A release agent (also mold release agent, release coating, or mold release coating) is a

chemical A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., w ...

used to prevent other materials from bonding to surfaces. It can provide a solution in processes involving

mold A mold () or mould () is one of the structures certain fungi can form. The dust-like, colored appearance of molds is due to the formation of spores containing fungal secondary metabolites. The spores are the dispersal units of the fungi. Not ...

release, die-cast release,

plastic Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adapta ...

release,

adhesive Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation. The use of adhesives offers certain advant ...

release, and

tire A tire (American English) or tyre (British English) is a ring-shaped component that surrounds a Rim (wheel), wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide Traction (engineering), t ...

and

web Web most often refers to: * Spider web, a silken structure created by the animal * World Wide Web or the Web, an Internet-based hypertext system Web, WEB, or the Web may also refer to: Computing * WEB, a literate programming system created by ...

release. Release agents provide the critical barrier between a molding surface and the substrate, facilitating separation of the cured part from the mold. Without such a barrier in place, the substrate would become fused to the mold surface, resulting in difficult clean-up and dramatic loss in production efficiency. Even when a release agent is used, factors such as irregular applications or improper release agent choice may have a dramatic effect on the quality and consistency of the finished product. Many kinds of release agents are used. They are waxes, fatty ester,

silicone A silicone or polysiloxane is a polymer made up of siloxane (−R2Si−O−SiR2−, where R = organic group). They are typically colorless oils or rubber-like substances. Silicones are used in sealants, adhesives, lubricants, medicine, cookin ...

s, and metallic soaps. 420 px, Magnesium stearate is a release agent.

Functionality

Cosolvent

Volatile organic compound Volatile organic compounds (VOCs) are organic compounds that have a high vapour pressure at room temperature. High vapor pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, a ...

(VOC) reduction along with the elimination of health and safety concerns surrounding solvent-based release agents were primary drivers in the development of cosolvent mold release. Cosolvent based release agents combine the benefits of a solvent based system and the safety of water-based release agents.

Semi-permanent

One of the key attributes of a release agent is its degree of permanence: how long will it last before reapplication is necessary. A semi-permanent release agent does not need to be reapplied for every cycle of a molding operation and even works better when it is not over-applied to the mold surface. How many releases can be achieved before reapplication is necessary varies by process, material, and application method. In order to achieve multiple releases per application, the semi-permanent release coating generally must be applied to a clean, dry surface free of dirt, rust, grime or previous coatings. This allows the release agent to properly bond to the mold and mold tooling, improving durability and longevity of the coating.

Sacrificial

Sacrificial coatings must be applied before every cycle of a molding operation and are therefore considered more labor intensive. Most molders will prefer semi-permanent coatings to sacrificial coatings, especially when molding rubber and plastic parts. These coatings contain fewer solid ingredients, and thus do not last as long as semi-permanent coatings.

Water- or solvent-based

Release agents may be water or solvent-based and use of either will depend on the personal preference of the molder, plant safety regulations, hazardous materials shipping costs, state, local, or federal regulations, and/or desired drying times of the release coating. Water-based die lubricant (WBD) has been used for about 40 years. All die casting machines have been designed with the use of WBD. Water-based release coatings generally dry slower than solvent-based release agents but present fewer health and safety concerns. Water-based release agents will be less expensive to ship because of their inherently non-flammable nature and satisfy most plant-safety goals. Solvent-based release coatings dry almost instantly but present serious health and safety concerns. Fumes from solvent-based release agents may be hazardous without proper ventilation of the work area. Most solvents used in release agents are flammable.

Applications

Asphalt

Asphalt release agents are chemical products developed and manufactured as alternatives to diesel and solvents commonly used for cleaning equipment associated with hot mix asphaltic concrete (HMAC) production and placement on government and private facilities. The United States Oil Pollution Act of 1980 was used as the foundation to build the current program. The intent of asphalt release agents is to eliminate harmful stripping products that come into contact with bituminous products and strip the asphalt (binding agent) from the aggregates causing potholes, raveling, and other detrimental pavement failures.

Concrete

In the

concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wid ...

construction industry, form release agents prevent the adhesion of freshly placed concrete to the forming surface, usually

plywood Plywood is a material manufactured from thin layers or "plies" of wood veneer that are glued together with adjacent layers having their wood grain rotated up to 90 degrees to one another. It is an engineered wood from the family of manufactured ...

, overlaid plywood,

steel Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistan ...

aluminum Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...

. In this application, there are two types of release agents available: barrier and reactive. Barrier release agents prevent

adhesion Adhesion is the tendency of dissimilar particles or surfaces to cling to one another ( cohesion refers to the tendency of similar or identical particles/surfaces to cling to one another). The forces that cause adhesion and cohesion can ...

by the development of a physical

film A film also called a movie, motion picture, moving picture, picture, photoplay or (slang) flick is a work of visual art that simulates experiences and otherwise communicates ideas, stories, perceptions, feelings, beauty, or atmospher ...

or barrier between the forming surface and the concrete. Reactive release agents are chemically active and work by the process of a

chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking ...

between the release agent and the free limes available in fresh concrete. A soapy film is created which prevents adhesion. Because it is a chemically reactive process, there is generally little to no residue or non-reacted product left on the forming surface or concrete which provides for a cleaner process.

Food processing

Release agents are used to aid in the separation of

food Food is any substance consumed by an organism for nutritional support. Food is usually of plant, animal, or fungal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is in ...

from a cooking container after

baking Baking is a method of preparing food that uses dry heat, typically in an oven, but can also be done in hot ashes, or on hot stones. The most common baked item is bread but many other types of foods can be baked. Heat is gradually transferred " ...

roasting Roasting is a cooking method that uses dry heat where hot air covers the food, cooking it evenly on all sides with temperatures of at least from an open flame, oven, or other heat source. Roasting can enhance the flavor through caramelizatio ...

. Traditionally fat or

flour Flour is a powder made by grinding raw grains, roots, beans, nuts, or seeds. Flours are used to make many different foods. Cereal flour, particularly wheat flour, is the main ingredient of bread, which is a staple food for many cul ...

have been used, but in industrial food processing other chemicals might be used. The application is called bakery release. In

bakery paper Parchment paper, or vegetable parchment, is a cellulose-based composite that has been processed to give it additional properties like non-stickiness, grease resistance, and resistance to humidity. It is commonly used in baking as a disposable ...

greaseproof paper Greaseproof paper is paper that is impermeable to oil or grease, and is normally used in cooking or food packaging. It is usually produced by refining the paper stock and thus creating a sheet with very low porosity. This is then passed between ...

release agents like

catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

-cured

release coatings may be used.

Metal casting

Mold release agent also can be used in die casting or metal forging process of metal, such as aluminum, aluminum alloy, zinc, zinc alloy, magnesium, etc.

Paper

In industrial

papermaking Papermaking is the manufacture of paper and cardboard, which are used widely for printing, writing, and packaging, among many other purposes. Today almost all paper is made using industrial machinery, while handmade paper survives as a speciali ...

release agents are used to get slip effect of the paper from the processing equipment. A release agent may be applied on the process rolls (like the

yankee dryer A Yankee dryer is a pressure vessel used in the production of machine glazed (MG) and tissue paper. On the Yankee dryer, the paper goes from approximately 42–45% dryness to just over 89% dryness. In industry, MG cylinders or Yankee dryers are pri ...

) or in the

paper coating Coated paper (also known as enamel paper, gloss paper, and thin paper) is paper that has been coated by a mixture of materials or a polymer to impart certain qualities to the paper, including weight, surface gloss, smoothness, or reduced ink absor ...

. Some

paper Paper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, rags, grasses or other vegetable sources in water, draining the water through fine mesh leaving the fibre evenly distribu ...

types are made with low

surface energy In surface science, surface free energy (also interfacial free energy or surface energy) quantifies the disruption of intermolecular bonds that occurs when a surface is created. In solid-state physics, surfaces must be intrinsically less ener ...

release coatings: * Release liners for pressure-sensitive adhesive laminates and tapes *Casting papers *General industrial release papers *Food-grade release and packaging papers

Pharmaceuticals

Release agents (e.g., magnesium stearate) are added to powdered and granulated drug compositions, to serve as a lubricant for mold release purposes during tabletting.

Plastics

Release agents are coated onto some plastic films to prevent adhesives from bonding to the plastic surface. Some release agents, also known as de-molding agent, form oil, parting agent or form releaser, are substances used in molding and

casting Casting is a manufacturing process in which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a ''casting'', which is ejecte ...

that aid in the separation of a mould from the material being moulded and reduce imperfections in the moulded surface. Slip Additives are similarly used to prevent thin

polyolefin A polyolefin is a type of polymer with the general formula (CH2CHR)n where R is an alkyl group. They are usually derived from a small set of simple olefins (alkenes). Dominant in a commercial sense are polyethylene and polypropylene. More speciali ...

films from adhering to metal surfaces (or each other) during processing, for instance in film blowing.

Rubber

There are two types of release agents used in the molding of rubber products. Both are

based. The decision on which to use has to do with lubricity and release. Water-diluted silicon is used when you have rubber sliding over a hot mold (sheets or slugs). The silicon keeps the rubber from sticking to the mold but just as important it lubricates the rubber so it will slide over the hot mold as it is loaded. Diluted silicon typically has to be applied every cycle. Semi-permanent mold release builds a silicon matrix on the mold that becomes a barrier between the rubber and the metal surface of the mold. The matrix is created by the other ingredients in the semi-permanent mold release. Applications of semi-permanent mold release vary from every cycle to once daily applications depending on the compound being molded and the design and quality of the mold. Silicone-based rubber products, however, require a non-silicone based releasing agent.

References

{{reflist Plastics industry Process chemicals