Acrylic Emulsion Sealant

Acrylic emulsion (55% solids)  40  Surfactant  1  Plasticizer  7  Mineral spirits  2  Ethylene glycol  2  Calcium carbonate (ground)  46  Miscellaneous fillers and pigments  2

PROCESSING

Once the base emulsion polymer is obtained, it is then mixed with all other liquid ingredients and additives except for the fillers. When this blend is complete, add the filler slowly, blending well between all additions. Generally, high shear mixers are sufficient to produce a heavily bodied sealant.

APPLICABLE BASE POLYMER PROPERTIES

Acrylic emulsion based sealants have taken over many of the applications where a higher movement capability is required than for polyvinyl acetate sealants. Acrylic sealants can also be used outdoors, whereas the polyvinyl acetate sealants have inferior exterior durability. Acrylic emulsion polymers are ideally suited to the formulation of medium performance sealants. There is a significant variation in the types of base polymer emulsions that are available, and these emulsions are easy to formulate. This gives the formulator a wide latitude for compounding to meet specific requirements. Sealants based on acrylic emulsions provide tough, elastic systems, with high adhesion and durability, and they are very environmentally friendly and easy to use.

RESULTING PROPERTIES

A broad product line with a wide range of properties can be developed by only varying the pigment-to-binder ratio. With high pigment-to-binder ratios, water based acrylic sealants are able to compete against the low cost polyvinyl acetate and vinyl acrylic sealants. On the other end of the formulation spectrum, low pigment-to-binder ratios provide competition to high performance sealants. In this way acrylics can compete against the polyurethane and silicone sealants meeting ASTM C 920. A typical formulation for a standard acrylic latex sealant is given above.

TIPS and TRICKS

Fillers are commonly used in water based acrylic sealants. They are used as a rheology modifier, polymer reinforcement, cost reducer, and pigment. Fillers give a formulation higher solids content, which results in less shrinkage. They can also be used to provide a mastic like consistency or even thixotropic (non-slumping) properties. The properties provided by the fillers will depend on the type, particle size, particle size distribution, and surface character of the filler. Sealants are sometimes classified by their filler to base polymer ratio (pigment to binder). Using too much filler can result in a decrease in adhesion and aging properties such as crack resistance. Lower levels of filler loading improve adhesion, but can result in excessive volume shrinkage, slump or sag, and possible crack formation.(This article was contributed by a visitor of this site)