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Polyacetal - POM (PolyOxyMethylene) is a high crystalline thermoplastic with a high level of stability and rigidity as well as good sliding properties and wear resistance with a low level of moisture absorption. Its good dimensional stability, exceptional fatigue resistance and excellent machining properties make Polyacetal a versatile design material also for complex components. It satisfies high surface finish requirements and offer better surface hardness, toughness and excellent solvent and gasoline resistance. A High Degree of crystallinity makes acetals stiffer and stronger than most thermoplastics, yet they are tough at ambient and low temprature, good dimensional stability is a key property. Acetals absorb little water, minimizing its effect on their physical properties. Main properties
Areas of Use
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Polyacetal - POM |
| There are two basic types of acetal resins; Homopolymer and Copolymer. The homoplymers’ strength properties tend to be slightly higher than those of the copolymers. Delrin® is a homopolymer Polyacetal. Delrin® has higher (short term) heat deflection temperatures than copolymers, but their continuous use temprature is 85°C (185°F) compared to 100°C (212°F) for copolymers. The homopolyemrs, tend to have somewhat greater surface hardness, higher degree of density and a slightly lower coefficient of friction. The copolymers, comapred to homopolymers, tend to absorb less water, are more resistant to hysrolysis and have superior processing characteristics. Copolymers, however, have higher impact toughness, greater wear resistance and thermal / chemical resistance. Acetals are mostly used in applications where excellent surface finish & accuracy with good dimensional stability are required. These are also preferred as a good material for food & pharmaceutical, chemical & oil industries. Sliding properties POM-C has excellent sliding properties and good wear resistance. Together with its other outstanding properties, POM-C is well suited for sliding applications with medium to high loads. This also applies to applications where high levels of humidity or wetness are to be expected. Because of the close static and dynamic coefficients of friction, low start-up moments can be implemented. This does not apply to the types filled with glass, as their sliding properties are much worse than the unfilled types. Weathering effects POM-C is not resistant to UV rays. UV rays, in combination with atmospheric oxygen, oxidise the surface, and discolouration occurs or the surface becomes matte. If the material is subject to the effects of UV rays for a long time, it tends to become brittle. Chemical resistance POM is resistant to weak acids, weak and strong alkaline solutions, organic solvents such as petrol, benzene, oils and alcohols. POM-C is not resistant to strong acids (pH < 4) or oxidising materials. Behaviour in fire POM-C is rated as normal flammable. When the source of ignition is removed, POM-C continues to burn, forming droplets. During thermal decomposition, formaldehyde can form. The oxygen index (= the oxygen concentration required for combustion) at 15 % is very low compared to other plastics. Applications
To limit material deformation due to internal residual stress in semi-finished products, the parts should always be machined from the geometrical centre of the semi-finished product, removing an even quantity of material from all sides. If maximum dimensional stability is demanded from the finished components, the parts to be manufactured should be rough machined and stored for an interim period or heat treated. |
Mr. Girish Dhawan
(Proprietor)
No. 170, Gali Bandook Wali, Ajmeri Gate
New Delhi,
Delhi -
110 006,
India
Telephone:+(91)-(11)-23215389/ 32972567
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