| Thermoplastic elastomer (TPSiV) based on silicone rubber and polyurethane(TPU) is a kind of thermoplastic elastomer with excellent high-temperature resistance. The technical prominent problem to obtain this kind of elastomer is to solve the compatibility of TPU and VSR. There have already been some relevant mature products abroad, but fewer domestic research has been carried out. Adding compatibilizer is a common way to improve the compatibility of the blends by reviewing relevant literature. In recent years, hyperbranched polymers have received more attention in polymer modification applications, but a relatively small application as compatibilizers has been studied. In this paper, a silicone-modified hyperbranched polyurethane (HPU-Si) is used to improve VSR /TPU blends compatibility, and the excellent performance of TPSiV is developed based on the hyperbranched compatibilized system.Firstly, a hyperbranched polyurethane (HPU) was synthesized by the monomer of AB2 type. The hydroxyl value by determining the hydroxyl content of hyperbranched polyurethane was 41.1. Based on hyperbranched polyurethane 13C-NMR analysis, it has proved that the hyperbranched structure of HPU was successfully obtained, and the degree value of branching was 0.73. Based on a molar ratio of hydroxyl content, HPU-modified silicone oil (HPU-Si) was synthesized and the molecular structure was characterized by IR and XPS. The Mw value of HPU-Si was(3,1±0.1)×104by laser light scattering testing. The thermal decomposition temperature of HPU-Si was 300℃, which was higher than the processing temperatures of VSR/TPU blends. HPU-Si could improve the mechanical properties of VSR/TPU blends. When its amount was 3phr, the tensile strength and elongation at break of TPSiV reached the maximum value of 13.94 MPa and 573%, compared with the blank sample, increased by 72.1% and 38.4%. The HPU-Si in VSR and TPU phase interface to form an interface layer and improve the system compatibility was confirmed by rheological experiments. From the SEM results, it can be deduced that the compatibilizer HPU-Si reduced the interfacial tension of VSR and TPU two-phase, and increased its interface binding force and refined VSR dispersion size.The research results of preparing TPSiV technology showed that 190℃ was the optimum processing temperature,70 r/min was the optimal speed, and 6 min was the optimal mixing time. Through the mechanical properties of materials and the data analysis of micro-phase scanning electron micrographs(SEM), the processing order greatly affected the physical properties. The best way for dynamic vulcanization process of VSR and TPU was simultaneously adding the reactor at melt blending time of 6 min, then adding the dynamic vulcanization vulcanizing agent.By comparing two different vulcanizing system of DBPH and DCP, it showed that the TPSiV obtained by vulcanizing system of DBPH exhibited excellent overall performance including excellent processing properties and repeated anti-aging properties. During the dynamic vulcanization process of the phase tracking, VSR phase in the TPU phase was distributed substantially uniformly and the size of dispersed phase VSR was significantly reduced in the first 6 min. The system phase structure became perfect and the process of dynamic vulcanization had been completed within 9 min.When the VSR content in TPSiV was less than 50%, a rubber phase VSR was uniformly distributed in the continuous phase of TPU by tens of nanometers or several micrometers fine particles. The phase inversion occurred within the rubber ratio of 50:50-60:40. With the increase of VSR content, the solvent resistance was deteriorated and the melt index was increased and the thermal decomposition rate was decreased. When VSR: TPU rubber ratio was 40:60, TPSiV showed good mechanical properties and the material combined high strength and elongation at break. |
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