Study On Properties Of SB-g-HVPBR And SB-g-HVPBR/SBR Blends

Adjustable structural styrene-butadiene macro-monomer (SB) was synthesized by anionic polymerization with butyl-lithium as initiator,tetrahydrofuran as structure regulator. Styrene-butadiene copolymer grafted high vinyl polybutadiene rubber, SB-g-HVPBR,was synthesized by coordination copolymerization of SB and butadiene used with MoCl3(OC8H16)2 and Al((OPhCH3)(i-Bu)2) catalyzed system. The effect of molecular weight and addition amount of SB on the structure and properties of SB-g-HVPBR, as well as the influence of SB-g-HVPBR’s structure and the blending ratio of SB-g-HVPBR/SBR on the compatibility of blends were studied by means of FT-IR,1HNMR, GPC, GPC-MALLS-Viscometer Analysis System, DSC, DMA, RPA, SEM etc.The vinyl content of SB-g-HVPBR was over 80%, which was unaffected with the change of SB’s molecular weight and the addition amount. After grafting modification, the SB-g-HVPBR’s molecular weight and molecular weight distribution increased, while, the gel raised slightly, the glass transition temperature(Tg) decreased. The solution dynamic viscosity of HVPBR were decreased to a great extent as a result of grafted with SB,which could solve the problem of high viscosity of glue solution during polymerization industrialization. The wear resistance, wet skid resistance, aging resistance, dry or wet traction and turning operation of HVPBR were increased while the compression set% and compression heat were decreased due to the SB grafted chains.The frequence, strain and temperature sweeping of crude rubber detected by RPA showed that the storage modulus (G’)decreased, meanwhile, the loss modulus (G") and loss factor (tanδ) raised. With the increase of addition amount of SB from 0 to 7 weight percent in monomer, the grafting index value of SB-g-HVPBR decreased before increased. While the additon amount was 3 percent, the grafting index value was lowest and the grafting degree was highest, as well as the wear resistance and combination properties of vulcanized rubber were best. With increasing molecular weight of SB from 3.2～22.1×103,the molecular weight, intrinsic viscosity, grafting index value and dynamic viscosity of SB-g-HVPBR increased. And the grafting degree increased to the high point while the dynamic viscosity decreased to the lowest point as the molecular weight of SB was 3.5×103.When the molecular weight was greater than 1×104, the structure that more than two main HVPBR molecular chains were grafted with the same one SB macro-monomer added. So the molecular weight, solution viscosity and solution dynamic viscosity of copolymer raised.The grafting of SB could reduce the value of Mooney viscosity and shorten the vulcanizing time after SB-g-HVPBR blending with SBR.The wear resistance,aging resistance were strengthed while compression set% and compression heat were reduced.The over-all properties were the most cxcellent of all the blending ratios when the SB(the styene content of which was 30%, the molecular weight was 3.6×103 and the adition was 3%) was grafted. The results of DSC、DMA and SEM revealed that the grafed modification of SB was in effect to the compatibility of HVPBR/SBR, while, it didn’t affect the dispersancy of fillings in blends.