Study On Effect Of Mixing Sequence In Polymer Procesing On Block Copolymer Compatibilization

This paper mainly studies the effect of mixing sequence in polymer blend on the block ompatibilization. According to the paper, the inherent relationships between the molecular structures of compatibilzer, processing conditions, phase morphologies and fatigue behaviors in polymer blends were investigated, and a new mixing strategy that forcely distributing the block copolymer into the interface of polymer blend has been concluded. The main studies of this work are as follows:1、In the 2nd chapter of this paper: Natural rubber(NR) and Butadiene rubber(BR) were taken as the matrices. Without considering the NR/BR blend, we firstly investigated the effect of liquid isoprene-butadiene block copolymer rubber(LIR-390, weight ratio of butadiene to isoprene is 90:10) on the mirco-structures and properties of NR and BR, respcively. The results showed that LIR-390 formed into micelles in NR and BR homopolymers, respectively, although it can improve the processing performance of NR and BR. The structures of micelles were opposite, with inverted cores and coonas. The addition of LIR-390 decreased the tensile properties, dynamic viscoelasticities and cannot help to reduce the rolling resistance of NR vulcanizate. As the “defect”, LIR-390 micelles induced the growth of fatigue crack, and reduced the service life of the final products as well.2、After clarifying the role of LIR-390 in NR and BR, respectively, the influence of mixing sequence on LIR-390 compatibilized NR/BR blend was investigated in the 3rd chapter. Comparing to the other mixing strategies, the domain size of dispersed BR phase was the smallest when LIR-390(the amounts of polyisoprene is about 10 wt%) firstly mixed with NR, and then blended with BR, which was denoted as(NR+LIR)/BR. The dynamic storage modulus, complex viscosity and tensile properties were got significantly increased by this sequential mixing. The fatigue crack propaogtion rates of(NR+LIR)/BR vulcanizate were reduced. Meanwhile, the compatibilizing mechanism of this sequential mixing was investigated in this chapter.3、In view of the summarized mixing sequence, i.e.(NR+LIR)/BR, in chapter 3, whether this sequential mixing lead to almost all of the block copolymer spanning the interface, a model system, composed of poly(cyclohexyl methacrylate) and poly(methyl methacrylate)(PCHMA/PMMA blend) was chosen in the 4th chapter. Two kinds of poly(styrene-b-methacrylate)(PS-b-PMMA), the block ratio of which are similar with that of LIR-390 in in chapter 3, were taken as the compatibilizer. In this system, only PS block is strongly stained by ruthenium tetroxide(RuO4) and appears dark when imaged with transmission electron microscopy(TEM). The results showed that sequential mixing can really improve the percentage of block copolymer residing at the interface and only the lower-amount block in diblock copolymer has the same mer unit with the matrix, and the diblock copolymer firstly mixed with the matrix, then blended with the dispersed hompolymer, can the diblock copolymer span the interface, and improve the compatibilizing effectiveness. It also confirmed the reasonableness of the sequential mixing in chapter 3.