the values decreased with the weight persents of comonomers. The theoretical molecular wight value of polymers was deduced. It was M_max=1.75×10⁶. The viscosity average molecular weight was measured with Ubbelohde viscometer. The values decreased with the weight persents of comonomers.The theoretical reactivity ratios was calculated by Q-e equation proposed by Alfrey Price. Elementary analyser was used to draw reactivity ratio-intercept graph and experimental values were got. Both theoreticalvalues and experimental values declared that,——AN^* tended tocopolymerize, while the reactivity was MA＞IA＞AN.——MA^* tended tohomopolyerize, while the reactivity was IA＞AN＞MA. The reactivity with——MA^* was AN＞MA＞IA.Infrared ray (IR) discoveried carbonyl ( C = O ), hydroxy (-O-H ), carbon oxygen bond ( C-O ) from ester sturcture of MA and its partly hydrolyzation. They c at 3500cm^-1, strengthened the peak at 1750-1650cm^-1, and overlaped the peaks at 333-909cm^-1 .Stereoregularity, calculated by Masatomo Minagaw method, declared that IA reduced the values, while MA increased the values. Meanwhile, stereoregularity increased with the content of MA was enhanced in terpolymers, but the effect was not obvious.DSC and TG were used to analyse the thermal performance of terpolymers. It was found that, IA was propitious to cyclization, and it decreased the initial temperature (T_i) and the peak temperature (T_p), while MA increased T_i and decreased T_p. Both IA and MA widened the peak, further decreased the rate of heat release (V_H) of PAN during the pro-oxidation and the possibility of fiber-broken. Obvious cyclization and oxidation had happpened when the temperature was still low. New side groups increased the activity of polymers, such as -COOH from IA. While excess MA units brought excess side groups, and steric effect decreased the activity。There was a optimal value of MA content at about 6%.Three kind of polymers with molecular weight of 39.8×10⁴, 41.8×10⁴ and 79.0×10⁴ respectively were dissolved in dimethyl sulfoxide (DMSO). It was found that, the viscosity increased with molecular weight and solid content, while decreased with the temperature. And the time to dissolve should be prolonged corresponding. These parameters were not in linear relation. Besides, the solutions with low molecular weight polymer were more sensitive than the solutions with high ones.