Effect of Olefin-based Compatibilizers on the Formation of Cocontinuous Structure in Immiscible HDPE/ i PP Blends

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POLYMER SCIENCE    

https://doi.org/10.1007/s10118-020-2433-7 Chinese J. Polym. Sci.

Effect of Olefin-based Compatibilizers on the Formation of Cocontinuous Structure in Immiscible HDPE/iPP Blends Fei Yanga, Li Pana, Hui-Zhen Dua, Zhe Maa*, and Yue-Sheng Lia,b* a Tianjin Key Laboratory of Composite and Functional Materials, and School of Materials Science and Engineering, Tianjin University, Tianjin 300072, China b Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, China

 Electronic Supplementary Information Abstract   In this work, the formation of cocontinuous structure in immiscible high density polyethylene/isotactic polypropylene (HDPE/iPP) blends was investigated for various olefin-based compatibilizers of distinct molecular architectures, including ternary random copolymer EPDM, olefin block copolymer (OBC), polypropylene-based OBC (PP-OBC), ethylene/α-olefin copolymer (POE), bottlebrush polymer poly(1-dodecene), and comb-like poly(propylene-co-high α-olefin) (PPO). The scanning electron microscopy results show that after adding OBC, PP-OBC, and POE copolymers, the finer droplet-in-matrix morphologies were obtained in 70/30 HDPE/iPP blend. Interestingly, for 70/30 HDPE/iPP blend with just 5 wt% of PPO copolymers, the phase inversion from droplet-in-matrix to cocontinuous morphology can be observed. It was proposed that the development of cocontinuous morphology contained the following steps: (1) interfacial saturation of compatibilizers and droplet deformation, (2) droplet-droplet coalescence, (3) continuity development, and (4) the formation of dual-phase continuity. Among the diverse copolymers studied in this work, PPO copolymer can be easily removed out of the interface during droplet coalescence and stabilize the curvature of minor fiber phase, facilitating the formation of cocontinuous morphology. In contrast, other olefin-based compatibilizers (EPDM, OBC, PP-OBC, and POE) exhibit the distinct steric repulsion effect to prohibit droplet coalescence. Moreover, the cocontinous interval varies with the compatibilizer architectures. Surprisingly, after adding 10 wt% of PPO copolymers, the cocontinuous interval was greatly broadened from HDPE/iPP range of 45/55−60/40 to that of 40/60−70/30. Keywords   Compatibilizer; polyolefin; Cocontinuous structure; Droplet-coalescence; Phase inversion Citation: Yang, F.; Pan, L.; Du, H. Z.; Ma, Z.; Li, Y. S. Effect of olefin-based compatibilizers on the formation of cocontinuous structure in immiscible HDPE/iPP blends. Chinese J. Polym. Sci. https://doi.org/10.1007/s10118-020-2433-7

 

INTRODUCTION The melt blending of two or more polymers has attracted considerable attention in both academia and industry, because of the significantly improved properties. For blend system, the formed phase morphology is critical for the performance of materials.[1−4] The typical morphologies include dropletin-matrix and cocontinuous structures. Among these morphologies, the cocontinuous structure, which has the interpenetrated po