Friction and wear study of NR/SBR blends with Si3N4Filler

Interaction of Silane Coupling Agents with CaCO3

Abstract: A study of eight silane coupling agents showed very different effect of these compounds on the mechanical properties of PP/CaCO3 composites. The application of aminofunctional silane coupling agents resulted in the reactive coupling of the two inactive components leading to increased strength and decreased deformability. A detailed study of the interaction between CaCO3 and the various coupling agents was carried out in order to find an explanation for the strong coupling effect. The amount of coupling agent creating a monolayer coverage was determined by a dissolution method for each coupling agent. The obtained values changed between 0.3 and 1.0 wt% calculated for the CaCO3 . An attempt was made to determine the orientation of the adsorbed molecules to the filler surface. Most of the coupling agents are oriented perpendicularly to the surface with the exception of a methacryl functional silane compound. Possible interactions between hydrolyzed or condensed silane coupling agents and the filler were studied by Fourier transform infrared spectroscopy using transmitting (FTIR-TS) and diffuse reflectance (DRIFT) modes, as well as gel permeation chromatography (GPC). The results showed that bulky organofunctional groups form a caged, polycyclic, low-molecular-weight structure on the surface, while silanes with smaller groups tend to condense into open, ladder type, high-molecular-weight polysiloxane chains. Polymer/filler adhesion, however, depends primarily on the chemical character of the organofunctional group. Aminofunctional silane coupling agents adhere well to the filler surface and react also with the polymer. In the case of similar functionality the size of the organofunctional group determines the strength of the adhesion.

Cure and mechanical properties and abrasive wear behavior of natural rubber, styrene–butadiene rubber and their blends reinforced with silica hybrid fillers

Abstract: This work investigated the mechanical properties of natural rubber (NR), styrene–butadiene rubber (SBR) and NR/SBR blends filled with silica hybrid filler, and their abrasive wear behavior against different counterface materials. The silica hybrid filler included bagasse ash silica (BASi) and precipitated silica (PSi). The BASi content used was 0, 5, 10 and 15 phr, which was incorporated into rubber compounds filled with 20 phr PSi. The wear behaviors of NR, SBR and their blends were examined using an in-house built abrader in a pin-on-plate (POP) configuration; they were tested against various counterface materials, including steel, concrete, and fabric materials under dry and wet conditions. The results suggested that BASi could be used as co-reinforcing filler with PSi for SBR and NR/SBR compounds, resulting in an improvement in the dispersive and distributive properties of PSi agglomerates in the rubber matrix, as indicated by an increase in tensile strength and elongation at break. However, this was not the case for the NR system. The BASi/rubber composites demonstrated greater abrasive wear resistance against a fabric counterface than against steel and concrete counterfaces, respectively. In the case of a fabric counterface, the addition of BASi tended to greatly increase the specific wear rate of the rubbers due to the detachment of fabric and BASi particles acting as three-body abrasive wear. In addition, all rubber composites abraded against steel, concrete and fabric under wet conditions showed less wear than composites under dry condition, except for SBR rubber composites on a concrete counterface.

Selection of dispersants for the dispersion of carbon black in organic medium

Abstract: The dispersion of the carbon black pigment in non-aqueous medium requires the use of dispersant additives. Two carboxylic dispersants of different chemical nature and molar masses have been investigated regarding this purpose. Their adsorption behavior has been evaluated by means of adsorption isotherms. The molecular interactions taking place at the surface have been inferred from IR and 13 C RMN spectroscopies. The rheological behavior of the dispersions has considerably been improved by the presence of the copolymer dispersant of higher molar mass. It might adsorb at the surface by hydrogen bindings while taking a flat conformation with tails and possibly few loops that contributed to the steric stabilization of particles. The consequences of the deflocculation of the suspension on the colorimetric properties are an enhanced tinting strength and improved color stability.

Macromolecular coupling agents for flame retardant materials

Abstract: Polypropylene (PP) is a large-consumed polymer employed in many applications. For some uses, good flame resistance is desirable and this can be achieved by the addition of metallic hydroxides. However, high loads of metallic hydroxides are needed causing marked deterioration of the physical properties. Addition of interfacial agents is a useful way of minimizing these effects. In this study, PP was modified with vinyltriethoxysilane (VTES) and maleic anhydride (MA) and the products were used as coupling agents for PP/aluminum hydroxide (ATH) composites. The composites were characterized by TGA, SEM, tensile and flammability tests. It was observed that both coupling agents were efficient but PP modified with VTES showed better effect on the mechanical properties. Two types of ATH were used for comparison.

Effect of normal load on friction coefficient for sliding contact between rough rubber surface and rigid smooth plane

Abstract: This study focused on the normal load dependence of the friction coefficient for the sliding friction of a rubber material with a rough surface. A developed friction tester was used to visualize the real contact regions distributed within the transparent contact interface between poly-dimethyl siloxane (PDMS) and glass surfaces. Based on experimental results, an adhesion friction model was developed to explain the normal load dependence of the friction coefficient. This model provides a simple technique that can roughly but easily estimate the real contact area and shear stress without in situ observation of the contact interface.