Interface rubber-metal

The important criteria for a plasticiser is that it must be compatible with the elastomer for which it is used, otherwise bleeding will occur. Exudation of plasticiser in this way can be a problem in subsequent manufacture and a disaster if it occurs at a rubber/metal interface during service. 

The system with the extreme layers made of metal is heated in the same way as it is made in a mold so as to cure the rubber and increase the adherence between the rubber-metal interface. Thus, the equations are as follows ... 

The rubber-metal system is heated on both extreme metal surfaces, and when the heating system of the new mold is at the mold-metal interface, the temperature is kept constant on the extreme metal surfaces. 

The temperature range is 30 K. One layer of elements modeled the base the coating was divided into five layers of similar width. As Fig. 4.6 displays, the maximal value of the internal stresses in the epoxy rubber coating is observed at the interface with metal. 

The environment in which the component is to work will also affect the stresses to which the rubber-metal bond will be subjected. Some oil and solvent environments will penetrate a bond at the interface and thus may weaken or destroy the integrity of the bond until the stress becomes relieved by failure. 

During the curing process, cobalt inhibits the formation of ZnS at the cord surface by acting as a selective diffusion barrier [29, 30] to allow the rapid formation of Cu S. For systems containing a thin layer of cobalt, copper migrates via grain boundary diffusion to the rubber-metal interface to react to form Cu,(S. However, zinc cannot diffuse by the same mechanism because cobalt acts as a selective diffusion barrier, and so promotes the growth of Cu S at the expense of surface ZnS. 

It has been reported [37] that a combination of cobalt and boron improve the retention of adhesion after steam-ageing and that boric esters increase the mobility of cobalt so that increased concentrations of cobalt were detected at the rubber-metal interface. 

However, boron also accumulated at the interface and borates are known to act also as corrosion inhibitors, particularly with steel and so there is a possible dual effect. It has also been postulated that borates may act by buffering the environment at the rubber-metal interface and so help to inhibit corrosion mechanisms. 

This book emphasises the empirical approach and it is not intended to include a review on the theoretical approach here. The theoretical approach at this stage contains many crude assumptions for example, gum rubber is considered to be an inelastic, viscous fluid and consequently the steady-state viscosity is used. The fill factor is ignored the presence and importance of the vacant space in the chamber is not recognised. Generally, slip at the rubber-metal interface is not considered. Non-affine deformation at the microscopic level for the filled system is not treated. 

Resilient materials such as rubber and some plastics may be useful in certain applications, especially under conditions of low cavitation intensities. However, such materials are subject to disbondment at the metal and elastomer interface at high cavitation intensities, even if the exposure is brief. 

To study the effect of contaminants (chlorides and sulphates) at the interface metal/coating, a set of panels (surface A Sa 3) was prepared and dosed with solutions of NaCl and FeSO in distilled water and methanol. Subsequently, two paint systems (chlorinated rubber and polyurethane) were applied on these contaminated surfaces. 

Moisture acts as a debonding agent through one of or a combination of the following mechanisms 1) attack of the metallic surface to form a weak, hydrated oxide interface, 2) moisture assisted chemical bond breakdown, or 3) attack of the adhesive. (2 ) A primary drawback to good durability of metal/adhesive bonds in wet environments is the ever present substrate surface oxide. Under normal circumstances, the oxide layer can be altered, but not entirely removed. Since both metal oxides and water are relatively polar, water will preferentially adsorb onto the oxide surface, and so create a weak boundary layer at the adhesive/metal interface. For the purposes of this work, the detrimental effects of moisture upon the adhesive itself will be neglected. The nitrile rubber modified adhesive used here contains few hydrolyzable ester linkages and therefore will be considered to remain essentially stable. 

It is immediately apparent that in many processes involving rubber heat flow across the interface between two surfaces has to be considered. This is true in mixing, moulding, cooling after processing and conditioning of test pieces but, nevertheless, very little attention has been paid to the measurement of the coefficient. The effect of the heat transfer coefficient on net heat flow is greatest with thin articles and where one of the materials is a gas. It is probably reasonable to assume a value of infinity for the transfer coefficient when rubber is pressed into intimate contact with a metal but in other cases it will be finite. 

When using peel tests on such products as belts to separate the plies, it can be difficult to obtain interfacial failure. Loha et al47 successfully used test pieces including a perforated metal sheet at the interface to measure rubber to rubber adhesion strength. 

---