Rabindra Mukhopadhyay

Effect of vulcanization temperature and vulcanization systems on the structure and properties of natural rubber vulcanizates

Abstract The effect of vulcanization temperature (150°–180°C) on the structure and technical properties of gum natural rubber vulcanizates with four different 2-(morpholinodithio)-benzothiazole: sulphur ratios (A, 0.6:2.4; B, 1.5:1.5; C, 2.4:0.6; D, 3.0:0.0) at the respective optimum cure times has been determined. The influence of cure temperature on (a) the chemical crosslink density; (b) the distribution of crosslink types; (c) the extent of sulphidic main chain modifications and (d) the zinc sulphide formation was investigated. Results show that elevated cure temperatures produce a network with lower crosslink density, in particular a lower polysulphidic crosslink density. The formation of intramolecular sulphidic groups and zinc sulphide increase with increasing cure temperatures. The possibility of chain scission during vulcanization, as examined by a quantitative analysis of the sol—gel data, was found to be negligible. The network results have been correlated with the technical properties.

Effect of Anion in Cobalt Promoters on the Adhesion between Steel Cord and Rubber Compound

Abstract There is widespread use of two main groups of adhesion promoters, the SRH-system and an organic cobalt salt. They are used either jointly or individually in the rubber compound for promotion and maintenance of good adhesion of rubber to brass-coated steel cord in radial tyres. This paper describes the influence of anions associated with cobalt promoters on the adhesion energy and the pull-out force between brass-coated steel cord and rubber and their relationship to other relevant physical properties, under the influence of various environments which simulate tyre service conditions. It is observed that incorporation of a cobalt promoter greatly enhances the adhesion energy and influences the Youngs modulus and crosslink density of the rubber compound in a similar fashion. The study establishes the supremacy of boroacylate among the anions considering its overall good performance and the protection offered against various hostile environments. However, the benefits of the cobalt promoter is not ...

High Temperature Vulcanization of Elastomers

Abstract Vulcanization is a process which decreases the plastic properties of rubber while maintaining or improving the elastic properties. The term vulcanization has been applied in the past mainly to the reaction of rubber with sulfur, but now is generally used for the process which results in changes in properties, by sulfur or some other agent. There are four principal changes brought about by vulcanization: (1) rubber is changed from essentially a plastic to a non-plastic material; (2) rubber is changed from a material soluble in a number of solvents to one which is insoluble; (3) rubber is changed to a material with greatly improved physical properties; (4) these properties of vulcanized rubber are maintained over a much wider range of temperature than those of unvulcanized rubber. What is meant by high vulcanizing temperature? There is no unique answer. About 160°C can be taken conveniently as the lower limit; this temperature has been suggested as the highest suitable for some normally compounded ...

SEM/EDX studies of the influence of a cobalt adhesion promoter on the interface between rubber skim compounds and tire steel cord

The failed interfaces between natural rubber skim compounds and tire steel cord used as tire cord adhesion test (TCAT) specimens have been studied by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis in order to understand the influence of cobalt boroacylate in the rubber compound as an adhesion promoter. SEM studies indicated a mixture of cohesive failure in the rubber and interfacial failure between the rubber and the brass coating. Cobalt boroacylate leads to more cohesive failure of the rubber (about 88% of the cord area covered by the rubber compared with 73% by the control), due to its degradative effects on rubber. EDX analysis of the failed cord and rubber surfaces at various points gave the concentrations of copper, zinc, cobalt, iron, silicon, sulfur, oxygen, and carbon. Assuming van Ooijs model of interfacial sulfide film formation over the brass (Cu/Zn) layer and analyzing the EDX results, it is clear that the failure occurs at the Cu/Zn and CuxS/ZnS sub-layers.

Composition Analysis of Carbon Black-Filled Polychloroprene Rubber Compound by Thermo-Oxidative Degradation of the Compound

This study describes a method for the composition analysis of the carbon black-filled polychloroprene rubber (CR) compound. Good agreement of the experimental data with the actual value was found. The method is based on three experiments namely thermogravimetric analysis, solvent extraction, and newly developed thermo and thermo-oxidative degradation of the vulcanized CR compound in the presence of nickel catalyst. Thermogravimetric analysis experiment gives the amount of inorganic material in the rubber compound. Solvent extraction gives the extractable amount. Thermo-oxidative degradation experiment gives the polymer amount. In thermo-oxidative degradation experiment, liberated chloride ion was titrated by Mohr’s method, and the amount of CR was back calculated from the chlorine content.

Studies of dynamic adhesion between steel cord and rubber using a new testing method

Abstract A new dynamic test for steel cord/rubber adhesion has been developed. The Tyre Cord Adhesion Test (TCAT) specimen selected as the test piece is subjected to cyclic extension using a Monsanto Fatigue-to-Failure Tester. Cord pull-out tests have been conducted before and after cyclic extension, or the number of cycles required to pull-out the cord from TCAT-specimen has been utilised for evaluation of dynamic adhesion. The effect of various parameters, e.g. cord embedment length, number of extension cycles, degree of extension, aerobic ageing, thermal ageing, compound hardness etc. on adhesion has been investigated using this dynamic adhesion testing technique. The method developed without any extra capital investment is found to be very simple, reliable, reproducible with high discriminating power and capable of providing high quality statistical data.

Reverse Engineering of Rubber Products : Concepts, Tools, and Techniques

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Graphene-Based Elastomer Nanocomposites: Functionalization Techniques, Morphology, and Physical Properties

Understanding the fundamentals involved in the fabrication of an elastomer nanocomposite is crucial for the development of high performance materials. Despite a plethora of studies of different types of elastomer nanocomposites, work related to the development of graphene-based elastomer nanocomposites has only gained precedence in recent years. Because the inherent structure of graphene often limits its processability inside a high molecular weight elastomer matrix, various strategies have been adopted to control the dispersion of graphene in an elastomer. In this chapter, representative and commercially important elastomers are selected for discussion. The effect of different processing routes for the preparation of elastomer/graphene nanocomposites and their correlation with dispersion of the graphene-based filler in the elastomer matrix are discussed in detail. Parameters controlling strength, thermal stability, barrier properties, and dielectric behavior are discussed. This chapter gives a comprehensive review of the preparation of graphene/elastomer nanocomposites and also provides an idea of the structure–property relationships that exist for such nanocomposites.

Stearyl Amine Ethoxylate (SAM) Grafted Montmorillonite Clay-Styrene Butadiene Rubber (SBR) Nanocomposites

The present study describes the modification of montmorillonite clay (kunipia F) surface by grafting Stearyl Amine Ethoxylate (SAM). Wide-angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM) provided the evidence of formation of a nanocomposite. The interlayer spacing of the kunipia clay was increased from 1.22 nm (unmodified) to 1.53 nm (modified). The TEM study revealed the intercalated and partially exfoliated nature of the nanocomposites. When the modified clay was compounded with SBR rubber, the interlayer spacing was further increased to 1.88 nm. Remarkable improvements in the mechanical properties were found by the addition of a small amount of modified clay.

The influence of the cation in organometallic boroacylate adhesion promoters on the adhesion between steel cord and skim rubber compound

Abstract The influence of transition metal cations (cobalt, nickel and zinc ion) associated with organometallic boroacylate adhesion promoters on the adhesion between brass-coated steel cord and rubber skim compound under the influence of various environments, which simulate tyre service conditions, has been studied. Incorporation of adhesion promoters individually in the steel cord-skim formulation leads to increase in crosslink density, Youngs modulus and cord pull-out force. The adhesion energy is enhanced significantly with the addition of cobalt adhesion promoter. The performance of the promoter is influenced by the ease of dissociation of the transition metal ion from the promoter, its participation in the rubber curing and the modification of the interfacial film responsible for adhesion. During aerobic ageing, cobalt followed by nickel is found to be effective, whereas cobalt and, partially, zinc salts offer certain resistance to thermal ageing. Against salt and steam ageing, cobalt boroacylate i...