spore: profile
id: momentive-rtv-566
spore_version: 0.2
family: silicone
name: Momentive RTV566 low-outgassing silicone
abbreviation: RTV566
role: low-outgassing two-part room-temperature-cure silicone for bonding, potting and thermal insulation
category: seals-adhesives
type: potting-compounds
summary: |
  Momentive RTV566 is a red, two-part, room-temperature-cure silicone rubber sold for low-outgassing use in vacuum. Momentive's datasheet gives a continuous service range of -115 °C to 260 °C, with short periods up to 316 °C, and a total mass loss of 0.14 % and a volatile condensable material of 0.02 % in the ASTM E595 test (cured 7 days at 25 °C and 50 % R.H.). NASA's outgassing compilation (RP-1124 Rev. 3) lists 18 RTV 566 records, with total mass loss of 0.08 % to 0.13 % for the six records at 0.1 % catalyst.
best_for: Low-outgassing bonding, potting and thermal insulation of vacuum hardware that runs between -115 °C and 260 °C continuously
weakest_at: 'Strength and cure speed: tensile strength of 56 kg/cm2 (800 psi) and Shore A 61 when cured 7 days at 25 °C, and a primer is needed to bond non-silicone surfaces'
identity:
  formula: 'Two-part room-temperature-vulcanising silicone rubber: RTV566A base compound and RTV566B curing agent. The datasheet does not print the polymer or filler chemistry.'
  source: rtv566-tds
  where: Description; Typical Physical Properties (uncured table, RTV566A and RTV566B columns)
tags:
  environments: []
  stresses:
    - vacuum-and-outgassing
    - extreme-cold
    - extreme-heat
  applications:
    - heat-shields
    - thermal-control
    - electronics-and-chips
    - solar-arrays
properties:
  - benchmark: max_service_temp
    label: Continuous maximum service temperature
    value: 260
    unit: °C
    scope: material
    conditions:
      state: cured RTV566
      basis: continuous use, printed as 260 °C (500 °F)
    method: Continuous service limit printed in the datasheet key features
    status: ground
    source: rtv566-tds
    where: Key Features and Benefits, last bullet
  - benchmark: max_service_temp
    label: Short-period maximum temperature
    value: 316
    unit: °C
    scope: material
    conditions:
      state: cured RTV566
      basis: printed as 316 °C (600 °F) for short periods of time; the period is not defined in the datasheet
    method: Short-period limit printed in the datasheet key features
    status: ground
    source: rtv566-tds
    where: Key Features and Benefits, last bullet
  - benchmark: min_service_temp
    label: Continuous minimum service temperature
    value: -115
    unit: °C
    scope: material
    conditions:
      state: cured RTV566
      basis: continuous use, printed as -115 °C (-175 °F)
    method: Low-temperature limit printed in the datasheet key features
    status: ground
    note: Momentive's aerospace page prints -130 °C (-200 °F) to 260 °C (500 °F) as the range for its low-outgassing silicones in general, not for RTV566 specifically. The two low-temperature figures are not reconciled.
    source: rtv566-tds
    where: Key Features and Benefits, last bullet
  - benchmark: specific_gravity
    label: Specific gravity of the RTV566A base
    value: 1.49
    unit: '-'
    scope: material
    conditions:
      state: RTV566A base compound, uncured
      temperature: not printed
    method: Printed as specific gravity of the uncured base component
    status: ground
    note: The curing agent RTV566B has a specific gravity of 1.15 in the same table.
    source: rtv566-tds
    where: Typical Uncured Properties table, Specific Gravity row
  - benchmark: viscosity
    label: Viscosity of the RTV566A base
    value: 42700
    unit: cps
    scope: material
    conditions:
      state: RTV566A base compound, uncured
      temperature: not printed
    method: Printed as viscosity of the uncured base component
    status: ground
    source: rtv566-tds
    where: Typical Uncured Properties table, Viscosity row
  - benchmark: shore_a_hardness
    label: Shore A hardness
    value: 61
    unit: Shore A
    scope: material
    conditions:
      state: cured 7 days at 25 °C and 50 % R.H.
      test: Shore A durometer as printed
    method: Printed in the typical cured properties table
    status: ground
    source: rtv566-tds
    where: Typical Cured Properties table, Hardness row
  - benchmark: ultimate_tensile_strength
    label: Tensile strength
    value: 56
    unit: kg/cm2
    scope: material
    conditions:
      state: cured 7 days at 25 °C and 50 % R.H.
      printed_as: 56 kg/cm2 (800 psi)
    method: Printed in the typical cured properties table
    status: ground
    source: rtv566-tds
    where: Typical Cured Properties table, Tensile Strength row
  - benchmark: elongation
    label: Elongation
    value: 120
    unit: '%'
    scope: material
    conditions:
      state: cured 7 days at 25 °C and 50 % R.H.
    method: Printed in the typical cured properties table
    status: ground
    source: rtv566-tds
    where: Typical Cured Properties table, Elongation row
  - benchmark: lap_shear_strength
    label: Lap shear strength on primed aluminium
    value: 33
    unit: kg/cm2
    scope: material
    conditions:
      substrate: primed aluminium (the primer is not named in the table)
      state: cured 7 days at 25 °C and 50 % R.H.
      printed_as: 33 kg/cm2 (465 psi)
    method: Printed in the typical cured properties table, lap shear on primed Al
    status: ground
    source: rtv566-tds
    where: Typical Cured Properties table, Lap Shear Strength row
  - benchmark: total_mass_loss
    label: Total mass loss, Momentive datasheet
    value: 0.14
    unit: '%'
    scope: material
    conditions:
      test: ASTM E595, as stated in the table footnote
      state: cured 7 days at 25 °C and 50 % R.H.
    method: Printed in the typical cured properties table with an ASTM E595 footnote
    status: ground
    source: rtv566-tds
    where: Typical Cured Properties table, Total Weight Loss row
  - benchmark: volatile_condensable_material
    label: Volatile condensable material, Momentive datasheet
    value: 0.02
    unit: '%'
    scope: material
    conditions:
      test: ASTM E595, as stated in the table footnote
      state: cured 7 days at 25 °C and 50 % R.H.
    method: Printed in the typical cured properties table with an ASTM E595 footnote
    status: ground
    source: rtv566-tds
    where: Typical Cured Properties table, Volatile Condensable Material row
  - benchmark: total_mass_loss
    label: Total mass loss, NASA records at 0.1 % catalyst (range)
    value: 0.08
    value_high: 0.13
    bound: range
    unit: '%'
    scope: material
    conditions:
      catalyst: 0.1 % by weight curing agent (BW CAT)
      cure: 7 days at 25 °C in air
      test: ASTM E595 as tabulated by NASA
      records: 'six records: GSFC6230, GSC12835, GSFC6503, GSCI0862, GSCI0865, GSCI0868'
    method: Range across the six RTV 566 records at 0.1 % catalyst, read from the table. The 0.3 % and 0.7 % catalyst records (0.34 % and 0.36 % total mass loss) and the primer sandwich records are excluded.
    status: ground
    source: nasa-rp1124
    where: Section 1 (Adhesives), RTV 566 rows at 0.1 % BW CAT
  - benchmark: volatile_condensable_material
    label: Volatile condensable material, NASA records at 0.1 % catalyst (range)
    value: 0
    value_high: 0.02
    bound: range
    unit: '%'
    scope: material
    conditions:
      catalyst: 0.1 % by weight curing agent (BW CAT)
      cure: 7 days at 25 °C in air
      test: ASTM E595 as tabulated by NASA
      records: 'six records: GSFC6230, GSC12835, GSFC6503, GSCI0862, GSCI0865, GSCI0868'
    method: Range across the same six NASA records at 0.1 % catalyst, read from the table
    status: ground
    source: nasa-rp1124
    where: Section 1 (Adhesives), RTV 566 rows at 0.1 % BW CAT
  - benchmark: water_vapor_regained
    label: Water vapour regained, NASA records at 0.1 % catalyst (range)
    value: 0.02
    value_high: 0.05
    bound: range
    unit: '%'
    scope: material
    conditions:
      catalyst: 0.1 % by weight curing agent (BW CAT)
      cure: 7 days at 25 °C in air
      test: as tabulated by NASA
      records: 'six records: GSFC6230, GSC12835, GSFC6503, GSCI0862, GSCI0865, GSCI0868'
    method: Range across the same six NASA records at 0.1 % catalyst, read from the table
    status: ground
    source: nasa-rp1124
    where: Section 1 (Adhesives), RTV 566 rows at 0.1 % BW CAT
  - benchmark: work_life
    label: Work life of the catalysed mix
    value: 1.5
    unit: hrs
    scope: material
    conditions:
      mix: 100 parts RTV566A to 0.1 part RTV566B by weight
      basis: printed under typical catalysed properties
    method: Printed in the typical catalysed properties table
    status: ground
    source: rtv566-tds
    where: Typical Catalyzed Properties table, Work Life row
  - benchmark: tack_free_time
    label: Tack-free time of the catalysed mix
    value: 2.2
    unit: hrs
    scope: material
    conditions:
      mix: 100 parts RTV566A to 0.1 part RTV566B by weight
      basis: printed under typical catalysed properties
    method: Printed in the typical catalysed properties table
    status: ground
    source: rtv566-tds
    where: Typical Catalyzed Properties table, Tack Free Time row
  - benchmark: application_rate
    label: Application rate through a 0.125 in orifice
    value: 180
    unit: gm/min
    scope: material
    conditions:
      measured: 45 minutes after mixing, 0.125 in orifice at 90 psi
      mix: 100 parts RTV566A to 0.1 part RTV566B by weight
    method: Printed in the typical catalysed properties table
    status: ground
    source: rtv566-tds
    where: Typical Catalyzed Properties table, Application Rate row
  - benchmark: outgassing_screening_limit
    label: NASA listing limit for total mass loss and CVCM (a criterion, not an RTV566 measurement)
    value: 1
    unit: '%'
    scope: material
    conditions:
      basis: NASA lists only materials with a total mass loss of 1.0 percent or less and a CVCM of 0.10 percent or less
    method: Criterion stated in the NASA introduction; not a measured value for RTV566
    status: ground
    source: nasa-rp1124
    where: Introduction (selection criteria) and Section C heading
  - benchmark: flash_point
    label: Flash point of the Part A base compound (SDS)
    value: 125
    unit: °C
    scope: material
    conditions:
      state: RTV566 Part A, liquid base component, as printed in the SDS
      test: Pensky-Martens closed cup, as printed
    method: Printed in the safety data sheet physical and chemical properties section
    status: ground
    source: sds-rtv566-32
    where: Section 9, Physical and chemical properties, Flash Point row
corrosion:
  - environment: Heated in air above 150 °C
    headline: Oxidative degradation above 150 °C in air forms small amounts of formaldehyde, per the Part A SDS.
    effect: Measurements above 150 °C in air found that small amounts of formaldehyde form through oxidative degradation. The SDS gives no amount, time or rate.
    conditions:
      temperature: above 150 °C
      atmosphere: air (oxygen)
      basis: SDS statement; no time, amount or rate is printed
    source: sds-rtv566-32
    where: Section 10, Stability and reactivity, Hazardous Decomposition Products
    rating: unknown
risks:
  hazards:
    - text: Momentive's SDS for RTV566 Part A (version 3.2, revised 02/20/2025) gives the product as not classified under 29 CFR 1910.1200, with no signal word, no hazard symbol and no hazard statement. Hazard(s) not otherwise classified is None.
      ghs: []
      source: sds-rtv566-32
      where: Section 2, Hazard(s) identification
    - text: A second copy of the Part A SDS (version 3.1, revised 08/30/2023) gives the same not-classified status and the same 125 °C flash point.
      ghs: []
      source: sds-rtv566-31
      where: Section 2, Hazard Classification; Section 9, Flash Point
    - text: The same Part A SDS lists the product as not classified for acute oral, dermal or inhalation toxicity, and gives no data for skin or eye irritation, sensitisation, carcinogenicity or mutagenicity.
      ghs: []
      source: sds-rtv566-32
      where: Section 11, Toxicological information
    - text: 'Part A ingredients per the SDS, all by weight: red iron oxide (CAS 1309-37-1) 20 to under 50 %, kieselguhr, soda ash flux-calcined (CAS 68855-54-9) 10 to under 20 %, and silicic acid, ethyl ester (CAS 11099-06-2) 1 to under 5 %. The SDS notes workplace exposure limits for red iron oxide and kieselguhr.'
      ghs: []
      source: sds-rtv566-32
      where: Section 3, Composition/information on ingredients; Section 8, Exposure controls
    - text: PubChem's GHS summary for silicic acid, ethyl ester (CID 9877350, CAS 11099-06-2) lists H226 flammable liquid and vapour (75.1% of notifications), H302 harmful if swallowed (16.7%), H319 causes serious eye irritation (70%), H332 harmful if inhaled (10.5%), H335 may cause respiratory irritation (27.2%) and H411 toxic to aquatic life with long lasting effects (47.1%). PubChem also notes that 24.9% (64 of 257) of reports do not meet GHS hazard criteria. These are notifications for the single ingredient, not a classification of the Part A product.
      ghs:
        - H226
        - H302
        - H319
        - H332
        - H335
        - H411
      source: pubchem-ethyl-silicate
      where: Safety and Hazards, GHS Classification (CID 9877350)
  failure_risks:
    - mode: Voids in the cured product from entrapped air
      trigger: Mixing or pouring without deaeration
      consequence: Air bubbles stay in the cured part. The datasheet calls for a vacuum of 25 mm (29 inches) of mercury minimum, and says deaeration after pouring may be needed in complex potted assemblies.
      severity: low
      source: rtv566-tds
      where: Processing Recommendations, Deaeration
    - mode: Poor adhesion to non-silicone surfaces
      trigger: Bonding without a primer
      consequence: The datasheet says RTV566 requires a primer to bond to non-silicone surfaces; it names SS4155 silicone primer.
      severity: moderate
      source: rtv566-tds
      where: Processing Recommendations, Bonding
  side_effects:
    - text: Hanrahan and Ianno (2014) analysed RTV566 among five spacecraft RTV silicones by Raman and FTIR spectroscopy. They report that the outgassing products of each material are polydimethylsiloxane (PDMS) and tetra-n-propylsilicate (NPS).
      affects: Nearby optical surfaces, where the paper addresses photofixed films from outgassing
      source: unl-rtv-composition
      where: Abstract
  handling:
    - text: Mix 100 parts RTV566A with 0.1 part RTV566B curing agent by weight, in a container 4 to 5 times larger than the volume of the compound. Scrape the sides and bottom so the mix is homogeneous, and avoid high mixer speeds that entrap air or overheat the mix.
      source: rtv566-tds
      where: Processing Recommendations, Mixing
    - text: Deaerate the mixed compound under a vacuum of 25 mm (29 inches) of mercury minimum until the bubbles break and the compound settles back.
      source: rtv566-tds
      where: Processing Recommendations, Deaeration
    - text: The compound cures enough for gentle handling after 24 hours at 25 °C and 50 % R.H. For best outgassing and adhesion, cure for 7 days at the same conditions.
      source: rtv566-tds
      where: Processing Recommendations, Curing
    - text: 'For service above 150 °C (302 °F), condition the cured part first: 8 hours at 100 °C, then an extra 8 hours at each 28 °C (80 °F) step up to the service temperature. Larger or deeper parts need longer at each step.'
      source: rtv566-tds
      where: Processing Recommendations, Curing (conditioning paragraph)
    - text: 'Part A SDS handling advice: do not taste or swallow, avoid contact with eyes, skin and clothing, wash hands after handling, keep the container closed, and keep away from sources of ignition.'
      source: sds-rtv566-32
      where: Section 7, Handling and storage
  mitigations:
    - text: Clean non-silicone substrates with naphtha or methyl ethyl ketone (MEK) and let them dry. Apply a uniform thin film of SS4155 primer, air dry it for one hour or more until a uniform chalky white haze shows, then apply freshly mixed RTV566.
      source: rtv566-tds
      where: Processing Recommendations, Bonding
uses:
  - application: heat-shields
    device: Cast-in-place heat shielding
    example: Momentive lists cast-in-place heat shielding among the potential applications of RTV 566 Paste. The page names no mission or flight.
    source: momentive-aero-page
    where: Key Features, RTV 566 Paste
  - application: thermal-control
    device: Cast-in-place thermal insulation
    example: Momentive lists thermal insulation among the potential applications of RTV 566 Paste.
    source: momentive-aero-page
    where: Key Features, RTV 566 Paste
  - application: electronics-and-chips
    device: Potting and encapsulation of electrical assemblies
    example: Momentive lists potting and encapsulating electrical assemblies as potential uses. The datasheet adds that deaeration may be needed after pouring in complex assemblies.
    source: momentive-aero-page
    where: Key Features, RTV 566 Paste; datasheet Processing Recommendations, Deaeration
  - application: solar-arrays
    device: Photovoltaic module assembly
    example: Momentive lists assembly of photovoltaic (PV) modules as a potential application of RTV 566 Paste.
    source: momentive-aero-page
    where: Key Features, RTV 566 Paste
  - application: electronics-and-chips
    device: Adhesive and potting records in NASA's outgassing list
    example: NASA RP-1124 Rev. 3 lists 18 RTV 566 records, of which 15 are labelled ADHESIVE, 2 POTTING-ADH and 1 POTTING. The list gives outgassing test results for each record, not flight results.
    source: nasa-rp1124
    where: Section 1 (Adhesives), RTV 566 rows
supply:
  - subject: Silicon (silicon metal, the feedstock for silicone polymers)
    abundance: 'USGS: world and domestic resources for making silicon metal are abundant, and the source of the silicon is silica in natural forms such as quartzite.'
    producers:
      - country: China
        share_percent: 87
        year: 2025
      - country: Brazil
        share_percent: 3.9
        year: 2025
      - country: Norway
        share_percent: 2.8
        year: 2025
      - country: France
        share_percent: 1.5
        year: 2025
    critical_lists:
      - list: USGS 2025 Final List of Critical Minerals (silicon added in the 2025 list)
        listed: true
    recycling: 'USGS: recycling of silicon is insignificant.'
    substitutes:
      - 'USGS: gallium arsenide and germanium are the principal substitutes for silicon in semiconductor and infrared applications; the chapter does not discuss silicone feedstock.'
    source: usgs-mcs2026-silicon
    where: 'World Production table, silicon metal, 2025 (world total 4,600 thousand t of silicon content; shares calculated by Space Mushroom from the printed figures: China 4,000, Brazil 180, Norway 130, France 68); Domestic Production and Use (silicones named as a main consumer); Recycling; Substitutes; Events, Trends, and Issues (critical list)'
media: []
documents:
  - title: RTV566 Technical Data Sheet, Momentive Performance Materials (HCD-RTV566, Rev. 2021-05-05), copy hosted by chemical-concepts.com
    type: datasheet
    url: https://www.chemical-concepts.com/wp-content/uploads/2022/12/RTV566-TDS.pdf
    year: 2021
  - title: Outgassing Data for Selecting Spacecraft Materials, NASA Reference Publication 1124 Revision 3
    type: report
    url: https://ntrs.nasa.gov/api/citations/19940017416/downloads/19940017416.pdf
    year: 1993
  - title: Momentive Performance Materials RTV566 Safety Data Sheet, version 3.2 (revised 02/20/2025), Part A, copy hosted by blacksky.com
    type: sds
    url: https://blacksky.com/wp-content/uploads/2026/02/MomentivePerformance_RTV566-Dimethyl-Diphenyl_2025-02.pdf
    year: 2025
  - title: Momentive Performance Materials RTV566 Safety Data Sheet, version 3.1 (revised 08/30/2023), Part A, copy hosted by a BigCommerce product file
    type: sds
    url: https://cdn11.bigcommerce.com/s-jifykode7m/product_images/uploaded_images/msds/SGP210218.pdf
    year: 2023
  - title: Mineral Commodity Summaries 2026, Silicon (USGS, February 2026)
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-silicon.pdf
    year: 2026
  - title: 'PubChem: Silicic acid, ethyl ester (CID 9877350), GHS classification summary'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/9877350
    year: 2026
  - title: Relationship between photofixed condensate, effluent and bulk composition of several common RTV materials (Hanrahan and Ianno, Journal of Spacecraft and Rockets 51:3, April 2014)
    type: paper
    url: https://digitalcommons.unl.edu/electricalengineeringfacpub/541
    year: 2014
gaps:
  - Part A (base compound) is the only RTV566 part with a safety data sheet read here, and both copies are third-party hosted (version 3.2 and version 3.1). No safety data sheet for the curing agent RTV566B was read, Momentive's own SDS library was not checked, and no GHS label is printed for the product.
  - The silicone polymer is named only in the 2014 Raman and FTIR study (polydimethylsiloxane, silicic acid, tetraethyl orthosilicate and others, found in all five RTV silicones tested). The study gives no quantities for RTV566, and no CAS number was read for the RTV566 product itself; the CAS numbers in the record belong to Part A ingredients.
  - The supply rows are for silicon metal, the feedstock the USGS names for silicones. No producer, capacity or supply data for Momentive's own RTV566 were read.
  - No UV, humidity, radiation or atomic-oxygen result for RTV566 was found. The only degradation statement is the SDS note on oxidation above 150 °C in air, which gives no amount or time. The NASA table gives outgassing only.
  - No flight result, thermal-vacuum result or space environment test beyond ASTM E595 outgassing was read. Momentive's aerospace page names crew capsules and satellites for the low-outgassing line in general, not for RTV566, so no environment tags are set.
  - Low-temperature limit is -115 °C in the datasheet and -130 °C on the Momentive page (for the product line in general). The two are not reconciled.
  - The NASA table has 18 RTV 566 records, not dozens. Ranges use only the six clean records at 0.1 % catalyst; OCR-damaged values (for example 0.ii and 0 O2) and the 0.3 %, 0.7 % and lot ED221 records were not used as RTV566 values.
  - The datasheet's 0.14 % total mass loss and 0.02 % VCM are a single set of values and are not matched to a NASA record; no lot number is printed for them.
  - The primer used for the lap shear result is not named in the datasheet table.
  - Viscosity, Shore A hardness, work life, tack-free time, application rate and the outgassing screening limit are not in property-canon.yaml. They use the snake_case names above, and outgassing_screening_limit is a new name.
  - The sources now cover the datasheet, the Momentive aerospace page, NASA RP-1124, two Part A SDS copies, USGS silicon, PubChem and the 2014 study. The two SDS copies are third-party hosted copies, not Momentive's own library, and no ESA paper on RTV566 was found.
license: CC-BY-4.0
updated: '2026-11-02'
review:
  status: draft
  method: assistant
  checked_values: 19
  unreachable: 0
  caveats: 3
  note: Written by an AI assistant on 2026-11-01 from three sources and deepened on 2026-11-02 with two Part A safety data sheets, USGS Mineral Commodity Summaries 2026 (silicon), PubChem GHS data and a 2014 Raman and FTIR study. Values are copied as printed. The Momentive datasheet and the NASA table are unchanged.
sources:
  rtv566-tds:
    title: RTV566 Technical Data Sheet (HCD-RTV566, Rev. 2021-05-05), Momentive Performance Materials
    id: HCD-RTV566 (Rev. 2021-05-05); copy hosted by chemical-concepts.com
    url: https://www.chemical-concepts.com/wp-content/uploads/2022/12/RTV566-TDS.pdf
    year: 2021
    kind: datasheet
    license: manufacturer datasheet, cited and not reproduced
  momentive-aero-page:
    title: Low Outgassing Silicones, Momentive Performance Materials aerospace page
    id: undated web page, read 2026-11-01
    url: https://www.momentive.com/en-us/industry/aerospace-aviation-defense/aerospace/low-outgassing-silicones
    year: 2026
    kind: web
    license: manufacturer web page, cited and not reproduced
  nasa-rp1124:
    title: Outgassing Data for Selecting Spacecraft Materials, NASA Reference Publication 1124, Revision 3 (Campbell and Scialdone, Goddard Space Flight Center)
    id: NASA RP-1124 Rev. 3; NTRS 19940017416
    url: https://ntrs.nasa.gov/api/citations/19940017416/downloads/19940017416.pdf
    year: 1993
    kind: report
    license: public domain (NASA)
  sds-rtv566-32:
    title: Momentive Performance Materials RTV566 Safety Data Sheet, version 3.2 (revised 02/20/2025), Part A, copy hosted by blacksky.com
    id: SDS_US, version 3.2, revision date 02/20/2025; Momentive Performance Materials USA LLC
    url: https://blacksky.com/wp-content/uploads/2026/02/MomentivePerformance_RTV566-Dimethyl-Diphenyl_2025-02.pdf
    year: 2025
    kind: datasheet
    license: manufacturer safety data sheet, cited and not reproduced
  sds-rtv566-31:
    title: Momentive Performance Materials RTV566 Safety Data Sheet, version 3.1 (revised 08/30/2023), Part A, copy hosted by a BigCommerce product file
    id: SDS_US, version 3.1, revision date 08/30/2023
    url: https://cdn11.bigcommerce.com/s-jifykode7m/product_images/uploaded_images/msds/SGP210218.pdf
    year: 2023
    kind: datasheet
    license: manufacturer safety data sheet, cited and not reproduced
  usgs-mcs2026-silicon:
    title: Mineral Commodity Summaries 2026, Silicon
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-silicon.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  pubchem-ethyl-silicate:
    title: 'PubChem, Silicic acid, ethyl ester (CID 9877350, CAS 11099-06-2): GHS classification and regulatory information'
    id: CID 9877350; CAS 11099-06-2
    url: https://pubchem.ncbi.nlm.nih.gov/compound/9877350
    year: 2026
    kind: database
    license: public database entry, cited and not reproduced
  unl-rtv-composition:
    title: Relationship between photofixed condensate, effluent and bulk composition of several common RTV materials (Hanrahan and Ianno, Journal of Spacecraft and Rockets 51:3, April 2014, pp 978-982)
    id: University of Nebraska-Lincoln repository, electricalengineeringfacpub/541
    url: https://digitalcommons.unl.edu/electricalengineeringfacpub/541
    year: 2014
    kind: paper
    license: published paper, open repository copy, cited and not reproduced
story:
  recipe:
    line: RTV566 is a two-part silicone rubber that cures at room temperature. The base compound RTV566A is mixed with the curing agent RTV566B at 100 parts base to 0.1 part curing agent by weight, the most commonly used ratio. The Part A safety data sheet lists red iron oxide, kieselguhr and silicic acid, ethyl ester as ingredients, and a 2014 Raman and FTIR study names polydimethylsiloxane in RTV566.
    parts:
      - name: RTV566A base compound
        share: 100 parts by weight
        role: The silicone base compound. It is a red paste with a viscosity of 42700 cps and a specific gravity of 1.49 before cure.
      - name: RTV566B curing agent
        share: 0.1 part by weight
        role: Starts the room-temperature cure once mixed into the base. It is yellow-brown and has a specific gravity of 1.15 as printed.
      - name: Red iron oxide (Part A ingredient)
        share: 20 to under 50 % by weight of Part A
        role: Listed as the ingredient with the widest range in the Part A safety data sheet. The SDS gives a workplace exposure limit for it and does not state its function in the compound.
      - name: Kieselguhr, soda ash flux-calcined (Part A ingredient)
        share: 10 to under 20 % by weight of Part A
        role: Listed in the Part A safety data sheet with a workplace exposure limit. The SDS does not state its function.
      - name: Silicic acid, ethyl ester (Part A ingredient)
        share: 1 to under 5 % by weight of Part A
        role: Listed in the Part A safety data sheet. PubChem gives GHS hazard statements for it, and the 2014 Raman and FTIR study reports silicic acid and tetraethyl orthosilicate in RTV566.
  risk_groups:
    - title: For people
      level: 0
      verdict: Not classified under 29 CFR 1910.1200 (Part A SDS)
      lead: Momentive's Part A safety data sheet gives the product as not classified under 29 CFR 1910.1200, with no signal word and no hazard statement. No safety data sheet for the curing agent RTV566B is among the sources of this profile.
      points:
        - label: Part A
          line: The SDS gives no hazard class, no signal word and no hazard statement. Its flash point is 125 °C, and it has no data for skin or eye irritation.
        - label: Ingredient
          line: 'PubChem lists GHS hazard statements for silicic acid, ethyl ester, a Part A ingredient at 1 to under 5 %: flammable liquid and vapour, harmful if swallowed, causes serious eye irritation, harmful if inhaled, may cause respiratory irritation, and toxic to aquatic life.'
        - label: Primer
          line: The bonding primer SS4155 is named in the datasheet. Its own hazards were not read, and the datasheet says other materials may need additional precautions.
    - title: Bonding and processing
      lead: These steps come from the Momentive datasheet and set how the compound is mixed, degassed and bonded.
      points:
        - label: Mixing
          line: Mix 100 parts RTV566A with 0.1 part RTV566B by weight, in a container 4 to 5 times larger than the compound volume.
        - label: Air bubbles
          line: Degas under a vacuum of 25 mm (29 inches) of mercury minimum. Potted assemblies may need deaeration after pouring.
        - label: Bonding
          line: Non-silicone surfaces need a primer. Clean with naphtha or methyl ethyl ketone (MEK), apply a thin film of SS4155 primer, let it air dry for one hour or more, then apply freshly mixed RTV566.
    - title: Cure and heat
      lead: The cure schedule sets how long a part must wait before it is handled or used hot.
      points:
        - label: Cure
          line: The compound is handleable after 24 hours at 25 °C and 50 % R.H. The datasheet recommends 7 days for best outgassing and adhesion.
        - label: Above 150 °C
          line: 'Condition the cured part before service above 150 °C: 8 hours at 100 °C, then 8 more hours at each 28 °C step up to the service temperature.'
  why: Momentive RTV566 is a red, two-part, room-temperature-cure silicone rubber from Momentive Performance Materials, sold for low-outgassing use in vacuum. Its datasheet gives a continuous service range from -115 °C to 260 °C and up to 316 °C for short periods. The datasheet reports a total mass loss of 0.14 % and a volatile condensable material of 0.02 % in the ASTM E595 test. NASA's outgassing compilation lists 18 RTV 566 records, which is why the material is a common reference for spacecraft adhesives and potting.
  uses:
    - where: Cast-in-place heat shielding and thermal insulation
      line: Momentive lists cast-in-place heat shielding and thermal insulation among the potential applications of RTV 566 Paste. The page names no mission or flight.
    - where: Potting and encapsulating electronics
      line: Momentive lists potting and encapsulation of electrical assemblies, and the assembly of photovoltaic modules, among its potential applications. The datasheet adds that deaeration may be needed after pouring in complex assemblies.
    - where: Outgassing-tested spacecraft adhesives and potting
      line: 'NASA''s outgassing list (RP-1124 Rev. 3) has 18 RTV 566 records: 15 labelled ADHESIVE, 2 POTTING-ADH and 1 POTTING. These are ground test results, not flight results.'
  can_do:
    - label: Temperature range
      benchmark: max_service_temp
      value: '-115 °C to 260 °C continuous'
      line: The datasheet gives continuous service from -115 °C to 260 °C, and up to 316 °C for short periods. The Momentive aerospace page prints -130 °C as the low end for its low-outgassing silicones in general, which is not reconciled with the -115 °C figure.
    - label: Outgassing
      benchmark: total_mass_loss
      value: 0.14 % total mass loss
      line: The datasheet reports 0.14 % total mass loss and 0.02 % volatile condensable material under ASTM E595, after 7 days at 25 °C. The six NASA records at 0.1 % catalyst range from 0.08 % to 0.13 % total mass loss.
    - label: Adhesion
      benchmark: lap_shear_strength
      value: 33 kg/cm2 on primed aluminium
      line: The datasheet gives a lap shear of 33 kg/cm2 (465 psi) on primed aluminium, a tensile strength of 56 kg/cm2 and 120 % elongation for the same cured compound.
    - label: Working time
      benchmark: work_life
      value: 1.5 hrs work life
      line: The catalysed mix has a work life of 1.5 hrs and a tack-free time of 2.2 hrs, both printed in the datasheet.
  compare: 'RTV566 is a moderate-strength silicone (tensile strength 56 kg/cm2, Shore A 61), not a structural adhesive. On outgassing it sits at the listing limit: the datasheet''s total mass loss of 0.14 % is just above the 0.08 % to 0.13 % range that NASA records show at 0.1 % catalyst, and both are well under the NASA listing limits of 1.0 % total mass loss and 0.10 % volatile condensable material. The silicone-rtv profile in this collection describes a different product, so its values are not compared here.'
  compare_rows:
    - label: Continuous maximum service temperature
      benchmark: max_service_temp
    - label: Total mass loss
      benchmark: total_mass_loss
    - label: Continuous minimum service temperature
      benchmark: min_service_temp
  handling:
    - Mix 100 parts RTV566A with 0.1 part RTV566B curing agent by weight, in a container 4 to 5 times the compound volume.
    - Degas under a vacuum of 25 mm (29 inches) of mercury minimum. Use a primer on non-silicone surfaces, SS4155 per the datasheet.
    - Cure 24 hours at 25 °C and 50 % R.H. before gentle handling, and 7 days for best outgassing and adhesion.
    - 'Above 150 °C in service, condition the cured part: 8 hours at 100 °C, then 8 hours at each 28 °C step up to the service temperature.'
    - Read the latest safety data sheet before handling. The Part A SDS says not to taste or swallow the product, to avoid contact with eyes and skin, and to wash hands afterwards. No safety data sheet for the curing agent is among this profile's sources.
  good_for:
    - Low-outgassing bonding and potting where a service range of -115 °C to 260 °C is needed. NASA records at 0.1 % catalyst show 0.08 % to 0.13 % total mass loss.
    - Cast-in-place heat shielding and thermal insulation, the uses Momentive names for RTV 566 Paste.
  watch_out:
    - Non-silicone surfaces need a primer, SS4155 per the datasheet.
    - 'Two low-temperature limits are printed: -115 °C in the datasheet and -130 °C on the Momentive page, which covers the product line in general.'
    - Outgassing varies with catalyst level. NASA's 0.3 % and 0.7 % catalyst records show 0.34 % and 0.36 % total mass loss, well above the 0.1 % records.
  verdict: RTV566 is a moderate-strength, low-outgassing silicone for thermal insulation, heat shielding and potting in vacuum hardware. Its datasheet total mass loss of 0.14 % sits next to NASA's 0.08 % to 0.13 % range. The Part A SDS gives no hazard classification, and the silicon supply rows describe the feedstock rather than this product. No supply data for RTV566 itself and no ageing data beyond the SDS note on oxidation above 150 °C were read, so those parts stay incomplete.