Zhen Xiang Xin

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.

Expanded Waste Ground Rubber Tire Powder/Polypropylene Composites: Processing-Structure Relationships

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.

Synergistic effects of kaolin and talc in a bromobutyl rubber compound for syringe plunger application

The effectiveness of separate and combined incorporation of two natural, inexpensive, and nontoxic filler materials, kaolin and talc, at their various proportions in a bromobutyl rubber (BIIR) compound for a medical syringe plunger was investigated. The dispersion of kaolin was finer and more homogeneous than talc in BIIR. The curing was also enhanced in the presence of kaolin than talc. The difference in dispersion as well as reinforcing effects of the different fillers were reflected in the dynamic mechanical properties of the compounds. Tensile properties of the compounds were not significantly varied with varying kaolin/talc ratio of the compounds, however, tear strength decreased for higher contents of talc in the compounds. A significant synergistic reduction of compression set was achieved for 75/15 ratio of kaolin and talc in the rubber compound, very important for a plunger compound.

Fabrication of Fine-celled PP/Ground Tire Rubber Powder Composites Using Supercritical Carbon Dioxide

PP/Ground Rubber Tire (GRT) powder microcellular blend foams were prepared by supercritical carbon dioxide. The effects of blend composition like the content of GRT and maleic anhydride-grafted polypropylene (PP-g-MA) on crystallinity, solubility, diffusivity, morphology and mechanical properties of PP/GRT microcellular composites were studied. The results showed that the PP/GRT composite foams with a unique bimodal (large and small) cellular structure, in which the large-cells embrace a GRT powder. Depending on the composition, generally, the higher content of GRT results in the smaller cell sizes, higher cell densities and relative densities, whereas the 20 wt% GRT composite shows the lowest relative density. The mechanical properties of the microcellular PP/GRT composite foams are directly related to the blend composition and the processing conditions. The PP-g-MA/GRT (50/50) produced microcellular foams with a very fine and uniform cell structure, lower relative densities and improved mechanical properties.

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.

Fabrication of a superhydrophobic LLDPE film by thermal lamination and peeling

Abstract Fabrication of superhydrophobic films of polypropylene and of three different types of polyethylene was performed using a facile hot-press lamination and peeling process, which successfully fabricated a superhydrophobic film of linear low-density polyethylene (LLDPE). The water contact angle on the superhydrophobic reached as high as 160°, and the roll-off angle decreased to below 7°. The superhydrophobicity of the LLDPE film was attributed to a special surface morphology comprising micron- and submicron-sized fiber-like structures fabricated on the film surface by the hot-press lamination and peeling process. The method is based on the mutual adhesion and interdiffusion of polymer chains at the film interface during hot-press lamination and on the subsequent unzipping of the morphology during the peeling at room temperature. The effects of varying hot-pressing temperature and time on the surface morphology and wetting characteristics of the fabricated LLDPE films were also investigated.

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%.