Glass-Filled Nylon: 7 Property Changes, Grades, Additive Package and Selection

Glass-filled nylon is a polyamide compound in which short E-glass fibres, coated with a reactive sizing, carry the mechanical load that the nylon matrix transfers to them by interfacial shear. The fibre alone reaches 3,445 MPa tensile strength and a 76.0 GPa modulus at 2.58 g/cm³ density, far above the surrounding polyamide, but it only delivers that stiffness where the sizing, applied at 0.5 to 2.0 wt% of the fibre weight, has bonded it to the matrix. Glass content in flame-retardant PA6 and PA66 compounds typically runs from 10 to 50 wt%, the range Clariant gives for its Exolit OP series. So how much glass does a grade need, and what else goes into the compound around it?

Glass fibre is the reinforcement family within the wider set of plastic additives a polyamide compounder works with, alongside the heat stabilizers, antioxidants, lubricants, colorants, flame retardants and impact modifiers a glass-filled grade still needs. PA6 melts at 215 to 218 °C and PA66 at 264 °C, and both take the same chopped E-glass reinforcement, in a moulding compound or an extruded and cast stock shape.

This page covers the 7 property changes glass fibre makes in nylon, how aminosilane sizing bonds it to the polyamide, how much glass each loading band carries, the stabilizer, lubricant, colorant, flame-retardant and impact-modifier package still needed, how the compound is dried, compounded, moulded and tested, where it is cleared for food contact and electrical use, and who supplies it.

Key figures

• E-glass fibre: 3,445 MPa tensile strength, 76.0 GPa modulus, 2.58 g/cm³ density
• Sizing on the fibre: 0.5 to 2.0 wt% of the fibre weight
• Glass content in flame-retardant PA6 and PA66 compounds: typically 10 to 50 wt% (Clariant)
• Copper heat stabilizer dosage: 0.001 to 0.03 wt% dissolved copper with 0.1 to 5 wt% halide (DuPont US 2,705,227)

What Is Glass-Filled Nylon?#

Glass-filled nylon, written PA GF in European material data sheets, is a polyamide reinforced with chopped E-glass fibres, usually PA6 or PA66, supplied as a moulding compound or as extruded and cast stock shapes. The fibre is drawn, sized and chopped separately from the resin, then melt-compounded into the polyamide on a twin-screw extruder, so the finished pellet carries its full additive package before it reaches an injection-moulding machine.

The comparison of glass with carbon, aramid, basalt and natural fibres sits on the hub for reinforcing fibers for plastics, which this page does not repeat. Here the focus stays on what glass specifically does inside a polyamide matrix, from the sizing chemistry that bonds it to its regulatory status.

Which nylons are reinforced with glass?#

PA6 and PA66 carry almost all glass-filled nylon volume, with PA6 melting at 215 to 218 °C and PA66 at 264 °C, while PA46, PA6T and other semi-aromatic polyamides take the same glass reinforcement at higher service temperatures. PA6 has a glass transition temperature of 47 °C and a limiting oxygen index of 21.0. PA66 processes at roughly 240 to 320 °C, shared with several engineering polymers. High-temperature polyamides, including PA6T/66, PA6T/DT, PA9T, PA10T, PA4T, PA46 and MXD6, accept the same E-glass and sizing chemistry but hold their properties at higher continuous service temperatures, closest to an engine or another heat source.

*Exact melting points for PA46, PA6T/66 and MXD6 are not established in this dataset; each runs above PA66's 264 °C service ceiling.

What does GF30 mean?#

GF30 means that 30 % of the compound's weight is glass fibre, so a 60 g PA66-GF30 bracket contains 18 g of glass and 42 g of polyamide plus additives. Material data sheets write loading this way, in weight percent, because it is the figure a compounder weighs at the extruder and a buyer pays for, even though volume percent actually governs the mechanics of load transfer. A 33 % grade carries proportionally more glass than a 30 % grade for the same part weight, raising stiffness but also melt viscosity and density.

Is glass-filled nylon a plastic or a composite?#

Both: glass-filled nylon is a thermoplastic that is processed like any other injection-moulding grade, and it is a composite, because the load is carried by a second, stiffer phase that the polyamide only transfers it to. The thermoplastic matrix can be remelted and reprocessed, which is what makes injection moulding and even reprocessing of regrind possible, while the composite classification is what explains why its properties depend on fibre orientation and content, not on the resin alone.

What is glass-filled nylon used for?#

Glass-filled nylon is used where a metal part would otherwise be moulded in plastic: under-hood automotive components, electrical connectors and switchgear, appliance housings, rail interior parts, power-tool bodies and wear parts such as gears, wheels and wear rings. These uses fall into six sectors.

• Automotive under-hood components, such as intake manifolds, engine covers and mounting brackets
• Electrical connectors, switchgear and terminal blocks that need dimensional stability under load
• Appliance housings for products that see sustained heat near a motor or a heating element
• Rail interior parts specified under fire, smoke and toxicity standards
• Power-tool bodies that replace a metal housing at lower weight
• Wear parts, including gears, wheels and wear rings that run against a mating surface

The full under-hood package is set out on additives for automotive plastics.

What Does Glass Fibre Change in Nylon? The 7 Property Changes#

Glass fibre changes 7 properties of nylon: tensile strength, stiffness, heat deflection temperature and creep resistance rise, mould shrinkage becomes directional, toughness turns notch-sensitive, and the effect of absorbed moisture on stiffness is reduced but not removed. They are ordered here from the strongest benefit to the clearest cost.

Strength and stiffness: how load reaches the fibre#

Load reaches a glass fibre only through shear at its surface: the polyamide drags on the fibre along its length, which is why a fibre shorter than the critical length lc = σf·d/(2τ) never reaches its own strength and pulls out instead of breaking. This shear-lag mechanism was first modelled by H.L. Cox in British Journal of Applied Physics 3 (1952) 72, and the critical-length concept was formalised by A. Kelly and W.R. Tyson in Journal of the Mechanics and Physics of Solids 13 (1965) 329.

1. The matrix transmits stress to the fibre surface through interfacial shear as the compound is loaded.
2. Stress builds along the fibre length from each end toward the centre, reaching a plateau only once the fibre exceeds its critical length.
3. The fibre carries load in proportion to its volume fraction and aspect ratio, following the Halpin-Tsai equations for modulus (J.C. Halpin and J.L. Kardos, Polymer Engineering and Science 16 (1976) 344-352), where the shape factor ξ is about twice the fibre's aspect ratio.

How the glass itself is drawn, sized and chopped before it reaches a compounder is covered under glass fiber reinforced plastics.

The strength of the bond, not the fibre's own strength alone, decides how much of this theoretical stiffness a compound reaches. B. Pukánszky quantified adhesion with an interaction parameter B in Composites 21 (1990) 255-262, and the review by S.-Y. Fu, X.-Q. Feng, B. Lauke and Y.-W. Mai in Composites Part B 39 (2008) 933-961 still frames how compounders reason about the interface.

Heat deflection temperature and creep#

Heat deflection temperature rises steeply when nylon is reinforced, because above the polyamide's glass transition the load is carried by the fibre network rather than by the softening matrix. Creep resistance follows the same logic under sustained load: the fibre restrains matrix flow, though the restraint is weakest across the fibre direction, where the load has no continuous fibre path to follow.

The scale of what a reinforcement can do to HDT in a polyamide has a documented benchmark, though not a glass-fibre one: Kojima, Usuki, Kawasumi and Okada, at Toyota Central Research and Development Laboratories, reported in Journal of Materials Research 8 (1993) 1185-1189 that 4.7 wt% montmorillonite nanoclay raised the HDT of nylon 6 to 152 °C, 87 °C above the neat polymer. That figure describes a nanocomposite, not a glass-fibre compound, and no HDT value for glass-filled PA6 or PA66 is established in this dataset; the load and specimen conditions behind every heat deflection temperature value are explained on the test method page.

Mould shrinkage, warpage and anisotropy#

Glass-filled nylon shrinks less than unfilled nylon, but it shrinks unevenly: fibres align with the melt flow and hold the part back along that direction while it shrinks almost freely across it. That directional restraint turns a symmetric problem, uniform shrinkage, into an asymmetric one, warpage. Four factors drive it.

• Flow direction relative to the part's ribs and walls, which sets where fibres align
• Cross-flow shrinkage, which runs closer to the unfilled resin's own shrinkage rate
• Differential shrinkage between a thick and a thin section fed from the same gate
• Gate position and number, which together decide the flow front and the resulting fibre orientation pattern

No shrinkage value, such as a flow-direction or cross-flow percentage, is established in this dataset for glass-filled PA6 or PA66; the mechanism above explains the direction of the effect, and a moulding trial against the grade's own data sheet sets the number for a specific tool and part.

Toughness, notch sensitivity and moisture#

Reinforced nylon is tougher than unfilled nylon in an unnotched impact test and more sensitive in a notched one, because every fibre end is a stress concentration inside the part. An unnotched specimen has no pre-existing crack, so the fibres simply add load-bearing capacity; a notched specimen already has a crack, and the closest fibre ends become where it keeps propagating instead of being blunted by the ductile polyamide alone. Why notched and unnotched results move in opposite directions is explained under impact strength (Izod, Charpy).

Moisture changes the balance a second way. PA6 absorbs up to about 2.4 % water by weight at standard conditions, in a reversible equilibrium with the surrounding humidity, not a one-way degradation. Only the polyamide fraction takes up water, since the glass does not, so a higher glass content mutes the swing in stiffness and dimensions between a dry-as-moulded part and a conditioned one without eliminating it. A saturation figure beyond the 2.4 % standard-conditions value is not established in this dataset.

How Does Glass Fibre Bond to Nylon? Sizing and Coupling Agents#

Glass does not bond to polyamide by itself: the bond is made by the sizing applied to the fibre at the bushing, a coating of 0.5 to 2.0 wt% of the fibre that contains a film former, a coupling silane and a lubricant. Without that coating the glass surface and the polyamide melt sit next to each other with no chemical connection, and the load-transfer mechanism described above never engages.

Silanes, titanates and maleated polyolefins used across filler and resin combinations are compared on the hub for coupling agents for filled and reinforced plastics.

What glass-fibre sizing is made of#

Sizing is a water-based formulation applied to the filaments immediately after drawing, typically at 0.5 to 2.0 % silane in the bath, then dried and cured at 110 to 120 °C for 20 to 30 minutes. The formulation is built from three functional components.

• A film former, which protects the freshly drawn filaments from abrasion as they are gathered into a strand
• A coupling agent, almost always an organofunctional silane matched to the target resin
• A lubricant and, where needed, an antistatic agent that let the fibre process through chopping and compounding without excessive fuzz

Film formers, size-bath ratios and cure schedules are covered in full under glass fiber sizing.

Why aminosilanes are used for polyamide#

Polyamide is sized with aminosilanes such as 3-aminopropyltriethoxysilane because its primary amine reacts with the polyamide's own end groups, while the hydrolysed silanol end of the same molecule condenses onto the glass surface. The ethoxy groups hydrolyse in the aqueous size bath to form silanols, which condense with the silicon and metal hydroxyl groups on the glass surface. At the other end, the primary amine reacts with or hydrogen-bonds to the carboxylic-acid and amine end groups that terminate every polyamide chain, bridging two otherwise incompatible surfaces.

The full class of silane coupling agents is compared by functional group and target polymer, not just the aminosilane used for polyamide.

In an integral-blend application, where the silane is added separately during compounding rather than pre-applied at the bushing, dosage runs 0.2 to 1.0 wt% of the total mix, though silanes of this type are ineffective on calcium carbonate and are specific to glass and other silanol-bearing mineral surfaces. Identity, dosage and regulatory status for the aminosilane itself sit on the substance page for 3-aminopropyltriethoxysilane (APTES), including its food-contact clearance.

What a failed interface looks like in the part#

A failed fibre-matrix interface shows up as 4 symptoms: low tensile strength at normal glass content, fibres visible and pulled out on the fracture surface, weak weld lines and a surface that turns fibrous after ageing.

• Low tensile strength at the stated glass content, because the fibre is not transferring load as the Cox and Kelly-Tyson models predict
• Fibres visible and pulled out, rather than broken, on a fracture surface, showing they debonded before reaching their own strength
• Weak weld lines, where two flow fronts meet with fibres oriented across rather than along the local stress
• A surface that turns visibly fibrous after thermal or humidity ageing, as a degraded sizing layer lets moisture attack the interface

The Pukánszky interaction parameter B measures adhesion strength, and a poorly chosen filler surface can weaken more than the bond: acidic, silanol-rich mineral surfaces also adsorb phenolic antioxidants out of the melt, so a bad interface choice undermines the stabilizer package too.

Which Glass and How Much Does a Nylon Compound Need?#

Almost all glass-filled nylon uses chopped E-glass, because E-glass is the alumino-borosilicate grade with under 1 % alkali oxides developed specifically for glass-reinforced plastics. Which form of that glass a compound uses, and how much, depends on the strength, cost and processing balance the part needs.

Glass types: E-glass, E-CR, S-2 and D-glass#

E-glass carries 3,445 MPa tensile strength and a 76.0 GPa modulus at a density of 2.58 g/cm³, which is why it is the default reinforcement in polyamide compounds. Other glass types trade some of that balance for a specific property.

Continuous filament glass fibre carries an IARC Group 3 classification, not classifiable as to carcinogenicity to humans, under IARC Monographs volume 81 (2002). S-2 and other high-strength glasses appear far less often than E-glass, reserved for parts where the extra strength justifies the extra cost.

Short glass, long glass and milled fibre#

Short-glass nylon starts from chopped strand a few millimetres long, long-fibre nylon starts from 10 to 12 mm pellets that keep at least 6.35 mm of fibre in the finished part, and milled glass is a short, low-aspect-ratio form that reinforces comparatively little. Short-glass compounds lose fibre length to attrition every time the melt passes through the extruder screw and the mould gate, which is why long-fibre thermoplastics exist as a separate category: keeping the pellet's fibre long enough that attrition still leaves a useful length in the part. Pellet length, part fibre length, and where long-fibre grades earn their impact advantage are set out under long fiber thermoplastics (LFT).

How much glass: loading levels and what they cost#

Glass content in polyamide compounds typically runs from 10 to 50 % by weight, the range Clariant gives for flame-retardant PA6 and PA66, with 30 % the grade many compounders describe as the industry standard. Loading is stated in weight percent because that is what is weighed and paid for, but volume percent governs the mechanics: two grades with the same weight percent of glass can differ in volume fraction if base resin density differs.

Loading bands are industry ranges; the grade's own data sheet and a moulding trial decide the final specification.

Request quotes for glass-filled nylon compounds, or for the glass, sizing and additives separately, through the plastic additive supplier finder: specify polymer, glass content, flame-retardant rating, colour and volume, and compounders and distributors respond with matching grades.

What Else Is in a Glass-Filled Nylon Compound?#

A glass-filled nylon compound is never glass and polyamide alone: it also carries a heat stabilizer, a phenolic antioxidant, a lubricant and mould-release package, a colorant and, depending on the part, a flame retardant or an impact modifier. Each family does a job the glass fibre cannot.

The complete additive package for PA6, PA66 and the high-temperature grades is set out on additives for nylon (polyamide), which this section summarises only for the families a glass-filled compound specifically needs.

Heat stabilizers: copper halide, phenolic and polyhydric alcohol#

Glass-filled nylon needs a heat stabilizer because the methylene group next to the amide nitrogen oxidises at the 120 to 200 °C that under-hood and appliance parts see in service, which discolours the part and embrittles it before the glass itself fails. That reaction runs alongside a slower, reversible hydrolysis wherever moisture is present.

The classic answer is the copper halide system DuPont patented in US 2,705,227, filed 15 March 1954: 0.001 to 0.03 wt% dissolved copper with 0.1 to 5 wt% halide. Its PA66 example, with copper acetate, potassium iodide and phosphorous acid, gave about 2,000 hours of heat stability at 150 °C in air. The mechanism is a copper redox cycle: Cu(I) and Cu(II) decompose hydroperoxides and trap radicals, while the halide regenerates Cu(I) and prevents it from precipitating out.

Proprietary systems extend that chemistry further: BRUGGOLEN TP-H1804 gives more than 5,000 hours of tensile retention at 190 °C in PA66 GF30, and H1805 retains more than 50 % after 3,000 hours at 200 °C, reaching 230 °C in PA66. Compounders should state the retention target as a percentage after a defined time and temperature, not as a maximum service temperature. For 210 to 230 °C service, a polyhydric alcohol supplements rather than replaces the copper system: DuPont US 2010/0029819 A1 describes pentaerythritol, dipentaerythritol and tripentaerythritol at 0.25 to 15 wt%. In PA66 GF30, 3 % dipentaerythritol with 0.3 % copper stabilizer kept 99.1 % of tensile strength after 500 hours at 210 °C, against 78.2 % for a copper-only control. The patent data behind dipentaerythritol sit on its own substance page.

Electrical parts add a further constraint beyond raw thermal reach: migrating halide from a copper stabilizer can corrode contacts over time, which is why E&E grades increasingly move to halogen-free copper complexes, even though the classic copper-iodide chemistry remains the benchmark for long-term heat resistance. Copper(I) iodide carries the iodide side of that classic system, and each system is compared grade by grade under heat stabilizers for nylon.

Antioxidants and process stabilizers#

The standard antioxidant for polyamide is the amide-type phenolic Irganox 1098, used at 0.05 to 1.0 wt% and typically at 0.05 to 0.2 wt%, because it survives the 240 to 320 °C melt that a glass-filled compound passes through twice, once in compounding and once in moulding. Under Regulation (EU) No 10/2011, Irganox 1098 is listed as FCM 631 with a specific migration limit of 45 mg/kg, and 21 CFR 178.2010 clears it at up to 1 % in nylon and 0.75 % in nylon 12. Irganox 1098 is the amide-type phenolic written specifically for polyamide.

Irgafos 168 is listed at up to 1 % in nylon under 21 CFR 178.2010 conditions E through G, and Irganox 1330 at up to 1 % under the same regulation, both typically paired with the primary phenolic. BRUGGOLEN H10 is a process stabilizer formulated to counter yellowing in glass-filled grades.

Lubricants, flow improvers and die-drool control#

A glass-filled melt is far more viscous than unfilled nylon, so the compound carries lubricants and flow improvers such as BRUGGOLEN P14, P130, P1507 and P1810 to keep the mould fillable at a given wall thickness. These additives do three distinct jobs inside the same compound.

• Internal lubrication, reducing melt viscosity so a thin-walled part still fills before the gate freezes
• External lubrication and mould release, letting a heavily filled part eject without sticking or scuffing on the abrasive glass at the surface
• Die-drool and bearding control, where Struktol TR 063A at 0.2 to 2.0 wt% reduces the buildup of exuded additive at the die lip during extrusion or compounding

BRUGGOLEN P2201 is formulated for V-0 flame-retardant compounds, where a general-purpose lubricant can interfere with the flame-retardant package. Internal and external lubricants are separated by function across every resin on the hub for processing lubricants for plastics.

Colorants: nigrosine and carbon black#

Black glass-filled nylon is coloured either with nigrosine, the classic polyamide black that covers the fibre and gives a high-gloss surface, or with carbon black. Nigrosine, chemically Solvent Black 7 under CAS 8005-02-5, is documented to decrease the crystallization rate of PA66 alongside its colouring effect, according to a 2025 study in Polymers 17, 360. ECHA lists both Nigrosine Base (EC 616-851-1) and Solvent Black 7 (EC 934-134-4) under that CAS number.

The REACH tonnage band and the EU and US food-contact status of nigrosine are not established in this dataset, so this page names the pigment and its colouring and crystallization effect without stating a regulatory status; a claimed laser-welding transparency benefit is likewise unverified and not repeated here. Nigrosine (Solvent Black 7) carries the full detail on its own page. Carbon black is the alternative black, covered with its full grade range under carbon black in plastics.

Flame retardants and the wick effect#

Glass-filled nylon is harder to make flame retardant than unfilled nylon because the fibres act as wicks that carry molten, burning polymer along the specimen, which is why reinforced grades need a higher flame-retardant loading for the same UL 94 rating. Unreinforced polyamide reaches a non-dripping V-0 rating more easily than a glass-filled grade for exactly that reason.

Clariant's Exolit OP 1312, OP 1314 and OP 1400 are aluminium diethylphosphinate systems paired with a synergist, used at 15 to 20 wt% in glass-filled PA6 and PA66. At that loading they reach UL 94 V-0 from 0.4 to 3.2 mm, a glow-wire flammability index (GWFI) of 960 °C, and OP 1312 specifically reaches a glow-wire ignition temperature (GWIT) of 775 °C and a comparative tracking index (CTI) up to 600 V; PA66 GF compounds on this chemistry reach EN 45545-2 R22 HL3. OP 1400 holds that performance in hot, humid environments, since aluminium diethylphosphinate with melamine polyphosphate can otherwise bloom as a white frost after ageing at 85 °C and 85 % relative humidity. OP 1312 and OP 1314 both carry harmonised classifications for reproductive toxicity and long-term aquatic hazard.

The mechanism of each flame-retardant chemistry available for polyamide, not just the phosphinate route described here, is compared in full under flame retardants for nylon, and the phosphinate mechanism itself, together with its PA and PBT grades, is set out separately under phosphinate flame retardants (DEPAL).

Impact modifiers for glass-filled nylon#

Reactive impact modifiers, usually maleic-anhydride-grafted POE or EPDM, are added to glass-filled nylon when the part has to survive cold impact, and they work once the rubber particles are dispersed closer together than the critical interparticle distance, about 0.3 µm in PA66. That criterion, developed by Wu, sets the practical dispersion target during compounding. Reactive MAH-grafted POE or EPDM modifiers toughen polyamide down to as low as minus 40 °C according to Brüggemann's application data. Because the modifier competes with the glass fibre for the same volume, adding it trades stiffness for toughness, so it is specified only where cold-impact survival is an actual requirement. Dispersion and dosage for this trade-off are covered under impact modifiers for nylon.

How Is Glass-Filled Nylon Dried, Compounded and Moulded?#

Glass-filled nylon is dried before processing, compounded on a twin-screw extruder with the glass fed downstream of the melting zone, and moulded at the 240 to 320 °C that PA6 and PA66 both need. Each stage has its own failure mode if skipped or rushed.

Downstream feeding of the fibre, after the resin has melted, is one case of the wider practice of plastic compounding, where different additive forms need their own feed point along the screw.

Drying and melt temperature#

Polyamide granules are dried before moulding because the water they absorb hydrolyses chains in the melt, and that reaction is reversible only outside the extruder, where moisture can again diffuse out of the resin. The melt temperature then has to clear PA66's 264 °C melting point with margin for the colder mould-facing surface of the melt stream, which is why the 240 to 320 °C engineering-polymer window applies here. No specific drying schedule is established in this dataset; the reason to dry the resin, not a setpoint, is what this page states with confidence, and the grade's own data sheet carries the schedule.

Fibre attrition in the screw and the gate#

Fibres break every time they pass through a shear field, so the glass in a moulded part is shorter than the glass in the pellet, and once a fibre falls below its critical length it pulls out instead of carrying load. That attrition happens twice: once in the mixing section of the twin-screw extruder, and again at the narrow gate of the injection mould. Each pass shortens the fibre-length distribution further, which is the practical reason the critical-length rule costs a compound real strength rather than staying theoretical.

Screw design and side feeding, the two variables a compounder controls most directly to limit this attrition, are covered in full under twin-screw compounding of additives.

Machining, wear and mating surfaces#

Glass-filled nylon is abrasive: it wears screws, barrels, gates and cutting tools, and a glass-filled gear running against a softer mating part will abrade that part in turn. This abrasion is the most repeated complaint across competing stock-shape data sheets, and it shapes several practical decisions.

• Tooling steel and gate inserts specified for glass-filled grades typically use hardened or wear-resistant steel rather than standard mould steel
• Screw and barrel wear accelerates with glass content, raising maintenance frequency on dedicated glass-filled production lines
• Mating parts in a wear application are chosen to be at least as hard as, or a sacrificial component against, the glass-filled part itself

Release and flow additives suited to heavily filled melts are covered under additives for injection molding, alongside the broader set of processing aids that ease abrasive compounds through a standard machine.

How Is Glass-Filled Nylon Tested?#

The first test on any glass-filled nylon is the glass content itself: ISO 1172 burns the polyamide away and weighs the glass that remains, which is also how an incoming batch is checked against its own data sheet. ISO 3451-1 and ASTM D5630 give an equivalent ash-content result by a related calcination method. Mechanical testing follows the sequence used across reinforced thermoplastics generally: ISO 75 or ASTM D648 for heat deflection temperature, ISO 178 for flexural properties, and ISO 179 or ISO 180 for Charpy and Izod impact strength. Electrical testing adds IEC 62631-3-1 for volume resistivity, and particle-size analysis uses ISO 13320 laser diffraction.

No pass or fail values for glass-filled polyamide are established in this dataset; each method names what is measured, and the compound's own specification sets the limit a batch has to meet. Retention targets after long-term thermal ageing are defined under long-term heat aging and RTI, and the methods behind measuring fibre length and glass content together sit under fibre length and glass content measurement.

Where Is Glass-Filled Nylon Allowed? Food Contact and Electrical Requirements#

A food-contact glass-filled nylon part has to satisfy three separate rules at once: one for the glass, one for the sizing on it and one for every stabilizer in the polyamide. No single clearance covers the whole compound.

The glass, the sizing and the stabilizers under EU 10/2011 and 21 CFR#

Glass fibre itself is straightforward: it is listed as FCM 38 in Regulation (EU) No 10/2011 with no specific migration limit, and the polyamide resins are covered in the United States under 21 CFR 177.1500. The sizing chemistry is where compliance becomes specific to glass-filled polyamide.

FDA levels are maximum use levels, not recommended dosages. Check the food type and condition of use in 21 CFR 178.2010.

The point no competitor page carries: the epoxy sizing silane authorised under FCM 1068 covers glass fibre embedded in PET, PC, PBT, thermoset polyesters and epoxy bisphenol vinylester, and polyamide is not on that list. A food-contact glass-filled nylon part therefore needs its sizing chemistry confirmed directly with the fibre supplier, since the FCM 1068 clearance does not extend to polyamide. What each FCM number and SML means is explained on EU 10/2011, and food types and conditions of use for the US entries are decoded on 21 CFR 178.2010.

Electrical, appliance and rail requirements#

Electrical glass-filled nylon is specified by four numbers: the UL 94 rating at a stated wall thickness, the glow-wire values GWIT and GWFI, the comparative tracking index, and for rail interiors the EN 45545-2 requirement set. Each answers a different question about how the part behaves near an electrical or thermal fault.

• UL 94 rates whether a specimen self-extinguishes and drips flaming particles, tested at a stated wall thickness under UL 94 flammability ratings
• GWIT and GWFI, tested under IEC 60695-2-12 and -13, measure ignition risk from a simulated overheating wire, with IEC 60335-1 applying to unattended appliances
• CTI, tested to IEC 60112, measures the leakage current across the surface that causes electrical tracking
• EN 45545-2 sets fire, smoke and toxicity requirements at hazard levels HL2 and HL3 for rail interiors

Migrating halide from a copper heat stabilizer can corrode electrical contacts over time, which is why E&E-grade compounds increasingly specify halogen-free copper complexes that still reach a CTI up to 600 V. The comparative tracking index (CTI) method is explained separately, and the full E&E additive set is on additives for electrical and electronics.

Who Supplies Glass Fibre, Sizing and Additives for Nylon Compounds?#

Glass-filled nylon is built by three layers of supplier: fibre producers who draw and size the E-glass, silane producers who supply the coupling chemistry, and additive suppliers whose stabilizers, lubricants and flame retardants go into the compound. No single company sells all three, so a specification usually names a system, not a source.

Clariant announced an expansion of Exolit OP production at Daya Bay on 5 June 2026, adding capacity for the phosphinate flame retardants used in glass-filled polyamide. Buyers should specify the compound by glass content, stabilizer class and the required GWIT, CTI or UL 94 rating, not by trade name, since more than one supplier's system can usually meet the same target. Silane and maleated-polyolefin producers across the wider market are listed under compatibilizer and coupling agent suppliers.

Send one specification to several compounders at once with the plastic additive supplier finder: polymer, glass content, flame-retardant rating, colour, volume and country.

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What Are the Alternatives to Glass-Filled Nylon?#

Glass is not the only way to reinforce a polyamide: mineral platelets and needles buy lower warpage, carbon fibre buys stiffness at a lower weight, and long-fibre compounds buy impact strength. Each alternative trades away a glass advantage for a property glass does not deliver as well.

Mineral-reinforced and hybrid nylon#

Mineral-reinforced nylon replaces some or all of the glass with wollastonite, calcined kaolin or mica, typically at 30 to 40 %, and buys a flatter part at the cost of strength. Wollastonite carries a 5 to 30 aspect ratio at 2.8 to 2.9 g/cm³ density and is listed under EU 10/2011 as FCM 613, while mica reaches a 20 to 100 aspect ratio under FCM 597. Both are needle- or platelet-shaped rather than fibre-shaped, which is why they restrain shrinkage more evenly in every direction. Aspect ratio and food-contact status sit under wollastonite in plastics.

A related route uses nanoscale platelets. The nylon 6-clay hybrid Kojima, Usuki, Kawasumi and Okada developed at Toyota Central Research and Development Laboratories, reported in Journal of Materials Research 8 (1993) 1185-1189, used only 4.7 wt% montmorillonite to raise HDT by 87 °C. Because acidic mineral surfaces adsorb phenolic antioxidants out of the melt, mineral- and nanoclay-reinforced grades generally need a stronger stabilizer package. The Toyota hybrid and modern grades built on the same principle are covered under nanoclay (organoclay) in plastics.

Carbon-fibre, long-fibre and glass-filled polypropylene compared#

Carbon fibre gives a higher modulus than glass at a lower density, and it conducts electricity, which rules it out wherever the part has to insulate. Carbon fibre runs 5 to 10 µm in filament diameter, against 10 to 20 µm for basalt fibre, and civil-engineering-grade carbon-fibre-reinforced polymer reaches about 3 GPa strength and 150 to 250 GPa modulus, well above E-glass on both counts. That conductivity removes it from consideration anywhere the part must insulate, which is most of the connector and switchgear applications glass-filled nylon serves.

Glass-filled polypropylene answers the "vs" comparison differently: it needs a maleic-anhydride-grafted PP compatibilizer grafted into the matrix before an aminosilane-sized fibre can bond, because polypropylene has no reactive end groups of its own. Polyamide needs no such step, since its amine and acid end groups react directly with the aminosilane sizing described earlier. Filament diameter and conductivity for the carbon route sit under carbon fiber reinforced plastics, and why glass-filled polypropylene needs that grafted step is explained there.

Glass-filled nylon filament for 3D printing#

PA6-GF filament for fused-filament printing is the same glass-reinforced polyamide in a different product form, with the same abrasion problem transferred from the compounding screw to the printer nozzle. Filament-specific handling and nozzle-wear guidance are covered under additives for 3D printing filaments, since the printing process, not the compound chemistry, is what differs from injection moulding.

Is glass-filled nylon brittle?#

Not brittle in the sense of a glassy polymer, but notch-sensitive: fibre ends act as stress concentrations, so notched impact falls while unnotched impact rises, and an impact modifier is added when cold impact matters. The two results move in opposite directions because a notch already supplies the crack a fibre end otherwise has to initiate.

Is glass-filled nylon expensive?#

The price of a glass-filled nylon compound is set less by the glass, a commodity mineral product, than by the polyamide grade, the stabilizer package and any flame retardant, since a phosphinate flame retardant at 15 to 20 wt% costs more than the glass beside it. No price figure for glass fibre, polyamide resin or a finished compound is established in this dataset, so this page names the cost drivers rather than a number: resin grade, stabilizer class, flame-retardant loading and compounder versus stock-shape distributor sourcing all move price independently of glass content alone.

Can glass-filled nylon be recycled?#

Glass-filled nylon can be reprocessed, but every pass shortens the fibres, so regrind loses strength and is usually blended back at a limited ratio with a chain extender such as BRUGGOLEN M1251 to restore the polyamide's viscosity. BRUGGOLEN M1253 performs the same linear chain-extension role, while M1417 works as a chain breaker for upcycling high-viscosity waste. How fibre and filler content change sorting and reprocessing is covered under design for recycling.

Is glass-filled nylon stronger than aluminium?#

On a weight basis a highly reinforced nylon competes with cast aluminium in stiffness-driven parts, which is why metal replacement is its main commercial use, but it does not match aluminium in absolute strength, creep at temperature or dimensional stability under changing humidity. No specific property comparison against an aluminium alloy is established in this dataset, so the answer stays at the level of design logic: where stiffness per unit weight and part consolidation matter most, glass-filled nylon is the metal-replacement candidate; where absolute strength, high-temperature creep or humidity-driven dimensional stability decide the design, aluminium still holds the advantage.

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