Film-forming lubricating oils, solid lubricants, waxes, or fluids that prevent other materials from sticking or adhering to an underlying surface are called mold releases and release agents. Unlike permanent non-stick coatings, release agents typically require replenishment and are non-curing.
There are two basic types of mold releases and release agents: non-permanent and semi-permanent. Non-permanent products may require re-application after each use, usually in the form of a mold release spray. Semi-permanent mold releases and release agents perform over multiple production cycles, but eventually break down due to sensitivity to moisture and other chemicals.
Non-permanent release agents:
Barrier release agents prevent adhesion by depositing a physical barrier that covers the mold or forming surface. They are typically composed of heavy oil which is diluted by lighter oil in order to increase spreadability. During application the lighter oil evaporates, leaving an oil film.
Reactive release agents undergo a chemical reaction with either the working material or forming surface creating a weak boundary layer. Reactive release agents dissipate leaving little to no residue.
Semi-permanent release agents:
Solvent-based, semi-permanent release agents are wax- or polymer-based mold release systems. A durable coating is deposited on the forming surface that allows several cycles to be performed before reapplication. Solvent-based systems are quick drying and outperform water-based alternatives in extreme environments.
Water-based, semi-permanent release agents replace solvent-based release agents in manufacturing process where extreme temperatures and pressures are not present. They are an environmentally friendly alternative.
Mold releases and release agents are integral to several manufacturing processes. They enhance productivity, improve surface quality, reduce defect rates, and extend tool, die, or mold life expectancy. Common applications include:
Concrete – The concrete industry uses both barrier and reactive release agents in order to prevent adhesion between the forming surface and the concrete mixture.
Die casting – Die casting is a process utilizing relatively high-melting temperature alloys of aluminum and magnesium under high pressure. With the advance of technology die casting has evolved to produce large as well as intricate part designs. Release agents, which may be referred to as die lubricants, are engineered to promote material flow, equalize temperature gradients, and thereby reduce cycle times and increase die life.
Food processing - Food and beverage processing equipment may require a release agent to aid in the separation of food from containers used during baking, roasting, blending, or other food processing operations.
Molding – Compression, injection, transfer, as well as many other application-specific molding operations rely on mold release agents as a processing aid in order to consistently produce desired shapes from a wide range of materials including composites, elastomers, thermoplastics, and even metallic objects.
Mold releases and release agents primarily function by lowering the surface energy of the forming surface. Only reactive release agents differ as they establish a weak boundary layer that dissolves. Lowering the surface energy decreases surface tension as the polarity of molecules in the working material have no attraction to the release agent and therefore no surface tension. To determine the surface tension of a solid surface indirect measurements of the contact angle between the surface and a liquid of known surface tension, such as water, are made. The contact angle, known as the angle of incidence, exhibits the surface tension in relation to the liquid it is compared to.
Mold releases and release agents must be compatible with their working environment. Criteria used to depict a product suitable for an application includes the following:
Material compatibility is essential when selecting release agents. Chemical companies are the main suppliers and manufacturers of mold releases and release agents and supply material safety data sheets that illustrate both substrate and working material compatibility. Common mold release materials include:
CFC / Chlorofluorocarbon
Ester / diester
Fluoropolymer / PTFE (e.g., Teflon®)
Molybdenum / metal sulphide
Natural (vegetable oil / animal fat)
Petroleum / mineral oil based
Synthetic / semi-synthetic
Wax / stearate
Mold manufacturers may offer proprietary mold release and release agents.
Mold release agents may fail due to embrittlement in temperatures below their operating temperature range, or they may bake off, contaminating the working material, when temperatures exceed upper limits.
Depending on the application specialized features may be desired, such as:
- Biodegradable - Products are designed or suitable to decompose or break down into harmless chemicals when released into the environment.
- EP (extreme pressure / active) - EP additives include chemically active agents such as sulfur, phosphorous, or chlorinated compounds that are reactive and form a film to prevent seizure, sticking, or surface adhesion under loads causing high pressure conditions.
- Corrosion inhibitor / rust preventative - Corrosion inhibitors and rust preventatives prevent corrosion or otherwise greatly reduce the rate at which metallic surfaces corrode. They often have penetrating lubricant or water displacement characteristics.
- Food grade / FDA H1 - Food grade, FDA H1, release agents are suitable for applications in processing equipment where contact with food, beverages, or pharmaceuticals may occur.
- Low / non-foaming - Fluids do not produce foam or produce only small amounts of foam. Non-foaming characteristics are achieved through the use of additives that break out entrained air.
SAE AMS3091 - This specification covers a mold release agent in the form of a liquid.
CS CAS37 - This document describes the categories of release agents currently available in the concrete industry, outlining their advantages and disadvantages.