PRODUCT COMPOSITION: BASIC INGREDIENTS
Elastomer sealants are products designed to hamper air and water infiltrations through the exterior and interior joints of a building. Adhesives are used for gluing surfaces together.
Did you ever wonder why some products apply better than others? Or why some sealants are more elastic and last longer? Or even why certain adhesives are more flexible and dry faster? The answer lies in their ingredients and the proportions in which they are mixed.
What are these ingredients?
Sealants and adhesives consist of solid and liquid ingredients. Some are volatile, others are not. Non-volatile ingredients form a paste that clings to the surface. These include pigments and binders. Volatiles ingredients are added to sealants and adhesives to make them more fluid and easier to apply. They evaporate as the product dries and are called diluents. Sealants and adhesives also contain additives to improve their properties. These additives may or may not be volatile.
There are no products that can meet every need. That is why different products contain different proportions and combinations of ingredients.
Pigments
Pigments are very fine particles about one micron (one thousandth of
a millimeter or 1/25,000 of an inch) in size. Organic (vegetable or
animal) or inorganic (mineral) in origin, pigments are responsible for
many properties like hardness, color and opacity for sealants, and
hardness and viscosity for adhesives. These properties depend on the
types and quantities of pigments used.
Elastomer sealants
Elastomer sealants contain two types of pigments: color and extender
pigments.
The main color pigments used in elastomer sealants are titanium dioxide
and various ferrous oxides. Most elastomer sealants contain white
pigments, like titanium dioxide. To obtain other colors, color pigments
are added.
Extender pigments enhance certain elastomer sealant properties and cost
less than color pigments. Clay, talc, calcium carbonate and silica are
among them. However, extender pigments cannot be used in place of color
pigments. Their excessive use can reduce the elasticity and longevity of
elastomer sealants.
In addition to color, pigments may provide other properties to elastomer
sealants such as durability and solar radiation resistance.
Binders
Binders fuse pigments together and form an even paste that adheres to
the surface. It plays the role of a glue for adhesives and acts as a
glue and elastic for elastomer sealants. Without binders, pigments could
not adhere to the surface. Following application, volatile ingredients
evaporate and the binder dries, hardens and welds the paste to the
surface.
Binders are made from rubber and natural or synthetic resins. They
affect many properties of the product including adhesion, flexibility,
durability and color retention (sealants).
Modern products contain different kinds of rubber and resins.
- Adhesives: acrylic, acrylic vinyl, polyvinyl acetate, styrene-butadiene, bitumen, etc.
- Sealants: vegetable oil, acrylic, acrylic vinyl, polyvinyl acetate, butyl, urethane, styrene-butadiene, silicone, thermoplastic, bitumen, etc.
Elastomer sealants generally bear the names of the types of rubber
they contain. The chart below lists the main types of rubber used in
modern elastomer sealants.
Chart of the Main Types of Rubber used in Modern Elastomer Sealants
Diluents
Diluents are liquid ingredients added to products to make them more
fluid and easier to apply. When they evaporate, the product dries,
leaving an elastic paste which adheres to the surface.
Diluents permit the classification of elastomer sealants in three
categories : solvent-based, water-based and chemical-based elastomer
sealants which contain few diluents or none at all. They also allow the
classification of adhesives in two categories: solvent-based and water-based
adhesives.
Solvents are used as diluents in solvent-based products. These include:
mineral spirits (emitting odors or odor-free), toluene, xylene, etc.
Solvents are substances that can dissolve other substances. Mineral
spirits, for example, are solvents because they can dissolve binders.
Water is the diluent in water-based products. Water-based products
contain very small quantities of solvents to help binders fuse together.
We call such solvents coalescing agents (additives). Water-based
products are also known as latex products. Latex is a dispersion of
small particles of synthetic rubber in water. Latex products are thus
water-based products.
Additives
Additives are solid and liquid ingredients added in very small quantities to products to improve their properties. Here are the main additives used in elastomer sealants and adhesives.
Coalescing agents: Help binders in water-based product to fuse together.
Dispersing agents: Facilitate the dispersion of pigments in binder.
Drying agents: (driers) Accelerate the drying process in drying oil-based caulking compounds or chemically polymerized caulking.
Rheology: control agents Regulate product viscosity to prevent running when products are applied to surfaces. This characteristic is very important since the products are often applied to vertical surfaces: thickness of 5 to 10 mm and sometimes even greater for sealants; thickness of 1/4 of an inch (5 mm) and sometimes more for adhesives.
Antifreeze: (ethylene glycol) Controls the freezing of water-based products so that they may withstand a few freeze/thaw cycles.
Bactericides and fungicides Protect products against mildew and prevent the growth of microorganisms.
Plasticizers: Impart more elasticity and flexibility to the paste (sealants). Elasticity allows the sealant to modify its shape; flexibility, in return, allows the sealant to bend without causing any damages.
Adhesion promoter: Provides better adhesion on some surfaces (sealants and adhesives).
Without naming them all, there are a number of other additives which boost adhesion, durability and flame resistance, etc.
PRODUCT COMPOSITION: WATER-BASED, SOLVENT-BASED OR CHEMICAL-BASED?
Since water-based and solvent-based products are formulated differently,
they possess different properties. Such differences are used to
determine which type of product is best suited to a particular job. The
chart below presents the main properties of water-based and solvent-based
adhesives. The chart on the following page shows the main properties of
various types of sealants.
Main Properties of Water-Based and Solvent-Based Adhesives
Caulkings and Elastomer Sealant Chart
 PRODUCT COMPOSITION:
PRODUCT COMPOSITION AND STORAGE |
