Chemically resistant joint sealant

flexothane® CTW is a semi-flexible, hard wearing expansion joint sealant based on modified epoxy, polyurethane, tar and inert fillers. Due to its unique composition it is flexible yet hard and is resistant to a wide range of acids and alkalis.

flexothane® CTW will bond to a damp substrate.


flexothane® CTW is used for sealing low-movement construction joints in acid resistant construction such as acid brickwork and chemical resistant screeds. Because it will bond to a damp substrate, flexothane® CTW is ideal for use in not only new construction projects but also in repair and maintenance work. Also suitable for trafficked floor joints where constant wheel contact demands a high shore A hardness sealant.

  • High shore A hardness offers protection against arris damage
  • Good chemical resistance, joint sealing in chemical plants, acid lining brick work and chemically resistant screeds
  • Suitable for new concrete construction
  • Good primerless adhesion
  • Will bond to damp surfaces
  • Good flexing properties with excellent adhesion to properly prepared substrates
Joint Geometry

In joints of 6 mm to 12 mm wide, the depth of the sealant should equal the width. In joints in excess of 12 mm wide, the sealant depth should be half of the width. The recommended joint width for flexothane® CTW is 6-9 mm.

Surface Preparation

Thorough preparation of joints is essential if a satisfactory seal is to be obtained. For concrete surfaces traces of dust, laitance, mould oil, any previous sealant and all other foreign material must be removed by mechanical grinding, followed by blowing out with dry, oil free compressed air.

Typical Physical Properties
 Material Epoxy polyurethane tar
Colour Black
Coverage Refer table
Setting time 4-6 hours dependent upon temperature
Trafficable cure 24 hours
Full cure 7 days
Maximum temperature Laying 35ºC Service 70ºC
Toxicity Inert when cured, but do not use in direct contact with foodstuff or drinking water
Water tainting Will taint potable water
Mechanical Properties
 Tensile strength 1,6 MPa
Shore A Hardness 75
M.A.F. 5%
Chemical resistance Resistant to a wide range of acids and alkalis but limited resistance to solvents
Porosity Non-porous
Consumption for Estimating Purposes
 Joint width x depth (mm)  Metres per litre 
6 x 6 27,8
9 x 9 12,3
12 x 12 6,9
15 x 8 8,3

No allowance made for waste.

Protection of Surfaces

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

Bonding / Priming

Under normal circumstances, no priming of joints is required. However in joints exceeding 12 mm wide, to improve adhesion, epidermix® 116 can be used as a primer.

Back-up Material

Suitable back up material must be used to adjust sealant depth in the joint to comply with the joint geometry cited in this data sheet. Backing cord is a self-releasing material, but if soft-board is used as the joint filler, a plastic strip bondbreaker must be placed on the filler surface before the sealant is applied. Under a pressure head of liquid, backing cord should be at least 2,5 times greater in diameter than the width of the joint slot.


Add entire contents of the activator to the base material and mix thoroughly using a suitable paddle attached to a slow-speed drill. Mix for 4-5 minutes, stopping occasionally to scrape the sides and base of the tin to ensure complete blending of the activator throughout the base.

Note: If the material is not mixed properly it’s performance will be impaired.


Application can be by hand operated or pneumatic gun, or by pouring, according to the cross-section of the joint to be filled. It is essential to ensure complete contact between the sealant and the joint surfaces. Tooling of sealants is necessary to avoid air entrapment and to assist in wetting out the surfaces to which the sealant is applied. The sealant should be tooled by pulling a thin metal rod through the sealant to release all air bubbles.


All tools must be cleaned before the sealant cures with abe® super brush cleaner. Cured material can only be removed by mechanical means.

Application Temperature

Surface and ambient temperature must be at least 5°C and rising, ideally between 20°C and 30°C.

Model Specification

Pitch polyurethane trafficable joint sealant with good chemical resistance. The sealant will be flexothane® CTW, a gun grade two component, epoxy/polyurethane/tar compound applied in accordance with the recommendations of a.b.e.® , including epidermix® 116 primer where necessary. The sealant will have a Shore A hardness of 75.


flexothane® CTW is supplied in 2 litre kits.

Health & Safety

flexothane® CTW is toxic. Ensure the working area is well ventilated during application and drying. Avoid flames in vicinity. Always wear gloves when working with the material and avoid excessive inhalation and skin contact. If material is splashed in the eye, wash with plenty of clean water and seek medical attention.

Cured flexothane® CTW is inert and harmless.

Important Note

This data sheet is issued as a guide to the use of the product(s) concerned. Whilst a.b.e.® endeavours to ensure that any advice, recommendation, specification or information is accurate and correct, the company cannot accept any liability for application – because a.b.e.® has no direct or continuous control over where and how a.b.e.® products are applied.

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

a.b.e.® has a wealth of technical and practical experience built up over the years in the company’s pursuit of excellence in building and construction