ADDITIVES AND CHEMICAL SPECIALTIES

Accelerating and Vulcanizing Agents

Vulcanizing agents are used to crosslink rubber compounds. The most commonly used material is elemental sulfur, although peroxides are used with some elastomer types. Accelerators are used to speed up the vulcanization process and improve the properties of the vulcanized material—many different types are available depending on the specific elastomer and vulcanizing agents, including amine-aldehydes, thiazoles, guanidines, sulfenamides, dithiocarbamates, and xanthates.

Accelerating and Vulcanizing Agents, Abrasives

Materials used as accelerating and vulcanizing agents.

Accelerating and Vulcanizing Agents, Dithiocarbamates

A chemical used as an accelerating and vulcanizing agent.

Accelerating and Vulcanizing Agents, Sulfur

A readily available raw material. Chemically and physically compatible with traditional interior and exterior glues.

Accelerating and Vulcanizing Agents, Thiazoles

Thiazoles are additives used as accelerating and vulcanizing agents.

Accelerating and Vulcanizing Agents, Thiuram Sulfides

Chemical used to accelerate and vulcanize.

Accelerating and Vulcanizing Agents, Zinc Oxides

Additives used to improve holding power.

Additives

An additive is a material used to change, or prevent or minimize changes in properties in a formulation.

Adhesion Promoters

Adhesion promoters are usually acid-modified or hydroxyl monomers. Their dual functionality helps formulators increase adhesion and lower viscosity. Depending on the application, polyester oligomers and specialty resins may also function as adhesion promoters.

Adhesion promoters crosslink on the surface, which may be glass, plastic, or another substrate. The surface material plays a critical role in product selection because different materials require specific adhesion promoters in order to achieve optimal results. The adhesion promoter’s reactive sites must be adaptable to reacting with the surface material. Dual-functionality monomers are often used as adhesion promoters for this reason because they help activate many surface materials and make them more responsive. Additionally, acid esters are often used because they provide a proton or neutron that can be linked on the surface.

Although adhesion promoters are used across a wide range of adhesives applications, they are most often found in laminating adhesives.

Adhesion Promoters, Adhesive Bonding Primers

An agent used to increase fixture times.

Adhesion Promoters, Alpha Methylstyrene Polymers

Alpha methylstyrene (AMS) is a chemical intermediate that is used in the synthesis of specialty polymers and copolymers.

Adhesion Promoters, Hydrogenated Resins

Materials that promote tack and enhance adhesion.

Adhesion Promoters, Pentaerythritol Esters

Rosin esters used to aid adhesion in a formulation.

Adhesion Promoters, Phenolic Resins

Phenolic resins are a type of synthetic thermosetting resin invented by Leo Baekeland, Ph.D., in 1907. The material was originally called Bakelite. The resins are used in the production of molded products such as billiard balls and laboratory countertops, and as adhesives and coatings.

Adhesion Promoters, Resorcinol

A crystalline compound originally obtained from galbanum resin.

Adhesion Promoters, Silane

When added to adhesives, silanes can provide improvement in adhesion by reducing moisture attack at the interface. This results in improved moisture, temperature, and chemicals resistance.

Adhesion Promoters, Silicone

Silicone anti-foams are typically formulations of dimethylpolysiloxane fluids and silica. They are chemically inert and insoluble in most foaming systems. This enables them to retain their activity over a long period of time.

Anti-Foaming Agents

Anti-foams are used in water-based systems to minimize the generation of foam, particularly during high-shear mixing operations. Anti-foams are usually immiscible with water, and very small amounts are usually very effective. Defoamers are additives that, when added to a liquid, break foam.

Anti-Foaming Agents, Non-Silicone

These are materials for applications where silicone is deemed undesirable. They are typically based on polyalkylene/polyethylene glycols and refined hydrocarbon oils.

Anti-Foaming Agents, Silicone

Most anti-foams are based on simple hydrocarbons or silicone fluids. The latter often function most effectively in parts-per-million concentrations. (See also Anti-Foaming Agents.)

Antioxidants

Antioxidants are compounds that inhibit chemical reactions with oxygen. Oxidation reactions may involve highly reactive molecules called free radicals. Free radicals are molecules that have lost an electron and try to replace it by reacting with other molecules. This causes the substance to break down. Metals often catalyze reactions with oxygen. Antioxidants inhibit these changes by reacting with the free radicals before they can react with oxygen (free radical scavenging) or by reacting with the metals.

Antioxidants, Phenolic

Many antioxidants are phenolic compounds. Phenolic antioxidants are excellent hydrogen donors and are widely used to stabilize polymers. (See also Antioxidants.)

Antioxidants, Phosphite

Phosphite antioxidants are high-performance solid antioxidants. They offer processing stability, color stability, and protection properties for thermoplastic polymers (polypropylene, high-density polyethylene, low-density polyethylene, polycarbonate, etc.). They produce excellent effects when used with phenolic antioxidants and contribute significantly in achieving color stability during compounding. (See also Antioxidants.)

Anti-Settling Agents

Anti-settling agents are additives used to prevent or retard pigment settling and to maintain uniform consistency during storage and application.

Anti-Skinning Agents

Anti-skinning agents are added to materials to prevent or retard the processes of oxidation or polymerization, which result in the formation of an insoluble skin on the surface of the material.

Anti-Static Chemicals

Surface treatment compound used to reduce or eliminate buildup of static electricity.

Anti-Tack Agents

Materials designed to eliminate adhesion.

Catalysts

Catalysts, preferably called “initiators” in the adhesives and sealants industry, are used to cure or crosslink monomers and polymers. Typical types include organic peroxides and hydroperoxides, sulfur compounds used in rubber vulcanization, and UV initiators used in adhesives and coatings.

Coalescing Agents

Coalescing agents improve the curing or film formation of a resin and are specific to the resin chosen. Very slow evaporating solvents are used because the coalescing solvent must remain in the voids between the resin particles during the early stages of evaporation and still be in the film during the late states so it forms evenly and doesn’t clump. After the film formation is complete, the coalescing solvent evaporates altogether.

Bio-based and environmentally friendly coalescing agents have also been developed to address the growing trend of sustainability. For example, many of these products do not include volatile organic compounds (VOCs).

Colloidal Stabilizers

The adsorption of homopolymers and block copolymers at solid-liquid interfaces is crucial for controlling the colloidal stability and, hence, the rheology of concentrated suspensions used in many applications, including adhesives, ceramics for electronic and structural purposes, paint, pharmaceutical products, and paper coatings. Block copolymers that form self-assembled brush layers have proven to be particularly effective colloidal stabilizers.

Colloidal Stabilizers, Cellulose Ethers

Polymers produced by the chemical modification of cellulose.

Colloidal Stabilizers, Soaps

Colloidal in nature, soaps act through adsorption or emulsification.

Corrosion Inhibitors

A corrosion inhibitor is a material that provides physical protection against corrosive attack or reduces the open-circuit potential difference between local anodes and cathodes. Examples of corrosion inhibitors include hexamine, phenylenediamine, dimethylethanolamine, sodium nitrite, and others.

Crosslinking and Curing Agents

Crosslinking improves three basic properties of the adhesive: it provides a higher temperature resistance, it provides improved shear resistance, and it increases solvent resistance. All of these stem from the same cause—reduction of mobility of the polymer. An added benefit to crosslinking, which is not readily apparent, is that the product is less prone to oxidation, which increases working life. The degree of crosslinking can be manipulated by the quantity of crosslinking agent used. A crosslinked polymer is often referred to as “having been cured.”²

Crosslinking and Curing Agents, Epoxy Curing Agents

Epoxies can be formulated as one-component or two-component systems. One-component systems are heat-cured and usually use dicyandiamide (DiCy) as a curing agent. Two-component epoxies are more common, and a range of curing agents is available. The cure kinetics and the glass-transition temperature (Tg) of the cured resin are dependent on the molecular structure of the curing agent. Curing agents include aliphatic amines, amidoamines, aromatic amines, cycloaliphatic amines, imidazoles, polyamides, anhydrides, polysulfides, and boron trifluoride adducts. (See also Crosslinking and Curing Agents.)

Crosslinking and Curing Agents, Hexamine

Hexamine (hexamethylenetetramine) is a heterocyclic organic compound with the molecular formula (CH₂)6N₄. It is prepared by the reaction of formaldehyde and ammonia, which yields crystalline hexamine. Hexamine is used as a crosslinking agent for hardening phenol formaldehyde resins and for vulcanizing rubber.

Crosslinking and Curing Agents, Melamine Formaldehyde Resins

Hard, thermosetting plastic material made by polymerization of melamine and formaldehyde.

Crosslinking and Curing Agents, Silane

Silane crosslinking technology can allow for higher extrusion speed. Compared to traditional crosslinking processes that involve organic peroxide, no crosslinking occurs inside the extruder, even at high temperatures.

Crosslinking and Curing Agents, Silicone

Crosslinkers or curing agents used in silicone formulations typically contain R-Si-X3 or Si-X4, where R can be amethyl, vinyl, or phenyl group, and X can be acetoxy, alkoxy, enoxy, or oxime groups. (Source: www.honeywell.com)

Defoamers

An additive that, when added to a liquid, breaks foam. This is in contrast to antifoam, which prevents foam formation.

Defoamers, Castor Oil

Insoluble material used to knockdown foam.

Defoamers, Pine Oil

Pine oil is an essential oil generated by the steam distillation of needles, twigs, and cones from a variety of species of pine trees.

Defoamers, Silicone Oils

Silicone-based defoamers are polymers with silicon backbones; they can be delivered as an oil or a water-based emulsion.

Defoamers, Stearic Acid

A saturated fatty acid with an 18 carbon chain, stearic acid is a waxy solid.

Defoamers, Tri-Butyl Phosphate

Tri-butyl phosphate finds use as a defoamer in vinyl latex emulsions, rubber-based paints, casein, inks, cement, protein- or resin-based adhesives, and textile sizings.

Dispensing Agents

Dispensing agents are chemicals that aid in the dispersion and stabilization of pigments and other finely divided solid particles.

Dispersing Agents

Dispersing agents are chemical compounds that, when added to a colloidal suspension, tend to make the particles more disperse. (See also Introduction to Fillers, as well as Surfactants and Dispersing Agents.)

Driers

A drier is a compound that catalyzes or accelerates the drying (curing) of a coating or adhesive, or the crosslinking of polymers or drying oils. Driers are not the same as curing agents, which chemically react with functional groups in the polymer. Driers are catalytic in nature and do not chemically react with the polymeric material.

Driers, Cobalt

Common oxidative drier with a deep blue/purple color.

Driers, Water Dispersible

Water-dispersible driers are designed for use in water-based systems.

Elastomers

Any of various polymers having the elastic properties of natural rubber.