Technical Data Sheet (TDS)

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PU 2638

PU Building sealant, medium hardness

Uses

BOSTIK PU2638 is a single part, fast curing, polyurethane-based sealing compound which cures by reaction with atmospheric moisture. The cured sealant is rubbery and highly elastic and, in general, can be over painted.
 
Building construction:  Sealing both internal and external joints in a wide variety of materials, including concrete, stone, fibro/cement, wood, metals, ceramic tiles, enameled substrates, GRP, etc.
 
BOSTIK PU2638 may be used in conventional weather sealing applications such as expansion and control joints in poured and precast concrete panels and metal curtain walls, perimeter sealing of door and window openings and other building components.
 
Industry:  Ventilating and air-conditioning ducts, vehicle body joints, containers, caravanning, general maintenance and DIY.
 
BOSTIK PU2638 is not designed as a glazing sealant in which the adhesive bond to glass is exposed to sunlight and appreciable amounts of UV radiation.
It should not be used for plastic materials with high plasticizer contents and corrosion/crack-sensitive plastics.

Benefits

  • Highly elastic product
  • Good adhesion to most substrates
  • Good temperature resistance

 

Properties

Physical:

 Basis   
 Polyurethane
 Colours
 White, grey, brown
 Specific gravity
 1,32 approx.
 Tack free time
 1-2 hours approx
 Cure time
 <3 mm/day approx. at 23ºC &  50% RH
 Hardness, Shore A
 40  approx.
 Modulus at 100% elongation
 0,4 MPa. approx.
 Elongation
 > 250%
 Temperature resistance
 -30ºC to  +80ºC
 Chemical resistance
    - water, cleaning agents
    - petrol                                  
    - mild acids and basis, oils                  
    - solvents, strong acids and basis
 
 Good
 Temporary
 Medium
 Poor
 Application temperatures
 +5ºC to +40ºC

Safety:

BOSTIK PU 2638 contains reactive isocyanate and a small amount of solvent. Accordingly maintain good general ventilation during sealant application and whilst it cures. Do not smoke. Keep out of reach of children.

Shelf life:

1 year from date of manufacture stored under dry conditions between +10 and +25ºC.

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Application

Joint design considerations
For conventional construction joints subject to movement it is important that the dimensional proportions of the joint are correct. These should be:
 
                                              
Width mm
Depth mm
8
8
10
10
15
10
20
12
25
15
 
Joint preparation
Ensure that the joint surfaces are dry and clean, being free from dust and grease.
Remove residues of mortar or cement mechanically, also weathered paint on metal and wood.
 
Where appropriate, prefill joints with a cross linked polyethylene foam to give the required joint depth for the sealant. Materials containing oil, tar or bitumen, also hemp and mineral wool, are unsuitable as prefillers.
 
Priming
BOSTIK PU2638 will adhere without priming to many surfaces such as concrete, wood, stone, enameled substrates, GRP, anodized aluminium, etc.
On certain surfaces, however, the use of a primer may be necessary before sealant application, e.g. absorbent surfaces such as cellular concrete, mild steel and untreated aluminium. In these cases advice on priming should be sought from BOSTIK S.A.
 
Sealant application
Ambient temperature should be in the range +5 to +35ºC. The temperature of the sealant itself should not be lower than +10ºC. When necessary sealed cartridges may be warmed up, preferably to a temperature of +15 to +20ºC, in a water bath.
 
Pierce the membrane at the top of the cartridge and screw on the nozzle, having previously cut this to give the required bead size. Place the cartridge in a suitable BOSTIK extrusion gun, and press the trigger. Apply the sealant smoothly, with even pressure, along the prepared joints. Smooth down the applied sealant, when necessary, using a spatula or similar tool which has been dipped in water containing a little detergent.
 
Coverage
Determine the cross-sectional area of the joint, then calculate from the formula:
 
 
                                                        300
                                        _______________________           =  meter run per cartridge
                                        Cross-sectional area in mm2
 

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Packaging

Presentation Bar code Bostik code
sausage - white - 600 ml 8412663513322 160830
sausage - grey - 600 ml 8412663514411 160831
sausage - brown - 600 ml 8412663513544 160832

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