| Binary graft copolymers could have the performances of the two kinds of polymers at the same time, and satisfy the request of different uses; the preparation processes are relatively simple, so they are widely applied in industry. The graft polymerization kinetic research is very important for exploring the polymerization mechanism, and the optimized design of the polymerization process and reactor. Vinyl acetate(VAc) bath and semi-bath graft polymerization in the presence of polyethylene glycol(PEG) was carried using tert-Butyl peroxy-2-ethyl hexanoate (TBPO) and tert-Buty peroxypivalate (TBPV) as initiators respectively in order to study thekinetics thoroughly.Firstly, the effects of initiator activity and concentration, temperature, VAc:PEG ratio and PEG molecular weight on the polymerization rate in the bath bulk graft polymerization were investigated. The results showed that the polymerization rate enhanced with the increase of initiator activity and concentration, VAc:PEG ratio and polymerization temperature. The influence of PEG molecular weight on polymerization rate was small. The TBPV initator activity was and high, and the initator decomposed so much at the early stage of polymerization that the normal polymerization could not maintain as the lack of initiator decomposition at the later period of polymerization. f1/2kp/kt1/2 did not change with initiator activity and concentration and PEG molecular weight, but it increased a little with rising VAc:PEG ratio because of the cage effect. The temperature had great influence on overallreaction rate coefficient K (= kp((fkd)/kt)1/2), Its overall activation energy E=83.5 kJ/mol.Secondly, the changes of PVAc grafting efficiency(Ge), PEG grafted efficiency(Gd), PVAc grafting ratio basing on total PEG(Gr), and PVAc grafting ratio basing on the grafted PEG(G'r) along with conversion, initiator activity and concentration, temperature, VAc:PEG ratio and PEG molecular weight in the bath bulk graft polymerization were studied. The results showed Ge was generally very high and kept unchanged throughout whole polymerization time. Ge can reach above 95% at low VAc:PEG ratio and increased by raising VAc:PEG ratio. Other factors had not influences on the change of Ge. Although Gd was enhanced with the increase of monomer conversion, initiator activity and concentration, VAc:PEG ratio and polymerization temperature, the overall Gd was generally low within our investigated conditions. The high VAc grafting efficiency and low PEG grafted efficiency indicated that the PEG chain active sites was not easy to produce, and the 'Graft From' polymerization system may undergo a 'Graft Onto' mechanism. Gr increased linearly with monomer conversion, Other factors had little effect on Gr except VAc:PEG ratio which resulting in the increasing Gr. G'r reduced along with increasing of covension, initiator activity and concentration, temperature and PEG molecular weight and decreasing of VAc:PEG ratio.Thirdly, the changes of graft copolymer molecular weight along with conversion, initiator activity, initiator concentration, temperature, VAc:PEG ratio and PEG molecular weight in the bath bulk graft polymerization was investigated. The results showed that the PEG-g-PVAc number-average molecular weight could be calculatedwith (?)=MwPEG(1+ Gr/Gd) according to the definition which was more accuratethan PVAc and PEG universal calibration results via GPC test. The change trend of the three calculation results was identical. The graft copolymer number-average molecular weight reduced with raising of conversion, initiator activity and concentration, decreasing of VAc:PEG ratio, and increasing of temperature and PEG molecular weight. The phenomena that VAc:PEG had great influence on the graft copolymer molecular weight was related to the strong chain transfers in the polymerization system. Via the experiments of various VAc:PEG ratios, we could calculate the chain transfer constants to VAc (CM)≈3*10-4 and the chain transfer constant to PEG (CS)≈30*10-4Finally the PEG/VAc semi-bath bulk graft polymerization was carried. The influences of monomer feed speed and method on the the kinetics of polymerization was studied. The results showed that the polymerization rate was less than feed rate, so along with the polymerization process, the monomer concentration in reactor increased at the early stage of polymerizaiton; and the polymerization rate was growing and continued to grow at the end of the monomer feeding. This phenomena indicated the exist of gel effect in the polymerization system. For a period of time after the monomer feeding, the polymerization rate reached the maximum value, and then declined slowly. Although the faster the feed speed, the higher the polymerization rate; the polymerization rate of semi-bath was lower than bath polymerization at all times. The Ge and Gd were higher than those of bath polymerization; moreover, the slower the feed speed, the more the raising Gd Value. The graft copolymer molecular weight increased at first and then decreased as the increasing conversion; this phonemena was related to the VAc growing at first and then decreasing. The slower the feed speed, the greater the monomer concentration, the higher the molecular weight.
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