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The development of thermoplastic elastomer blends from waste tire powder and two polyolefins, Viz. maleic anhydride grafted polypropylene and LDPE, was studied. The polymer blends were processed using a twin-screw extruder equipped with a well-designed screw configuration. The blends studied contained a dispersed phase of waste rubber powder obtained from waste tire in a thermoplastic matrix. The effect of ultrasonic treatment on the rubber powder was compared. Contrary to our expectation, ultrasonically treated samples gave poor mechanical properties compared to untreated samples. Significant improvement in the mechanical properties was obtained with the addition of maleic anhydride-grafted styrene-ethylene-butylene-styrene (SEBS-g-MA) as a compatibilizer in treated and untreated waste tire powder / polyolefin blends.

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. [ABSTRACT FROM AUTHOR]

The article discusses polymer engineering research wherein the surface of waste ground rubber tire (WGRT) powder was modified by allylamine through an ultraviolet (UV) treatment. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, energy dispersive X-ray analysis, thermogravimetric analysis, and surface energy measurements are used to confirm the degree of grafting of the modified-WRGT. They are then incorporated into a polypropylene (PP) matrix, and the effects of UV radiation time, WGRT loading, and allylamine concentration on the mechanical properties of the composites are measured.

Blends of Polypropylene (PP) and waste ground rubber tire powder are studied with respect to the effect of ethylene-propylene-diene monomer (EPDM) and polypropylene grafted maleic anhydride (PP-g-MA) compatibilizer content by using the Design of Experiments methodology, whereby the effect of the four polymers content on the final mechanical properties are predicted. Uniform design method is especially adopted for its advantages. Optimization is done using hybrid Artificial Neural Network-Genetic Algorithm technique. A rubber formulary with respect to the four ingredients are optimized having maximum tensile strength and then compared with a blend predicted to have maximum elongation at break. It is concluded that the blends show fairly good properties provided that it has a relatively higher concentration of PP-g-MA and EPDM content. SEM investigations also corroborates with the observed mechanical properties. A quantitative relationship is then shown between the material concentration and the mechanical properties as a set of contour plots, which are then tested and confirmed experimentally to conform to the optimum blend ratio. [ABSTRACT FROM AUTHOR]

The physical gelation of triblock copolymer poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) in different hydrocarbon oils with different concentrations is studied in this article. The linear viscoelastic behavior, thermal transitions, swelling behavior, and gel properties on physical gelation are presented. The linear viscoelastic behavior is highly dependent on the copolymer concentration and type of oils. The degree of moduli responses of SEBS gels increase with higher gelation temperature, thereby indicating the longer lifetime of gel junctions. Small amounts of aromatic content in the hydrocarbon oil decreases the thermal stability of micelle formation of the gel and increases the compatibility of the solvent with copolymer, thereby resulting in low gelation temperature, lower moduli, as well as gel strength. With an increase in paraffinic content and molecular weight of hydrocarbon oil, the gelation temperature, moduli, and gel properties show improvement. Differential scanning calorimetric results show phase separation of soft segment and hard segment. The glass transition temperature (Tg) of soft ethylene-butylene (EB) midblock is not dependent on the triblock copolymer concentration nor on the type of oil, whereas the Tg of hard segment styrene endblock is highly dependent on triblock copolymer concentration and type of oil. The molecular weight and paraffinic hydrocarbon content of the oils are found to contribute to the stability of micelles and the incompatibility of hydrocarbon oil in SEBS triblock copolymer. [ABSTRACT FROM AUTHOR]

A co-rotating twin screw extruder was used for blending thermoplastic elastomeric blends of ground rubber tire (GRT) and maleic anhydride grafted polypropylene (PP-g-MA). The dynamic reaction occurring between the blends necessitates a study of the processing parameters of the extruder. The effects of the extruder screw configurations, screw speed, compatabilizer and blend ratios on the mechanical properties, and morphology was studied. Out of the four different screw configurations A, B, C, and D, screw D with reverse flow elements was found to be highly efficient with respect to mechanical properties, particularly at 100 rpm screw speed. SEM studies revealed that GRT and PP-g-MA are thermodynamically miscible under optimized screw configuration and processing condition of 100 rpm screw speed. SEM studies also show that the addition of compatibilizer increases the miscibility and, consequently, the mechanical properties. Finally, a composition involving GRT/PP-g-MA/SEBS-g-MA as 65/35/10 by weight was found to be optimum. [ABSTRACT FROM AUTHOR]