Papers by Author: Wen Hong Ruan

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Authors: Wen Hong Ruan, Min Zhi Rong, Ming Qiu Zhang
Abstract: To prepare polymer nanocomposites with enhanced performance, well dispersion of nanoparticles in matrices is necessary. In this work a new route that combines graft pre-treatment and drawing technique with melt mixing was applied. That is, nano-SiO2 particles were firstly modified by graft polymerization and then the grafted nanoparticles were melt-compounded with polypropylene (PP) producing composites filaments via drawing. Finally, the filaments were injection molded into bulk materials. The resultant PP based nanocomposites are much tougher than the unfilled polymer as characterized by either static or dynamic test, besides showing a simultaneous increase in strength and stiffness. Morphology studies indicated that drawing induced extension and separation of the grafted nano-silica agglomerates in PP matrix during making the filaments are frozen to a certain extent after nanocomposites manufacturing. In this way, the nanoparticles are well distributed in the matrix and correlated with each other throughout the entire composites, which might ensure an overall improvement of mechanical properties. Besides, β-crystal of PP developed in the drawing process can be retained in the nanocomposites, which also contributes to the toughening of PP. In view of these, the proposed drawing aided dispersion of nanoparticles might also be applicable to the preparation of other nanoparticles/polymer composites.
Authors: Li Feng Cai, Min Zhi Rong, Ming Qiu Zhang, Wen Hong Ruan
Abstract: To promote dispersion of nano-silica in polypropylene (PP), a polymerizable foaming agent p-vinylphenylsulfonylhydrazide was synthesized and grafted onto the nanoparticles via free-radical polymerization. The results of thermogravimetric analysis (TGA) showed that the sulfonyl hydrazide groups of poly(p-vinylphenylsulfonylhydrazide) acquired the desired thermal decomposition ability, which might be related to their internal oxidation-reduction. Electron microscopy observation indicated that the grafted nanoparticles exhibit greatly improved dispersion in PP owing to the fact that the sulfonyl hydrazine groups on the grafted polymer inside the agglomerates decomposed like blowing agent to form polymer bubbles, leading to rapid inflation of the surrounding matrix that pulled apart the agglomerated nanoparticles during melting mixing.
Authors: Tong Hui Zhou, Wen Hong Ruan, Min Zhi Rong, Ming Qiu Zhang
Abstract: In our previous works, a double percolation mechanism of stress volumes was proposed to explain the special effects generated by small amounts of grafted nanoparticles. Accordingly, it is inferred that strengthening nanoparticle agglomerates and enhancing nanoparticles/polymer matrix interfacial interaction are the key issues to improve mechanical performance of the matrix polymer. To confirm this idea, in-situ crosslinking was adopted to prepare nanocomposites by adding reactive monomers and crosslinking agents during melt compounding of nano-silica with polypropylene (PP). It was found that the grafted polymer chains were successfully crosslinked and chemically bonded to the nano-silica forming crosslinked networks. Meanwhile, matrix molecular chains penetrated through the networks to establish the so-called semi-IPN structure that interconnected nanoparticles by the networks and improved filler/matrix interfacial interaction. As a result, the tiny nanoparticles were well distributed in the matrix and the toughening and reinforcing effects of the nanoparticles on the matrix were brought into play at rather low filler loading, as evidenced by mechanical performance tests. Besides, β-crystal was detected in the nanocomposites experienced in-situ crosslinking reaction.
Authors: Wen Hong Ruan, Ming Qiu Zhang, Ming Hui Wang, Min Zhi Rong, Tamás Bárány, Tibor Czigány
Abstract: To improve the properties of polypropylene (PP), a new route that combines nanoparticles filling with self-reinforced technique was applied in this work. That is, nano-silica particles were firstly modified by graft polymerization to increase interfacial interaction between nanoparticles and matrix. Then the grafted nanoparticles were melt-compounded with PP producing composites sheets, and the sheets were stretched under a temperature slight lower than the melt point of PP at a constant velocity. Finally, the stretched sheets were film-stacked with random PP copolymer by a special designed mold and were hot pressd at different processing temperature (T=150-175°C) and holding pressure (2.0-5.0MPa) under constant holding time of 5min. The resultant self-reinforced nanocomposite are much stronger and stiffer than the unfilled polymer as characterized by mechanical test. The results show that the optimum processing conditions for hot consolidation are 160°C and 2.5MPa. Addition of nanoparticles increases crystallinity of PP, and induces the formation of craze and cause much more surrounding matrix polymer to involve in large-scale plastic deformation, which might ensure an overall improvement of mechanical properties.
Authors: Klaus Friedrich, Min Zhi Rong, Ming Qiu Zhang, Wen Hong Ruan
Abstract: Nano-sized silica particles were pre-grafted with poly(glycidyl methacrylate) (PGMA) by solution free-radical polymerization. When these grafted silica nanoparticles were melt compounded with polypropylene (PP), reactive compatibilization effect was perceived due to the chemical bonding between the grafted PGMA and amine functionalized PP, which led to a significant increase of tensile strength and notch impact strength of PP at rather low filler content. Accordingly, compatibility of each kind of the functionalized PP with grafted SiO2 nanoparticles was evaluated through investigating the mechanical properties, crystallization behavior and rheological performance of the composites. The results show that the reactive compatibilization is capable of providing stronger interfacial adhesion.
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