Aramid Fibres in Plastics: 2 Types (Para and Meta), Properties, Uses and Selection

Aramid fibres are aromatic polyamide fibres in which at least 85 % of the amide linkages are attached directly to two aromatic rings, and in plastics they serve as a reinforcing and wear-reducing fibre in compounds such as POM and PTFE. The 85 % rule, set by the US Federal Trade Commission in 1974 and adopted by ISO in 1977, separates aramid fibre (aramid fiber) from the other polyamides; so what does that aromatic backbone change when the fibre sits inside a plastic part?

Aramid is one of 5 reinforcing fibres among the plastic additives covered on this site, next to glass, carbon, natural and basalt fibre. It comes in 2 types, para-aramid (sold as Kevlar and Twaron) and meta-aramid (sold as Nomex), and para-aramid has a melting point above 500 °C, so it does not melt in the barrel when POM, polyamide or even PEEK is processed around it.

This page covers the name and its link to Kevlar, the 2 types, the established properties, the comparison with carbon and glass, the 2 roles of aramid in a plastic (reinforcement and wear), forms, host polymers, loading, compounding, tests, regulatory status and the founding producers. How aramid compares with the other 4 fibres in loading and coupling is set out on reinforcing fibers for plastics.

Four figures that define aramid fibre

• 85 %: the minimum share of amide linkages attached to two aromatic rings (FTC 1974, ISO 1977)
• 2 types: para-aramid (Kevlar, Twaron) and meta-aramid (Nomex)
• Above 500 °C: the melting point of para-aramid
• 41,000 t/year (2002): world para-aramid capacity in 2002, then growing 5 to 10 % a year

What Is Aramid Fibre?#

Aramid fibre is a synthetic aromatic polyamide fibre in which at least 85 % of the amide (-CO-NH-) linkages join two aromatic rings directly, a structure that gives para-aramid a melting point above 500 °C. This site identifies aramid fibre by CAS 24938-64-5, the same number the reinforcement hub uses, and divides it into para-aramid and meta-aramid. Aramid belongs to the high-performance fibres, a group that also includes carbon fibre and S-2 glass.

Inside a plastic, aramid works as a reinforcement, not a filler: it is bought to carry load and resist wear rather than to cut cost or add volume. The general difference between fillers and reinforcements is defined on the reinforcing fibres hub.

What does "aramid" mean?#

"Aramid" is short for aromatic polyamide, the generic name the US Federal Trade Commission adopted in 1974 for fibres whose amide linkages sit at least 85 % on aromatic rings; ISO adopted the same definition in 1977. The word therefore names a chemical class defined by a threshold, not a brand. "Aromatic" refers to the benzene rings in the polymer chain, and "polyamide" to the amide links that join them, so any fibre that clears the 85 % line is an aramid whoever makes it.

Is Kevlar an aramid fibre, and is aramid just Kevlar?#

Yes, Kevlar is an aramid: it is the para-aramid fibre DuPont introduced in 1973, but aramid is not just Kevlar, because Twaron, introduced by Akzo in 1978, is a second para-aramid and Nomex is a meta-aramid. Kevlar, Twaron and Nomex are trade names, while "aramid" is the class name all three fall under. A specification written with the class name stays open to every fibre that meets the definition.

Is aramid fibre a plastic?#

Aramid fibre is a polymer but not a plastic in the everyday sense: it is a polyamide spun into fibre that does not melt below 500 °C, and it becomes part of a plastic only as the reinforcement in a compound or composite, which is then called aramid fibre reinforced plastic (AFRP). The AFRP term follows the pattern of GFRP for glass and CFRP for carbon, and it is the term Xu and co-workers used in the title of their 2025 review of aramid fibre-reinforced plastics in aerospace. In a thermoplastic compound the polymer melts and the aramid does not, so the fibre stays a separate solid phase from the extruder to the moulded part.

What Are the 2 Types of Aramid Fibre?#

The 2 types of aramid fibre are para-aramids such as Kevlar and Twaron, whose chains link through opposite (1,4) positions of the benzene ring and form stiff, high-strength fibres, and meta-aramids such as Nomex, whose 1,3 links give a less ordered fibre used mainly for heat and flame resistance. Both types meet the same 85 % definition, so the difference lies in the geometry of the chain rather than in its chemistry. Table T1 compares the 2 types on the data our sources hold.

Table T1. The 2 types of aramid fibre at a glance.

Copolyamide para-type fibres such as Technora are not listed until their identity is sourced.

1. Para-aramid (Kevlar, Twaron)#

Para-aramid is the aramid type whose amide links join opposite positions of the benzene ring, sold since 1973 as DuPont's Kevlar and since 1978 as Akzo's Twaron, and it is the only aramid type for which our sources hold a melting point and a capacity figure. Its melting point lies above 500 °C. World para-aramid capacity stood at 41,000 t a year in 2002 and was growing 5 to 10 % a year, the most recent capacity figure in our sources.

In plastics, aramid appears in our sources as a wear fibre in POM and PTFE compounds, where it is combined with glass fibre. Those sources name aramid without saying which type the wear grades use, so this page does not assign the POM and PTFE grades to para-aramid, even though para-aramid is the type with the documented heat resistance and capacity.

2. Meta-aramid (Nomex)#

Meta-aramid is the aramid type whose amide links join the 1 and 3 positions of the benzene ring, best known as DuPont's Nomex, and it is valued for heat and flame resistance rather than for reinforcing plastics. Our sources hold no melting point, oxygen index or plastics compound for meta-aramid, so this page covers it for completeness.

What Are the Properties of Aramid Fibre?#

The best-established property of aramid fibre is its heat resistance: para-aramid has a melting point above 500 °C, far above the 240 to 320 °C at which engineering thermoplastics such as PA66, PBT, PET and PC are processed. The other values that decide a reinforcement, namely density, tensile strength, tensile modulus and elongation at break, are not established in our sources for any aramid grade, and none is estimated here, so Table T2 shows only what is established.

Table T2. Aramid fibre properties established in our sources.

Strength, modulus, density and elongation are not established in our sources; producer datasheets give them per grade.

Why aramid does not melt in a plastics process#

Para-aramid has a melting point above 500 °C, so it passes through POM (melting at 175 °C), PA66 (264 °C) and even PEEK (343 °C) as a solid fibre, unlike most organic additives, which PEEK's processing temperature rules out. The 4 host polymers below show the margin between their melting or processing temperature and the melting point of para-aramid.

The margin is measured to the melting point, not to the start of thermal decomposition, which a thermogravimetric (TGA) scan would give and which is not established in our sources. The fibre stays solid in the barrel, but its stability over a long residence time at PEEK temperatures is not proven.

Aramid vs Carbon Fibre vs Glass Fibre: Which Reinforces a Plastic Better?#

Carbon fibre gives the highest stiffness documented in our sources, 150 to 250 GPa modulus in civil-engineering composite grades, E-glass gives 76.0 GPa as a filament value at a density of 2.58 g/cm3, and aramid's case rests on its heat resistance and its use in wear compounds rather than on a stiffness figure our sources can confirm. The choice therefore follows the property the part is designed for: stiffness points to carbon, general-purpose reinforcement of thermoplastic compounds to glass, and sliding wear to aramid. Table T3 compares the fibres on the values our sources hold, in the order aramid, carbon, glass, basalt.

Table T3. Aramid, carbon, glass and basalt fibre compared.

Glass and basalt values are filament values; carbon values are composite values for civil-engineering grades and are not directly comparable. "Not established" means our sources hold no verified value; no aramid value is estimated. No fibre price is compared, because none is sourced.

The 2 glass rows in Table T3 are only part of the glass family. Glass types, sizing and loading are covered under glass fiber reinforced plastics.

Is aramid fibre better than carbon fibre?#

Aramid fibre is not better than carbon fibre in general: carbon is the fibre with documented stiffness, 150 to 250 GPa in civil-engineering composite grades, while aramid earns its place in plastics where heat resistance and sliding wear matter, as in the POM and PTFE compounds that combine it with glass. Neither fibre's electrical behaviour carries a value in our sources, so conductivity is not used here as a selection criterion. The 2 cases in which the choice is clear are listed below.

• Choose aramid when the part slides against a mating surface, as the POM and PTFE wear compounds in our sources do.
• Choose carbon when stiffness decides the design, since its composite modulus of 150 to 250 GPa is the highest value in Table T3.

Aramid vs glass fibre in thermoplastic compounds#

Glass fibre is the default reinforcement of thermoplastic compounds, while aramid joins or replaces it in sliding parts: POM and PTFE wear grades use both fibres, glass for stiffness and aramid for wear. Reinforcements as a group occupy 15 to 30 wt% of a plastic product, and E-glass adds 2.58 g/cm3 of density to that share, a figure our sources do not hold for aramid. Two further differences matter to a compounder. Glass fibres are listed on the EU Union list as FCM 38, while aramid has no entry in the sources we checked. Glass content is measured by burning the polymer away and weighing the residue, a route that does not capture an organic fibre such as aramid, which burns with the matrix.

How Does Aramid Fibre Work in a Plastic?#

Aramid fibre works in a plastic in 2 ways: as a reinforcing fibre it takes over load from the matrix through shear at its surface, and as a wear additive it protects sliding parts such as the gears and bearings made from POM and polyamide. The first role follows the general mechanism of every reinforcing fibre. The second places aramid among the tribological materials, next to solid lubricants such as PTFE and graphite.

Aramid as a reinforcing fibre: load transfer and fibre length#

As a reinforcement, aramid follows the same load-transfer rule as glass and carbon: the matrix passes load to the fibre through shear at the interface, so the fibre only works if it is longer than its critical length and bonded well enough to take that shear. The shear-lag model of Cox (1952) describes how stress builds along a fibre from its ends, and Kelly and Tyson showed in 1965 that a fibre needs a minimum length before interfacial shear can load it to its breaking stress. Halpin and Kardos gave the stiffness equations still used for short-fibre compounds in Polymer Engineering and Science 16 (1976) 344-352.

What does that rule mean for aramid in particular? No critical length for aramid in any polymer is established in our sources, and neither is the shear strength of its interface with POM, polyamide or PEEK, so the general rule applies without an aramid-specific number. The 3-step load-transfer sequence on the hub sets out the mechanism for all 5 fibres.

Aramid as a wear and friction additive#

Aramid is one of 5 materials compounded into plastics to cut wear and friction, next to the solid lubricants PTFE, silicone, molybdenum disulfide and graphite, and in POM and PTFE wear grades it is combined with glass fibre. The host polymers of these wear compounds are POM, polyamide, PBT and PEEK, and the parts are gears, bearings and bushings that slide against a mating surface. Our research records one mechanism for the class as a whole: a transfer film forms on the counter-surface, and low shear strength at that interface cuts friction. It records no wear rate or friction coefficient for an aramid-filled grade, so the size of the effect is not quantified here.

The lubricant side of these tribological compounds is a separate subject. How the 4 solid lubricants lower friction, and which polymers take each, is explained under tribological additives.

Which Forms of Aramid Fibre Go into Plastics?#

The forms in which aramid is sold for plastics compounds, and their cut lengths, are not yet established in our sources, so no form count is given here. Aramid, like glass, is handled as continuous and as cut fibre, but which form goes into which compound has not been verified against producer data. Long-fibre pellets show how form changes a compound for every fibre: the pellets are 10 to 12 mm long and leave 6.35 mm (0.25 in) or more of fibre in the finished part, as described for all fibres on long fiber thermoplastics (LFT).

Which Polymers Are Reinforced with Aramid Fibre?#

Aramid fibre is documented in our sources mainly in POM and PTFE wear compounds, where it is used together with glass fibre, and the same tribological role extends to polyamide, PBT and PEEK sliding parts. Table T5 lists the 4 polymer groups in the order POM, polyamide and PBT, PEEK and PPS, PTFE.

Table T5. Aramid fibre by host polymer.

Loadings are supplier or study examples once sourced; the final level is set by trials against the part's wear and stiffness targets.

POM (acetal) wear compounds#

POM is the polymer named first in our sources for aramid wear compounds: acetal gears, bearings and bushings combine aramid with glass fibre, and at POM's melting point of 175 °C the aramid stays a solid fibre with more than 325 °C to spare. Homopolymer grades melt at 172 to 184 °C, which still leaves more than 315 °C between the polymer and the fibre. What our sources do not hold is the aramid level in a commercial POM wear grade, so no loading is given. The rest of the acetal package, stabilizers and formaldehyde scavengers included, is on additives for POM (acetal).

PPS, PEEK and other high-temperature polymers#

PEEK and PPS are the hardest test for an organic additive, because PEEK melts at 343 °C and is processed above 340 °C, and aramid is an organic fibre whose melting point, above 500 °C, clears that window. PEEK's glass transition lies at 143 °C and PPS serves up to 240 °C. The PEEK and PAEK additive package consists mostly of fillers (carbon fibre, glass fibre, PTFE and graphite), because processing near 343 °C rules out most organic additives. Aramid's decomposition onset, and any commercial PEEK or PPS grade containing it, are not established in our sources. Which fillers survive PEEK and PPS processing is covered under additives for high-performance polymers.

Aramid-filled PTFE#

In PTFE the roles reverse: the fluoropolymer (CAS 9002-84-0) is the matrix and aramid the filler, added with glass fibre to cut PTFE's own wear. PTFE as a matrix is a plastics use and sits inside this site's scope, while PTFE inside other polymers acts as an additive. PTFE's other role, as an anti-drip and lubricating additive, is covered under PTFE (polytetrafluoroethylene) as a plastic additive, and its PFAS position is set out in the regulatory section below.

How Much Aramid Fibre Does a Compound Contain?#

No aramid-specific loading is established in our sources, but reinforced plastics in general carry 15 to 30 wt% reinforcement, the range Chea and co-workers published in 2025 from the additive inventory of John Hahladakis and colleagues (2018). That band covers all reinforcing fibres and is not an aramid dosage. The 3 factors that set the aramid level of a given compound are listed below.

• Wear target and counterface material: the mating surface and the wear rate the part must reach
• Stiffness target: how much of the stiffness the glass fibre in the same compound already carries
• Processability: melt viscosity and the fibre shortening that every melt step causes

How Is Aramid Fibre Compounded and Bonded to the Matrix?#

Aramid enters a compound as a solid fibre that does not melt in the process, so the result depends on dispersion and on the bond to the matrix. The extruder melts the polymer around the fibre, and every melt step shortens a fibre, as the hub describes for all reinforcements. Feeding, mixing and pelletising are described step by step under plastic compounding.

The bond is where aramid differs from glass. The silane chemistry developed for glass reacts with the hydroxyl groups of the glass surface; aramid's surface chemistry is different, and its surface treatments are not yet established in our sources.

Coupling is therefore an open question for aramid rather than a solved one. Why glass and mineral fillers use silanes and maleated polyolefins is set out under coupling agents for filled and reinforced plastics.

How Are Aramid-Reinforced Plastics Tested?#

Aramid-reinforced plastics are tested with the same tensile (ISO 527), impact (ISO 179 or ASTM D256) and heat-deflection (ISO 75) methods as glass-filled grades, plus a friction and wear test, but ashing, the standard route to fibre content, returns only the inorganic glass and mineral fraction, because aramid is an organic polymer that burns away with the matrix. Table T6 lists the 5 properties with the method and the standard for each, and every method is indexed under testing plastic additives.

Table T6. Tests for aramid-reinforced plastics.

ASTM D5630-22 covers ash contents of 0.01 % and above in materials stable to 900 °C, with Procedure A using a 5 to 50 g sample and Procedure B a 2 to 10 g rapid-ash sample, and it reports how much residue there is rather than what it is. In a POM wear grade with both glass and aramid, the ash therefore measures the glass alone, and PTFE compounds fall outside the method entirely, because fluorinated polymers are excluded from it. Why ashing returns only the glass and mineral fraction is explained under ash content and filler content testing.

No validated method for aramid content is established in our sources.

Thermogravimetric analysis (TGA) and FTIR spectroscopy, the instrumental routes for organic components, are covered under additive analysis and deformulation of plastics; whether either is validated for aramid content is not established in our sources.

What Is the Regulatory and Health Status of Aramid Fibre in Plastics?#

Aramid fibre is a polymer, so REACH exempts it from registration under Article 2(9), and our sources show no entry for it on the EU Union list of Regulation (EU) No 10/2011, which matters only if the plastic touches food. The open points are indirect: no IARC or CLP classification for aramid fibre is recorded in our sources, and the PTFE that aramid wear compounds sit in or next to falls within the EU PFAS restriction proposal. The 4 sections below take each layer in turn.

REACH: a polymer exempt from registration#

Aramid fibre needs no REACH registration of its own, because Regulation (EC) No 1907/2006 exempts polymers under Article 2(9), and the revision that would have brought polymers into registration was set aside on 27 April 2026. Additives, by contrast, are substances and must be registered at 1 t a year or more per manufacturer or importer, including when they arrive inside a masterbatch. The registration and Candidate List position of the aramid monomers is not established in our sources, so no statement is made about them. The registration duties that do apply to additives are on REACH and plastic additives.

Food contact: EU 10/2011 and US FDA#

No entry for aramid fibre appears on the Union list of Regulation (EU) No 10/2011 in the sources we checked, while glass fibre is listed as FCM 38 (Ref 55520), so a food-contact part reinforced with aramid needs its own compliance route. An absence in the sources checked is not a prohibition. The Union list in Annex I, Table 1 covers monomers, additives and polymer production aids, and every plastic in contact with food also has to meet the overall migration limit of 10 mg/dm2. In the US, our sources hold no 21 CFR citation for aramid fibre; 21 CFR 177.2600 lists nylon among the fillers for repeat-use rubber articles, which is not an aramid listing. How the Union list works, and what an absence from it means, is explained on EU 10/2011.

Respirable aramid fibrils and occupational exposure#

Our sources hold no IARC or CLP classification for aramid fibre, whereas continuous-filament glass fibre is IARC Group 3 (Monograph volume 81, 2002), so this page makes no health claim for aramid dust either way. The glass result cannot be transferred to an organic fibre. The exposure a compounder manages is respirable dust from cutting and handling dry fibre, and compounders should take the handling measures from the producer's safety data sheet until a classification is confirmed.

PTFE in aramid wear compounds and the PFAS restriction proposal#

Aramid itself contains no fluorine, but aramid wear compounds are used in PTFE and alongside it, and PTFE (CAS 9002-84-0) falls within the EU universal PFAS restriction proposal, whose Annex XV dossier was published on 7 February 2023 and is still pending. A PTFE-matrix aramid compound, and a compound that pairs aramid with PTFE micropowder as the lubricant, both contain a fluoropolymer inside the proposal's scope, while a compound with aramid and no PTFE contains none. Whether aramid can replace PTFE in a given part is not established in our sources. Every PFAS rule and date that touches fluoropolymer additives is tracked under PFAS restrictions and plastic additives.

Who Makes Aramid Fibre and Aramid-Reinforced Compounds?#

Aramid fibre was introduced by 2 companies: DuPont, which launched the para-aramid Kevlar in 1973 and also makes the meta-aramid Nomex, and Akzo, which launched the para-aramid Twaron in 1978. Current producers, brands and compounders of aramid-filled grades are not listed until each record carries a source, and the same applies to capacity and price. Buyers should specify the aramid type and form, not only the brand, because a trade name identifies the fibre type but not the form a compound needs. Company profiles are collected in the plastic additive manufacturers and suppliers directory.

Table T7. The founding aramid producers in our sources.

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Where Else Is Aramid Fibre Used, and What Happens to It at End of Life?#

Aramid is also used outside plastics, in textiles and protective equipment, which this site does not cover. Inside plastics, the end-of-life question is the one every fibre raises: what happens to a compound whose reinforcement cannot be separated by melting?

Aramid-reinforced plastics in recycling#

When an aramid-reinforced thermoplastic is reground and remelted, the aramid stays a solid fibre, because it does not melt below 500 °C, so the recyclate carries the fibre forward rather than separating it. How much of its properties an aramid compound keeps after regrind is not established in our sources; for glass, the hub records that fibre length falls at every melt step. Fibre-filled compounds in sorting and remelting are discussed under how additives affect plastic recyclability.

Is aramid fibre flame retardant or flame resistant?#

Aramid is flame resistant rather than flame retardant: like PEEK and PPS, it resists burning by its own chemistry, while a flame retardant is an additive mixed into a plastic that would otherwise burn. "Resistant" names an inherent material property and "retardant" an additive or treatment. Additives that make burning plastics self-extinguish are compared under flame retardants for plastics.

Is aramid fibre conductive?#

Our sources do not yet hold a resistivity value for aramid, so its electrical behaviour is not stated here. The claim that aramid insulates while carbon conducts is common in vendor comparisons, but neither half carries a value in the sources this page uses; carbon fibre's electrical behaviour is treated on carbon fiber reinforced plastics.

What are high-performance fibres?#

High-performance fibres are the synthetic reinforcing fibres chosen for strength and stiffness, such as para-aramid, carbon fibre and S-2 glass (4,890 MPa tensile strength, 85.5 GPa modulus). Of the 3, S-2 glass and carbon carry property values in our sources, carbon as a composite value, while para-aramid's documented attribute is its melting point above 500 °C.

Which other organic fibres reinforce plastics?#

Besides aramid, the organic fibres used in plastics are natural fibres such as flax, hemp, jute, kenaf, sisal and bamboo, and synthetic fibres such as UHMWPE, PET and polyamide fibres. The 2 groups are listed below.

• Natural fibres: flax, hemp, jute, kenaf, sisal and bamboo, reviewed as a class by Faruk, Bledzki, Fink and Sain in Progress in Polymer Science 37 (2012) 1552-1596
• Synthetic organic fibres: UHMWPE fibre, PET fibre and polyamide fibre

Flax, hemp and the other plant fibres are covered under natural fiber composites.

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