Volume 4 - Loctite.ph

Acetal HomopolymerThermoplasticTrade Names• Celcon• Delrin• Iupital• Kemlex• Tenac• UltraformManufacturerHoechst CelaneseE.I. DuPontMitsubishi GasFerro CorporationAsahi ChemicalBASFGeneral DescriptionAcetal homopolymer is a highly crystalline thermoplastic produced bypolymerizing formaldehyde and capping each end of the polymer chainwith acetate groups. The polymer is properly called polyoxymethylene(POM) and has a backbone comprised of repeating -CH 2 O- units. Acetalcopolymer is manufactured by copolymerizing trioxane with relativelysmall amounts of a comonomer. The comonomer randomly distributescarbon-carbon bonds in the polymer chain which helps to stabilize theresin against environmental degradation. The relatively low cost ofacetals, in addition to their good balance of mechanical, chemical andelectrical properties, makes them well suited for replacing metal andother structural materials. Specialty grades available include glassfilled,low friction/low wear, antistatic and conductive, mineral-coupled,UV stabilized, pigmented, toughened (elastomer modified), and abrasionresistant grades. In 2004, the price of acetal homopolymer rangedapproximately from $1.25 to $2.00 per pound at truckload quantities.General PropertiesAcetals exhibit high physical strength, as well as excellent creep andimpact resistance. Due to their extremely low water absorption rate, theelectrical properties and dimensional stability of acetal resins areminimally affected by atmospheric moisture. The dielectric constant ofan acetal resin varies only slightly over a wide frequency range, itsdielectric strength is high, and a volume resistivity of 1015 ohm-cmmakes it a good electrical insulator. Acetals are resistant to solvents,ethers, oils, greases, gasoline, and other organic compounds, and areespecially well suited for use with methanol-based fuels. They areresistant to moderate strength acids, but are not recommended for usewith strong acids. Acetal homopolymer is very resistant to wear due toits hard surface and low coefficient of friction (0.1 to 0.3). Acetalhomopolymer is UL94HB rated for flammability, and has continuousservice temperatures in the range of 212°F (100°C) to 221°F (105°C).Typical Properties of Acetal HomopolymerAmerican EngineeringProcessing Temperature 350°F to 420°F 117°C to 216°CLinear Mold Shrinkage 0.001 to 0.025 in./in. 0.001 to 0.025 cm/cmMelting Point 325°F to 355°F 163°C to 179°CDensity 84.3 to 96.1 lb./ft. 3 1.35 to 1.54 g/cm 3Tensile Strength, Yield 6.0 to 10.0 lb./in. 2 x 10 3 4.2 to 7.0 kg/cm 2 x 10 2Tensile Strength, Break 5.8 to 10.0 lb./in. 2 x 10 3 4.2 to 7.0 kg/cm 2 x 10 2Elongation, Break 5.0 to 80.0% 5.0 to 80.0%Tensile Modulus 3.0 to 5.0 lb./in. 2 x 10 5 2.1 to 3.5 kg/cm 2 x 10 4Flexural Strength, Yield 7.1 to 15.6 lb./in. 2 x 10 3 5.0 to 11.0 kg/cm 2 x 10 2Flexural Modulus 2.2 to 5.7 lb./in. 2 x 10 5 1.5 to 4.0 kg/cm 2 x 10 4Compressive Strength 4.5 to 17.6 lb./in. 2 x 10 3 3.2 to 12.4 kg/cm 2 x 10 2Izod Notched, R.T. 0.5 to 2.8 ft.-lb./in. 2.7 to 15.1 kg cm/cmHardness R117 - R120 Rockwell R117 - R120 RockwellThermal Conductivity 1.6 to 2.5 BTU-in./hr.-ft. 2 -°F 0.23 to 0.31 W/m-°KLinear ThermalExpansionDeflection Temperature@ 264 psiDeflection Temperature@ 66 psiContinuousService Temperature0.5 to 11.0 in./in.-°F x 10 -5 0.9 to 19.8 cm/cm-°C x10 -5SI195°F to 325°F 91°C to 163°C300°F to 345°F 149°C to 174°C212°F to 221°F 100°C to 105°CDielectric Strength 380 to 500 V/10 -3 in. 1.5 to 2.0 V/mm x 10 4Dielectric Constant@ 1 MHzDissipation Factor@ 1 MHzWater Absorption,24 hr.3.5 to 4.2 3.5 to 4.20.001 to 0.009 0.001 to 0.0090.16 to 0.35% 0.16 to 0.35%Typical Applications• Automotive – Fasteners, carburetor floats, knobs,fuel pump housings• Industrial Machinery – Valves, conveying equipment,rollers, springs• Plumbing – Ballcocks, faucet cartridges, impellers, shower heads,faucet underbodies• Electronic – Keytops, switches, buttons• Miscellaneous – A/V cassette components, toiletry articles,zippers, bearings, toy parts14The Loctite ® Design Guide for Bonding Plastics, Volume 4