Zhen Xiu Zhang

Microcellular Structure of PP/Waste Rubber Powder Blends with Supercritical CO2 by Foam Extrusion Process

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 CO2 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 CO2 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.

TEMPO-mediated oxidation of microcrystalline cellulose: Influence of temperature and oxidation procedure on yields of water-soluble products and crystal structures of water-insoluble residues

A series of microcrystalline cellulose samples were reacted with catalytic amounts of 2, 2, 6, 6-tetramethyl-1-piperidine oxoammonium salt (TEMPO), sodium hypochlorite and sodium bromide in Na2CO3/NaHCO3 buffer solution at different temperature (15 °C, 20 °C, 30 °C, 35 °C, 40 °C, 50 °C). The oxidation procedures included first and second oxidation. The first oxidation was a classical process for activating cellulose for the second oxidation. A substantial increase in the reactivity of the second oxidation cellulose samples was observed in comparison to those in the first oxidation and a relationship between oxidation procedures and accessibility of cellulose primary hydroxyl groups was directly established. For the characterization, we have used several methods, mainly XRD, FTIR. In all samples, the partial primary alcohol groups were selectively oxidized into carboxyl groups. The reaction during the first oxidation procedure mainly occurs in disordered regions of MCC and crystal surface. But the second oxidation procedure took place not only in disordered regions and crystal surface but inside crystalline region of cellulose I.

Study on Thermoplastic Elastomers (TPEs) of Waste Polypropylene/Waste Ground Rubber Tire Powder

Recycling represents a valid alternative to the disposal of postconsumer materials if it is possible to obtain new materials with good properties. In this work the possibility to produce secondary materials by blending waste polypropylene (WPP) and waste ground rubber tire powder (WGRT) was studied. Several comparative experiments were made to evaluate the influence of bitumen content and different compatibilizers on the properties of WPP/WGRT blends using a universal testing machine (UTM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and capillary rheometry. The results suggested that the properties of WPP/WGRT blends were dependent on the content of bitumen and the kind of compatibilizer.

Effect of Silanes on Mechanical and Thermal Properties of Silicone Rubber/EPDM Blends

The effect of four types of silane coupling agents on the mechanical and thermal properties of silicone rubber and ethylene–propylene–diene monomer (M-class) rubber (EPDM) blends is studied, namely, isobutyltriethoxysilane (BUS), acryloxypropyltriethoxysilane (ACS), aminopropyltriethoxysilane (AMS), and vinyltriethoxysilane (VIS). ACS and VIS increase the crosslink density of the blends, which results in higher tensile strength, modulus, and thermal stability, but lower elongation at break compared with the other silanes. However, the blend containing BUS shows highest tanδ in the temperature range of 45°C to 200°C. Thermogravimetric analysis shows two steps of degradation for all the samples, but little difference with the varied silanes.

Microcellular Foaming of Biodegradable PLA/PPC Composite Using Supercritical CO2

Poly (lactic acid) (PLA)/poly (propylene carbonate) (PPC) composite foams were microcellular foamed with CO2 through a batch foaming process. The influences of PPC contents, foaming temperature, and saturation pressure on the cell structure and foam density were investigated. The biodegradable PLA/PPC composite foam showed a controlled structure of microcellular and nanocellular. With an increase in saturation temperature and pressure, the cell size was increasing and both the cell density and foam density were decreased simultaneously.

Effects of Blend Ratio on Rheology, Morphology, Mechanical and Oil-Resistant Properties in Chlorinated Polyethylene Rubber and Copolyamide Blends

The elastomeric chlorinated polyethylene (CPE) blended with a low melting point copolyamide (PA6/PA66/PA1010, PA) was prepared by a melt mixing technique. The mixing characteristics of the blends were analyzed from the rheographs. The influence of copolyamide (PA) content on the morphology, mechanical properties, crystallization and oil-resistance, and the addition of compatibilizers on the mechanical properties were also systematically investigated. Morphological examinations clearly revealed a two-phase system in which CPE/PA blends exhibit a cocontinuous morphology for 50/50 composition, and the continuous phase of PA turns into a disperse phase for 70/30, 80/20, and 90/10. There is a distinct interface between the two phases. The mechanical properties, crystallization, and oil-resistance have a strong dependence on the amount of PA. The blends with higher proportions of PA have superior mechanical properties; they are explained on the basis of the morphology of the blend and the cystallinity of PA. In addition, compatibilizers, including chlorinated polyethylene-graft-copolyamide (CPE-G-PA), chlorinated polyethylene-graft-maleic anhydride (CPE-G-MAH), ethylene-n-butyl acrylate-monoxide (EnBACO), and ethylene-n-butyl acrylate-monoxide-graft-maleic anhydride (EnBACO-g-MAH) were added into the blends. Tensile strength and elongation at break go through a maximum value at a compatibilizer resin content (on the basis of the total mass of the blend) of 20 wt% while the PA content is 30 wt%.