Polyurethane Construction Sealant

flexothane 27 is an elastic, one part, low modulus, gun grade moisture curing polyurethane sealant.


flexothane 27  is an elastic, one part, low modulus, gun grade moisture curing polyurethane sealant.

  • One component, easy to gun.
  • Non-sag consistency.
  •  Non-tack/does not pick up dirt.
  • Good adhesion on the most common. construction materials.
  • Over paintable with water solvent based paints.
  • Good weathering and ageing properties.
  • Can be applied vertically or horizontally.
  • Suitable for usage in areas in continuous immersion in sewage water
  • Suitable to be used with potable water
  • Excellent resistance to chemical micro organisms
  • Meets ASTM C 920 and ISO 11600 Classification F 25 LM
Preparation of Joints

Thorough preparation of joints is essential if a satisfactory seal is to be obtained. For concrete, stone, or masonry surfaces, all traces of dust, laitance, mould release oil and dry. The previous sealants and all other foreign materials must be removed by sandblasting or mechanical abrasion, followed by blowing out the joints with dry, oil free compressed air. For glass, metal, and other non-porous surfaces, ensure these are free of coatings, oils, and grease by cleaning with a suitable solvent. Suitable solvents include abe® thinners no. 3, IPA, or MEK. Ensure the solvent is compatible with the substrate prior to cleaning.


Grey, White, Black.

Priming of Joints

flexothane 27 has good adhesion properties without the use of a primer.



Where a triangular pointing fillet cannot be avoided, the fillet must be applied such that it is not less than 10 mm across the face and with a rounded (convex) surface. Where there is a gap greater than 5 mm between the adjoining surfaces, a back-up material must be inserted, and the sealant applied in a sufficiently large fillet to ensure adequate adhesion area on each surface.

Typical Physical Properties of Cured Material
Chemical basis Polyurethane
Cure mechanism Moisture curing
Specific gravity 1.23 – 1.25
Tack free time at 23 °C and 50% R.H. Approximately 60 minutes
Curing at 23 °C and 50% R.H. 3 mm/24 hours
Hardness shore A (DIN 53505) ~40 after 28 days (+23 °C / 50% r.h)

***Download the technical datasheet for a full table of Typical Physical Properties.

Back-Up Material

Suitable back-up materials must be used to adjust sealant depth in the joint such as dura.cord (a closed cell polyethylene cord).

Protection of Adjacent Surfaces

Masking tape applied to areas adjacent to the joint will protect them from contamination and enable the joints to be finished in a neat line. The tape should be applied after the joint has been prepared, prior to any priming or sealing operation and removed after all finishing and tooling operations have been completed, but before the sealant has cured.


Theoretical Coverage for Estimating Purposes

Joint Dimensions (mm)  Metres per 600 ml sausage 

Metres per 280 ml sausage

25 x 12 2.00 0.93
20 x 12 2.50 1.16
12 x 12 4.17 1.95
6 x 6 16.67 7.79



Application by gun. It is essential to ensure complete contact between the sealant and the joint surfaces.


Tooling of sealants is necessary for complete air-free filling of voids and to assist in making contact to the surfaces to which the sealant is applied. The surfaces of the joint should be smoothed with a clean putty knife or spatula. 


Not required.

Painting over Sealant

It is not recommended that a flexible sealant be over-coated by less flexible coatings as joint movement will cause rupturing of the coating. Also, plasticisor migration from the sealant into the coating could result in excessive dirt pick-up. Based on the outcome of preliminary tests the sealant may be over painted with a good quality water or solvent based paint.


Tools should be cleaned immediately after use, and before the material has cured, with abe® super brush cleaner followed by washing with soap and water.

Model Specification

The one part polyurethane construction sealant will be flexothane 27 a single-pack, medium modulus, moisture curing hybrid construction sealant as supplied by a.b.e.® Construction Chemicals.

flexothane 27 will be applied in accordance with the recommendations of a.b.e.® Construction Chemicals.


600 ml sausages packed 20 per box and 280 ml cartridges packed 12 per box.

Handling & Storage

Shelf life of 12 months, but shorter if in extreme conditions. Keep tightly sealed in a dry cool place in the original packaging.

Health & Safety

Uncured flexothane 27 is toxic and should not be allowed contact with skin and eyes. The use of gloves and eye protection is advised. Splashes into eyes should be washed immediately with plenty of clean water and medical advice sought. Ensure the working area is well ventilated during application and drying. Always wear gloves when working with the material and avoid excessive inhalation and skin contact.

Cured flexothane 27 is inert and harmless.

Examples of Joints


Important Note

This data sheet is issued as a guide to the use of the product(s) concerned. Whilst a.b.e.® Construction Chemicals endeavors to ensure that any advice, recommendation, specification or information is accurate and correct, the company cannot – because a.b.e.® has no direct or continuous control over where and how a.b.e.® products are applied – accept any liability either directly or indirectly arising from the use of a.b.e.® products, whether or not in accordance with any advice, specification, recommendation, or information given by the company.

Further Information

Where other products are to be used in conjunction with this material, the relevant technical data sheets should be consulted to determine total requirements.