Cristina R. G. Furtado

Mica as additional filler in SBR–silica compounds

Abstract The mechanical properties of mica–silica–SBR (styrene butadiene rubber) compositions were studied with special emphasis on fatigue resistance, using the Monsanto Fatigue-to-Failure Tester (FTFT) and De Mattia flexing machine. It was found that the addition of mica, in little concentrations, has a positive contribution to modulus, and does not change tensile strength, elongation at break and tear strength. Moreover, the addition of silane coupling agent enhances silica–rubber interactions, whereas the fatigue life of silica filled elastomeric compounds is adversely affected by the addition of mica. These behaviours were supported by scanning electron microscopy observations of the fracture surfaces.

Efeito do óleo de mamona em composiçõesde borracha natural contendo sílica

The possible use of castor oil fatty acid as an activator for the vulcanization reaction in silica-filled natural rubber (NR) compounds was investigated. The design and analysis of the experiments were carried out by keeping constant the concentration of silica and the other ingredients while the amounts of stearic acid, castor oil and poly(ethylene glycol) were varied. Cure was carried out on a TI-100 oscillating disk rheometer, and the tensile strength was chosen as the control variable. The results show that the addition of castor oil does not significantly change the mechanical performance of silica-filled natural rubber compounds.

Fatigue resistance of mica–carbon black–styrene butadiene rubber (SBR) compounds

Abstract The mechanical properties of mica–carbon black–styrene butadiene rubber (SBR) compounds were studied with special emphasis on fatigue resistance, using the Monsanto fatigue-to-failure tester (FTFT) and the De Mattia flexing machine. It was found that the addition of mica significantly reduces the fatigue life of carbon black-filled elastomeric compounds up to a certain value, beyond which no significant decrease is observed. Failure surfaces were examined by scanning electron microscopy (SEM) and the fractographs were correlated with the fatigue resistance of the compounds.

Cinética de Vulcanização de Composições de Borracha Natural com Incorporação de Cinza de Casca de Arroz

Rice husk ash was incorporated into natural rubber (NR) using a laboratory size two-roll mill. A conventional vulcanization system (CV) was chosen and cure studies were carried out on a TI-100 Curometer. The torque curves were obtained at 150, 160, 170, and 180 °C. The overall rate and the apparent activation energy for the vulcanization process were calculated for each compound assuming that vulcanization follows first-order kinetics. For the purpose of comparison, two commercial fillers, precipitated silica (Zeosil-175) and carbon black (N762), were also used. In comparison to the other fillers used, the addition of rice husk ash to NR compounds increased the crosslinking rate and lowered the apparent activation energy in a more marked way.

SBR-mica-silica compositions and their physico-mechanical behaviour

SummaryBrazilian muscovite mica was used as filler in vulcanized compositions of styrenebutadiene rubber (SBR) in partial replacement of silica. Physico-mechanical properties of the compositions, such as tensile and tear strength, 100% modulus, elongation at break, hardness, abrasion loss and resilience have been studied. The investigations have shown that it is possible to partially replace silica for mica, without remarkable changes in some properties. Relationships between mechanical behaviour and structure have been examined under scanning electron microscopy (SEM) on the fracture surface of the compositions.

Evaluation of mica-filled styrene butadiene rubber

Abstract The possibility of replacement of active fillers, e.g. carbon black, for cheap products, e.g. mica, were investigated. The physical-mechanical properties of SBR composites with mica and carbon black, using a constant total filler content (50 phr) have been studied. Tensile strength shows the best results when 10 phr of mica are used in combination with 40 phr of carbon black. These results are better than those for formulations in which carbon black is used alone. Relationships between mechanical behaviour and structure have been examined under scanning electron microscopy (SEM) on the fracture surface of the compositions.

The emulsion polymerization of methyl methacrylate initiated by Ce(IV)/dodecyl poly(ethylene oxide) redox system

Abstract The acidic aqueous emulsion polymerization of methyl methacrylate, initiated by ceric ammonium nitrate-dodecyl poly(ethylene oxide) redox system at 30°, was studied. The polymerization was characterized by a pronounced gel effect and showed deviations from the Smith-Ewart theory established for styrene because of the higher polarity of methyl methacrylate.

Avaliação reológica de elastômeros e suas composições

Resumo: Os materiais elastomericos apresentam tanto caracteristicas de materiais solidos como de liquidos, sendo assim considerados materiais viscoelasticos. Nas operacoes convencionais de processamento, esses materiais ficam sujeitos a varios tipos de deformacoes, devido a complexidade dos equipamentos. Esses materiais respondem a acao das deforma- coes com um comportamento reologico viscoelastico, ou seja, uma combinacao de respostas elasticas e viscosas. As propriedades viscoelasticas tem grande influencia sobre o desempenho dos artefatos de borracha. Essas propriedades podem ser determinadas, permitindo assim, em alguns casos, o estabelecimento de uma relacao com o comportamento dos materiais elastomericos durante o seu processamento. Esta pequena revisao aborda com maior enfase a utilizacao do Analisador de Processamento de Borracha - RPA (Rubber Process Analyzer) na determinacao do comportamento reologico dos elastomeros. O RPA apresenta uma grande flexibilidade na realizacao de testes reologicos, pois permite a combinacao de diferentes frequencias, deformacoes e temperaturas. Palavras-chave: Elastomeros, reologia, composicoes elastomericas, Analisador de Processamento de Borracha (RPA). Rheological Evaluation of Elastomers and their Compounds Abstract: Elastomers are viscoelastic materials; they combine solid and liquid characteristics. During processing operations, these materials are deformed in different ways and show a viscoelastic behavior. The viscoelastic properties have a powerful influence on the rubber products performance. These properties should be measured in order to predict, in some cases, the elastomers behavior during processing. This brief review gives more emphasis to the elastomer rheological characterization using the Rubber Process Analyzer (RPA).

CHAPTER 23:Life Cycle Analysis, Ageing and Degradation Behaviour of Natural Rubber Based Blends and IPNs

Polymeric materials have the potential to generate a significant impact on the environment throughout their life cycle, including depletion of finite, non-renewable resources and generation of solid waste. Therefore, it is essential to identify more sustainable ways of using and managing polymers. Thus, it becomes quite important to evaluate the ageing and degradation of these polymers. The purpose of the present chapter is to give an overview of recent works carried out in the field of life cycle analysis, ageing and degradation of natural rubber based blends and interpenetrating polymer networks (IPNs).