Introduction
Pressure sensitive adhesives (like this manufactured by 3M) are a type of agent which forms bonds when the force is applied in order to join the adhesive to the adherent. No heat, water or solvent is required to activate this binder. Such binding material depends entirely on the amount of force exerted in order for proper bondage to take place. Other factors that can affect this bonding include: surface energy, smoothness and removal of any contaminants. They have been designed to provide a bond at room temperature and can be used for either removable or permanent applications. Some of the permanent applications are vehicle interior trims units, safety labels for various power equipment, foil tapes for HVAC ducts vibration/sound damping films, amongst others.
How PSAs are manufactured
PSAs are China Adhesive Manufacturers in two ways, either as 100% solid form or as a liquid carrier. Many of the labels and the tapes are made from liquid PSAs. This is done by coating on the support and evaporating the water carrier or organic solvent by using a hot air dryer. A dry viscous is heated in order to create a cross linking reaction which helps to increase molecular weight. Solid PSAs are low viscosity polymers which are coated and passed through radiation for the purpose of increasing the molecular weight which forms the adhering. Hot melt PSAs are heated to reduce the level of viscosity in order to allow coating to be done before being cooled into their last form.
They are made up of special bonding tapes which are comprised of fluid adhesive micro wed and a composite backing. These adherents are only applied by the use of force exerted by using one’s fingers. The process of application for PSAs is cleaner compared to other types of adhering agents and the bond is much stronger. The basic composition includes an elastomer which has one of the following: acrylics, natural rubber, styrene copolymers, vinyl ethers, nitriles, butyl rubber and silicones. To ensure that the adherents have the best tackiness, the elastomer is mixed with tackifier which is a lighter molecular compound. Tackifiers add the benefit of providing stiffness during high strain while at the same time retaining high stress compliance. Commonly used tackifiers include terpenes, hydrocarbon resins, aromatic resins and terpene resins.
How are PSAs used in a membrane switch construction?
PSA switches are used in most of the applications of membrane switches. One needs to identify the environmental situations these switches will be subjected to. PSA switches are likely to fail if subjected to very high temperatures or when they are in contact with certain chemicals or solutions. Therefore, it is imperative to note that extreme temperatures, moisture and chemicals are common enemies of PSA membrane switches. PSA switches are popular in switch construction since they are compatible, durable, flexible and repositionable.
Adherents are supposed to be compatible with various switching mechanics which will include metallic dome, polyester dome and flat switch. There is high stress that is imparted to these switches. PSA bonds are able to offer a high level of elasticity and are resistant to moisture, heat and chemicals. Common adhesives manufactured by 3M used in membrane switches are their 467 and 468 styles.
Mike Ryan is the owner and President of RSP, Inc in Milwaukee, WI & Shenzhen, China. He has over 10 years experience designing, building, and testing membrane switches, touch screens, silicone rubber keypads and other user interfaces. RSP is a global contract manufacturer offering engineering, design, testing and full turn key supply of finished packaged products.
