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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>
Zhang, Bao Sheng,Lv, Xiu Feng,Zhang, Zhen Xiu,Liu, Yang,Kim, Jin Kuk,Xin, Zhen Xiang Elsevier 2010 Materials & design Vol.31 No.6
<P><B>Abstract</B></P><P>Chlorinated polyethylene rubber (CPE) foams filled with various content of carbon black were prepared by compression molding. The effect of carbon black content on the cure characteristics, foam characteristics and physical properties of the CPE compounds were investigated. The results showed that adding ZnSt as activator could lower the decomposition temperature of azodicarbonamide. The results of a moving die Rheometer suggested that the cure characteristics were influenced by the content of carbon black, and the cure rate index increased with carbon black content. The morphology and physical properties results indicated that the content of carbon black played important roles in the cell morphology and physical properties of CPE rubber foams.</P>
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,Sridhar, V.,Kim, Jin Kuk Wiley Subscription Services, Inc., A Wiley Company 2008 Polymer composites Vol.29 No.11
<P>Microcellular composites made from polypropylene and waste ground rubber tire powder using azodicarbonamide as chemical blowing agent have been investigated. A small quantity of SEBS-g-MA has been added as compatibilizer. The effect of variation in processing variables such as pressure, heating time, and operating variables such as blowing agent and crosslinker concentrations have been investigated to establish a relationship between the structure and morphology of the microcellular composite and ultimate performance characteristics such as tensile strength, tear strength, and elongation at break. The results indicate that both processing and operating variables have tremendous effect on the morphological features such as average, minimum, and maximum cell size as observed from scanning electron microscopy. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers</P>
Zhang, Zhen Xiu,Zhang, Shu Ling,Kim, Jin Kuk De Gruyter 2008 E-Polymers Vol.8 No.1
<P><B>Abstract</B></P><P>Polymer blends of WRT (waste rubber tire) powder/LLDPE (linear low density polyethylene) have been attempted to prepare thermoplastic elastomers (TPEs). The effects of maleic anhydride-grafted styrene-ethylene-butylene-styrene (SEBS-g-MA) and dicumyl peroxide (DCP) on mechanical, morphological and thermal properties of the blends were evaluated using universal testing machine (UTM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetric analyses (TGA). It was found that combination of SEBS-g-MA and DCP could better enhance the mechanical properties of WRT powder/LLDPE blends compared to SEBS-g-MA or DCP alone. Better compatibility between WRT powder and LLDPE was responsible for the enhancement of mechanical properties, as supported by SEM. The incorporation of SEBS-g-MA and DCP with WRT powder/LLDPE blends reduced the crystallizable perfectness of the blends, but slightly increased the thermal stability of the blends, as shown from DSC and TGA results</P>
Microcellular foams of thermoplastic vulcanizates (TPVs) based on waste ground rubber tire powder
Zhang, Zhen Xiu,Zhang, Shu Ling,Lee, Sung Hyo,Kang, Dong Jin,Bang, DaeSuk,Kim, Jin Kuk Elsevier 2008 Materials letters Vol.62 No.28
<P><B>Abstract</B></P><P>With the increased adoption of thermoplastic vulcanizates (TPVs) in automotive weather seal systems, the foams of TPVs present an important milestone in providing key applications such as trunk and door seals. In this study, microcellular foams of TPV based on waste ground rubber tire powder (WGRT) were investigated. In order to investigate the relationship between processing conditions and structure of TPV foams, we first prepared the thermoplastic vulcanizates of PP-g-MA/WGRT, then the samples were saturated with carbon dioxide and the saturated specimens were expanded during the pressure-quench process. The results indicated that the microcellular structure was dependent on the processing conditions. Cell size increased with saturation temperature, whereas cell density and relative density decreased. Different nucleation processes were produced with saturation pressure.</P>
Zhang, Shu Ling,Zhang, Zhen Xiu,Xin, Zhen Xiang,Pal, Kaushik,Kim, Jin Kuk Elsevier 2010 MATERIALS AND DESIGN Vol.31 No.4
<P><B>Abstract</B></P><P>Polypropylene (PP)/waste ground rubber tire powder (WGRT) composites were studied with respect to the effect of bitumen and maleic anhydride-grafted styrene–ethylene–butylene–styrene (SEBS-g-MA) content by using the design of experiments (DOE) approach, whereby the effect of the four polymers content on the final mechanical properties were predicted. Uniform design method was especially adopted for its advantages. Optimization was done using hybrid artificial neural network–genetic algorithm (ANN–GA) technique. The results indicated that the composites showed fairly good ductibility provided that it had a relatively higher concentration of bitumen and SEBS-g-MA under the studied condition. A quantitative relationship was presented between the material concentration and the mechanical properties as a set of contour plots, which were confirmed experimentally by testing the optimum ratio.</P>
Xiu-Zhen Zhang,Ling Wang,Dongwu Liu,Guang-Yan Tang,Hongyu Zhang 한국식품영양과학회 2014 Journal of medicinal food Vol.17 No.9
This study aims at evaluating the anticancer effects of berberine hydrochloride (berberine) and d-limonene, alone and in combination, on human gastric carcinoma cell line MGC803 to determine whether berberine and d-limonene work synergistically and elucidate their mechanisms. MGC803 cells were treated with berberine and d-limonene, alone and in combination, for 24–48 h. The inhibitory effects of these drugs on growth were determined by MTT assay. The combination index and drug reduction index were calculated with the Chou–Talalay method based on the median-effect principle. Flow cytometry and laser scanning confocal microscopy were employed to evaluate the effects of both drugs on cell-cycle perturbation and apoptosis, generation of reactive oxygen species (ROS), mitochondrial membrane potential, and expression of Bcl-2 and caspase-3 in MGC803 cells. Berberine or d-limonene alone can inhibit the growth of MGC803 cells in a doseand time-dependent manner. Berberine and d-limonene at a combination ratio of 1:4 exhibited a synergistic effect on anti-MGC803 cells. The two drugs distinctly induced intracellular ROS generation, reduced the mitochondrial transmembrane potential (DCm), enhanced the expression of caspase-3, and decreased the expression of Bcl-2. The combination of berberine and d-limonene showed more remarkable effects compared with drugs used singly in MGC803 cells. The combination of berberine and d-limonene exerted synergistic anticancer effects on MGC803 cells by cell-cycle arrest, ROS production, and apoptosis induction through the mitochondria-mediated intrinsic pathway.
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>