Single component acrylic co-polymer mastic


Polymastic is a single component acrylic co-polymer mastic, which is designed for pointing applications. The mastic on curing forms a pliable flexible seal which can accommodate moisture and thermal movements with minimal shrinkage.

Polymastic can be used in both horizontal and vertical applications and has a movement accomodation factor (maf) of ±10%.


  • Good compatibility with paints and emulsions. Can be over painted
  • Excellent resistance to weathering
  • Good resistance to water and water vapour
  • Excellent adhesion to most building substrates. Can be used without the use of primer in new substrates
  • Fast drying
  • Odorless
  • Resists mildew and mould growth
  • Easy to apply, one component sealant. No mixing required
  • Non-staining

This TDS is applicable for the United Arab Emirates only. Please contact your local Polybit sales office for the available TDS in your region

step by step

Joint preparation

All cracks and joint edges must be clean, dry and free from oil, loose particles, cement laitance and other contaminants which may affect the adhesion. A thorough wire brushing, grinding, sand blasting or solvent cleaning may be required to expose a clean and sound substrate. When applied on glazed surfaces like ceramic or terrazzo tiles or porcelain enamel joint surfaces, the glaze should be removed by abrading with sandpaper or wire brush. Usually priming is not required, however on highly absorbent surfaces, dilute Polymastic with water (1:3 by vol.) and prime the joints with it. The

primer shall be applied by a brush in a thin coat application and shall be allowed to become tack free prior to the application of the sealant. For obtaining a clean and neat finish, masking tape shall be applied on both the edges of the joint before the application of the primer or the mastic.

Back-up Material

A bond breaking backing rod (Polyrod)* shall be inserted into all movement joints to avoid a three sided adhesion. The diameter of the backing rod shall be at least 20% larger but not greater than 33% of the joint width. this will ensure that the backer rod remains in compression and in place during sealant installation. For static and joints depths which does not allow the installation of a backing rod, a bond breaking tape may be applied to prevent the three side adhesion.


Polymastic is available in a ready to use pail which can applied with a spatula or a putty knife. On vertical areas, the mastic application shall start from the bottom of the crack/joint and continued to the top. Once the mastic has been installed, tool it to obtain a smooth profile. DO NOT USE SOAPY WATER SOLUTION. Any masking tape applied should be removed immediately after the sealant is installed.