spore: profile
id: s2-glass
spore_version: 0.2
family: glass-and-composites
name: AGY S-2 Glass fibre and S-2 glass composites
abbreviation: S-2 glass
role: reinforcement fibre
category: composites
type: glass-fiber-reinforced
summary: |
  AGY S-2 Glass is a magnesium aluminosilicate fibre of the S-glass family, made of about 65 wt% SiO2, 25 wt% Al2O3 and 10 wt% MgO. The lookpolymers datasheet for AGY ZenTron S-2 gives a tensile strength of 4890 MPa at 23.0 °C and 4445 MPa at 371 °C, a Young's modulus of 86.9 GPa and an elongation at break of 5.7 %. A patent background quotes 89 to 90 GPa for S-2 glass, so the stiffness value is not settled. This is a draft: no S-2 safety data sheet, glass corrosion number or fibre-form test condition was read in this run.
best_for: Composite parts that must carry high tensile loads and resist impact, such as helicopter blades, armour, filament-wound pressure vessels and the hard upper torso of a spacesuit (uses named in the sources read)
weakest_at: 'Cost and melting: a patent background says S-2 is hard to melt and refine, forms bubbles and crystallises fast, and calls production small-scale, low-efficiency and costly'
identity:
  formula: 'Magnesium aluminosilicate glass fibre (S-glass family): about 65 wt% SiO2, 25 wt% Al2O3 and 10 wt% MgO, with SiO2 and Al2O3 together about 90 wt%'
  source: us8252707
  where: Background section, S-2 glass paragraph (about 65% SiO2, 25% Al2O3, 10% MgO); the same patent cites DIN 1259-1 for S-glass as an aluminosilicate with no added CaO and about 10% MgO. Second patent US 11,339,085, same paragraph (SiO2 and Al2O3 together 90%, MgO about 10%)
  designations:
    - system: Trade name
      code: S2 Glass
      note: AGY trademark for S-2 glass fibre
      source: agy-chop
      where: Footer line of the last page, S2 Glass is a registered trademark of AGY
    - system: Trade name
      code: ZenTron
      note: AGY product line name shown on the datasheet title
      source: lookpolymers
      where: Page title, AGY ZenTron S-2 Generic S-Glass Fiber
tags:
  environments: []
  stresses: []
  applications:
    - structures
    - habitats-and-suits
    - propulsion-and-tanks
properties:
  - benchmark: density
    label: Density, S-2 glass fibre
    value: 2.46
    unit: g/cc
    scope: material
    conditions:
      form: fibre; the datasheet does not name a filament, strand or roving
      temperature: not stated
    method: Printed as 2.46 g/cc (0.0889 lb/in³) in the Physical Properties table. No test method or temperature is printed.
    status: ground
    source: lookpolymers
    where: Physical Properties table, Density row
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, ultimate, at 23 °C
    value: 4890
    unit: MPa
    scope: material
    conditions:
      form: fibre; form not stated
      temperature: 23.0 °C (73.4 °F)
    method: Printed as 4890 MPa (709000 psi) at 23.0 °C. The datasheet gives no test method.
    status: ground
    source: lookpolymers
    where: Mechanical Properties table, Tensile Strength, Ultimate row, 23.0 °C line
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, ultimate, at 371 °C
    value: 4445
    unit: MPa
    scope: material
    conditions:
      form: fibre; form not stated
      temperature: 371 °C (700 °F)
    method: Printed as 4445 MPa (644700 psi) at 371 °C, in the same row as the 23.0 °C value.
    status: ground
    source: lookpolymers
    where: Mechanical Properties table, Tensile Strength, Ultimate row, 371 °C line
  - benchmark: elongation
    label: Elongation at break
    value: 5.7
    unit: '%'
    scope: material
    conditions:
      basis: elongation at break, printed with the note in 50 mm
      temperature: not stated
    method: Printed as 5.7 % with the note in 50 mm in the Mechanical Properties table.
    status: ground
    source: lookpolymers
    where: Mechanical Properties table, Elongation at Break row
  - benchmark: elastic_modulus
    label: Modulus of elasticity, datasheet
    value: 86.9
    unit: GPa
    scope: material
    conditions:
      form: fibre; form not stated
      temperature: not stated
    method: Printed as 86.9 GPa (12600 ksi). A patent background gives a different range, which is recorded as a separate entry below.
    status: ground
    source: lookpolymers
    where: Mechanical Properties table, Modulus of Elasticity row
  - benchmark: elastic_modulus
    label: Young's modulus, patent background
    value: 89
    value_high: 90
    bound: range
    unit: GPa
    scope: material
    conditions:
      basis: typical value quoted as relevant data in a patent background; form and test not stated
    method: Quoted from the background section, which says the elastic modulus of S-2 glass is typically 89-90 GPa. The patent names no test method, and the value differs from the datasheet figure of 86.9 GPa.
    status: ground
    source: us11339085
    where: Background section, S-2 glass paragraph
  - benchmark: poissons_ratio
    label: Poisson's ratio
    value: 0.22
    unit: '-'
    scope: material
    conditions:
      temperature: not stated
    method: Printed as 0.22 in the Mechanical Properties table.
    status: ground
    source: lookpolymers
    where: Mechanical Properties table, Poissons Ratio row
  - benchmark: moisture_absorption
    label: Water absorption
    value: 0
    unit: '%'
    scope: material
    conditions:
      basis: water absorption as printed; test method, time and temperature not stated
    method: Printed as 0.00 % in the Physical Properties table, row Water Absorption.
    status: ground
    source: lookpolymers
    where: Physical Properties table, Water Absorption row
  - benchmark: cte
    label: Coefficient of thermal expansion, linear
    value: 1.6
    unit: µm/m-°C
    scope: material
    conditions:
      temperature: '-30.0 to 250 °C (-22.0 to 482 °F)'
      basis: average, isotropic, as printed
    method: Printed as 1.60 µm/m-°C (0.889 µin/in-°F) in the Thermal Properties table, CTE linear row.
    status: ground
    source: lookpolymers
    where: Thermal Properties table, CTE linear row
  - benchmark: specific_heat
    label: Specific heat capacity at 23 °C
    value: 0.737
    unit: J/g-°C
    scope: material
    conditions:
      temperature: 23.0 °C (73.4 °F)
    method: Printed as 0.737 J/g-°C (0.176 BTU/lb-°F) at 23.0 °C in the Thermal Properties table.
    status: ground
    source: lookpolymers
    where: Thermal Properties table, Specific Heat Capacity row, 23.0 °C line
  - benchmark: specific_heat
    label: Specific heat capacity at 200 °C
    value: 0.935
    unit: J/g-°C
    scope: material
    conditions:
      temperature: 200 °C (392 °F)
    method: Printed as 0.935 J/g-°C (0.223 BTU/lb-°F) at 200 °C in the same row.
    status: ground
    source: lookpolymers
    where: Thermal Properties table, Specific Heat Capacity row, 200 °C line
  - benchmark: thermal_conductivity
    label: Thermal conductivity
    value: 1.1
    value_high: 1.4
    bound: range
    unit: W/m-K
    scope: material
    conditions:
      temperature: not stated
    method: Printed as 1.10 - 1.40 W/m-K (7.63 - 9.72 BTU-in/hr-ft²-°F) in the Thermal Properties table, with no test condition given.
    status: ground
    source: lookpolymers
    where: Thermal Properties table, Thermal Conductivity row
  - benchmark: melting_point
    label: Melting point, datasheet
    value: 1466
    unit: °C
    scope: material
    conditions:
      basis: melting point as printed on the datasheet
    method: Printed as 1466 °C (2671 °F) in the Thermal Properties table, row Melting Point. The patent background gives a higher figure, recorded as a separate entry.
    status: ground
    source: lookpolymers
    where: Thermal Properties table, Melting Point row
  - benchmark: melting_point
    label: Melting temperature, patent background
    value: 1600
    unit: °C
    scope: material
    conditions:
      basis: printed as up to over 1600° C, a lower bound and not a single measured value
    method: Quoted from the background section, which gives the melting temperature as up to over 1600° C. The figure differs from the datasheet value of 1466 °C, and both are kept.
    status: ground
    source: us11339085
    where: Background section, S-2 glass paragraph
  - benchmark: liquidus_temperature
    label: Liquidus temperature, datasheet
    value: 1466
    unit: °C
    scope: material
    conditions:
      basis: liquidus as printed on the datasheet
    method: Printed as 1466 °C (2671 °F) in the Thermal Properties table, row Liquidus.
    status: ground
    source: lookpolymers
    where: Thermal Properties table, Liquidus row
  - benchmark: liquidus_temperature
    label: Liquidus temperature, patent background
    value: 1470
    unit: °C
    scope: material
    conditions:
      basis: printed as up to 1470° C in the background section
    method: Quoted from the background section, in the same sentence as a forming temperature of up to 1571° C.
    status: ground
    source: us11339085
    where: Background section, S-2 glass paragraph
  - benchmark: forming_temperature
    label: Forming temperature, patent background
    value: 1571
    unit: °C
    scope: material
    conditions:
      basis: printed as up to 1571° C in the background section
    method: Quoted from the background section. The patent does not name a viscosity or test method for the forming temperature.
    status: ground
    source: us11339085
    where: Background section, S-2 glass paragraph
  - benchmark: glass_transition_temperature
    label: Transformation temperature, Tg
    value: 845
    unit: °C
    scope: material
    conditions:
      basis: printed on the row labelled Transformation Temperature, Tg
    method: Printed as 845 °C (1550 °F) on the row labelled Transformation Temperature, Tg. The datasheet names no test method.
    status: ground
    source: lookpolymers
    where: Thermal Properties table, Transformation Temperature, Tg row
  - benchmark: softening_point
    label: Softening point, datasheet
    value: 1056
    unit: °C
    scope: material
    conditions:
      basis: softening point as printed
    method: Printed as 1056 °C (1933 °F) in the Thermal Properties table. The AGY brochure prints the same metric value, recorded as a separate entry.
    status: ground
    source: lookpolymers
    where: Thermal Properties table, Softening Point row
  - benchmark: softening_point
    label: Softening point, AGY brochure
    value: 1056
    unit: °C
    scope: material
    conditions:
      basis: softening point as printed in the features table
    method: Printed as 1056°C (1932°F) in the features and benefits table. The Fahrenheit value differs by one degree from the datasheet, and the metric value agrees.
    status: ground
    source: agy-chop
    where: Features and benefits table, Softening point line
  - benchmark: annealing_point
    label: Annealing point
    value: 816
    unit: °C
    scope: material
    conditions:
      basis: annealing point as printed in the features table
    method: Printed as 816°C (1500°F) in the features and benefits table of the AGY brochure.
    status: ground
    source: agy-chop
    where: Features and benefits table, Annealing point line
  - benchmark: strain_point
    label: Strain point
    value: 766
    unit: °C
    scope: material
    conditions:
      basis: strain point as printed in the features table
    method: Printed as 766°C (1410°F) in the features and benefits table of the AGY brochure.
    status: ground
    source: agy-chop
    where: Features and benefits table, Strain point line
  - benchmark: max_service_temp
    label: Maximum service temperature, air
    value: 875
    unit: °C
    scope: material
    conditions:
      atmosphere: air
    method: Printed as 875 °C (1610 °F) for Maximum Service Temperature, Air, with the page's note 'Well above Tg, due to reversible phase separation'.
    status: ground
    source: lookpolymers
    where: Thermal Properties table, Maximum Service Temperature, Air row
  - benchmark: max_service_temp
    label: Maximum service temperature, inert atmosphere
    value: 875
    unit: °C
    scope: material
    conditions:
      atmosphere: inert
    method: Printed as 875 °C (1610 °F) for Maximum Service Temperature, Inert.
    status: ground
    source: lookpolymers
    where: Thermal Properties table, Maximum Service Temperature, Inert row
  - benchmark: refractive_index
    label: Refractive index
    value: 1.521
    unit: '-'
    scope: material
    conditions:
      wavelength: not stated
    method: Printed as 1.521 in the Optical Properties table.
    status: ground
    source: lookpolymers
    where: Optical Properties table, Refractive Index row
  - benchmark: electrical_resistivity
    label: Electrical resistivity
    value: 9050000000000
    unit: ohm-cm
    scope: material
    conditions:
      temperature: not stated
    method: Printed as 9.05e+12 ohm-cm in the Electrical Properties table, with no test condition given.
    status: ground
    source: lookpolymers
    where: Electrical Properties table, Electrical Resistivity row
  - benchmark: dielectric_constant
    label: Dielectric constant at 1e+10 Hz
    value: 5.2
    unit: '-'
    scope: material
    conditions:
      frequency: 1e+10 Hz
    method: Printed as 5.2 at 1e+10 Hz in the Electrical Properties table.
    status: ground
    source: lookpolymers
    where: Electrical Properties table, Dielectric Constant row, 1e+10 Hz line
  - benchmark: dielectric_constant
    label: Dielectric constant at 1e+6 Hz
    value: 5.3
    unit: '-'
    scope: material
    conditions:
      frequency: 1e+6 Hz
    method: Printed as 5.3 at 1e+6 Hz in the Electrical Properties table.
    status: ground
    source: lookpolymers
    where: Electrical Properties table, Dielectric Constant row, 1e+6 Hz line
  - benchmark: dielectric_strength
    label: Dielectric strength
    value: 18
    unit: kV/mm
    scope: material
    conditions:
      basis: not stated
    method: Printed as 18.0 kV/mm (457 kV/in) in the Electrical Properties table.
    status: ground
    source: lookpolymers
    where: Electrical Properties table, Dielectric Strength row
  - benchmark: dissipation_factor
    label: Dissipation factor
    value: 0.002
    unit: '-'
    scope: material
    conditions:
      frequency: 1e+6 Hz
    method: Printed as 0.0020 at 1e+6 Hz in the Electrical Properties table.
    status: ground
    source: lookpolymers
    where: Electrical Properties table, Dissipation Factor row
corrosion:
  - environment: Acid and alkali exposure
    headline: Acid resistant, with moderate alkali resistance, per the datasheet.
    effect: The datasheet's Material Notes say 'Acid resistant. Moderate alkali resistance.' No pH, concentration, time or temperature is given, so no corrosion rate can be taken from this source.
    conditions:
      basis: qualitative datasheet statement; test conditions not stated
    source: lookpolymers
    where: Material Notes
    rating: unknown
  - environment: 'Organic fibres for comparison: aramid and carbon, chemical resistance and high-temperature stability'
    headline: AGY says S2 outperforms aramid and carbon fibres in chemical resistance, but gives no number.
    effect: AGY's product page says S2 surpasses organic fibres such as aramid and carbon in electrical insulation, chemical resistance, durability and high-temperature stability. This is the maker's comparison and has no test value.
    conditions:
      basis: manufacturer comparison; no test conditions given
    source: agy-s2-page
    where: Introduction paragraph
    rating: unknown
  - environment: High temperature in air
    headline: The datasheet prints 4445 MPa at 371 °C against 4890 MPa at 23.0 °C, and a softening point of 1056 °C.
    effect: AGY's brochure gives an annealing point of 816°C (1500°F) and a strain point of 766°C (1410°F), and says S2 keeps greater fibre tensile strength and stability at elevated temperatures. The datasheet gives a maximum service temperature in air of 875 °C (1610 °F), with the note that it is well above Tg.
    conditions:
      basis: values as printed; time at temperature not stated
    source: agy-chop
    where: Features and benefits table, Greater fiber tensile strength and stability at elevated temperatures row
    rating: unknown
  - environment: Ballistic impact, intense fire and repeated pressure cycling in composites
    headline: AGY says composites with S2 keep high performance after these tests. It gives no test values.
    effect: AGY's product page says S2 glass helps composites keep high performance after ballistic impact, intense fire or repeated pressure cycling. The page prints no test data, so these are claims to be verified.
    conditions:
      basis: manufacturer claim; no test values or standard read
    source: agy-s2-page
    where: Second main paragraph
    rating: unknown
  - environment: Water exposure
    headline: The datasheet prints 0.00 % water absorption, with no test method.
    effect: Water absorption is printed as 0.00 % without a test method, time or temperature. Long-term wet ageing of S-2 is therefore not known from the sources read.
    conditions:
      basis: printed value; test method not stated
    source: lookpolymers
    where: Physical Properties table, Water Absorption row
    rating: unknown
risks:
  hazards:
    - text: 'LfU: fibres shorter than 250 µm and thinner than 3 µm can reach the lung. The most critical fibres are longer than 5 µm, thinner than 3 µm and have a length-to-diameter ratio above 3:1 (WHO fibres).'
      ghs: []
      source: lfu-kmf-2018
      where: Section 3, Kritische Fasern 1 and WHO 2 fibres
    - text: LfU's table of fibre types says most textile glass fibres (diameter 5 to 25 µm) are not respirable and are not carcinogenic. The table gives no GHS class for S-2.
      ghs: []
      source: lfu-kmf-2018
      where: Table of fibre types, Textilglasfasern row
  failure_risks:
    - mode: Impact damage in a 2D laminate
      trigger: Impact on a 2D laminate with no through-thickness reinforcement
      consequence: NASA's programme describes the current S-2 hard upper torso as a 2D laminate without through-thickness reinforcement, and tested 3D woven and braided versions for improved impact strength. No S-2 impact value was printed in the source.
      source: nasa-nsmms
      where: Innovation slide
    - mode: Melting and refining defects in production
      trigger: Melting S-2 in refractory-lined furnaces
      consequence: The patent background says S-2 forms excess bubbles and crystallises fast, which it says prevents large-scale production in refractory furnaces, leading to small production scale, low efficiency and high cost.
      source: us11339085
      where: Background section, S-2 glass paragraph
  side_effects: []
  handling:
    - text: 'LfU: small amounts of KMF-containing waste must be packed at once in tear-resistant, dust-tight sacks or big bags, which must be labelled.'
      source: lfu-kmf-2018
      where: Waste section, paragraph under Abb. 7
  mitigations: []
supply:
  - subject: Silica (SiO2, about 65 wt% of S-2)
    abundance: 'USGS: quartz-rich sand and sandstone, the main sources of industrial silica sand, occur throughout the world. 2025 mine production in thousand metric tons as printed: United States 120,000; China 92,000; Netherlands 68,000; world total 430,000 (rounded).'
    producers:
      - country: United States
        share_percent: 27.9
        year: 2025
      - country: China
        share_percent: 21.4
        year: 2025
      - country: Netherlands
        share_percent: 15.8
        year: 2025
    critical_lists: []
    substitutes:
      - 'USGS (Sand and Gravel (Industrial) chapter): the United States was the leading producer of industrial sand and gravel, and the 2025 production of 120,000 thousand tons is an estimate.'
    source: usgs-mcs2026
    where: Sand and Gravel (Industrial) chapter, World Mine Production and Reserves table, 2024 and 2025 columns. Shares calculated by Space Mushroom against the printed world total of 430,000 (rounded); the table unit is thousand metric tons.
  - subject: Magnesium (MgO, about 10 wt% of S-2, from magnesite)
    abundance: 'USGS: magnesite gross weight in thousand tons as printed for 2025: China 12,700; Brazil 1,800; Russia 1,700; Turkey 1,600; world total 21,000 (rounded). USGS also says magnesium can be recovered from seawater and brines, which are not counted in the magnesite table.'
    producers:
      - country: China
        share_percent: 60.5
        year: 2025
      - country: Brazil
        share_percent: 8.6
        year: 2025
      - country: Russia
        share_percent: 8.1
        year: 2025
      - country: Turkey
        share_percent: 7.6
        year: 2025
    critical_lists: []
    substitutes: []
    source: usgs-mcs2026
    where: Magnesium Compounds chapter, World Magnesite Mine Production and Reserves table, 2025 column. Shares calculated by Space Mushroom against the printed world total of 21,000 (rounded); footnote 6 gives the gross weight basis. Magnesium compounds chapter also says China was the leading producer and principal source of magnesia and magnesite imports to the United States.
media: []
uses:
  - application: structures
    device: Helicopter blades
    example: The patent background says S-2 glass is used in helicopter blades, armour and windings for high-pressure tanks, such as scuba tanks.
    source: us8252707
    where: Background section, S-2 glass paragraph
  - application: habitats-and-suits
    device: Composite hard upper torso (CHUT) of the xEMU spacesuit
    example: NASA's NSMMS presentation says the current CHUT is a 2D laminate of S-2 glass with an epoxy resin matrix, without through-thickness reinforcement.
    source: nasa-nsmms
    where: Innovation slide, first bullet
  - application: propulsion-and-tanks
    device: Filament-wound rocket motor casings, aircraft fuel tanks and commercial pressure vessels
    example: AGY says S2 Glass gives improved strength for fabrics, prepregs and laminates, such as filament-wound structures like rocket motor casings, aircraft fuel tanks and commercial pressure vessels.
    source: agy-s2-page
    where: Second main paragraph
  - application: structures
    device: Radar-transparent composite parts
    example: AGY's chop brochure lists radar transparency as a benefit of a lower dielectric constant than E Glass fibres. The brochure states the reduction as a percentage, which is recorded under gaps.
    source: agy-chop
    where: Features and benefits table, dielectric constant row
documents:
  - title: AGY ZenTron S-2 Generic S-Glass Fiber datasheet (lookpolymers.com)
    type: datasheet
    url: https://www.lookpolymers.com/polymer_AGY-ZenTron-S-2-Generic-S-Glass-Fiber.php
  - title: AGY S2 Glass Chop product information
    type: datasheet
    url: https://www.agy.com/wp-content/uploads/2025/02/AGY_Chop_SS_v7.pdf
  - title: US 8,252,707 B2, Composition for high performance glass fibers and fibers formed therewith
    type: report
    url: https://patents.google.com/patent/US8252707
  - title: US 11,339,085 B2, Glass fiber composition, glass fiber and composite material thereof
    type: report
    url: https://patents.google.com/patent/US11339085
  - title: 3D Reinforced Composites for Improved Impact Resistance in Spacesuits (NASA NSMMS, NTRS 20260004015)
    type: report
    url: https://ntrs.nasa.gov/api/citations/20260004015/downloads/Higginson_NSMMS_DistroA-RevA.pdf
  - title: Mineral Commodity Summaries 2026 (USGS), full report
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026.pdf
  - title: 'UmweltWissen: Künstliche Mineralfasern (Bayerisches Landesamt für Umwelt, 2018)'
    type: report
    url: https://www.lfu.bayern.de/buerger/doc/uw_32_kuenstliche_mineralfasern.pdf
  - title: Glass fiber (Wikipedia)
    type: report
    url: https://en.wikipedia.org/wiki/Glass_fiber
gaps:
  - 'Not found in any source read: an S-2 safety data sheet, a GHS classification, or an OSHA or IARC entry for S-2 glass. The hazard text is LfU guidance on fibres in general.'
  - 'Corrosion and ageing: no numeric S-2 corrosion rate, acid or alkali test, or moisture-ageing test was printed in the sources read. The corrosion entries are qualitative manufacturer or datasheet statements.'
  - 'Failure, side effects and mitigations: only NASA and patent statements were found, and no source gives a severity rating, so the severity field reads not rated in source.'
  - 'Radar and radome performance: AGY claims radar transparency, but no radome test was read. A university record on NASA radome coupons (KU ScholarWorks) returned HTTP 403 and was not read.'
  - 'Composition limits: the 65, 25 and 10 wt% figures are typical values quoted in a patent background, not an AGY specification with tolerances.'
  - 'Designations: no ASTM D578, ISO, EN or UNS code for S-2 was printed on a page read. The patent cites ASTM D578-05 as the S-glass family definition, not as a grade code, so it is not listed as a designation.'
  - 'Form and test conditions: the lookpolymers datasheet does not say whether its values are for a filament, strand, roving or chop. The 9 micron filament diameter on the AGY chop brochure belongs to the chop product and is not stored as a glass property.'
  - 'Manufacturer comparison claims with E-glass, kept as claims and not as values: AGY''s product page says 15% higher strength in impregnated strand tensile and 25% greater modulus than conventional glass fibre. AGY''s chop brochure says 30% higher strength and 15% higher tensile modulus than E Glass at the same fibre volume fraction, 34% stiffer than conventional glass fiber, and a 20% reduction in dielectric constant over E Glass fibers.'
  - 'Non-canonical property names used: softening_point, annealing_point, strain_point, liquidus_temperature and forming_temperature, because spores/property-canon.yaml has no entry for them.'
  - 'Melting point: the datasheet (1466 °C) and the patent background (up to over 1600° C) differ. Both are listed; the true figure is not settled by the sources read.'
  - Tensile strength of 4890 MPa appears on one datasheet only (lookpolymers). Neither AGY document read prints an absolute S-2 glass strength.
  - 'Supply: silica sand and magnesite are covered from the USGS 2025 data. Alumina (Al2O3) supply was not written, and the critical-mineral status of silica sand and magnesite was not checked in this run.'
  - 'Environments: NASA''s solicitation names Martian and lunar surface EVA suits as the target, but no S-2 test in a lunar or Martian environment was read, so the environments tag is empty. No vacuum or space-radiation data for S-2 was found.'
  - 'Media: none. No licensed S-2 image was checked.'
  - Wikipedia (Glass fiber) is cited for the S-glass definition only. Its property tables were not used.
  - The AGY S-2 glass datasheet with the full table was not found in this run. The lookpolymers page is a reseller copy of AGY data.
license: CC-BY-4.0
updated: '2026-11-01'
sources:
  lookpolymers:
    title: AGY ZenTron S-2 Generic S-Glass Fiber datasheet (lookpolymers.com)
    id: lookpolymers, polymer_AGY-ZenTron-S-2-Generic-S-Glass-Fiber
    url: https://www.lookpolymers.com/polymer_AGY-ZenTron-S-2-Generic-S-Glass-Fiber.php
    kind: datasheet
    license: datasheet page, cited not reproduced
  agy-chop:
    title: AGY S2 Glass Chop product information (AGY, 2024 copyright)
    id: AGY_Chop_SS_v7.pdf
    url: https://www.agy.com/wp-content/uploads/2025/02/AGY_Chop_SS_v7.pdf
    kind: datasheet
    license: manufacturer document, cited not reproduced
  agy-s2-page:
    title: S-2 Glass Fibers for Composite Materials (AGY web page)
    id: AGY S2 Glass web page
    url: https://www.agy.com/s2-glass/
    kind: web
    license: manufacturer web page, cited not reproduced
  us8252707:
    title: US 8,252,707 B2, Composition for high performance glass fibers and fibers formed therewith (background section)
    id: US 8,252,707 B2
    url: https://patents.google.com/patent/US8252707
    kind: report
    license: patent document
  us11339085:
    title: US 11,339,085 B2, Glass fiber composition, glass fiber and composite material thereof (background section)
    id: US 11,339,085 B2
    url: https://patents.google.com/patent/US11339085
    kind: report
    license: patent document
  nasa-nsmms:
    title: 3D Reinforced Composites for Improved Impact Resistance in Spacesuits (NASA NSMMS, NTRS 20260004015)
    id: NTRS 20260004015
    url: https://ntrs.nasa.gov/api/citations/20260004015/downloads/Higginson_NSMMS_DistroA-RevA.pdf
    kind: report
    license: NASA public release, distribution statement A
  usgs-mcs2026:
    title: Mineral Commodity Summaries 2026 (USGS), full report
    id: USGS MCS 2026, full report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026.pdf
    kind: report
    license: US government work, public domain
  lfu-kmf-2018:
    title: 'UmweltWissen: Künstliche Mineralfasern (Bayerisches Landesamt für Umwelt, 2018)'
    id: LfU Bayern, UmweltWissen Abfall, 2018
    url: https://www.lfu.bayern.de/buerger/doc/uw_32_kuenstliche_mineralfasern.pdf
    kind: report
    license: Bavarian state publication, cited not reproduced
review:
  status: draft
  method: assistant
  checked_values: 30
  unreachable: 1
  caveats: 4
  note: Written by an AI assistant on 2026-11-01 from the lookpolymers datasheet, the AGY chop brochure and AGY web page, two US patent background sections, NASA NSMMS (NTRS 20260004015), USGS MCS 2026 (industrial sand and magnesite), the Bavarian LfU (2018) and Wikipedia for the S-glass definition only. The KU ScholarWorks radome record returned HTTP 403 and was not read. No S-2 safety data sheet was read.
story:
  recipe:
    line: S-2 glass is a magnesium aluminosilicate glass. The patent background describes it as about 65% SiO2, 25% Al2O3 and 10% MgO, so silica and alumina together make up about 90%. A second patent says S-2 is hard to melt and refine, gives a melting temperature of up to over 1600° C and crystallises fast.
    parts:
      - name: Silica
        symbol: SiO2
        share_note: about 65% by weight (patent background)
        role: Main network former of the glass. Silica and alumina together make up about 90% by weight.
        source: us8252707
        where: Background section, S-2 glass paragraph
      - name: Alumina
        symbol: Al2O3
        share_note: about 25% by weight (patent background)
        role: Second oxide of the aluminosilicate network, with silica.
        source: us8252707
        where: Background section, S-2 glass paragraph
      - name: Magnesia
        symbol: MgO
        share_note: about 10% by weight (patent background)
        role: Gives S-glass its high MgO content. DIN 1259-1, as quoted in the patent, defines S-glass with about 10% MgO and no added CaO.
        source: us8252707
        where: Background section, S-glass definition paragraph
  risk_groups:
    - title: For people
      level: 1
      verdict: Respirable fibres are the concern. Most textile glass…
      lead: No S-2 safety data sheet or GHS entry was read in this run. The hazard text below is Bavarian LfU guidance on artificial mineral fibres in general.
      points:
        - label: Fibre size
          line: 'LfU: fibres shorter than 250 µm and thinner than 3 µm can reach the lung. The most critical fibres are longer than 5 µm, thinner than 3 µm and have a length-to-diameter ratio above 3:1.'
        - label: Textile glass fibres
          line: LfU's table of fibre types says most textile glass fibres (diameter 5 to 25 µm) are not respirable and are not carcinogenic. This is general guidance, not an S-2 test.
        - label: Waste
          line: 'LfU: even small amounts of KMF-containing waste must go at once into tear-resistant, dust-tight big bags, which must be labelled.'
  why: S-2 glass is a high-strength glass fibre of the S-glass family. Wikipedia describes S-glass as an aluminosilicate glass without CaO and with high MgO, used "when high tensile strength (modulus) is important". AGY sells S-2 as S2 Glass in yarn, chop and roving forms. The datasheet gives a tensile strength of 4890 MPa at 23.0 °C and a modulus of 86.9 GPa. A patent background quotes 89 to 90 GPa for the same glass, so the stiffness figure needs a test to settle it.
  uses:
    - where: Helicopter blades and pressure tanks
      line: The patent background says S-2 glass is used in helicopter blades, armour and windings for high-pressure tanks, such as scuba tanks.
    - where: Spacesuit hard upper torso
      line: NASA's NSMMS work describes the current composite hard upper torso as a 2D laminate of S-2 glass with an epoxy matrix. The programme compared 3D woven and braided versions to improve impact strength and reduce mass.
    - where: Rocket motor casings, fuel tanks and pressure vessels
      line: AGY lists filament-wound rocket motor casings, aircraft fuel tanks and commercial pressure vessels among the laminate uses of S2 Glass.
  can_do:
    - label: Tensile strength
      benchmark: ultimate_tensile_strength
      value: 4890 MPa at 23.0 °C
      line: The datasheet prints 4890 MPa at 23.0 °C and 4445 MPa at 371 °C. It gives no test method, and no second source for the 4890 MPa value was read.
    - label: Stiffness
      benchmark: elastic_modulus
      value: 86.9 GPa
      line: The datasheet prints 86.9 GPa. A patent background quotes 89 to 90 GPa for S-2 glass. The two sources disagree, and no S-2 modulus test was read in this run.
    - label: Elongation
      benchmark: elongation
      value: 5.7 %
      line: Elongation at break is 5.7 % on the datasheet, printed with the note in 50 mm.
    - label: Heat tolerance
      benchmark: softening_point
      value: 1056 °C
      line: The datasheet and AGY's chop brochure both print a softening point of 1056 °C. The brochure adds an annealing point of 816 °C and a strain point of 766 °C.
    - label: Dielectric constant
      benchmark: dielectric_constant
      value: 5.2 at 1e+10 Hz
      line: The datasheet prints a dielectric constant of 5.2 at 1e+10 Hz and 5.3 at 1e+6 Hz. AGY links its lower dielectric constant to radar transparency.
  compare: E-glass is the common reinforcement that S-2 is measured against. This profile holds no E-glass value of its own, so the comparison rests on AGY's manufacturer claims. AGY's chop brochure claims 30% higher strength and 15% higher tensile modulus than E Glass at the same fibre volume fraction, and its product page claims 15% higher strength in impregnated strand tensile and 25% greater modulus than conventional glass fibre. These are the maker's own comparisons, not independent tests. The E-glass profile in this collection gives its own values.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Tensile strength
      benchmark: ultimate_tensile_strength
    - label: Young's modulus
      benchmark: elastic_modulus
  handling:
    - Pack small amounts of KMF-containing waste at once in tear-resistant, dust-tight big bags, labelled, as LfU advises for artificial mineral fibres.
    - No S-2 rule on cutting, dust or storage was found in the datasheets read. AGY's brochure lists long shelf life and good machinability as benefits.
  good_for:
    - Composite parts that must carry high tensile load and resist impact, for example helicopter blades and filament-wound pressure vessels, as named by the patent background and AGY.
    - Spacesuit shell parts, where NASA's programme set out to improve the impact strength of the hard upper torso.
  watch_out:
    - 'Stiffness disagrees between sources: 86.9 GPa on the datasheet against 89 to 90 GPa in a patent background.'
    - 'Melting point disagrees too: 1466 °C on the datasheet against up to over 1600° C in a patent background.'
    - The 4890 MPa tensile value comes from one datasheet. The AGY documents read here print gains over E-glass, not an absolute glass strength.
    - Melting and refining are hard. The patent background says S-2 forms bubbles and crystallises fast, which it blames for small production scale, low efficiency and high cost.
    - Corrosion data are qualitative only. The datasheet says acid resistant with moderate alkali resistance, and gives no numbers.
  verdict: S-2 glass is a high-strength magnesium aluminosilicate fibre, with a datasheet tensile strength of 4890 MPa at 23.0 °C and a softening point of 1056 °C. Two figures, stiffness and melting point, disagree between the datasheet and the patent background, and the corrosion, failure and radome performance data are still open.