H.B. Fuller STP 1921 Modified Silane Sealant

H.B. Fuller STP 1921 Modified Silane Sealant is a high-quality, neutral, elastic single-component adhesive/sealant based on silane-terminated polymer, which cures by reaction with moisture to an elastic product. The skin formation and curing time are dependent on humidity and temperature, and the curing time also depends on joint depth. By increasing the temperature and moisture, these times can be reduced; low temperatures as well as low moisture retard the process.

Product Type1K (1 component) Sealant, 2K (2 component) Adhesive, Membrane Adhesive, Solvent free (100% Solids) Sealant

Application AreaAir Conditioning , Caravans, Containers, Electrical Components, Joints, Membranes, Railway Carriage, Vehicle Body, Ventilation Systems

Compatible Substrates & SurfacesMetal, Plastics

Chemical FamilyPolyurethanes (PU)

FeaturesAcid Resistant, Excellent Substrate Adhesion, Good Adhesion, Good Color Stability, Good Elongation, Good Tensile Properties, Good UV Resistance, Long Open Time, Thixotropic

Technical Data Sheet

Enhanced TDS

Identification & Functionality

Chemical Family

Features & Benefits

Product Overview
  • STP 1921 is a good compromise between an adhesive and a sealant based on Silane-terminated Polymer. STP 1921 is suitable for elastic seal which also high strength is required.
  • STP 1921 is odourless and free of solvents, isocyanates, silicones and PVC. It demonstrates good adhesion without primer to many substrates and is compatible with suitable paint systems. The sealant also demonstrates good UV resistance and therefore can be used for interior and exterior applications.
Features & Benefits
  • Odourless
  • Non-corrosive
  • Primerless adhesion on many substrates
  • Colour stable and UV resistant
  • Ecological advantages – free of isocyanates, solvents, PVC

Applications & Uses

Compatible Substrates & Surfaces
Cure Method
  • Elastic bonding of metals and plastics.
  • Elastic, interior and/or exterior seam and joint sealing.
  • In the following areas: vehicle body, caravan, railway carriage, container, general metal and apparatus construction; the electrical, plastics, air-conditioning and ventilation industries.
Application Instructions
  • The substrates must be clean, dry, free of oil and grease.
  • Sausage is applied with the corresponding Hand or Air pressure pistols. In the case of compressed air application, a pressure of (0.2-0.4) MPa is required.
  • After application, STP1921 can be smoothed with soapy water.
Application Limitations

When bonding and sealing PMMA and polycarbonate, under tension, stress corrosion cracking may occur. In such cases STP 1921 should not be utilized.


Physical Form
Typical Properties
ValueUnitsTest Method / Conditions
Specific Gravityapprox. 1.45
Thermal Properties
ValueUnitsTest Method / Conditions
Application Temperature5 - 40°C
Operating Temperature- 50 - 90°C
Short Exposure120.0°C
Cured Properties
ValueUnitsTest Method / Conditions
Skin Formation Time (21 - 25°C, 45 - 55% relative humidity)approx. 30min
Cure Rate (21 - 25°C, 45 - 55% relative humidity)approx. 3mm/24h
Hardnessapprox. 35ISO7619, GB/T531, Shore A
Tensile Strengthapprox. 1.8MPaISO37, GB/T528
Elongation at Breakapprox. 350%ISO37, GB/T528
Rheological Properties
ValueUnitsTest Method / Conditions
Sag ResistanceNo sagging

Technical Details & Test Data

Technical Details
  • Adhesion - STP 1921 has been tested and found to have excellent adhesion to the following unprimed substrates: aluminum, acrylic-coated aluminum, brass, steel, stainless steel, glass, fiberglass, ABS, rigid PVC, polyester and etc. Depending on the surface it can be necessary to roughen the surface or to use a primer as an adhesion promoter to provide optimum adhesion.
  • Paintability - STP1921 may be over-painted, however due to the large number of paints and varnishes we strongly recommend a compatibility test before application. The drying time of alkyd resin based paints may increase.

Packaging & Availability

Packaging Type
Typical Packaging
  • Cartridge 310ml
  • Sausage 400ml, 600ml

Storage & Handling

Shelf Life
12 Months
Storage Conditions

Recommended storage temperature: 8°C - 28°C