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Xin, Zhen Xiang,Zhang, Zhen Xiu,Pal, Kaushik,Lu, Bing Xue,Deng, Xu,Lee, Sung Hyo,Kim, Jin Kuk Wiley Subscription Services, Inc., A Wiley Company 2009 Journal of vinyl & additive technology Vol.15 No.4
<P>This paper presents an experimental study of the foaming behavior of polypropylene (PP)/(waste ground rubber tire powder) (WGRT) blends when using a chemical blowing agent in an extrusion foaming process. The effects of formulations (i.e., WGRT content, blowing agent content, compatibilizer) and the processing parameters (i.e., die temperature, screw speed) on the void fraction, average cell size, cell density, and cell morphology of the PP/WGRT foams were investigated. The blowing agent loading affected the cell structure of the foams and the average cell size, and the void fraction increased with increasing blowing agent loading. Both increasing the screw speed and decreasing the die temperature could establish a high pressure drop in the extruder die, and these were beneficial to the foaming extrusion. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers</P>
Xin, Zhen Xiang,Zhang, Zhen Xiu,Zhang, Bao Sheng,Pal, Kaushik,Deng, Xu,Lee, Sung Hyo,Kim, Jin Kuk SAGE Publications 2009 Journal of composite materials Vol.43 No.24
<P>The usage of waste tire powder as dispersed phase in polypropylene matrix offers an interesting opportunity for recycling of the waste tire. In order to obtain ‘value added products’ from polypropylene (PP)/waste ground rubber tire powder (WGRT) composites, in this study, the processing of foamedPP/WGRT composites was investigated using a single-screw foam extrusion setup and chemical blowing agent. The regression models were constructed to study the relationships between the foam structure (i.e., void fraction, average cell size, and cell density) of foamed PP/WGRT composites, the processing conditions (extruder’s die temperature and screw speed), and the formulation compositions (WGRT content and blowing agent concentration) by applying a four-factor central composite design (CCD) statistical approach. The response surface plots generated using the regression models allow the rapid selection of the proper process parameters to obtain PP/WGRT composite foams with the desired density and morphology.</P>
Xin, Zhen Xiang,Zhang, Zhen Xiu,Pal, Kaushik,Kim, Kwang-Jea,Kang, Dong Jin,Kim, Jin Kuk,Bang, Dae-Suk SAGE Publications 2009 Journal of cellular plastics Vol.45 No.6
<P>A new approach towards the recycling of waste ground rubber tire (WGRT) powder was demonstrated in this study by introducing the polypropylene/ waste ground rubber tire (PP/WGRT) foaming method by using CO<SUB>2</SUB> as the foaming agent in an extrusion foaming process. The regression models were constructed to study the relationships between the foam structure (i.e., void fraction, average cell size, and cell density) of foamed PP/WGRT blends, the processing parameters (extruder’s die temperature and CO<SUB>2</SUB> concentration), and WGRT content by applying a three-factor central composite design (CCD) statistical approach. The response surface plots generated using the regression models allow the rapid selection of the proper process parameters to obtain microcellular PP/WGRT blends with the desired density and morphology.</P>
Xin, Zhen Xiang,Zhang, Zhen Xiu,Pal, Kaushik,Kang, Dong Jin,Lee, Sung Hyo,Kim, Jin Kuk Wiley Subscription Services, Inc., A Wiley Company 2009 Journal of Vinyl and Additive Technology Vol.15 No.4
<P>Microcellular polypropylene (PP)/WGRT blends, a new outlet for the recycling of waste tire rubber, were prepared in an injection-molding process by using a chemical blowing agent. The effects of WGRT content and chemical blowing agent content on the density, cell morphology, and physicomechanical properties of the foamed PP/WGRT blends were investigated. The foam morphologies were characterized in terms of void fraction, average cell size, and cell density. The results indicated that both the WGRT and the blowing agent content had huge effects on the cell morphology and tensile properties of the PP/WGRT foams. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers</P>
Surface Modification with Pluronic P123 Enhances Transfection Efficiency of PAMAM Dendrimer
Xiang Wang,Shen Gao,Xin Wu,Wei Fan,Baoyue Ding,Xiaoyu Wang,Wei Zhang,Xueying Ding,Jing Gao,Quangang Zhu,Jiyong Liu,Zhen Cai 한국고분자학회 2012 Macromolecular Research Vol.20 No.2
To improve gene delivery efficiency and decrease cytotoxicity of polyamidoamine (PAMAM) polymers,P123-g-PAMAM was synthesized by modifying PAMAM with pluronic P123. The structure of the synthesized polymers was analyzed using proton nuclear magnetic resonance. The polymers were able to self-assemble with DNA,forming nanometer-scale complexes. Particle size measurement confirmed that the mean diameter of the polyplexes was 100-250 nm. The cytotoxicity and transfer efficiency were measured and compared with those of PEI and PAMAM. All of the polyplexes showed significantly low cytotoxicity in the MCF-7, HepG2, and 293T cell lines. In addition, the low level of P123 grafting to PAMAM showed significantly higher transfection efficiency than unmodified PAMAM at the optimal N/P ratio. These results suggest that P123-ylated PAMAM may prove as a useful carrier for gene delivery.
Zhang, Zhen Xiu,Lee, Sung-Hyo,Kim, Jin-Kuk,Zhang, Shu Ling,Xin, Zhen Xiang The Polymer Society of Korea 2008 Macromolecular Research Vol.16 No.5
In order to obtain 'value added products' from polypropylene (PP)/waste ground rubber tire powder (WGRT) composites, PP/WGRT microcellular foams were prepared via supercritical carbon dioxide. The effects of blend composition and processing condition on the cell size, cell density and relative density of PP/WGRT micro-cellular composites were studied. The results indicated that the microcellular structure was dependent on blend composition and processing condition. An increased content of waste ground rubber tire powder (WGRT) and maleic anhydride-grafted styrene-ethylene-butylene-styrene (SEBS-g-MA) reduced the cell size, and raised the cell density and relative density, whereas a higher saturation pressure increased the cell size, and reduced the cell density and relative density. With increasing saturation temperature, the cell size increased and the relative density decreased, whereas the cell density initially increased and then decreased.
Zhang, Zhen‐,Xiu,Fan, Jun‐,ling,Pal, Kaushik,Kim, Jin Kuk,Xin, Zhen‐,Xiang Wiley Subscription Services, Inc., A Wiley Company 2011 Journal of Vinyl and Additive Technology Vol.17 No.4
<P><B>Abstract</B></P><P>Nowadays the economic recycling of waste tires has become a global challenge. The use of waste tire powder as a dispersed elastomeric phase in a polypropylene (PP) matrix offers an interesting opportunity for recycling of waste tire rubber. Compatibilized PP/(waste tire powder) composites are microcellularly processed to create a new class of materials with unique properties. Recent studies have demonstrated the feasibility of developing microcellular structures in PP/waste ground rubber tire (WGRT) composites. Microcellular PP/WGRT composites are prepared by an injection‐molding process using a chemical blowing agent. In this study, cell sizes, cell density, void fraction, and mechanical properties of the composite foams were measured, as well as the shear viscosity of the unfoamed composites. The influence of various compatibilizers and processing temperatures on cell morphology and the mechanical properties of injection‐molded PP/WGRT composites were investigated. It was seen that the addition of maleic anhydride‐grafted styrene‐ethylene‐butylene‐styrene (SEBS‐<I>g</I>‐MA) increased the shear viscosity of the composites. The void fraction and cell density of the PP/WGRT composites increased with addition of compatibilizers, whereas the average cell sizes decreased. A processing temperature range of 180–195°C gave finer microcellular structure and regular cell distribution. The SEBS‐<I>g</I>‐MA enhanced the elongation properties and acted as an effective compatibilizer in this particular system. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers</P>