There are 2 types of acrylic sealants:
Emulsion-based
Solvent-based
They display good adhesion to the absorbing materials such as wood, concrete, plaster, and they also have fairly good adhesion to metals and glass, although not as good as silicones on glass.
They are only plastomeric, with a maximum movement capability in service of 10 to 15%.
Dry solids vary from 80 to 85% so that they show 10 to 20% shrinkage during drying through the evaporation of the water that they contain.
They have fair to good weather resistance because they are sensitive to water. One can expect 15 years of durability for outside use.
They have very good resistance to UV and discoloration, and may be formulated in a large variety of colors in order to match the colors or the materials (brown like wood, white for plastic windows or tiles, grey like concrete or aluminum like the windows).
Acrylic solvent-based sealants have outstanding adhesion to many materials, such as concrete, aluminum, steel, wood etc. They have excellent weather resistance, resist to UV and staining.
Acrylic solvent-based sealants are only plastomeric, their movement capability is only 10% for long-range service outdoor. They are generally used for joints, such as:
Curtain walls joints, exterior sidings,
Masonry prefabricated panels,
Metal to concrete joints such as joints between metal windows and concrete,
Wood to concrete joints (between wood windows and concrete).
In these sealants, the base polymer is usually an 80% solids acrylic dissolution which accounts for 50% of the total weight of the formula. There is also some 50% of fillers (mainly calcium carbonate, plus some pyrogenated silica, magnesium silicate and/or talc or clay), a small amount of plasticizer may be added such as DOP, DBP, pine oil may be added as a filler dispersant, and some solvent is added in order to adjust viscosity.
The maximum solids content is usually 85% so that there is some shrinking during drying, therefore it is necessary to start with an elastomeric acrylic polymer and to add some plasticizer so that the shrinkage will not bring too much stress at the interface between the sealant and the materials to be jointed.
Common Additives Used in Acrylic Sealants
Fillers reinforce and increase the volume of the sealant and lower the cost. Common fillers used are calcium carbonate, clays, barium sulfate and fumed silica. Fumed silica, a thixotropic filler, reduces the sag and improves gunnability.
Plasticizers, such as phthalates, dibenzoates, propylene glycol alkyl phenyl ether, etc. increase flexibility and elongation, and reduce the glass transition temperature which improves low-temperature flexibility.
Dispersing aids improve the incorporation of fillers and improve also the viscosity and package stability (if there are no dispersing aids, the fillers will slowly absorb the polymer at its surface and consequently the viscosity will increase during the shelf life). Low molecular weight polycarboxylic acid salts may be used as dispersing agents.
Silanes may be used also to improve the adhesion to impervious substrates such as metals and glass. The acrylic sealants which contain small proportions of silanes are often called siliconized acrylics.
