For a homogeneous object, Density = Mass Divided By Volume. The higher the density, the tighter the particles are packed inside the substance. The Specific Gravity is the ratio of Density of the material to the Density of water at a specified temperature. It is common to use the density of water at 4°C as reference - at this point the density of water is at the highest i.e. 1 g/cm3. So Specific Gravity of less than “1” means that the material will float in water.
Acetal plastic Description
Acetal also known as POM (PolyOxyMethylene) is an engineering thermoplastic often used for precision components that require high stiffness, low friction and excellent dimensional stability. Generally two grades of Acetal available: Acetal Copolymer and Acetal Homopolymer which is made by the DuPont company under the trade name Delrin
Advantages of Acetal parts
Excellent abrasion resistant Good working temperature, Glossy appearance, Excellent durability Self-lubricant Good stiffness, strength & Hardness. Wide range Chemical resistance (including many solvents). Good Electrical and Dielectric properties.
Acetal plastic Uses
Gears, Bearings, Screws, Pump parts, Electronic components, Insulators, Medical parts, Furniture hardware, Valve bodies, Zippers, Underwater applications.
Finishing examples of Acetal prototypes
Acetal (POM) material Spec
Easy to machine but very difficult to bond. Good appearance with gloss finish. Acetals often compete with Nylons for many of the same applications but dimensionally stabler than Nylon under wet and humid conditions.
Very difficult to bond, Poor resistance to acids, Flammable and High Specific Gravity. Difficult to paint. Large and thin parts with irregular wall section are prone to warpage.