Acetal plastic, scientifically known as Polyoxymethylene (POM), is a high-performance synthetic material used for demanding mechanical and industrial applications. It belongs to the class of engineering thermoplastics, valued for superior mechanical properties compared to standard commodity plastics. Acetal is exceptionally rigid, dimensionally stable, and exhibits a low coefficient of friction. It is frequently chosen when a project requires a durable, low-wear material that maintains its integrity under continuous stress.
Chemical Identity and Structure
The foundation of Acetal plastic is Polyoxymethylene (POM), a semi-crystalline polymer composed of repeating formaldehyde units. This highly ordered structure contributes significantly to the material’s overall strength and stiffness. Acetal is commercially available in two primary forms that differ in their core molecular structure: homopolymer and copolymer.
Homopolymer Acetal, often known by the brand name Delrin, has a uniform molecular chain structure. This uniformity leads to a higher degree of crystallinity, resulting in superior tensile strength, hardness, and enhanced resistance to long-term deformation (creep). Copolymer Acetal incorporates a second type of monomer unit, which interrupts the repeating structure. This modification provides the copolymer with improved resistance to chemical attack and reduced porosity, making it suitable for high-moisture or high-temperature environments.
Essential Physical Characteristics
Acetal plastic is distinguished by physical characteristics that make it an exceptional choice for precision engineering, often replacing metal components. The material exhibits high stiffness and strength, possessing an excellent strength-to-weight ratio for designing lighter, robust parts. Its superior dimensional stability means the plastic resists changes in size or shape when exposed to fluctuating temperature and humidity, due to its very low rate of moisture absorption.
The material’s surface is naturally slick, yielding a low coefficient of friction that allows components to slide smoothly with minimal wear. This inherent lubricity makes Acetal ideal for moving parts, contributing to excellent wear and abrasion resistance in both wet and dry conditions. It also possesses good fatigue endurance, enabling it to withstand repeated stress and cycling over long periods without structural failure. The continuous service temperature for Acetal generally extends up to 180°F (82°C).
Common Industrial Applications
The combination of Acetal’s strength, stability, and low friction properties leads to its widespread use across diverse industries. Its capacity for high precision and long-term durability makes it a staple material for mechanical components requiring tight tolerances. Products such as gears, bushings, bearings, and rollers utilize Acetal to ensure smooth operation and extended service life.
Acetal is frequently employed in the automotive sector for fuel system and transmission parts, benefiting from its chemical resistance to hydrocarbons. Consumer electronics and appliances incorporate the plastic for moving parts, including small gears and mechanisms in printers and domestic machinery. It is also utilized in medical devices, such as internal components of insulin pens and fluid delivery systems, where its non-porous nature and dimensional consistency are highly valued.