What Is a POM Washer?
A POM washer is a (flat) washer molded from Duracon.
Duracon® is a registered trademark of Polyplastics Corporation and is one of engineering plastics called POM (polyacetal resin). It has high electrical insulation properties and excellent impact resistance, creep resistance, chemical resistance, and abrasion resistance.
Taking advantage of the above advantages of POM, the POM washer is used in bolted joints to protect mating materials and provide electrical insulation.
Applications of POM Washers
Washers are used when the fastening force is large in relation to the size of the bolt head. By sandwiching a washer with a larger area than the bolt head, the washer expands the area of the seating surface, preventing the seating surface of the fastening part from sinking and loosening due to vibration or external force.
POM washers and other resin washers are used for the purpose of protecting the mating material from deformation by the fastening force and insulating the bolt and other members from current-carrying parts by utilizing the deformation and insulating properties of resin.
Rubber washers are used to prevent loosening when vibration is applied to the fastening part or when airtightness of the fastening part is important.
Characteristics of POM Washers
Duracon® (POM) is classified as a general-purpose engineering plastic and has many advantages, such as moldability, mechanical strength, impact resistance, abrasion resistance, fatigue resistance, insulation properties, and chemical resistance. Among these, insulation, material strength, and fatigue resistance are important for plastic washers. The advantage over engineering plastics, such as PTFE (Teflon resin) and PC (polycarbonate resin), which have similar characteristics, is that they are available at a lower cost.
Disadvantages of POM washer include flammability due to the presence of oxygen in its molecular structure, low weather resistance, poor adhesive bonding (welding is possible), and resistance to strong acids. Therefore, washers made of different materials should be selected for use in areas where the use of explosion-proof equipment is designated, such as facilities where volatile organic solvents are used, for outdoor use, or in environments where strong solvents or cleaning agents are applied.
POM washers cannot be transparent due to the crystalline nature of the resin, although this is a limited application. Black and white products are available.