Neat polyoxymethylene homopolymer (POM-H) records a coefficient of friction around 0.30–0.45 in dry sliding against steel, per ASME tribology data [S1]. Internal lubrication with PTFE micro-powder or silicone oil masterbatch drops that figure into the 0.05–0.10 range, the typical target for self-lubricating precision gears and bearings.
The two lubricant families behave very differently inside the melt and on the finished part surface. POM is a semi-crystalline engineering thermoplastic widely used in precision components, where its 0.2% moisture absorption and creep resistance complement its inherent lubricity [S4]. Choosing between PTFE-modified, silicone-modified, and the newer hybrid low-emission grades is a formulation call driven by service temperature, contact stress, regulatory exposure, and whether downstream coating or bonding is required.
How PTFE and silicone change POM tribology
PTFE forms a transfer film on the steel counterface during sliding, which is the primary mechanism behind the friction reduction reported across multiple POM/PTFE studies [S3]. The same Wear journal work on POM blends notes that PTFE powder agglomerates easily in highly viscous polymer melts, so masterbatch dispersion quality controls the actual wear improvement more than nominal loading [S3].
Silicone internal lubricants work by partial migration, bleeding a sub-micron silicone film to the part surface during and after molding. Silicone masterbatches produce effective surface slip in many resins, but the migration behaviour is what makes them a liability in cleanroom and post-coating environments [S2][S5]. For POM specifically, silicone oil addition is one of the long-standing routes to a low coefficient of friction, alongside PTFE and UHMWPE [S3].
PTFE-modified POM: strengths and trade-offs
PTFE-modified POM grades, including the Delrin Solution Series PTFE-modified formulation, target dry-sliding gears, bushings, and conveyor components where steady-state wear is the life-limiting factor [S6]. The trade-off is mechanical: adhesion between POM and PTFE is very weak, so POM/PTFE composites suffer reduced tensile strength and elongation at typical 5–20 wt% PTFE loadings, and Fine PTFE powder tends to agglomerate without high-shear compounding [S3].
PTFE also has the advantage of being a true non-migratory solid lubricant, so the surface chemistry of the part stays stable, which matters when components are later bonded, printed, or assembled next to silicone-sensitive processes [S2][S5]. Engineers should treat the lower mechanicals as a re-design input: wall thickness, load-bearing area, and safety factor all have to be re-checked, not just wear life. For broader context on engineering plastic specification discipline, see ISO 10350 single-point data comparisons.
Silicone-modified POM: lower cost, higher migration risk
Silicone masterbatches typically cost less per kilogram than PTFE concentrates and are easier to compound at standard screw speeds, which is why many general-purpose low-friction POM grades historically used silicone oil as the primary internal lubricant [S2][S4]. The recurring complaint in industry forums is migration: silicones tend to migrate and are very difficult to remove, and that contamination breaks bed adhesion, paint, and downstream bonding in adjacent production areas [S5].
For OEMs supplying into automotive interiors, medical devices, or any line that includes a painting or pad-printing step, specifying silicone-modified POM is a known root cause of field failures and line stoppages. The practical rule is to keep silicone-lubricated POM parts in sealed assemblies, away from secondary finishing lines. This is the same logic the medical device industry applies when restricting any silicone-based material inside production areas [S5].
Hybrid and low-emission grades: 2026 direction
Material suppliers have responded to the silicone-migration problem with silicone-free, PTFE-modified grades designed for low friction and low formaldehyde emission, with at least one commercial grade claiming formaldehyde emission below 5 μg/g [S7]. These grades preserve the non-migratory benefit of PTFE while addressing the perception issue around silicone in regulated sectors.
The Delrin Solution Series frames PTFE modification as one option among many for low-wear, low-friction performance, signalling that grade selection now depends as much on regulatory context as on the friction number [S6]. For load-bearing gear or bearing applications, the comparison often comes down to three engineering resin families rather than one: POM, PA66 with MoS2, and PPS with PTFE. For a more detailed look at engineering plastic data sheet comparability, see the ISO 10350 single-point data piece. For adjacent material-selection context on chemical-process polymers, see PP-H vs PPR for chemical process lines.
Decision criteria: which internal lubricant for which application
Comparing the three realistic options for internally lubricated POM parts, engineers can score the choice against four criteria: lowest achievable coefficient of friction, retention of tensile strength, surface migration risk, and regulatory/cleanroom compatibility. [S2]
PTFE-modified POM delivers the lowest dry-sliding friction (0.05–0.10 typical), but tensile strength drops roughly 15–30% at the 10–20 wt% loadings needed for the best wear numbers, and the powder is harder to disperse [S1][S3]. Silicone-modified POM holds mechanicals closer to neat POM and costs less, but the migrating silicone film can wreck downstream coating and bonding operations and is a known contamination source in medical and painting environments [S2][S4][S5]. Hybrid silicone-free, low-emission PTFE grades (formaldehyde below 5 μg/g per supplier data) preserve the non-migratory benefit and add regulatory headroom, at a premium price and with less published long-term wear data [S7]. The correct pick is the one where the lowest-scoring criterion matches the actual production risk.
Standards, sourcing, and what to verify on the datasheet
There is no single ISO or ASTM standard that pins down "low-friction POM" as a category; grade qualification is driven by the application standard (e.g. ISO 1043-1 for polymer marking, ASTM D3702 for wear testing, ASTM D1894 for coefficient of friction on plastic film, ASTM D3028 for kinetic friction of plastics). For parts that will be in food contact or drinking water exposure, FDA 21 CFR 177.2470 or EU Regulation 10/2011 compliance is a separate check that must be done against the specific grade, not the family. [S2]
On the datasheet, the numbers to ask for are: coefficient of friction against steel at a defined pressure and velocity (ASTM D3028), wear rate (ASTM D3702 or similar), tensile strength and elongation at break after compounding (ISO 527), and a statement on silicone content and migration tendency. POM chemical resistance differs between homopolymer (pH 4–9) and copolymer (pH 4–13, hot-water hydrolysis resistance to 85°C) [S4], and that difference, not the lubricant choice, often decides whether the part survives the service environment.
Failure modes and constraints specific to lubricated POM
The recurring failure modes on lubricated POM are not "the lubricant wore off" but: (1) adhesive wear on the steel counterface once the PTFE transfer film is starved, common in boundary-lubrication conditions; (2) creep and wear combined in high-static-load bearings, where PTFE reduces friction but does not raise the creep modulus; (3) formaldehyde emission in enclosed cabin or medical environments, especially for high-recycle-content POM-H grades; and (4) silicone contamination of painting, printing, or bonding lines on adjacent parts [S3][S4][S5].
For a part designer, the spec trap is to over-weight the published coefficient of friction and under-weight the noise, vibration, and harshness (NVH) impact of a migrating silicone film in a sealed assembly. For the specifying engineer, the verification step is to ask for the wear test method and the exact counterpart surface finish, because the 0.05 vs 0.10 friction number is meaningless without a defined Ra on the steel ring.
Two near-term signals worth tracking: further silicone-free, low-formaldehyde POM grades hitting the masterbatch market, building on the formaldehyde below 5 μg/g benchmark already published for 2026 [S7]; and any movement on tighter ASTM or ISO wear-test methods for internally lubricated engineering thermoplastics, which would let buyers compare the silicone-free and PTFE-modified options on a single number rather than a manufacturer-specific test report.
For the relevant spec sheets and selection criteria, see ptfe, industrial lubricant, and silicone rubber.