Technical textiles

In short

Technical textiles are textile materials and products made primarily for their performance and functional properties rather than for appearance or decoration - filtration, reinforcement, separation, protection, absorbency, insulation. They are classified worldwide into 12 application segments (Agrotech, Buildtech, Clothtech, Geotech, Hometech, Indutech, Meditech, Mobiltech, Oekotech, Packtech, Protech, Sportech), a classification India has adopted in its policy and HSN work. The subject is examined in textile-engineering papers and GATE TF (fibre science, nonwovens, fabric manufacture, testing), and is a major recruiter area - Arvind Advanced Materials, SRF, Garware Technical Fibres, Supreme Nonwovens, Kusumgar, Techfab India, Ahlstrom, Freudenberg, Welspun, Entremonde, Strata Geosystems and the Indian ordnance/defence supply chain. India's National Technical Textiles Mission (approved 2020, ₹1,480 crore) and successive mandatory-use orders in highways, railways and agriculture make this the fastest-growing part of the industry.

Explained

Definition, scope and what makes a textile "technical"

• Definition: textile material and products manufactured primarily for their technical performance and functional properties, rather than aesthetic or decorative characteristics (the Textile Institute / Techtextil definition, used in Indian policy documents).
• The test is intended function, not fibre or process: the same polyester yarn can go into a shirt (conventional) or a seat belt (Mobiltech).
• Performance is specified, measured and certified against a standard - a geotextile is bought on tensile strength, CBR puncture, permittivity and AOS, not on hand or drape.
• Borderline cases in exams: sewing thread and interlinings are Clothtech (technical), a printed curtain is not; sports shoe uppers are Sportech, a fashion sneaker's logo panel is not.
• Dual market: many items are "high value, low volume" (vascular grafts, ballistic panels) while others are "low value, high volume" (packtech woven sacks, agro shade nets). India's volume is dominated by Packtech.

The twelve segments (memorise with examples)

• Mnemonic often used: A-B-C-G-H-I-M-M-O-P-P-S. Note the two "M"s (Meditech, Mobiltech) and two "P"s (Packtech, Protech).

Fibres and materials used

• Commodity synthetics (bulk of volume): polypropylene (cheapest, lowest density 0.91 g/cc, chemically inert - sacks, nonwovens, geotextiles), polyester (high strength and modulus, good UV when stabilised - geotextiles, tyre cord, seat belts), polyamide 6/66 (toughness, abrasion - airbags, parachutes, fishing nets), HDPE (tapes, nets, ropes).
• High-performance fibres: para-aramid (Kevlar, Twaron - tenacity about 20-23 g/den, used for ballistic and cut protection), meta-aramid (Nomex - flame resistance, does not melt), UHMWPE (Dyneema, Spectra - highest specific strength, floats, but low melting ~147 °C), carbon fibre (very high modulus, composites), glass fibre (insulation, FRP), basalt, PTFE (chemical and high-temperature filtration), PPS and P84 polyimide (hot-gas filter bags in cement plants), modacrylic and FR viscose (inherently flame-retardant apparel).
• Natural and regenerated: jute and coir geotextiles (biodegradable, Indian strength - CSIR/NJB jute geotextile standards exist for road and slope work), cotton for medical absorbents and surgical gauze, alginate and chitosan for advanced wound dressings, PLA and PGA for bioresorbable sutures.
• Selection logic in exams: state the required function → the critical property → the fibre. Example: hot-gas filtration at 150-190 °C → continuous-use temperature and acid resistance → PPS or P84, not polyester.

Manufacturing routes

1. Woven: high strength in warp and weft, dimensionally stable. Plain and basket weaves for filter and geotextile fabrics; leno for sacks and nets (locks yarns, no slippage); tape fabrics from slit-film PP/HDPE on circular looms for sacks; 3-D and multi-layer weaving for composite preforms.
2. Knitted: warp knitting (raschel, tricot) gives directional stability with stretch - mosquito nets, shade nets, medical bandages, spacer fabrics for cushioning; weft knitting for seamless supports and vascular grafts.
3. Nonwoven (the dominant technical route):
   • Dry-laid: carded/air-laid web, then bonded by needle punching (barbed needles entangle fibres mechanically - geotextiles, automotive carpets, felts), thermal bonding (calender or hot air), chemical/latex bonding, or hydroentanglement/spunlace (high-pressure water jets - wipes, surgical drapes).
   • Polymer-laid (spun-laid): spunbond (polymer extruded, drawn, laid, thermally bonded - strong, used for geotextiles, medical gowns, bag liners), meltblown (hot air attenuates filaments to 1-5 µm - the filtration layer; the "M" of SMS and of N95 media, where it is electret-charged), SMS laminates combining strength and barrier.
   • Wet-laid: papermaking route for tea bags, battery separators, filter papers.
4. Braiding: ropes, cords, sutures, catheters, stent sleeves; over-braided preforms for composites.
5. Composites and coating/lamination: fabric + polymer matrix. Coating (knife-over-roll, dip, calendering) with PVC, PU, PTFE, silicone or acrylic; lamination bonds a film/membrane (e.g. microporous PTFE or hydrophilic PU) for breathable waterproof fabric. Prepregs of carbon or glass for structural composites.
6. Finishing for function: flame retardant, water/oil repellent (fluorocarbon and newer non-PFAS C0 chemistry), antimicrobial, UV stabilisation, anti-static, plasma and nano finishes.

Key functional properties, how they work and how they are measured

• Geotextile functions - the examinable five: separation (keeps subgrade soil out of aggregate), filtration (lets water pass, holds soil), drainage (conducts water in plane - transmissivity), reinforcement (takes tensile load the soil cannot), protection/cushioning (shields a geomembrane). Geogrids and geocells add confinement; geomembranes are for barrier (impermeable, so not a geotextile).
• Geotextile specifications: mass per unit area (GSM), thickness, wide-width tensile strength and elongation (kN/m), grab tensile, CBR puncture resistance (N), trapezoidal tear, apparent opening size AOS / O₉₅ (µm), permittivity (s⁻¹), transmissivity, UV retained strength after exposure.
• Filtration: depth filtration (nonwoven thickness captures particles) versus surface filtration (membrane/PTFE laminated bag). Rated by efficiency at a particle size, pressure drop, air permeability (m³/m²/s at 200 Pa), dust cake release. Electret meltblown adds electrostatic capture at low pressure drop.
• Barrier with breathability: water vapour transmission rate (WVTR) and hydrostatic head; microporous membranes pass vapour but block liquid water.
• Protective performance: Limiting Oxygen Index (LOI) - the minimum oxygen percentage to sustain burning; above about 26-28% a fabric is considered flame retardant. Thermal Protective Performance (TPP) for flame exposure, arc thermal performance value (ATPV) for electric arc, V₅₀ (velocity at which 50% of projectiles are stopped) and NIJ/BIS threat levels for ballistic panels, cut level on a 6-level scale for gloves.
• Absorbency (Meditech): absorbency rate and capacity, strike-through time, rewet - relevant to diapers and napkins with superabsorbent polymer (SAP) cores.
• Composite reinforcement: strength depends on fibre volume fraction, orientation, and fibre-matrix adhesion; the rule of mixtures gives the longitudinal modulus.

Indian standards, policy and regulation

• BIS: India has notified mandatory Quality Control Orders (QCOs) covering geotextiles, geomembranes, protective textiles, agrotextiles and medical textiles in phases from 2023 onwards, requiring BIS certification (ISI mark) for listed items; the covered lists and dates have been revised and extended more than once, so verify the current notification before quoting a date.
• Commonly cited standards: IS 16391 series and related standards for geotextiles (woven and nonwoven for roads/subgrade), IS 15351 for laminated HDPE woven geomembrane, IS 14887 for HDPE woven sacks for fertilisers, IS 16653 series for agro shade nets, IS 15741/15742 region of PP/HDPE woven sacks, IS 5405 for sanitary napkins, IS 758 for absorbent cotton wool. IS numbers are revised and some are withdrawn - cite the latest edition from the BIS catalogue rather than from memory.
• Testing methods: ASTM D4595 (wide-width tensile), ASTM D6241 (CBR puncture), ASTM D4751 (AOS), ASTM D4491 (permittivity), ISO 10319/12236/11058 equivalents; ISO 11612 and ISO 11611 for heat/flame and welding protective clothing; EN 388 for mechanical/cut gloves; NIJ 0101.06 (and the newer NIJ standard) for body armour.
• Policy: National Technical Textiles Mission (NTTM), approved February 2020 with an outlay of ₹1,480 crore over four years (implementation extended), with four components - research and development, promotion and market development, export promotion, and education/training/skilling; separate GREAT grants for start-ups and Taxila faculty-training programme. HSN codes for 207 technical textile items have been identified to track trade. Mandatory-use guidelines push geotextiles in NHAI/MoRTH and railway works and in North-East road projects; MoRTH IRC specifications (IRC:SP:59, IRC:113) govern geosynthetic use in roads and slopes.
• Other applicable law: goods attract GST at the applicable slab (slabs since 22 September 2025 are 5%, 18% and 40%) - most technical textile fabrics and made-ups fall in the lower slabs, but the rate is item-specific by HSN and must be checked. Factories and worker-safety obligations now run under the four Labour Codes in force from 21 November 2025, which replaced the Factories Act and the Minimum Wages, Industrial Disputes and BOCW Acts - relevant because PPE supply and use duties sit under the Occupational Safety, Health and Working Conditions Code. Medical devices (sutures, implants, some dressings) are regulated by CDSCO under the Medical Devices Rules, 2017.

Key points

• Technical textile - made for performance and function, not appearance; judged against a measured specification.
• 12 segments - Agro, Build, Cloth, Geo, Home, Indu, Medi, Mobil, Oeko, Pack, Pro, Sportech; India's largest by volume is Packtech.
• Nonwoven - web of fibres bonded mechanically, thermally or chemically, without spinning into yarn first; the dominant technical route.
• Needle punching - barbed needles entangle a fibre web; standard for geotextiles and auto carpets.
• Spunbond vs meltblown - spunbond gives strength (filaments 15-30 µm), meltblown gives filtration/barrier (1-5 µm); SMS laminates combine both.
• Five geotextile functions - separation, filtration, drainage, reinforcement, protection; geomembrane adds barrier.
• AOS (O₉₅) - apparent opening size in µm; must retain soil yet pass water (filtration criteria link AOS to soil D₈₅).
• Permittivity - cross-plane flow capacity per unit thickness, s⁻¹; transmissivity is in-plane drainage.
• LOI - minimum oxygen % to sustain combustion; roughly ≥26-28% means flame retardant (Nomex, FR viscose, modacrylic).
• Para-aramid vs UHMWPE - both ballistic; aramid resists heat better, UHMWPE has higher specific strength but low melting point.
• GSM - mass per unit area in g/m², the first number quoted in any technical fabric specification.
• Leno weave - locked crossing yarns, no slippage; used for sacks, nets and shade fabrics.
• SAP - superabsorbent polymer in diapers/napkins, absorbs many times its own weight by osmosis.
• Coating vs lamination - coating applies a polymer in fluid form; lamination bonds a pre-made film or membrane.
• NTTM - National Technical Textiles Mission, ₹1,480 crore, four components, approved 2020.
• QCO/BIS - mandatory ISI certification for listed geo-, agro-, medical and protective textiles, phased from 2023; verify current list.
• V₅₀ - projectile velocity at which 50% of shots are stopped, the basic ballistic rating.
• High value-low volume vs low value-high volume - the two economic halves of the sector.

Formulas and examples

Example 1 - GSM and tensile specification of a woven geotextile. A woven polypropylene geotextile has 12 warp ends/cm and 10 weft picks/cm; both yarns are 1000 denier.

• Convert denier to tex: tex = den × 0.1111 → 1000 den = 111.1 tex.
• Mass per m²: warp = 12 ends/cm × 100 cm = 1200 m of yarn per m² width... take per m²: warp length = 12 × 100 = 1200 m, weft length = 10 × 100 = 1000 m, total 2200 m.
• Mass = 2200 m × 111.1 g/1000 m = 244.4 g/m², so about 245 GSM (crimp adds 2-5% in practice).
• If a strip 200 mm wide breaks at 9.0 kN, wide-width strength = 9.0 / 0.20 = 45 kN/m - meeting a typical 40 kN/m road specification.

Example 2 - Permittivity from a constant-head test. A nonwoven geotextile specimen of area 0.0050 m² passes 1.5 × 10⁻⁴ m³/s of water under a head loss of 50 mm.

• ψ = q/(Δh·A) = 1.5 × 10⁻⁴ / (0.050 × 0.0050) = 1.5 × 10⁻⁴ / 2.5 × 10⁻⁴ = 0.60 s⁻¹.
• If the fabric is 2.0 mm thick, cross-plane permeability k = ψ × t = 0.60 × 0.002 = 1.2 × 10⁻³ m/s - about the permeability of a clean sand, so it drains freely.
• Design rule: for filtration the geotextile permeability should exceed the soil's (commonly k_geo ≥ 10 × k_soil); if k_soil = 1 × 10⁻⁵ m/s, 1.2 × 10⁻³ m/s passes comfortably.

Example 3 - Filter retention check (AOS). A subgrade soil has D₈₅ = 0.15 mm = 150 µm. A nonwoven geotextile has AOS O₉₅ = 120 µm.

• Criterion O₉₅ ≤ 2 × D₈₅ = 300 µm → 120 µm passes; even the strict C = 1 case (150 µm) is satisfied.
• But check clogging: openings far smaller than needed raise clogging risk, so a fabric with O₉₅ of about 100-200 µm is preferred here over a very fine 50 µm fabric.

Example 4 - Ballistic panel areal density. A vest panel uses 20 plies of 200 GSM para-aramid woven fabric over 0.30 m × 0.35 m.

• Areal density = 20 × 200 = 4000 g/m² = 4.0 kg/m².
• Panel area = 0.30 × 0.35 = 0.105 m² → mass = 4.0 × 0.105 = 0.42 kg per panel; front and back = 0.84 kg of ballistic fabric (plus carrier and any hard plate).
• At ₹1,400 per m² of fabric, fabric cost = 4000/1000 × ... compute directly: fabric used = 20 plies × 0.105 m² = 2.1 m² per panel, 4.2 m² for two → cost = 4.2 × ₹1,400 = ₹5,880 of fabric per vest.

Example 5 - Composite stiffness by the rule of mixtures. A unidirectional glass-fibre/epoxy laminate has V_f = 0.55, E_f = 72 GPa, E_m = 3.4 GPa.

• E_c = 72 × 0.55 + 3.4 × 0.45 = 39.6 + 1.53 = 41.1 GPa along the fibres.
• If σ_f = 2000 MPa and σ_m = 60 MPa, σ_c ≈ 2000 × 0.55 + 60 × 0.45 = 1100 + 27 = 1127 MPa.
• Transverse modulus (inverse rule) = 1 / (0.55/72 + 0.45/3.4) = 1 / (0.00764 + 0.1324) = 7.1 GPa - showing the strong anisotropy that forces cross-plied or woven preforms.

Where it is used

• Highways and railways: nonwoven separation geotextiles and geogrid-reinforced soil walls on NHAI projects; Strata Geosystems and Techfab India supply geocells and geogrids; MoRTH/IRC specifications govern design.
• Automotive (Mobiltech): Gujarat and Pune clusters supply airbag fabric, seat belts, needle-punched carpets and headliners to Maruti, Tata Motors and Mahindra; SRF and Century Enka make nylon/polyester tyre cord.
• Medical and hygiene (Meditech): spunlace and SMS gowns, drapes and masks; diaper and sanitary-napkin lines (Supreme Nonwovens, Ginni Filaments); surgical cotton and bandages under BIS and CDSCO rules.
• Protective (Protech): FR coveralls and arc-flash suits for refineries and power utilities, ballistic vests and helmets for the armed forces and police through Ordnance Factory Board successor companies, MKU and Tata Advanced Systems.
• Packaging (Packtech): PP/HDPE woven sacks, FIBC jumbo bags and leno bags from Gujarat, Rajasthan and Tamil Nadu units - India's largest technical-textile export segment by volume.
• Job roles: product development engineer (nonwovens/coating), quality and testing engineer at NABL-accredited labs and Centres of Excellence (SITRA, BTRA, SASMIRA, NITRA, Indian Jute Industries' Research Association), application/technical-sales engineer for geosynthetics, process engineer on spunbond and needle-punch lines.

Interview questions

• Q: How do you decide whether a product is a technical textile? A: By its intended purpose - if it is made and bought primarily for measurable performance (strength, filtration, barrier, protection) rather than appearance, it is technical, regardless of fibre or process.
• Q: Name the five functions of a geotextile. A: Separation, filtration, drainage, reinforcement and protection/cushioning; a geomembrane instead provides a barrier because it is impermeable.
• Q: Difference between spunbond and meltblown? A: Spunbond filaments are extruded and mechanically drawn to 15-30 µm giving strength; meltblown filaments are attenuated by hot air to 1-5 µm giving fine pores for filtration and barrier, but low strength - hence SMS laminates.
• Q: Why is needle punching preferred for geotextiles? A: It gives a thick, permeable, high-elongation fabric with good puncture resistance and in-plane drainage, with no binder that could be chemically attacked in soil.
• Q: What is AOS and why does it matter? A: Apparent opening size (O₉₅) is the pore size that 95% of a graded sand is retained by; it must be small enough to hold soil particles yet large enough to avoid clogging and to pass water.
• Q: Aramid or UHMWPE for a bullet-resistant vest? A: UHMWPE gives lower weight for the same stopping power but softens near 147 °C and creeps; aramid tolerates heat and is easier to mould with resin, so the choice depends on threat level, weight target and service temperature.
• Q: What does LOI tell you? A: The minimum oxygen percentage in an oxygen-nitrogen stream needed to sustain burning; values around 26-28% and above indicate a flame-retardant fabric, and inherently FR fibres like Nomex sit well above that.
• Q: Can polyester be used in a highly alkaline soil? A: Not preferably - polyester hydrolyses in high pH (above about 9-10), so polypropylene or polyethylene geosynthetics are specified for lime- or cement-treated and alkaline environments.
• Q: How is a waterproof breathable fabric made? A: By laminating or coating a microporous (PTFE) or hydrophilic (PU) membrane whose pores pass water vapour but block liquid water, rated by hydrostatic head and WVTR.
• Q: What is the NTTM and why was it created? A: The National Technical Textiles Mission, approved in 2020 with a ₹1,480 crore outlay and four components (R&D, promotion and market development, export promotion, education and skilling), to raise India's share in a sector dominated by imports of high-end products.
• Q: Which Indian segment is biggest and which is most import-dependent? A: Packtech leads in volume and value; high-end Meditech, Protech and specialty Indutech items - and most high-performance fibres such as aramid, carbon and UHMWPE - are still largely imported.
• Q: A cement plant's bag filter runs at 170 °C with acidic gas - which fibre? A: PPS or P84 polyimide, because polyester would hydrolyse and lose strength above about 150 °C and aramid is weak to acid; selection follows continuous-use temperature plus chemical resistance.

Common mistakes

• Classifying by fibre or fabric type instead of by end use - calling every nonwoven a technical textile and every woven a conventional one.
• Confusing geotextile (permeable) with geomembrane (impermeable barrier) and listing "barrier" as a geotextile function.
• Quoting grab tensile strength in N as if it were wide-width strength in kN/m, or omitting the specimen width.
• Mixing up permittivity (cross-plane, s⁻¹) with permeability (m/s) and transmissivity (in-plane, m²/s).
• Treating a smaller AOS as always better, ignoring clogging and the required flow.
• Reciting withdrawn IS numbers or an outdated QCO date - the standards and the mandatory lists are revised regularly and must be checked against the current BIS catalogue and notification.
• Using g/den and cN/tex interchangeably without the 8.83 conversion, and forgetting that denier is per 9000 m while tex is per 1000 m.

Related topics

• Nonwoven manufacturing technology · Fibre science and high-performance fibres · Textile testing and quality control · Textile composites and coated fabrics · Indian textile industry and exports · Geosynthetics in civil engineering.