About Release Agents and Anticorrosives
A release agent is something which stops one thing sticking to another. It is like butter which mothers wipe around their baking trays so that their cakes drop out easily after they are cooked. Release agents can be solid sheets such as vinyl or polyester, but generally manufacturers and users mean liquids or semi-liquids applied to a mould. Berryessa has experience and expertise in designing and manufacturing liquid release agents for three industries – fabrication of concrete articles, extrusion of plastics, and pressing of sheet metal.
Anticorrosive agents do a similar job – protecting a hard surface such as steel or aluminium from chemical attack. Water, and more particularly salts dissolved in water, are destructive of most metals. Metals in all kinds of applications commonly require anti-rust or anti-stain treatments for at least part of their processing and all of their service life.
Many different terms are used – mould release agent, mold release agent or form release agent. The term form oil has been used for decades for petroleum-based products used as release agents, but the term is avoided for water-based agents. The term bondbreaker is used for products which stop fresh concrete sticking to other concrete, either fresh or old. The term anti-adhesive describes a bondbreaker used to spray over any surface, particularly plant and equipment, to protect concrete spills and overspray, allowing easy removal without sticking or damage to painted surfaces, hoppers and the like. Slip agent is a term used especially for processes where the moulded material is extruded rather than poured and allowed to set: brick making and moulding of thermoplastics are obvious examples. Slip agent is also a good term for a release agent used on low water, pressure moulded concrete such as used to make concrete building blocks and some large mouldings.
For concrete, release agents have two functions: waterproofing and lubrication. Water-based emulsions achieve waterproofing by depositing oily or waxy materials as they dry, forming an impervious film. Setting concrete sticks tenaciously to most mould materials, and in wet concrete the watery solution is the bonding agent, so mould release agents have the job of providing a barrier between the concrete and the mould during setting. For very dry concrete mixes where there is no free water, the job of the release agent is to lubricate the interface, providing slip as the mixture moves slightly as it heats and cools.
Water-based mould release agents have evolved for good reasons. Petroleum-based release agents are smelly, flammable and unhealthy. Two years’ handling diesel-based products makes skin look twenty years older. Their environmental effects are substantial – see Clean and Green.
Release agents are made wholly or partly from petroleum oils, plant oils, or modifications of plant oils and sugars. Water-based products are emulsions or solutions of one or other of these materials.
All Repel products are type 3 products.
Type 1 water-based release agents leave a lesser but still significant burden on the environment. Vegetable oils, whether neat or in water emulsions, have a low environmental impact, but they tend to build up on moulds into a film which is very difficult to remove, similar to char in cooking ovens. Type 3 water-based products steer a middle course, aiming for reliable release with minimal residues left on moulds.
Different applications need different products and care with how products are applied, and how much. The general rule is –
least is always best