Tribological Additives: 4 Solid Lubricants (PTFE, Silicone, MoS2, Graphite) for Wear-Resistant Plastics

Tribological additives are solid lubricants, PTFE, silicone, molybdenum disulfide and graphite, that stay inside the finished plastic part and lower friction and wear during service instead of lowering melt viscosity during processing. They belong to the 12 functional families among the 43 families of plastic additives, and they are the only additive class whose work begins after the part leaves the mould. Which of the 4 solids belongs in a polyamide gear, how much of it goes in, and what do the food-contact and PFAS rules allow?

Our source library carries complete identity and regulatory records for 3 of the 4 named solids, PTFE (CAS 9002-84-0), polydimethylsiloxane (CAS 63148-62-9) and graphite (CAS 7782-42-5), plus a fourth solid lubricant, hexagonal boron nitride (CAS 10043-11-5). It carries no verified record for molybdenum disulfide, and it establishes no wear rates, no PV limits and no compound dosage ranges for wear applications. This page states what is verified, names each gap in the same sentence as the claim it would support, and separates the wear job from the 3 neighbouring surface jobs that share the same chemistry: melt lubrication, film slip and mould release.

What Are Tribological Additives?#

A tribological additive is a solid lubricant compounded into a polymer so that it remains in the moulded part and reduces friction and wear at a sliding or rolling contact. The site scope rule places 4 solids in this family: PTFE, silicone, molybdenum disulfide and graphite. Each one is a finely divided solid that is dispersed through the melt, so the finished gear, bearing, bushing or slide rail carries its own lubricant and needs no grease.

The family sits in the third functional group of the site taxonomy, next to flame retardants, blowing agents, antimicrobials, oxygen scavengers, barrier additives, odour control additives, laser marking additives, IR absorbers, tracers, repellents and biodegradation additives. What unites that group is that each family gives the polymer a property it does not have on its own, and a tribological additive gives it self-lubrication. The full classification of all 43 families, with the 7 functional groups they fall into, is on the plastic additives root page.

Which properties do tribological additives change?#

Tribological additives change the properties measured at a contact, not the bulk properties measured on a dumbbell specimen. The 4 properties named in the trade literature our source library draws on are listed below, with the status of each in our sources.

• Coefficient of friction at the contact between the part and its counterface. Our source library holds the film test methods, ASTM D1894-24 and ISO 8295, but no friction values for filled wear compounds.
• Wear rate of the plastic part, and of the steel or plastic counterface running against it. No wear rate for any solid lubricant in any polymer is established in our sources.
• Limiting PV (the product of contact pressure and sliding velocity a bearing tolerates). No PV value is established in our sources.
• Stick-slip behaviour at low sliding speed, which governs squeak and rattle in vehicle interiors. No quantified result is established in our sources.

The gap is deliberate rather than accidental. Wear numbers are compound-specific, counterface-specific and rig-specific, and every published figure we checked came from a supplier data sheet rather than from a primary standard or a peer-reviewed source, so none is stated here as a property of the additive.

Tribological additives versus processing lubricants and slip agents#

A tribological additive works in the part, a processing lubricant works in the machine, and a slip agent works on the film surface. The distinction is a hard scope rule on this site, because the word lubricant covers all 3 jobs in everyday use and covers greases and sprays as well. Processing lubricants for plastics are compounded into the polymer before or during melt processing and act on melt viscosity, metal release and fusion time, and their job ends when the machine stops.

Slip agents follow a different route again. A slip agent such as erucamide or oleamide migrates to the film surface after production and lowers the surface coefficient of friction so that reels unwind and bags open, which is why slip additives for plastic film are measured by bloom time rather than by wear. A tribological additive is not intended to migrate at all. It stays where the compounder put it, dispersed through the section thickness, for the service life of the part.

The fourth neighbour is the release family. Mold release agents for plastics act at the tool wall for a single moulding cycle, and the external grades are applied to the tool rather than compounded into the resin, which puts them outside the additive definition altogether. Table T1 sets the 4 jobs side by side.

Table T1. Four surface jobs that share the same chemistry.

How Do Tribological Additives Work?#

A solid lubricant lowers friction by presenting an interface that shears more easily than the polymer around it. Our source library records 2 distinct routes to that interface, one for the layered solids and one for silicone, and it records no mechanism at all for PTFE in a wear application, which is stated here as a gap rather than filled in.

Lamellar solids: graphite and boron nitride#

Graphite and hexagonal boron nitride are layered crystals whose properties differ by direction. ECHA and PubChem data on hexagonal boron nitride record a strongly anisotropic structure, with hardness, thermal conductivity and electrical conductivity much higher in the plane of the layers than across them. That anisotropy is what a lamellar lubricant exploits: the layers slide over one another far more readily than the crystal resists load across the layers, so a dispersed particle at a contact yields in shear while still carrying pressure.

Boron nitride carries the trade name white graphite for that reason, and PubChem records it as a lubricant up to 900 °C in an oxidising atmosphere, which is the highest working temperature our sources give for any solid lubricant used in plastics. No polymer survives 900 °C, so the figure describes the additive rather than the compound. Its practical meaning is that the lubricant does not limit the service temperature of an engineering thermoplastic.

Silicone: a low-surface-energy film#

Polydimethylsiloxane works by forming a low-surface-energy siloxane film at the interface, which is the mechanism our source library records for it in every role it plays in plastics. That single mechanism explains why the same chemistry appears as an external mould release, as a slip and lubricant additive in masterbatch form, and as the basis of the polyether-grafted silicone processing aids used to replace fluoropolymers. In each case the siloxane reaches an interface and lowers the energy of that interface.

The consequence for a wear compound is that silicone is a migrating additive by mechanism. A film has to be replenished from the bulk, which makes the additive's reservoir and its rate of supply to the surface as important as its concentration. Neither the reservoir requirement nor a replenishment rate is quantified in our sources.

What a solid lubricant costs the compound#

Every solid lubricant loading displaces load-bearing polymer, so a wear compound trades mechanical properties for surface properties. Solid lubricants enter the compound as particulate solids, which places them with the fillers for plastics in their effect on stiffness, notched impact strength and weld-line strength. Compounders answer that trade-off by combining a solid lubricant with a reinforcement, most often glass or carbon fibre, so that the fibre restores the stiffness the lubricant costs.

The quantitative form of that trade-off is not established in our source library. No source we hold gives the impact strength of a PTFE-filled polyamide against its unfilled control, so the direction of the effect is stated here and the magnitude is not.

4 Solid Lubricants Used in Wear-Resistant Plastic Compounds#

The 4 solid lubricants that define this family are PTFE, silicone, molybdenum disulfide and graphite, and a fifth solid, hexagonal boron nitride, appears in our sources with the same self-lubricating role. They are ordered below by how completely our source library documents them, which is also the order of their commercial importance in engineering compounds. Table T2 gives the identity and food-contact status of each.

Table T2. The 4 named solid lubricants plus boron nitride, as documented in our source library.

1. PTFE (polytetrafluoroethylene)#

PTFE is the reference solid lubricant of the family and the only one our source library classifies with a dual function, anti-dripping agent in UL 94 V-0 formulations and tribological wear and friction additive. Its identity is settled: CAS 9002-84-0, ECHA list number 618-337-2, repeat unit (C2F4)n, a fluoropolymer inside the PFAS group. ECHA CHEM, checked on 22 September 2026, records that PTFE is not on the REACH Candidate List of substances of very high concern.

Anti-drip grades are usually encapsulated in styrene-acrylonitrile, sold as TSAN, at PTFE to SAN ratios between 40/60 and 60/40. The encapsulation exists to stop fibrous PTFE agglomerates forming and to improve dispersion and surface quality, which is a dispersion problem shared by every fine fluoropolymer powder. A 2024 study in Materials on flame-retarded PC/ABS used 0.4 wt% PTFE with 20 wt% of a bisphenol A bis(diphenyl phosphate) type retardant to reach UL 94 V-0, and the patent literature gives a working range of 0.05 to 10 phr of active PTFE, with 0.1 phr common in the worked examples.

Those figures describe the anti-drip function, not the wear function, and our source library holds no dosage for PTFE in a wear compound. The regulatory position is the practical constraint instead: PTFE is a fluoropolymer within the scope of the EU universal PFAS restriction proposal, whose Annex XV dossier ECHA published on 7 February 2023 and which remains pending. No PFAS restriction is in force for fluoropolymers in articles, and PFAS in plastics sets out what each pending and adopted instrument actually covers.

2. Silicone (polydimethylsiloxane)#

Silicone enters wear compounds as polydimethylsiloxane, CAS 63148-62-9, EC 687-578-3, a polymer of the repeat unit (C2H6OSi)n. Our source library records 3 plastics roles for it, external mould release as oils and emulsions, slip and lubricant additive supplied in masterbatch, and the base chemistry of the silicone-type fluorine-free polymer processing aids that are built on polyether-grafted PDMS. The wear role rests on the same low-surface-energy film mechanism as the other 3.

Two regulatory facts shape its use. For food contact, PDMS is authorised under EU 10/2011 as FCM No 575, Ref 76721, with the restriction that the molecular weight exceeds 6,800 Da and the viscosity is at least 100 cSt at 25 °C, so low-viscosity silicone oils fall outside the authorisation. In the United States, polyoxyethylene-grafted PDMS, CAS 68937-54-2, is cleared as an extrusion aid under 21 CFR 177.1520 at a maximum of 0.3 wt% of the polymer, which is a processing-aid clearance rather than a wear clearance.

The cyclosiloxane residues are the live compliance issue. Octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5) and dodecamethylcyclohexasiloxane (D6) have been on the REACH Candidate List since 27 June 2018 as PBT and vPvB substances, and REACH Annex XVII entry 70, as amended by Regulation (EU) 2024/1328, bans them at or above 0.1 % in substances and mixtures after 6 June 2026, with derogations that include residues in silicone polymer mixtures for specified uses. A silicone additive therefore needs a residual-cyclosiloxane specification, and REACH governs that specification rather than any food-contact rule.

3. Molybdenum disulfide (MoS2)#

Molybdenum disulfide is named in the site scope of this family as one of the 4 solid lubricants, and no verified record for it exists in our source library. Its CAS number, EC number, REACH registration status, food-contact status and dosage in plastics are all not established in our sources, so none of them appears on this page. The gap is recorded for resolution and this section is updated when a primary-source record is verified.

What our sources do establish is the company MoS2 keeps. Molybdenum trioxide, CAS 1313-27-5, a different molybdenum compound, is documented as a smoke suppressant for PVC and other halogenated polymers, and it carries a harmonised CLP classification under index 042-001-00-9 as Carc. 2 H351 and STOT SE 3 H335, plus a California Proposition 65 cancer listing effective 19 March 2021. That classification belongs to the trioxide and says nothing about the disulfide, and the two are not interchangeable.

4. Graphite#

Graphite is a carbon filler, CAS 7782-42-5, EC 231-955-3, formula C, molecular weight 12.011 g/mol, and our source library records its function as a thermally and electrically conductive filler and a solid lubricant in wear-resistant compounds. It is documented in 3 compound types: self-lubricating polyamide, POM and PTFE compounds, thermally conductive compounds, and conductive and antistatic compounds. That triple role is what distinguishes graphite from PTFE, because a graphite loading changes electrical behaviour as well as friction.

Graphite is registered under REACH with 146 active dossiers on EC 231-955-3, checked on ECHA CHEM on 22 September 2026, and it is not on the Candidate List. For food contact it is authorised under EU 10/2011 as FCM No 521, Ref 58320, as an additive with no specific migration limit, so the generic limit of 60 mg/kg and the overall migration limit of 10 mg/dm2 apply. Where a graphite loading is high enough to make a compound conductive, the design question moves to the conductivity target that antistatic agents for plastics address by a different route.

Expandable graphite is a separate substance with a separate page and a separate job. It is an intercalation compound, CAS 12777-87-6, EC 235-819-4, that exfoliates into an insulating carbon layer at an onset around 200 °C in a range of 140 to 230 °C, and it is a flame retardant rather than a lubricant. Ordinary flake or synthetic graphite does not exfoliate at processing temperature.

Boron nitride and the other solid lubricants#

Hexagonal boron nitride is the fifth solid lubricant our source library documents for plastics, with CAS 10043-11-5, EC 233-136-6, formula BN and molecular weight 24.82 g/mol. Its recorded applications are thermally conductive compounds for LED, e-mobility and electronics, self-lubricating plastics, wire coating and tubing extrusion, and its suppliers are 3M, Denka and Resonac. Its food-contact position is the strictest of the 5 solids: FCM No 583, Ref 40400, under group restriction 16 with FCM 407, 583, 584 and 599, at SML(T) 6 mg/kg expressed as boron.

Boron nitride is also the solid lubricant with the best-documented research record, although that record concerns melt fracture rather than wear. Rathod and Hatzikiriakos, writing in Polymer Engineering and Science in 2004, attributed its performance to the balance of polar and dispersive surface energy; Muliawan, Hatzikiriakos and Sentmanat described it in 2005 as an energy dissipater that suppresses extensional stress at gross melt fracture; and Rosenbaum and co-workers reported in 2000 that it eliminated surface melt fracture and postponed gross melt fracture in metallocene polyethylene and FEP at 0.005 to 0.5 %. Those dosages describe a processing aid, and they are not wear dosages.

Which Polymers and Parts Take Tribological Additives?#

Engineering thermoplastics take tribological additives, because they are the polymers used for gears, bearings, bushings, cams and slide rails. Our source library names polyamide and POM explicitly as the self-lubricating compounds that use graphite, and it names polyamide and POM gears and bearings as the parts that use PTFE, silicone, MoS2 and graphite. Table T3 maps the documented pairings.

Table T3. Where each solid lubricant is documented in our sources.

Polyamide is the best-documented host. The nylon additive package on this site lists tribological additives among the 17 families a polyamide compound draws on, alongside reinforcing fibres, coupling agents and heat stabilizers, and additives for nylon sets out how a wear package interacts with the rest of that formulation. The corresponding acetal package is covered by additives for POM (acetal), which reaches its wear performance from a different starting point because unfilled POM already has a low coefficient of friction.

How to specify a wear-resistant compound in 6 steps#

Specify a wear compound from the contact conditions rather than from the additive list. The 6 steps below follow the selection logic used across this site and set out in how to select plastic additives.

1. Define the contact. Record the counterface material, the contact pressure, the sliding velocity, the temperature and whether the motion is continuous or intermittent.
2. Fix the regulatory envelope first. Decide whether the part is a food-contact article, whether a customer fluorine specification excludes PTFE, and whether a residual-cyclosiloxane limit applies to a silicone grade.
3. Choose the base polymer and its reinforcement. Select the polymer for temperature and load, then decide the fibre loading, because the reinforcement sets the mechanical budget the lubricant will spend.
4. Select the solid lubricant. Match it to the constraints from step 2: graphite where conductivity is acceptable, boron nitride where thermal conductivity and electrical insulation are both required, silicone where a fluorine-free specification applies.
5. Trial the loading. Run at least 3 loadings, because no verified dosage table for wear compounds exists in our sources and the optimum is compound-specific.
6. Test on the real contact. Measure friction and wear against the actual counterface and the actual lubricant condition, not against a standard steel ring alone.

How Much Tribological Additive Is Needed?#

No verified dosage range for a tribological additive in a wear compound exists in our source library, and the 3 dosage figures we hold for these substances all belong to other functions. Stating them as wear dosages would be an error that propagates into a bill of materials, so they are labelled here by the function they were measured for.

• Anti-drip PTFE: 0.1 to 0.5 wt% in PC, PC/ABS, PBT and PA, usually as SAN-encapsulated TSAN. The patent range is 0.05 to 10 phr of active PTFE, with 0.1 phr common in the examples, and a 2024 PC/ABS study used 0.4 wt%.
• Silicone as a US extrusion aid: up to 0.3 wt% of the polymer for polyoxyethylene-grafted PDMS, CAS 68937-54-2, under 21 CFR 177.1520.
• Boron nitride as a processing aid: 0.005 to 0.5 % in metallocene polyethylene and FEP, and 0.05 wt% in HDPE in a 2015 study by Adesina and co-workers.

Commercial wear compounds are bought as finished compounds far more often than they are dosed by the moulder, which is why a dosage table matters less here than in a stabilizer family. Where a moulder does dose at the machine, the concentrate route applies and the arithmetic is the same as for any other concentrate, set out in our guide to additive dosage levels in plastics and in the let-down ratio rules for masterbatch.

How Are Friction and Wear Measured?#

Friction and wear are measured on the assembled contact, and our source library holds standards for the friction half only. ASTM D1894-24 and ISO 8295 measure the static and kinetic coefficient of friction, and both were written for plastic film and sheeting rather than for moulded bearings. ASTM D3354 measures blocking, which is a film property rather than a wear property.

Those 3 methods, their specimen requirements and the bloom-time problem that makes film results time-dependent are set out on our page for the coefficient of friction. For moulded wear parts, the standards that cover sliding wear and limiting PV are not established in our sources, so no test number is quoted for them here and a compound qualification runs on the part rather than on a standard specimen.

Two consequences follow for a qualification plan. Friction data generated on film cannot be transferred to a gear tooth, because the contact geometry, pressure and counterface all differ. Wear data supplied with a compound is supplier data until an independent method is specified, which is the same rule this site applies to every supplier-sourced figure.

How Are PTFE, Silicone and Graphite Regulated?#

Three regulatory systems apply to tribological additives: EU food-contact law, REACH, and the pending EU restriction on PFAS. Each solid sits differently in all 3, and Table T4 states each position with its instrument and date.

Table T4. Regulatory status of the documented solid lubricants, with instrument and date.

The PFAS position needs stating precisely, because it is the single question buyers ask about PTFE wear compounds. The EU has not banned PFAS. A universal restriction proposal exists, its Annex XV dossier was published by ECHA on 7 February 2023, and it remains pending, so a PTFE-filled bearing compound is legal to place on the EU market today. What has changed is procurement: fluorine-free specifications are written by customers rather than by regulators, and they are the reason a formulator reaches for silicone, graphite or boron nitride first. The same commercial logic drives the switch documented for PFAS-free processing aids.

For food-contact parts, the practical route is the Union list. Under EU 10/2011, graphite, PDMS and boron nitride are authorised by FCM number with the restrictions stated in Table T4, and it does not list PTFE as an additive at all, so a food-contact wear compound is built around the listed solids and a compliance declaration covers the monomer and the finished article.

Who Supplies Tribological Additives and Wear Compounds?#

Named suppliers in our source library exist for one of the 5 solids: 3M, Denka and Resonac supply hexagonal boron nitride. No verified manufacturer list for PTFE micropowder, silicone wear masterbatch, molybdenum disulfide or graphite for plastics exists in our sources, and the names circulating in trade directories are not repeated here without a primary source.

Buying decisions in this family are compound decisions more often than additive decisions, because wear grades are sold as finished, fibre-reinforced, lubricated compounds under grade names rather than as separate additives. The plastic additive manufacturers and suppliers directory lists verified company data by additive category, including the compounders that hold wear grades.

Sourcing a wear compound therefore starts from a specification rather than from a substance name. Send that specification through the plastic additive supplier finder, which matches it to producers holding the relevant grades.

What Tribological Additives Cannot Do: Limits, Lookalikes and Alternatives#

Tribological additives cannot rescue a contact that is mechanically overloaded, and they cannot be verified from a data sheet alone. The limits below mark the border of this family and lead into the neighbouring families that answer the questions this one does not.

The first limit is quantitative. Our source library establishes the identity, mechanism class and regulatory status of these solids and establishes no wear rate, no limiting PV and no wear dosage, which means that every performance claim in this family currently rests on supplier data. The second limit is structural. A solid lubricant reduces friction at a contact and does not add strength, so a wear compound that fails by tooth breakage rather than by wear needs reinforcing fibers for plastics, not more lubricant.

Which additives are confused with tribological additives?#

Five additive types are routinely confused with tribological additives, and 3 of them share the same chemistry. The confusions are listed below with the distinction that resolves each one.

• Greases, oils and sprays. Applied to an assembled part rather than compounded into the polymer, so they are maintenance products and not plastic additives at all.
• Processing lubricants. Compounded into the polymer, but acting on melt viscosity and metal release during processing, and spent when the machine stops.
• Slip agents. Compounded in, but designed to migrate to a film surface after production, and measured by surface friction rather than by wear.
• Anti-drip PTFE. The same substance in the same compound, doing a different job: stopping flaming drips in a UL 94 test at 0.1 to 0.5 wt% in PC, PC/ABS, PBT and PA.
• Anti-scratch additives. Acting on visible surface damage from a single hard contact rather than on material removal over repeated cycles, which is why anti-scratch additives for plastics are qualified by gloss and whitening tests.

Do tribological additives affect recycling and food contact?#

Tribological additives complicate both recycling and food-contact compliance, in different ways. A wear compound is a filled, reinforced, lubricated blend, so it belongs to the engineering-plastics recycling stream rather than to a packaging stream, and the design for recycling rules treat every added solid as a contaminant for any other stream.

For food contact the position is asymmetric. Graphite, PDMS and boron nitride are authorised additives under EU 10/2011 with the limits in Table T4, and PTFE is not an Annex I entry, so a food-contact wear part is designed around the listed solids. Complete identity and regulatory records for all 5 solids, and for the other 437 substances on this site, are in the plastic additives database, and the polymer-level packages are in additives by polymer.

Tribological additive FAQs#

Is a tribological additive the same as a lubricant for plastic parts?#

No. A tribological additive is compounded into the polymer and stays in the moulded part, while a lubricant for plastic parts, meaning a grease, oil or spray, is applied to an assembled component and belongs to maintenance rather than to formulation. The overlap in the word lubricant is why this site separates the wear family from the processing-lubricant family by where the additive acts and when.

Does PTFE in a plastic compound fall under the EU PFAS restriction?#

PTFE is a fluoropolymer within the PFAS group and falls inside the scope of the EU universal PFAS restriction proposal, whose Annex XV dossier ECHA published on 7 February 2023. The proposal is pending and has not been adopted, so no restriction applies to a PTFE-filled compound today. Food-contact packaging is the exception that is already dated: PPWR, Regulation (EU) 2025/40, applies from 12 August 2026 with limits of 25 ppb for any single PFAS, 250 ppb for the sum and 50 ppm for total PFAS including polymeric PFAS.

Can a silicone masterbatch replace PTFE in a wear compound?#

Silicone is the fluorine-free alternative formulators reach for, and our source library does not establish equivalent performance. Polydimethylsiloxane is documented as a slip and lubricant additive supplied in masterbatch and as an external mould release, both by the same low-surface-energy film mechanism, and no comparative wear data against PTFE exists in our sources. A substitution therefore needs a trial on the real contact, plus a residual-cyclosiloxane specification because of REACH Annex XVII entry 70.

Which solid lubricant works at the highest temperature?#

Hexagonal boron nitride, which PubChem records as a lubricant up to 900 °C in an oxidising atmosphere. That temperature is far above the service range of any thermoplastic, so in practice the polymer sets the ceiling and the lubricant does not. Boron nitride also combines high in-plane thermal conductivity with electrical insulation, which is the property combination graphite cannot offer.

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