Multigraft Copolymers from an Upscalable Synthesis Route - Material Characteristics and Application Relevant Performance

Tetrafunctional multigraft copolymers (MGCP) based on polyisoprene (PI) and polystyrene (PS) are prepared by an upscalable pilot-scale anionic synthesis approach, prospectively making this new type of thermoplastic elastomers available for future industrial applications. The materials are characterized with respect to their molecular architecture, microphase-separated morphology, their thermal and mechanical properties under quasi-static conditions as well as regarding the damage behavior under dynamic deformation. For the latter, membrane demonstrators are prepared by melt pressing. The investigated multigraft copolymers show strain at break values between 1250 % and 2000 %, depending on the number of branch points, in connection with tensile strength values of 17 to 8 N mm-2, respectively. Their ultimate toughness is about 50 % higher than that of a reference diblock-triblock blend with similar chemical composition. They show superior behavior in hysteresis tests at large number of hysteresis cycles. Application relevant testing revealed that melt-pressed multigraft copolymer membranes are less affected by surface cracks after long term dynamic testing in comparison to the reference copolymer blend. Based on this property profile, multigraft copolymer-based thermoplastic elastomers can be considered as suitable candidates to substitute components made from silicon and polyvinyl chloride (PVC). Further, they can serve as more effective toughening additives in blends.