Pond T.J.,Tun Abdul Razak Research Center
Journal of Rubber Research | Year: 2010
Micrographs are shown of some typical types of structural damage that can occur in a vulcanisate as a result of electrochemical degradation (ECD) in the material. The importance of the carbon black content, the operating temperature, the coolant composition, a vulcanisates cure system and other compound ingredients on the size of the current that can flow through a vulcanisate and its impact on ECD were discussed as well as the effects of crosslink density on volume resistivity and current flow. Results from SEM X-ray analysis of ECD damaged material on the depletion of zinc and sulphur by ECD and the associated effects on current flow through a compound are also discussed.
Roberts A.D.,Tun Abdul Razak Research Center
Materials Science Forum | Year: 2011
This review describes early work on rubber wiper blades and subsequent investigations. Observations on model wipers pressed against glass showed that the dry contact width was greater than that predicted by the classical Hertz equation, due to adhesion. That led to the establishment of the JKR equation to account for the adhesion. Although originally intended for 'soft' contacts, the equation now finds wide use. Surprisingly, the boundary lubrication aspects of the work revealed the action of repulsive forces that could be directly measured between rubber and glass in the presence of water. The quality of lubrication is subject to the acidity/alkalinity of the water. © (2011) Trans Tech Publications.
Marshall R.S.,CNR Institute of Agricultural Biology and Biotechnology |
D'Avila F.,CNR Institute of Agricultural Biology and Biotechnology |
D'Avila F.,University of Milan |
Di Cola A.,University of LAquila |
And 6 more authors.
Plant Journal | Year: 2011
Summary The fate of the type I ribosome-inactivating protein (RIP) saporin when initially targeted to the endoplasmic reticulum (ER) in tobacco protoplasts has been examined. We find that saporin expression causes a marked decrease in protein synthesis, indicating that a fraction of the toxin reaches the cytosol and inactivates tobacco ribosomes. We determined that saporin is largely secreted but some is retained intracellularly, most likely in a vacuolar compartment, thus behaving very differently from the prototype RIP ricin A chain. We also find that the signal peptide can interfere with the catalytic activity of saporin when the protein fails to be targeted to the ER membrane, and that saporin toxicity undergoes signal sequence-specific regulation when the host cell is subjected to ER stress. Replacement of the saporin signal peptide with that of the ER chaperone BiP reduces saporin toxicity and makes it independent of cell stress. We propose that this stress-induced toxicity may have a role in pathogen defence. © 2010 The Authors. The Plant Journal © 2010 Blackwell Publishing Ltd.
Roberts A.D.,Tun Abdul Razak Research Center
Rubber Chemistry and Technology | Year: 2014
Research on rubber wiper blades led to the establishment of the now widely used Johnson, Kendall, Roberts (JKR) equilibrium equation that determines the strength of adhesion between surfaces. The equation was adapted to allow for the viscoelasticity of rubber, leading to explanations of how adhesion can impact on tack; rebound resilience; and rolling, static, and sliding friction. The adhesion of rubber to ice was found to depend on salt concentration in the ice, thus providing insight into winter tire performance. The development of optical techniques has greatly aided studies, particularly for measuring the thickness of thin liquid films sandwiched between rubber surfaces. Measurements on water films squeezed between rubber and glass revealed the action of repulsive surface forces that can reduce adhesion and friction. The efficacy of water lubrication depends upon whether surfactants are present and upon the acidity or alkalinity of the water. Improved understanding of adhesion and friction mechanisms offers design guidance for a range of rubber articles. © 2014, Rubber Division of the American Chemical Society. All rights reserved.
Karbakhsh Ravari A.,University of Malaya |
Bin Othman I.,University of Malaya |
Binti Ibrahim Z.,University of Malaya |
Ab-Malek K.,Tun Abdul Razak Research Center
Journal of Structural Engineering (United States) | Year: 2012
Seismic isolation systems constitute an accepted and simple technique for earthquake protection of structural systems and sensitive components. This approach has considerable potential in preventing the structures and their equipment from earthquake destruction. For predicting the behavior of an isolation bearing, Haringx's theory is usually employed. According to this theory, the mechanical properties of an elastomeric isolation bearing can be predicted and described. Many investigators have proposed a nonlinear, mechanical model for multilayer elastomeric bearings. However, in previous theoretical and experimental studies, the effects of initial rotation at the ends of the bearings have been neglected. In this study, Haringx's theory is extended and an analytical method is presented by considering the initial rotations of the upper and lower ends of multilayer rubber bearings as new boundary conditions. Three boundary conditions have been considered for modeling the elastomeric isolation bearing: (1)equal rotation at the bottom and top end of a bearing, (2)rotation only at the bottom end, and (3)rotation only at the top end of a bearing. According to these boundary conditions, variations of the lateral displacement and interior rotation of the laminated rubber bearings are obtained. The variations of horizontal stiffness, internal bending moment, and interior shear force of the bearing have also been presented. Examples are presented to demonstrate the validity of the development method in predicting the mechanical properties of elastomeric bearings with specified geometric parameters. The results of this study have shown that initial rotation as a boundary condition will change the mechanical properties of the laminated rubber bearings. © 2012 American Society of Civil Engineers.