FLEX PU-2K is a two-component joint sealant, based on polyurethane resins. When mixed, the two components are vulcanised to  an elastic and cohesive mass. The sealant has excellent UV resistance and shows thermal stability (it contains UV stabilizers and antioxidants). Available in two types:

• FLEX PU-2KV for vertical surfaces.
• FLEX PU-2KH for horizontal surfaces.

FLEX PU-2K is suitable for sealing vertical and horizontal concrete joints in buildings and civil engineering and hydraulic works (irrigation canals, water supply systems, tanks, airport runaways, etc). FLEX PU-2K is fuel and oil resistant. It has been tested according to EN 14187-4: Determination of the change in mass and volume after immersion in test fuels and liquid chemicals.

Substrate preparation

• The maximum anticapated joint deformity, which depends on the length of the structural elements, the expansion co-efficient of the substrate and the maximum anticipated temperature variation during the year, should not exceed 25-30 % of the original with the joint. Ideally, it is recommended that the minimum joint with  should be no less than 1.0-1.5 cm and the maximum no more than 5 cm. However, it can be used in applications where the joint width is up to 8 cm. The sealing depth can be adjusted to 50% of the joint width, but should be at least 1.5 cm. 
• The joint sidewalls need to be thoroughly cleaned from loose particles, dust, etc., by blowing with compressed air.
• When necessary, the sealing depth is regulated with CELLUFILL (backing rod from expanded polyethylene). This way, the sealant does not adhere to the bottom of the joint and is thus free to move, following the expansion-contraction movements of the joint.

Application

• The two components, packaged at a fixed ratio by weight, need to be thoroughly mixed with the use of a proper mixer, e.g. a helical spiral mixer attached to a drill. Mixing should continue  until the mixture is completely homogenized. Since the two components are of different color (A: white – B: black), the homogenization can be visually checked (when the mixture obtains a homogeneous grey color, without darker or lighter spots or streaks, mixing is complete).
• The mixed sealant is applied into the joint by means of a special gun or spatula (for minor applications). 
• The surface of the uncured sealant is smoothed with a spatula, so as to form a concave meniscus.