Acetal copolymer

Acetal copolymer, commonly abbreviated POM-C, is an engineering thermoplastic used for machined and molded components. The family name does not specify one strength, friction coefficient or chemical-service envelope. Identify the manufacturer, complete grade, supplied form and processing history before assigning properties or approving a substitution.

POM-C is not every acetal

Ensinger's US TECAFORM AH natural POM-C stock-shape sheet gives 316°F heat deflection at 66 psi and 230°F at 264 psi, both ASTM D648. The different test loads belong with the results. Assess sustained load, exposure and dimensional fit separately. Ensinger US test table

Mitsubishi Chemical Group distinguishes POM-H homopolymer from POM-C copolymer. Its Acetron GP overview describes the usual tradeoff as greater strength/stiffness for homopolymer versus improved hydrolysis and chemical resistance for copolymer. These are selection trends, not a universal percentage improvement or permission to substitute one grade for another.

The same overview notes that centerline porosity can affect thicker acetal sections and describes Acetron GP's particular approach to limiting it. Therefore, porosity should be checked against the named stock product and leak-sensitive geometry, rather than inferred solely from POM-C chemistry. A commercial comparison does not qualify a particular finished manifold or seal. Mitsubishi Chemical Group, Acetron GP overview

Ensinger identifies TECAFORM AH natural specifically as an unfilled POM-C stock-shape grade, offering rods, plates and tubes. Its porosity and machinability descriptions belong to that named product. They should not be transferred automatically to reinforced, lubricated, colored, conductive or other modified acetals. Preserve the complete grade and color code in the purchase record. Ensinger, TECAFORM AH natural

Resin, stock shape and finished part are different evidence

A resin-grade certificate does not by itself describe the internal stresses, dimensions or machining history of an extruded rod. Likewise, a stock-shape property table does not establish the performance of an injection-molded part with its particular gates, weld lines and geometry. State which product and process a claim describes.

A bounded property example

Ensinger's US TECAFORM AH natural stock-shape sheet carries Date 2017/10/06, Version A3. Selected guideline values include:

The sheet says values are guidelines, not guaranteed properties, and generally concern extruded shapes unless otherwise noted. The two heat-deflection results use different loads; neither is a universal continuous-use temperature. The friction result describes a specified test, not every counterface, lubricant or bearing load. Ensinger, US TECAFORM AH natural datasheet

For design, request data matching temperature, load duration, loading mode and environment. A short tensile test does not establish sustained-load deformation, gear life or dimensional retention. Require the relevant long-term or component test where those outcomes govern acceptance.

Moisture and chemical resistance are conditional

Ensinger's separate Brazilian stock-shape sheet, explicitly dated June 22, 2017, version AA, reports 0.25% / 0.48% water absorption after 24 / 96 hours at 23 °C, using ASTM D570. It identifies a specimen approximately 50.8 mm diameter × 3.3 mm high. Those entries must not be mixed with another regional sheet's differently conditioned values or assumed to predict dimensional change directly.

That sheet classifies hot-water/base resistance as limited and weathering resistance as poor. It expressly does not guarantee chemical resistance. A favorable family comparison therefore cannot establish unlimited hot-water, steam, outdoor or cleaner exposure. Ensinger, Brazilian TECAFORM AH natural stock-shape datasheet

For a proposed cleaning or process fluid, record chemical identity, concentration, temperature, exposure time, cycling and applied stress. Establish permissible swelling, surface change and retained mechanical properties on the actual grade. An industry application list is not a qualification of every sanitizer or sterilization routine.

Machining and dimensional stability

Ensinger's machining guidance explains how extrusion and uneven cooling create internal stresses, and how later stress relaxation or machining heat can change dimensions. It recommends sharp tools, effective chip removal and heat management; it also identifies intermediate annealing as potentially useful for critical geometries or large stock removal. Such treatment needs a grade- and geometry-specific procedure, with allowance for subsequent dimensional changes.

Support the workpiece without excessive distortion, plan balanced stock removal and inspect after cooling and any prescribed conditioning. A dimension measured immediately after a hot cut may not describe the released component. Do not replace process development with a universal cutting speed or annealing schedule. Ensinger, machining and dimensional-stability FAQ

Mitsubishi Chemical Group likewise highlights plastics' relatively slow heat dissipation, elasticity and thermal expansion when selecting tools and stabilizing methods. These factors explain why copying metal machining practice can be unsuitable even when the plastic cuts readily. Match workholding, cooling and inspection to the material and part. Mitsubishi Chemical Group, Machinist's Toolkit

Wear parts and assemblies need their own limits

For a bushing, sliding pad or gear, define counterface material/finish, contact geometry, load, speed, duty cycle, lubrication, contamination and temperature. Qualify friction, wear and allowable deformation on that system. A low-friction stock material does not establish unlimited dry operation or make the test coefficient a constant for the assembly.

For joints, state whether the design uses fasteners, interference fits, welding or adhesives and qualify the resulting loads and exposure. Preserve the final dimensions and any contact-surface requirements after assembly. Where food contact or other regulated use matters, obtain documentation for the exact product and intended conditions; family identity is insufficient.

Processing and handling

The TECAFORM AH natural SDS supplied through Ensinger is prepared and revised May 27, 2020. It calls for controlling airborne dust, avoiding dust accumulation and using suitable collection equipment, ventilation and eye protection. Its handling guidance specifically rejects sweeping or compressed-air cleaning that disperses dust. Apply the current product-specific SDS and process controls when machining or heating material; do not infer workplace handling requirements from a mechanical-property table. Ensinger, TECAFORM AH natural SDS

Release the finished part against its drawing and qualified service conditions. Keep typical data, contractual limits and test results distinct, retaining grade/batch identity through machining, cleaning and assembly. Undated webpages above are not assigned publication dates from copyright or crawl records.

Related reference

Material selection through production