Rubber, in all of its forms, shows the capacity to bind to a wide range of metals and other materials. Furthermore, bonded rubber is more durable. Molding rubber to metal bonding is a technique for mechanically attaching the rubber to a metal insert during the moulding process. Rubber to metal bonding is used in a variety of applications, including any component that requires the flexibility of rubber combined with the stability of metal. When it comes to the automobile sector, rubber-to-metal bonded goods have a broad range of uses, particularly as rubber springs. During service, these items are exposed to high temperatures, oil, and water, either purposefully or accidentally.
The Components of a Rubber-to-Metal Joint
The rubber, the bonding agents, and the substrate are the three main components of the bonding process, and they serve as the building blocks of the process. The selection of the polymer base and the related chemical is mostly dictated by the product specifications for the final product. Any rubber compound may be used to create a bond as long as the rubber is able to flow into the mould without generating a substantial degree of cross-linking (less than 2 percent). Using specific compounding components is not restricted, although it is recommended to avoid chemicals that may bleed quickly to the surface of uncured stock.
The Metal Bonding Process is a method of joining metals together
A quick summary: The process of bonding rubber and metal inserts starts with the inserts being prepped for production utilising a grease removal method to clear your components of any impurities before the adhesive is applied. Following that, the hot glue is applied on the inserts using a method similar to that of spray painting.
- Rubber to Metal Bonding is used for encapsulation
When a metal or plastic component has to be completely encapsulated with rubber, we utilise rubber – metal bonded products for rubber insert moulding, which is a variant of rubber to metal bonding, to accomplish this. Because the plastic or metal component is hung inside the bold chamber, we are able to more precisely bind the rubber to the part in the case of full encapsulation. Additionally, rubber may be moulded to fit a particular region of metal components. Rubber mechanically adhered to metal may improve the stability of metal components while also allowing them to retain their flexible properties. Metal components that have been moulded with rubber may also have improved part characteristics, such as the ability to create environmental sealing.
- Design and Manufacture ability of the Part
The shape of the metal insert should be designed in such a way that adequate rubber filling occurs during moulding, and the regions next to the insert should get sufficient mould pressure. To reduce the amount of flash produced by the metal insert, the mould should be constructed to have a positive shut-off. Provision should be provided to allow entrapped air to escape; otherwise, blisters or weak areas may form at the interface of the rubber and metal, resulting in a lack of bonding and early failure of the joint.
- Preparation of Metal
In most cases, a surface that has been recently sanded or grit blasted should be adequate to provide a solid connection. It is necessary to perform chemical adhesive treatments if more strength is needed. Commercial adhesives are sold in two-pack systems, which include a primer and an adhesive, to save money. Following the manufacturer’s instructions for application, curing, and ageing, it is essential that you adhere carefully to them. Because the surface of sandblasted metal is susceptible to oxidation, adhesive application or moulding should be completed as soon as possible. This will improve the bond quality. When it comes to high-performance bonding, the brass coating may be applied to the metal surface via elector deposition of copper and zinc, followed by a diffusion and maturation process to create a long-lasting brass coating.
- Adhesion Inducing Agents
The presence of adhesion promoters may make a significant difference in the adherence and long-term stability of a bond under hot and humid circumstances. Cobalt salts, such as cobalt naphthenate, have been shown to enhance adhesion in tyre skim compounds when they come into contact with steel cables in laboratory tests. Another class of additives that have been shown to be effective include silica, organic silanes.
- Base Polymer and Fillers are two types of polymer
In general, polar rubbers such as butyl rubber are found to be simpler to bind than non-polar rubbers such as ethylene vinyl acetate. In part, this is because sulphur is thought to interact with some of the bond accelerators that have been added to the formulation to make the rubber more bondable. Fillers must be carefully chosen in order to minimise the differential stress at the interface between the two materials. Excessive loading of fillers reduces the proportion of rubber hydrocarbons present at the interface and is thus not recommended. It has been discovered that using epoxy altered natural rubber as an adhesive enhancer may enhance the adhesive characteristics.