Studies On SBS Graft Copolymerization Modified By HCCP

Styrene-butadiene-styrene triblock copolmer (SBS) grafted with acrylic polymer exhibits better adhesion to PVC material. In order to further improve the performance, high chloride content polymer (HCCP) was introduced into the system. HCCP is referred to chlorinated polyethylene(CPE) and chlorinated polyvinyl chloride (CPVC).They were added respectively. This is a novel method and so far no reference about it was found.The effects of solvent, temperature, initiator and monomer dosage on the graft polymer were discussed. The optimum graft copolymerization conditions were as follows: mixed solvents of toluene butanone (10/3,m/m), the feeding ratio of backbone polymers: solvent: methyl methacrylate (MMA): benzoyl peroxide (BPO) 100:400:70:2, and reaction temperature 90℃..Based on the results mentioned above, the influence of HCCP on graft copolymerization was investigated.CPE and SBS were dissolved readily; however, CPVC and SBS must be dissolved by a two-step process. If they were added into the mixed solvent simultaneously, CPVC articles might be enwrapped in SBS molecules, which would prevent the polymers from being dissolved effectively.When SBS and HCCP were dissolved completely, the solution was heated to 80℃ ,and BPO and monomer were then put in the flask (BPO was dissolved in monomer).The graft copolymerization was carried out at constant temperature 90±1℃ until the glue had suitable viscosity.2,6-di-tert-butyM- methyl phenol(BHT) was used to terminate the reaction.The use of too much HCCP should be avoided because its brittleness and polarity are far different from SBS, or bond line was easily separated from the substrate during peeling strength test. Furthermore, the adhesive stability was poor. When the content of CPE was less than 25% and that of CPVC was between 20% and 30% (based on the total weight of SBS and HCCP),the adhesive had not only good stability and excellent water resistant property but also high adhesion to PVC artificial leather.In the presence of certain tackifier, the viscosity was decreased by big margin, the tack retention time prolonged and the final peeling strength decreased. Considering both adhesion property and coating operation, the viscosity value should be neither large nor small.The graft reaction was demonstrated by infrared(IR) spectra using the characteristic absorption band for MMA at about 1720cm"1.Scanning electron microscope(SEM)photographs revealed that the compatibility between the glue and PVC can be effectively improved by the incorporation of HCCP in SBS graft system. A comparison of SBS/HCCP-g-MMA with the blend of SBS-g-MMA and HCCP-g-MMA showed their difference, which was attributed to the fact that SBS/HCCP-g-MMA adhesive was superior in properties to the blend of graft polymers. There was reasonable agreement between the expected and experimental results.