Osmotic Blistering

CARDANOL CHEMICALS N.V.
International distributor of Cardolite Corporation
Offerlaan 116-118
B-9000 Gent
Belgium
• the pre-treated carried out properly
• the application is made in the right way
• the primer is solvent free
The coating is for most paint companies
the only parameter in control. We have to
make sure that the primer is not subject of
blistering:
• Adhesion: The most important factor is
the adhesion on the substrate. A low
viscous primer that spreads out well
and penetrates the concrete profound is
less likely to provoke blisters.
• Flexibility: The flexibility is not only
of importance in regard to the final use
of the coating. The flexibility and the
influence of temperature changes
correlates directly with the visual
aspect of blisters.
• Water soluble constituents: Research
has proven that humid concrete
substrates coated with a solvent free
primer - and preserved under humid
conditions - stay free of blister even
after several years (Ref.: 4, 5). Solvent
containing primers provoked blisters
under the same conditions (Ref.: 6).
The primer is stable under alkali
conditions and has no water dilutable
decomposition products.
Primer formulation:
We developed a concrete primer
complying too the above guidelines, A low
viscous Bisphenol A resin diluted with a
Constituents Primer 1 Primer 2
Part A
Bisphenol A (Eurepox 80 80
730)
Necires EPXL-2 20 20
Part B
Cardolite@ NC 558 50 50
Euredur 13 0 2
DFT (CL) 300 300
CARDOLITE
ARTICLES
Article regarding NC 558
hydrocarbon resin is used as A component.
Cardolitb NC 558, a low viscous
Phenalkamine hardener, cross-links the
system. Euredur 13 is used to adjust the
cure at lower temperatures (5”C/95%
R.H.). The primer is applied at 300~ film
thickness.
Necirez EPXL-2 is a non-reactive
flexibiliser but contains aromatic OHgroups
that bound in the hydrocarbon resin
to the rest of the primer. The dense crosslinking
obtained with Cardolite@ NC 558
further minimises migration of the
flexibiliser. The concentration of
accelerator is kept limited hence its
influence on the flexibility and
hydrophobicity of the primer. The water
vapour transmission rate of this primer is
extremely low (1.33 lo-” mih) and assures
a complete seal off the substrate.
Two types of humid concrete are used as
substrate:
• High performance concrete: The high
performance concrete (62 N/mm2) is
since its dense structure subject of an
increased capillarity and a less
profound penetration.
• Regular concrete: Concrete with
compression strength of 30 N/mm* is
more accessible for the epoxy primer
but may contain more water.
Accelerated test method:
Sandblasted concrete tiles, of which the
four edges are primed, are totally
submerged for 2 weeks in water. Three to
four hours prior to the application of the
primer they are taken out and dried with a
cloth. The water content of the substrate
varies between 5.5% and 6.8%, depending
on the type of concrete.
Date issued: 1999.05
Document #:
C-5.51/2/B
Revision: 0