The effects of the addition of styrene‐ethylene/butylene‐styrene copolymer (SEBS) with various functionalized groups on the rheological, mechanical, and tribological properties on polyamide 6 nanocomposite filled with layered silicate (PA6/Clay) were investigated. Four types of SEBS: unmodified SEBS (SEBS), maleic anhydride grafted SEBS (SEBS‐g‐MA), amine group grafted SEBS (SEBS‐g‐NH2), and carboxyl group grafted SEBS (SEBS‐g‐COOH) were added with PA6/Clay nanocomposite to prepare various polymer blends. These polymer blends were extruded by a twin screw extruder and injection molded. Dynamic viscoelastic properties of these blends in the molten state and their tensile, impact, and tribological properties were evaluated. The viscoelastic properties were found to increase with the addition of SEBS and were highly influenced by the types of functionalized groups contained. Influence of the addition of SEBS on the mechanical properties of these systems differed for each mechanical property. Although the tensile properties decreased with SEBS, Izod impact properties improved with the addition of various functionalized SEBS. These mechanical properties and viscoelastic properties correlated closely with the size of dispersed SEBS particles and interparticle distance. The tribological properties also improved with the addition of SEBS, and the influence of the amount added was higher than the type of SEBS used. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers

To develop new tribomaterials for mechanical sliding parts, investigations were carried out on the influence of adding styrene–ethylene/butylene–styrene block copolymer (SEBS) on the rheological, mechanical, and tribological properties of polyamide 6 (PA6) nanocomposite, which is a commercial product of layered silicate (clay) filled polyamide 6 (PA6/Clay). Two kinds of block copolymers, unmodified SEBS (SEBS) and maleic anhydride‐grafted SEBS (SEBS‐g‐MA), were added with PA6/Clay nanocomposite. Dynamic viscoelastic properties in the molten state of these nanocomposites and their tensile, impact, and tribological properties of these nanocomposites were evaluated. Dynamic viscoelastic properties were found to increase with the addition of SEBS and were influenced, in particular, by block copolymers containing SEBS‐g‐MA. Influence of the addition of SEBS on mechanical properties of these systems differed for each mechanical property. Although tensile properties decreased with SEBS, Izod impact properties were improved with the addition of SEBS‐g‐MA. Tribological properties were improved with the addition of block copolymer, and the influence of the amount of addition was higher than the type of block copolymer used. These results indicate that new tribomaterials developed have sufficient balance amongst moldability, mechanical, and tribological properties. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

This paper deals with the dynamic viscoelastic properties of long organic fibre (aramid fibre (KF), polyvinyl alcohol fibre (VF) and polyamide fibre (PA6)) reinforced polypropylene in the molten state. Long organic fibres mixed with polypropylene fibres by an apparatus called a “fibre separating and flying machine″ were compression moulded into 3mm thick composites. Dynamic viscoelastic properties of these composites were measured in the molten state using a rotational parallel plate rheometer. It was found that the dependence of angular frequency on storage modulus, G′, for long organic fibre reinforced polypropylene is different from that of volume fraction of fibre, Vf and the relationships depend on the characteristics of the reinforcing organic fibres. The slope of the dynamic viscosity, η′ vs. angular frequency, ω curves increases gradually up to 45 degrees with increasing Vf. Influence of fibre content on dynamic viscoelastic properties depends on the organic fibre used. For low fibre content, G′ increases with increasing Vf in the same way as η′. However, the opposite trend is observed for high fibre content composites. It can be deduced that there is an apparent yield from the relations between complex viscosity, η* and complex modulus, G*. The yield value, G*y increases gradually with increasing fibre content and approaches a fixed value. All of the long organic fibre reinforced polypropylenes studied here are more sensitive to temperature than inorganic fibre reinforced composites.

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The influence of surface treatment on the rheological behavior of long glass fiber reinforced polypropylene melts were investigated. Surface treatment by different kinds of silane coupling agents (aminosilane, diaminosilane, epoxysilane and acryl silane) with different concentrations was performed on glass fibers. Glass fiber and polypropylene fiber mixed mats were prepared by a mixing machine which is called "Fiber separating/flying machine" and then compression molded . Rheological behavior on a rotational parallel plate rheometer were evaluated . Dynamic visco-elastic properties are descussed in terms of various factors : angular frequency, concentration of silane coupling agent, various kind of silane coupling agent, volume fraction of fiber, temperature and strain amplitude. Surface treatment was shown to increase storage modulus (G') and also reduce the peak of loss tangent (tan s= G"/G'), which means that the adhesion between the polymer matrix and the fibers is improved. Dynamic viscosity (,'), however, was changed by the concentration of silane coupling agent. This is because coupling agents act to couple the fiber to the polymer matrix, as a wetting agent or as an internal lubricant. Diaminosilane coupling agent was the most effective of the various silane systems for enhancement of rheological behavior. The dependence of the visco-elastic properties on the concentration of silane coupling agent showed the existence of an optimum concentration for systems at each volume fraction of fiber. From the results of the measurement at different temperatures and strain amplitude, it was found that surface treatments decrease the temperature dependence of rheological behavior, and that the dependence of visco-elastic properties on strain amplitude (oscillatory angle) was minimal.

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The effect of surface treatment on the rheological properties of 20 and 40 wt.% short glass fibre reinforced polypropylenes (GF/PP) and of the same composites containing maleic anhydride modified polypropylene (GF/mPP/PP) were investigated. Glass fibres were surface-treated by aminosilane coupling agent (ASC, γ-aminopropyltriethoxysilane). Steady state shear and dynamic properties in the molten state were measured using a cone and plate type rotational viscometer. Surface treatment increased the rheological properties of the molten composites. This trend was more pronounced for composites containing modified PP. In the case of the GF/PP materials the increase was monotonous for all measured functions, while in the case of the GF/mPP/PP ones, the parameters representing elasticity showed peaks at 0.5 wt.% ASC. The Cox-Merz empirical law was found to be applicable to untreated GF/PP and GF/mPP/PP composites at low shear rates (angular frequencies), where the materials showed Newtonian plateaux. As for ASC surface treated materials, GF/mPP/PP followed the same trend. On the other hand, GF/PP exhibited a higher complex viscosity than the steady state shear one over the whole range of angular frequencies (shear rate) covered by the experiments. Surface treatment enhanced apparent yield stress, as did increasing the glass fibre content. The effect of the latter was more pronounced in the case of the GF/mPP/PP series. The viscosities of the re-mixed composites became lower than those of the original ones, and the difference between untreated and ASC treated systems was detectable only in the case of the complex viscosity of the GF/mPP/PP sample.

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