Characterization of polypropylene/hydrogenated styrene-isoprene-styrene block copolymer blends and fabrication of micro-pyramids via micro hot embossing of blend thin-films

Abstract

Polypropylene (PP)/hydrogenated styrene-isoprene-styrene block copolymer (HYBRAR) blends were proposed as a new material for the fabrication of micro-pyramids via the micro hot embossing of their blend thin-films. As a typical thermoplastic amorphous polymer, HYBRAR could promote the crystallinity and decrease the crystallization temperature of PP. With increasing HYBRAR proportion, mechanical behavior of PP/HYBRAR blends changed from a typical plastic to a typical elastomer. HYBRAR exhibited higher complex viscosity and much higher storage modulus dependence on shearing frequency than PP, which is attributed to the strong interaction between polystyrene segments on HYBRAR. Measurement of micro-pyramids by a laser scanning microscope indicated the embossing temperature and HYBRAR proportion in the blends were the two key factors determining the integrity of micro-pyramids. With higher deformation ability than PP, HYBRAR could effectively promote the moldability of PP/HYBRAR blends in the micro hot embossing, leading to a better integrity of micro-pyramids and low haze and high light transmittance of the embossed thin-films. In addition, the effects of T_m of PP and the thickness of the film base on the optical properties of embossed PP/HYBRAR blend thin-films were also discussed. PP/HYBRAR blends are proved to possess a promising prospect in the fabrication of optical thin-films.