The limitations of traditional methods of coalescence
Design and structural engineers are comfortable with the traditional methods of joining metal that include welding, riveting and the use of nuts and bolts. However, new challenges in the field of engineering have made these traditional methods less acceptable because of the need to reduce weight to minimize fuel consumption and concomitant emissions. This can only be achieved by the substitution of heavy parts made from steel to lighter components like aluminum or thinner sheet metal and by reducing the number of mechanical fasteners used. Plastics and composites cannot be welded together while thinner sheet metals will be distorted at the concentration points when metal fasteners or rivets or applied. Metals can be damaged by traditional welding methods due to heat distortion but structural epoxy provides a nice clean surface and at the same time reduces weight, costs and labor.
How to make a selection for adhesives
There are different technologies used in the adhesive industry in order to provide structural strength and bonding for large areas. Two-part urethanes are formulated to cure upon mixing and it is expected that a strong bond will be achieved at room temperature. One-part urethane sealants will cure slowly upon exposure to atmospheric or substrate moisture. Two-part urethanes provide strength and reliability with good impact resistance. Two-component acrylics are formulated to bond very strongly to metal even without priming. Acrylics have higher levels of heat performance than two-part urethanes but it tends to be more brittle that results into lower peel strength. For the best vibration and environmental resistance, structural epoxy is the best option because of its high structural strength and resistance to environmental challenges.
The history of structural epoxy
When epoxies were first introduced in the market in the 1950’s, it was intended for hobbyists but it was gradually improved so that by 1970, epoxies with greater flexibility and significant strength aroused the interest of many design engineers. In the 1980’s epoxies do not only provide a long reliable service life even when challenged with vibrations and thermal cycling since the more toughened epoxy is able to provide fatigue and impact resistance. Structural epoxy was formulated using higher modulus matrix to which micron-size rubber particles were embedded. These particles absorb energy under stress and prevent micro-cracks from occurring to provide significant fatigue and impact resistance. Today, toughened structural epoxy is used for the most demanding applications that include cell towers and armament bonding.