REACTIVE MIXING OF PET AND PET/PP BLENDS WITH GLYCIDYL METHACRYLATE-MODIFIED STYRENE-b-(ETHYLENE-co-OLEFIN) BLOCK COPOLYMERS

Blocks copolymers styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) and styrene-b-(ethylene-co-propylene) (SEP, SEPSEP), with different styrene content and number of blocks in the copolymer chain, were functionalized by melt radical grafting with glycidyl methacrylate (GMA) and employed as compatibilizers for PET based blends. Binary blends of PET with both functionalized (SEBS-g-GMA, SEP-g-GMA, SEPSEP-g-GMA) and neat (SEBS, SEP, SEPSEP) copolymers (75/25 wt.%/wt.%), and ternary blends of PET and PP (75/25 wt.%/wt.%) with various amounts (2.5¸10 phr) of both modified and unmodified copolymers were prepared in internal mixer and their properties were evaluated by SEM, DSC, melt viscosimetry, tensile and impact tests. The role of the chemical structure, grafting degree and concentration of the various copolymers on the blend compatibilisation was investigated. The blends with the grafted copolymers showed a neat improvement of phase dispersion and interfacial adhesion, when compared to the blends with non-functionalized copolymers. The addition of grafted copolymers resulted in a marked increase of melt viscosity, which was accounted for by the occurrence of chemical reactions between the epoxide groups of GMA and the carboxyl/hydroxyl end-groups of PET during melt mixing. Blends with SEPSEP-g-GMA and SEBS-g-GMA at concentration of 5-10 phr showed a higher compatibilizing effect with enhanced elongation at break and impact resistance. The effectiveness of GMA functionalised SEBS was then compared to that of maleic anhydride grafted SEBS.