Preparation Of Pvc Block Copolymers Via Raft Polymerization And Their Application Of Pvc Based Additives

Poly(vinyl chloride)(PVC)is one of the most widely consumed polymers in our daily life.Conventional free radical polymerization(FRP)of Vinyl chloride(VC)is the only available industrial process to produce the polymer in large scale.However,there are structural defects and less functional groups in PVC prepared via FRP process.So reversible deactivation radical polymerization(RDRP)methods such as reversible addition-fragmentation chain transfer(RAFT)polymerization can solve these problems for the polymerizaton of PVC.On the other hand,the performances of PVC will be improved by different additives such as plasticers.Dioctyl phthalate(DOP)is one of the most widely used PVC plasticizers but the migration of plasiticizers not only bring serious health hazards but also lose of flexibility of flexible PVC products.VC monomer was polymerized by RAFT polymerization with a xanthate RAFT agent containing hydroxyl groups,which can be used as a ring-opening polymerization(ROP)initiator in forming polymer plasticizers poly(vinyl chloride)-block-polycaprolactone(PVC-b-PCL).Low Mn 3 and 4-arm star PVC with the low glass transition temperature(Tg)can be used as alternatives to phthalate plasticizers.Trithiocarbonates RAFT agents for more active monomers(MAMs)were attached on the PVC-(OH)2 by esterification reaction,and these RAFT agents provide a universal stage to synthesize different types of additives.The main research contents are as follows:1.Well-defined nonmigratory polymeric plasticizers,PVC-b-PCL block copolymers,were synthesized by sequential RAFT and ROP with 2-hydroxyethyl 2-(ethoxycarbonothioylthio)propanoate(HECP)as RAFT agent and incipient initiator for ROP of ?-caprolactone(CL).Kinetic experiments demonstrated that HECP provided good control in RAFT polymerization of VC.Chain extension experiments with VC and vinyl acetate proved the end-group fidelity of the macroRAFT agent formed.The hydroxy-end-group of the PVC macroRAFT agent allowed its use as a ROP initiator in forming a series of PVC-b-PCL with different PCL block lengths by RAFT-T-ROP.Study indicates that there is enhanced chain entanglement for PVC-b-PCL block copolymers when compared to PCL homopolymers in PVC blends.PVC blends plasticized with PVC-b-PCL show similar or better ductility than PVC containing the archetypical PVC plasticizer,DOP for the same level of plasticiser.Most importantly,the PVC-b-PCL polymeric plasticizers are non-leaching and do not migrate under conditions where DOP is readily extractable.2.A series of 3-arm and 4-arm star like PVC with molecular weight from 1.2kDa to 6.5kDa were prepared using RAFT polymerization mediated by xanthates.Low Mn 4-arm star PVC with the lowest Tg which were used as alternatives to phthalate plasticizers,and physical properties and migration resistance were tested and exhibited non-migration properties and good plasticized effects.3.A series of three-mikto-arm star PVC based additives were synthesized using RAFT polymerization,including PVC based plasticizer poly(vinyl chloride)-star-[poly(n-butyl acrylate)]2(PVC-star-(PBA)2),PVC based thermal stabilizer poly(vinyl chloride)-star-[poly(3-methacryloxypropyltrimethoxysilane)]2(PVC-star-(PMPS)2),PVC based UV stabilizers poly(vinyl chloride)-star-[poly(2-hydroxy-4-acryloxybenzophenone)]2(PVC-star-(PHABP)2),poly(vinyl chloride)-star-poly(2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl methacrylate)2(PVC-star-(PBTEM)2),and PVC based flame retardants poly(vinyl chloride)-star-[poly(4-vinylbenzyl phosphonate)]2(PVC-star-(PVBP)2)and poly(vinyl chloride)-star-[poly(diethyl(methacryloyloxymethyl)phosphonate)]2(PVC-star-(PDEMMP)2).The Tg of PVC-star-(PBA)2 is lower compared with its linear counterpart PVC-b-PBA,and PVC-star-(PBA)2 polymeric plasticizers do not migrate out from plasticized PVC.The thermogravimetric analyser(TGA)and differential thermogravity(DTG)were characterized and confirmed the enhanced thermal stability of PVC after addition of PVC-star-(PMPS)2.The uniform distribution of silica nanoparticles in the PVC matrix was observed by scanning electron microscopy(SEM).The effect of PVC-star-(PHABP)2 and PVC-star-(PBTEM)2 were tested by ultraviolet-visible(UV)spectrophotometer.The PVC-star-(PDEMMP)2 had a better flame retardancy effect compared with PVC-star-(PVBP)2 according to limiting oxygen index(LOI)test.