• Description for Bostik 955-SL

    A one-component, self-leveling polyurethane sealant capable of dynamic joint movement totaling 50% of original joint geometry (±25%). The sealant cures to a tough, flexible rubber when exposed to moisture present in the atmosphere.

    *See Terms of Use Below

    Application Type Bond, Seal
    1 Part or 2 Part 1-Part
    Material Form Paste
    Substrate Aluminum, Ceramic, Steel, Stone, Wood
    Industry Light vehicle traffic
    Manufacturer Bostik
    Chemistry Polyurethane
    Cure Method Moisture
    Cure Temperature (°C) 25
    Cure Time (min) 2,880 to 4,320
    Viscosity (cPs) Self-leveling
    Ozone Resistance Excellent Ozone Resistance
    Key Specifications ASTM (American Standard Test Method): C-920: ASTM C-920, Type S, Grade P, Class 35, Use T, NT, A and M, CAN/CGSB (Canadian General Standards Board): Canadian Specification CAN/CGSB-19.13-M87., TT (U.S. Federal Specification): S-00230C: TT-S-00230C, Tipe I, Class A.
  • Technical Data for Bostik 955-SL

    • Application Type
    • 1 Part or 2 Part
      • 1-Part
    • Material Form
      • Paste
    • Substrate
    • Industry
      • Other Transportation - Foot traffic
      • Automotive - Light vehicle traffic
      • Construction - Cures to form a durable, flexible, waterlight bond with most building materials in any combination including: stone, masonry, blacktop, ceramic, marble, wood, steel, and aluminum, Sealing expansion joints, Masonry, Sealing control and perimeter joints in institutional floors, Sealing control and perimeter joints in factory, Sealing control and perimeter joints in driveway, Sealing control and perimeter joints in patios, Sealing control and perimeter joints in malls, Sealing control and perimeter joints in plazas, Sealing control and perimeter joints in pavement, Sealing control and perimeter joints in parking decks
    • Chemistry
    • Cure Method
      • Moisture / Condensation Cure - Moisture
    • Key Specifications
      • ASTM (American Standard Test Method) : C-920 : Class 35 - ASTM C-920, Type S, Grade P, Class 35, Use T, NT, A and M
      • CAN/CGSB (Canadian General Standards Board) : 19.13 - Canadian Specification CAN/CGSB-19.13-M87.
      • TT (U.S. Federal Specification) : S-00230C : Class A - TT-S-00230C, Tipe I, Class A.
    Cure Specs
    Cure Temperature (°C) 25 Test Method
    Cure Time (min) 2,880 to 4,320 Test Method
    Viscosity (cPs) Self-leveling
    Tack Free Time (min) 120 Test Method
    Work / Pot Time (min) 90 Test Method
    Bond Strength
    Peel Strength (piw) >30 Test Method
    Tensile Strength (psi) 171 Test Method
    Material Resistance
    Ozone Resistance Excellent Ozone Resistance
    UV Resistance Good Test Method
    Shore A Hardness 35 Test Method
    Elongation (%) 500 Test Method
    Modulus (psi) 80 Test Method
    Business Information
    Shelf Life Details Shelf life of Chem-Calk® 955-SL must be checked prior to using the product, do not use past its shelf life. Caulk past its shelf life may not perform or adhere as described by this data sheet. High temperature and high relative humidity may reduce significantly the shelf life of polyurethane sealants. If you are unsure of the expiration date of your Bostik product, please call customer service at 1-800-7/BOSTIK (1-800-726-7845) to check if the product is still within its shelf life.
    Not Good For
    Don't Use For Do not apply over damp, contaminated, loose surfaces, The self-leveling sealant should not be used in joints with more than a two degree slope. Joints formed with Chem-Calk® 955-SL can be expected to extend and compress a total of 50% of the installation width with no more than_x00D_ 25% movement in a single direction without affecting the seal or adhesive bond, must NOT be used to seal narrow joints or fillet joints, Smearing and feathering, continuous immersion in water or any other fluid, exterior or interior sealing below the waterline, do not expose to curing silicone_x00D_ sealants, alcohol, acids or solvent-based materials
  • Best Practices for Bostik 955-SL

    *See Terms of Use Below

    1. Design

      In general, more joint movement can be accommodated in a thin bead of sealant than a thick bead. Bostik Chem-Calk 955-SL polyurethane sealant should be no thicker than 1/2" (12.7mm) and no thinner than 1/4" (6.4mm). In joints between 1/2" and 1", the ratio of sealant width to depth should be approximately 2:1. Sealant width in joints between 1/4" and 1/2" should be 1/4" deep. Joints with dynamic movement should not be designed in widths less than 1/4".

    2. Surface Preparation

      Surfaces must be structurally clean, dry (no frost) and structurally sound, free of contaminants, including but not limited to dust, dirt, loose particles, tar, asphalt, rust, mill oil, etc. If substrate is painted or coated, scrape away all loose and weakly bonded paint or coating. Any paint or coating that cannot be removed must be tested to verify adhesion of the sealant or to determine the appropriate surface preparation if needed.

      To remove laitance and any other loose material, clean concrete, stone or other masonry materials with nonalcoholic-based solvent by washing, grinding, sandblasting or wire brushing as necessary . Do not use water to clean substrates. Dust must be thoroughly removed after cleaning.

    3. Application

      Priming is always required for any on or below grade application or where standing water is expected to accumulate. Priming is required on all ferrous-based metals and in all applications exposed to intermittent or continuous water immersion. If sealant is to be applied to a material with specially treated surfaces or of particularly unusual surface characteristics, or if the sealant system will be exposed to intermittent ponded water , consult Bostik Technical Service for primer recommendations.

      Bostik Chem-Calk 955-SL comes ready-to-use. Cut spout or tip to desired bead size. Apply moderate pressure to break seal inside the nozzle. Apply by using a professional caulking gun. Use opened cartridges and sausages the same day they are opened. Apply Bostik Chem-Calk 955-SL polyurethane sealant in a continuous operation using positive pressure to the bottom of the joint to properly fill and seal the joint. When applying, avoid air entrapment and overlapping. Tool the sealant before the skin forms with adequate pressure to spread the sealant against the backup material at the bottom and sides of the joint. A dry tool with a concave profile is recommended for that operation. Do not use water or soapy water for this operation. Avoid smearing and feathering of the sealant to allow full performance of the cured seam. Excess sealant should be dry-wiped or joints should be properly taped. Tooling of the uncured sealant will aid the wetting of the sealant to the substrate.

      If the sealant becomes damaged, replace the damaged portion by removing the old sealant completely, cleaning the surfaces and reapplying a fresh and appropriate amount of new sealant in accordance with the directions and information contained in this data sheet

    4. Clean-Up

      After dry-wiping uncured sealant from substrates and tools, remaining uncured sealant can be removed by using Xylene, Toluene or similar aromatic solvents. Please refer to the MSDSs provided for these solvents before use. Bostik® Hand and Tool towels can also remove uncured sealant. Cured sealant is usually very difficult to remove without altering or damaging the surface to which the sealant has been misapplied. Cured sealant can be removed by abrasion or other mechanical means (scrapers, putty knives).

    5. Testing

      Prior to any use, however, it is always recommended that the sealant be applied on the surface to test adhesion.

      A hand pull test must be run before the job starts and at regular intervals during the job. It must be run on the job site after the sealant is fully cured, usually within 7 to 21 days. (Adhesion may develop fully after at least 14 days.)

      The hand pull test procedure is as follows: Make a knife cut horizontally from one side of the joint to the other.

      Make two vertical cuts approximately two inches long, at the sides of the joint, meeting the horizontal cut at the top of the two-inch cuts.

      Grasp the two-inch piece of sealant firmly between the fingers and pull down at a 90° angle or more, and try to pull the uncut sealant out of the joint.

      If adhesion is sufficient, the sealant should tear cohesively in itself.

      Sealant may be replaced by applying more sealant in the same manner as it was originally applied. Care should be taken to ensure that the new sealant is in contact with the original, and that the original sealant surfaces are clean, so that a proper bond between the new and old sealant will be obtained.

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Cure Temperature Test Methods
Cure Temperature Cure Time Test Method
25°C Varies w/relative humidity
Cure Time Test Methods
Cure Time Test Method
2,880 to 4,320 min Varies w/relative humidity
Tack Free Time Test Methods
Tack Free Time Test Method
120 min Bostik Test Method
Work / Pot Time Test Methods
Work / Pot Time Test Method
90 min Bostik Test Method
Peel Strength Test Methods
Peel Strength Cure Time Cure Temperature Cure Humidity Substrate Test Method
>30 piw 10,080 min 25°C 50 % ASTM C-794, After 7 days cure at 77ºF and 50% RH
Tensile Strength Test Methods
Tensile Strength Cure Time Cure Temperature Cure Humidity Test Method
171 psi 10,080 min 25°C 50 % ASTM D-412, After 7 days cure at 77ºF and 50% RH
UV Resistance Test Methods
UV Resistance Test Method
Good ASTM C-793
Elongation Test Methods
Elongation Test Method
500 % ASTM D-412 (After 7 days cure at 77ºF and 50% RH)
Modulus Test Methods
Modulus Test Method
80 psi ASTM D-412, 100% Elongation (After 7 days cure at 77ºF and 50% RH)
Shore A Hardness Test Methods
Shore A Hardness Shore Hardness Test Method
35 ASTM C-661 (After 7 days cure at 77ºF and 50% RH)