The release agent developed in parallel with the plastic reinforcement industry and other advanced manufacturing processes has a history of 70 years. In the past, the industry standard was to use layer after layer of wax coating, which required a long drying time between coating and polishing. This long cycle and labor-intensive method gradually becomes less and less with the emergence of fiber reinforced plastic FRP products. In order to comply with the current competition and the pressure of market requirements to produce more products, now, although manufacturers admit that in fact they need to produce a large number of products at high speed, a major factor has been continuously ignored, and even authoritative manufacturers, that is demoulding. Many factories simply use wax to do this work. Compared with gel coating, resin and reinforced materials, the daily consumption of demolding in synthetic industry is not worth mentioning. However, as many synthetic material manufacturers finally found, no matter how well the mold is designed, how to improve the molding process and resin quality, if the release agent does not work, these problems will have no results.

Effective demoulding

In view of the important role of release agent in the production process, we must make sure that we know what to consider when choosing. Effective release is as follows:

Mold surface chemical activity. This is the basic condition to ensure that two ordinary surfaces will not bond. This condition is affected by permeability, chemical reaction and compatibility, surface tension, surface structure and polarization ability of the two materials

Low surface tension makes the mold release agent wet the mold to form a continuous film

Insoluble

Heat resistance, avoid curing or melting at process temperature

It has strong adhesion with the die surface, but has similar polarity with the wet resin, which can ensure easy separation. Two surfaces with different polarity often bond

Resist other factors causing bonding, such as high static electricity, high vacuum on two smooth surfaces, or sticking on one of the surfaces

Looking for what

Although it is helpful to choose the release agent to follow the above guidelines and may make the production process faster, cleaner and easier, there are other factors to consider. When it is difficult to demould, the common fault of the manufacturer is to blame the release agent. In fact, there are many other conditions that should be checked before condemning the release agent.

A significant but overlooked factor is climate. In cold climates, if the mold surface is lower than the room temperature, the outer surface of the resin or gel coating may solidify earlier. This will cause the interface surface not to cure or become sticky. In fact, this phenomenon will not only cause difficult demoulding, but also hinder the evaporation of free styrene monomer. Further, if there is residual uncured styrene, it will act as a solvent to dissolve the release agent film.

Another possible factor is that the release agent on the interface has not been cured. The same styrene monomer is often used for mold stripping. It can slowly dissolve the release agent film, although a good release agent has styrene resistance. In fact, the longer the residence time of gel, the greater the chance of styrene releasing agent. Moreover, many factories have sticky experience, especially when the seasons change. This may be due to the insufficient amount of catalyst, resulting in slow curing, prolonged curing time, or excessive addition of catalyst, too fast reaction and increased exothermic temperature. If the penetration resistance of wax release agent is low, it may melt during rapid high-temperature curing, resulting in the product sticking to the mold.

Another factor is gelation time. Gel coating and laminated resin contain a large amount of styrene, while styrene can be used to clean the mold. Therefore, when the gel coating is glued to the mold, a solvent is potentially applied. So the gel time is not too long is very important. In view of the good gelation time of 11-20min, the gelation time of 30-50min may dissolve the surface of demoulding agent due to the presence of styrene monomer. We know that any release agent on the market uses styrene as solvent except PVA (polyvinyl alcohol)

New and immature molds

It is impossible to accurately calculate the amount of unreacted styrene residue in gel coating or new mold. Therefore, there is no way to know how the residual styrene in the mold will affect the release agent used for the first time. With this in mind, the ideal approach is to pre mature new or uncured molds before use to minimize styrene residues.

Because when curing moulds, styrene runs to the surface of gel coating. The new mold can be simply baked with strong light for 2-3 days. The styrene monomer on the surface of the gel coating can be evaporated, which will increase the initial demoulding effect when using the new mold. However, the new mold will still have styrene residue after being placed indoors for two weeks, causing a series of problems. At the same time, if the mold is not fully matured, the styrene monomer will be released, and the new mold may be bonded with ten layers of wax. Considering that we do not have appropriate technology to accurately identify whether the mold is processed under ideal conditions, we usually recommend using PVA to complete the first few demoulding. PVA can inhibit styrene overflow during curing of the first batch of mold products. PVA should be used on the release agent, which is directly applied to the mold. After the first demoulding, the PVA shall be wiped off with a wet cloth and the release agent on the drawing shall be reapplied. This procedure should continue until PVA completely leaves the mold and adheres to the molded product.

Type of release agent

PVA

PVA is one of the first release agents used in resin reinforced plastics industry. When using new and immature molds, PVA is still one of the safest, most effective and very reliable release agents. The advantage of PVA is that it can inhibit the dissolution of styrene monomer. After changing the mold, styrene monomer often evaporates in the process, so that the PVA film can be completely transferred to the surface of molded products, which makes it impossible to continue to use. Next, it is time to replace another more convenient release agent.

Wax system

Wax release agent is the first release agent used in synthetic industry. For this reason, many factories prefer to use canned hard paste wax as release agent. These old release agents have been greatly improved from the initial paste use and liquid use. Some are still resistant to low temperature, while others are suitable for high temperature use. However, it is known that many waxes add silicon to improve gloss and ease of use. This is the "fish eye" in the selected coating, and there is a danger of premature demoulding.

Polymer based release agent

Polymer based release agent takes carbon fluoride as the matrix, including polytetrafluoroethylene (PTEE). Many suppliers have developed patented products of polymer release agent containing carbon fluoride. These models of release agents will form cross-linking with the mold and will not transfer. They can be demoulded multiple times in one use. For molded products obtained by using polymer based release agent, the two processes such as bonding or painting will be easy, because there is no bonding problem.

Internal release agent

The internal release agent can be based on vegetable oil or various special pure polymer chemicals.

They are used as additives for resins or gel coatings, which are about 0.5-1.0% of resin quality. When vegetable oil is used as a collective, the release oil and resin are completely incompatible and exudation can be realized.

Silicon system

Silicon is rarely used as a release agent in pure state. As mentioned in the previous wax system, the liquid release agent contains a large amount of silicon, which will cause early release and fish eye structure.

Semi permanent release agent

Using the mechanism of coating, a layer of silicone resin coating with low surface activity is formed on the mold surface, which can be demoulded continuously.

expectation

In the past footprint and competitive world of synthetic material manufacturing, engineers need to take advantage of all advantages over competitors. Customers no longer only demand quality, but mass production accompanied by high quality. Therefore, it is necessary to eliminate any factors that reduce production efficiency. One of the simplest ways to eliminate low efficiency is to select the appropriate release agent.

Whether your application requires wax, silicon, permanent or semi permanent release agents. Ensuring maximum efficiency is the most important principle of choice. For this reason, the research, development and production process of release agent for industrial production and engineering application should also be based on this criterion. Once you know the need for high-performance synthetic materials, you can choose from many series, models and various release agents - especially the products of manufacturers who constantly develop new products and provide better, faster and more effective release performance.

Shanghai Dongheng Chemical Co., Ltd. is a professional manufacturer of release agents and various additives. It provides various release agents, release agent formula analysis, customized release agents, customized chemical additives, customized release agents and mold washing water to replace various imported release agents and special chemicals.