Engineering Plastic Material Selection Guide – Nylon, Acetal, PTFE and UHMWPE Compared

Engineering Plastic Material Selection – Nylon, Acetal, PTFE and UHMWPE

Selecting the correct engineering plastic for a machined industrial component is a decision that directly determines wear life, dimensional stability, chemical resistance and service reliability. The four most widely specified materials in Kaybin's manufacturing range — nylon (PA6/PA66), acetal (POM), PTFE and UHMWPE — each have distinct properties that make them the right choice for specific applications and the wrong choice for others.

This guide provides a practical technical comparison of each material to support correct specification of plastic bushes, seals, gears, wear rings, liners, rollers, gaskets and other precision-machined polymer components.

Nylon — PA6 and PA66

Nylon is one of the most widely used engineering plastics for machined components in industrial equipment. Its combination of mechanical strength, toughness, impact resistance and reasonable wear performance makes it suitable for a broad range of structural, bearing and wear applications. PA6 (cast nylon) and PA66 (extruded or moulded nylon) have similar general properties with PA66 offering slightly higher stiffness and heat deflection temperature.

Nylon is the first choice for machined gears, heavy-duty bushes, structural spacers, impellers, bearing elements and components where mechanical load capacity is important. It machines cleanly and holds threads well. The primary limitation of nylon is moisture absorption — nylon absorbs water from the environment, which causes dimensional swelling that must be accounted for in clearance and fit design. In wet or submerged applications, dimensional change from moisture must be included in the tolerance calculation. Glass-filled and oil-filled nylon grades improve stiffness, dimensional stability and wear performance where standard grades are insufficient for the duty.

Acetal — POM (Polyoxymethylene)

Acetal (also known as POM, Delrin in its homopolymer form, and acetal copolymer in its alternative grade) is the preferred engineering plastic where tight dimensional tolerances, low moisture absorption and consistent running clearances are required. Unlike nylon, acetal has very low moisture absorption and maintains its dimensions in wet environments, making it reliable for precision components in humid, submerged or wet industrial conditions.

Acetal is commonly specified for precision bushes and bearing elements where stable running clearance is critical, dosing pistons and volumetric components requiring consistent displacement accuracy, gear profiles requiring backlash control, and components requiring consistently machinable thread forms. Acetal has lower impact toughness than nylon and is more notch-sensitive, making it less suitable for heavy shock loading. It also has lower maximum operating temperature than glass-filled nylon grades. Chemical resistance is good for neutral and mildly acidic or alkaline environments but acetal is not recommended for strong acids, oxidising agents or halogenated solvents.

PTFE — Polytetrafluoroethylene

PTFE has the lowest coefficient of friction of any engineering plastic and exceptional chemical resistance across a broader range of aggressive fluids than any other polymer in this group. These two properties make PTFE the specification of choice wherever chemical attack would destroy nylon or acetal, wherever zero lubrication dry-running is required, or wherever stick-slip must be minimised in precision sealing or bearing applications.

PTFE is used extensively for hydraulic and pneumatic seals, gaskets for aggressive chemical service, bushes and liners in chemically hostile environments, and wear surfaces in food processing and pharmaceutical equipment where material compliance is important. Virgin PTFE has low mechanical strength, significant creep under sustained compressive load, and moderate wear resistance — properties that limit its use in high-load structural applications. Filled PTFE grades address these limitations: carbon-filled PTFE improves wear resistance, glass-filled PTFE improves compressive strength, and bronze-filled PTFE improves thermal conductivity and load capacity. The correct filler is selected based on the duty conditions and the mating surface material.

UHMWPE — Ultra-High Molecular Weight Polyethylene

UHMWPE has the highest abrasion resistance of the four materials in this comparison and very low friction, making it the dominant specification for wear liners, chute liners, conveyor guides, star wheels and other components exposed to sliding abrasion from bulk materials, packaging surfaces or moving product contact. Its impact resistance is also excellent, making it well suited to impact zones in bulk handling and processing equipment.

UHMWPE is not a structural material in the same sense as nylon or acetal — its stiffness is lower, its creep under sustained compressive load is higher, and it cannot be machined to the same dimensional tolerances as acetal or nylon. It is selected for wear performance first, and structural performance second. Chemical resistance is good across a broad range of media including acids, alkalis and solvents that would attack nylon. It is not recommended for oxidising acids or halogenated solvents.

Direct Comparison Summary

For load-bearing structural components requiring toughness and good mechanical strength, nylon is typically the first choice. For precision components requiring dimensional stability and consistent clearance in wet environments, acetal is preferred. For seals, gaskets, bearings and components in chemically aggressive environments or requiring very low friction, PTFE is the material of choice with the correct filler grade selected for the duty. For abrasion-resistant wear liners, chute liners, guides and components in sliding bulk material contact, UHMWPE delivers the best wear performance of the four.

Machined Engineering Plastic Components from Kaybin

Kaybin manufactures precision-machined engineering plastic components in nylon, acetal, PTFE, UHMWPE, polyurethane and other engineering polymers for industrial and OEM applications across South Africa and Africa. Material is selected based on mechanical load, wear mode, chemical environment, temperature, dimensional requirements and duty conditions. To specify the correct material for your component, provide the application description, operating conditions, dimensions and any existing sample or drawing and Kaybin will confirm the correct polymer and manufacture the component to your specification.