JOINT SEALANT_MULTI SEAL PU 25_One Component Flexible Polyurethane Sealant - MCCSA
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When applied, MULTISEAL PU 25 cures to form a flexible rubber-like seal. It exhibits not only excellent expansion and compression characteristics but also very good resistance to weather, stress movement, water and many chemicals. It is available in cartridge and sausage packaging. 



MULTISEAL PU 25 requires no mixing and has excellent adhesion to both porous and non-porous substrates. It can be easily applied in both horizontal and vertical joints, is self-curing and bonds to many materials, including concrete, PVC, masonry, aluminium, and wood without the necessity to prime. Not for use in water retaining structures. Treated wood must have weathered for at least 6 months. UV exposure may discolour light colours. Do not contact oil-based caulking, silicone sealant, polysulphides, fillers impregnated with oil, asphalt or tar. 



  • Solvent free 
  • Moisture curing 
  • Moisture and oxidation resistance 
  • Easy application 
  • Good adhesion to concrete and steel 
  • Easy to maintain 
  • Non-cracking 
  • Variety of colours 



Colour on Setting: Various 

Tack-free time: 60min – 90min 

Cure Rate: 2mm / 24 hours 

Hardness: Shore A 25 

Elongation at Break: >200% 

Density: 1.4g/cm3 

Temp. Resistance: -30C to 80C 

Tensile Strength: 0.5MPa – 1.0MPa, Modulus 100% , 0.4MPa – 0.8MPa 

Joint Movement: 25% 

Application Temp: 5°C – 35°C 



  • The number of joints and joint width should be designed for a maximum of ±25% movement. 
  • In joints of 6-12mm, the sealant depth at midpoint should be 6mm. In joints of 12-25mm, the depth at midpoint should be 6-12mm. 
  • In deep joints, the sealant depth must be controlled by a closed cell backing rod. Where the joint depth does not permit the use of backing rod, a bond breaker (masking tape) must be used to prevent three-point bonding. 
  • To maintain the recommended sealant depth, install backing rod by compressing and rolling it into the joint channel without stretching it lengthways. Backing rod should be about 3-5mm larger in diameter than the width of the joint to allow for compression. Soft backing rod should be approximately 25% larger in diameter than the joint width. Backing rod becomes an integral part of the joint. The sealant does not adhere to it, and no separate bond breaker is required. Do not prime or puncture the backing rod. 




Surfaces must be structurally sound, dry, clean, free of dirt, moisture, loose particles, oil, grease, asphalt, tar, paint. wax, rust, water proofing, curing and parting compounds, and membrane materials. Clean concrete, stone and other masonry by grinding, sandblasting or wire brushing to expose a sound surface free of contamination and laitance. Wood must be clean and sound and free of any coatings or treatments. Metal must be free of rust, scale, coatings, residue or film.  



MULTISEAL PU 25 is generally considered a non-priming sealant, but special circumstances or substrates, e.g., protective coatings on aluminium may require a primer. It is the user’s responsibility to check the adhesion of the cured sealant on typical test joints at the project site before and during application. Refer to technical data sheet on MULTI POXY 1308. Apply primer full strength, with a brush or clean cloth. A light, uniform coating is enough for most surfaces; porous surfaces require a somewhat heavier although not excessive coat. Allow primer to be tack dry before applying MULTISEAL PU 25. Depending on temperature and humidity, primer will be tack free in 15-120 minutes. Priming and sealing must be done on the same workday. Consult MULTI CONSTRUCTION CHEMICALS technical services for additional information on primers for other surfaces. 



Fill joints from the deepest point to the surface by holding a properly sized nozzle against the back of the joint. Tooling is recommended. Tooling results in the correct bead shape, a neat joint, and maximum adhesion. The cure of MULTISEAL PU 25 varies with temperature and humidity. At 25C, 50% relative humidity and a joint 13mm width by 7mm depth, assume the following times: 

Skins overnight or within 24 hours 

Functional within 3 days 

Full cure in approximately 1 week



Immediately after use, clean equipment with MULTI THINNERS 1600. Use proper precautions when handling solvents. Remove cured sealant by cutting with a sharp-edged tool.



Supplied in 600ml sausages. 



Multi Construction Chemicals South Africa (PTY) Ltd production and testing programs comply with all local and international testing standards. MULTI EXPANSION TAPE jointing system shall be fastened in position to give continuous network with 100 mm minimum overlaps and installed in accordance with the manufacturer’s instructions.  



The information supplied is believed to be reliable. As we do not have any control over the processing or application of the product we cannot guarantee the results to be obtained.

Users assume all risks and liability resulting from the use of this product and must confirm suitability thereof by conducting their own tests.

No guarantee is expressed or implied. Liability to the replacement of faulty material.