Release agents and release processes in different industries

2022-02-22   Pageview:74

01. Overview of release agent

Release agent, also known as release agent, release agent. It is an interface coating between the mold and the molded object, which can make the surface of the object easy to release, smooth and clean.

02. The working principle of release agent

▶ The polar chemical bonds interact with the mold surface to form an absorbent film.

▶ When spread out into a unidirectional arrangement on the mold surface, the molecules adopt a characteristic stretched chain configuration.

▶ Covered in a densely packed manner, with increasing molecular weight and viscosity within a certain range, the release ability increases.

Due to the different production conditions, many requirements are also put forward for the performance of the release agent. Theoretically, the release agent must have application characteristics such as chemical corrosion resistance, high temperature resistance, wear resistance and tensile strength, good release continuity, no pollution to the mold, and no secondary transfer.

3. Application of release agent

With the rapid development of injection molding, extrusion, calendering, molding, lamination and other processes, the amount of release agent has also increased significantly. Mold release agents are widely used in the molding process of composite materials such as metal, rubber plastic, concrete, polyurethane, carbon fiber, unsaturated resin, epoxy, phenolic, vinyl resin, etc.

Casting is a process in which metal is smelted into a liquid that meets the requirements and poured into a mold. After cooling, solidification, and cleaning, a casting (part or blank) with a predetermined shape, size and performance is obtained.

Casting is divided into gravity casting and pressure casting (die casting) according to the casting process of molten metal.

Gravity casting includes sand casting (green sand, dry sand, chemically hardened sand) casting, metal casting, investment casting, lost foam casting, etc.; pressure casting refers to the process of injecting molten metal into the mold under the action of other external forces.

In the southern region of my country, water-containing emulsified hydrocarbon solvent oil is generally used for demoulding in green sand casting, which not only reduces the manufacturing cost, but also eliminates the potential safety hazards caused by the flammability and explosion of hydrocarbon solvent oil. In winter in northern regions, non-water hydrocarbon solvent oil products are usually used to prevent the products from freezing at low temperature and being unstable.

The die-casting release agent is usually a composite system of silicone emulsion, wax emulsion, fatty acid ester emulsion, etc. The synergistic compounding of various emulsions enables the release agent to have good lubrication and metal infiltration effects under high temperature conditions.

The hot core box molding sand release agent and the cold core box molding sand release agent use different forms of silicone products as the mold release material according to different processes.

Forging release agents play an important role in the plastic forming process of carbon steel, alloy steel, aluminum, magnesium, titanium, copper, etc. and their alloys.

Traditional forging release agents are mainly suspensions prepared from inorganic powders such as graphite, carbon powder, talc powder, molybdenum disulfide and binders, which account for most of the forging lubricants. With the increasingly serious environmental pollution, non-graphite environmentally friendly forging release agents have gradually been promoted and applied in the market in the forging of copper, carbon steel, aluminum, stainless steel and other metals.

Liquid die forging (vacuum extrusion casting) is usually a suspension composed of inorganic powder as the main component, supplemented by a small amount of wax emulsion, tackifying resin, etc. The lubricating coating has a good thermal insulation effect while isolating the mold, avoiding the premature cooling of the molten metal and the incomplete cold isolation type of the casting.

In China, which has the title of “infrastructure maniac”, its core infrastructure material is reinforced concrete. This type of release agent is mainly involved in the production of concrete and cement products such as sleepers, track slabs, bridges, piers, pipes, segments, pipe piles, and prefabricated houses. Generally, mineral oil, motor oil, fatty ester emulsion, fatty acid soap or solvent-based products are used to meet the needs of multiple factors such as different molds, climatic conditions, construction methods, material costs and appearance quality of concrete products.

Plastic and rubber mold release agents mostly use silicone systems, of which plastic mold release agents are generally spray-can-type silicone diluents. Rubber release agents are further divided into films, hoses and tire release agents, and mold release agents are used in the tire production process. Film-based release agents are mostly fatty acid soap powders and inorganic powders, which are low in cost, but easily cause dust pollution during production. Paste film release agents, butyl rubber or natural rubber inner tube release agents avoid these problems. Polyether and polyester can be used as mold release agents for rubber hoses because of their good cleaning properties and no residue.

Tire release agent (release agent), which can be coated on bladder or tire embryo. Due to the strict requirements on mold release and mold release continuity, it is necessary to use reactive silicone emulsion and silicone resin emulsion for mold release, spraying Once, it can achieve 12 consecutive demoulding. Silicone rubber release agents should use fluorine-containing surfactants, fluorine-containing polyethers, etc. in the selection of product raw materials.

Polyurethane products are used in a large amount and are of various types, including polyurethane soft foam, rigid foam, self-skinning polyurethane, polyurethane microcellular elastomer, high resilience polyurethane, etc. These products are dispersed in water-based wax emulsion, modified silicone oil emulsion, and solvent-based wax. liquid-based.

4. Release agent for composite materials

The field of composite materials is very extensive, and the products involve artificial stone, SMC (sheet molding compound), bulletproof helmet, bathroom, carbon fiber sports equipment, epoxy resistance, epoxy reactance, yacht, fan blade, cabin cover, ski, rotomolding, synthetic Fiber…covers materials such as epoxy, phenolic, unsaturated resin, vinyl resin, etc. Most of the above materials use compound wax emulsion or fatty acid ester, surfactant, etc. as internal mold release agent.

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