Mold Release Agents
Mold release agents are used to create a film layer between the mold and the product to allow the products to be easily removed from the mold. Although mold release agent is generally applied to the mold surface in the adhesive, food, furniture, glass, metal, plastic, rubber, printing, and packaging industries, it can also be used by adding it directly to the material [1]. Performance of mold release agents is determined by features such as easy applicability, easy release ability of mold, fast drying, homogeneous film formation, non-accumulation on surfaces, stability, high physical and chemical resistance, low flammability, and low toxicity effect [2, 3].
Mold release agents can be water-based or solvent-based. The use of water-based release agents has increased considerably today, as they are environmentally friendly, cost-effective, and do not pose a health and safety risk. Water-based release agents also have some disadvantages, for example, excessive drying time can cause water residues on the applied surface. These residues can have a negative impact on molding performance. However, this negative effect can be reduced by increasing the solid content of the mold release agent or by heating the mold surface [3-5].
There are different water-based mold release agents in chemically such as silicone-based, wax-based and fatty acid-based [4]. Silicone-based release agents are divided into three groups about being silicone rubbers, silicone resins, and silicone oils [6]. These mold release agents have the feature of giving shine to the surface, they can be easily applied to the surface in several layers at low concentrations. They have a high separation force, water-soluble silicones can be easily removed from the surface after use, and have a good thermal resistance. They are frequently used in rubber, plastic, glass production, and precision castings because it can be easily separated without damaging the mold and product and is non-toxic. However, if the appropriate silicone release agent is not selected and the selected silicone release agent is not used in an appropriate amount, it may penetrate the surface of the applied product and as a result, cause negative effects on the properties of the product. [2, 4, 7].
Wax release agents can be water-based and solvent-based, but there are some difficulties in the use of these mold release agents. Wax release agents are generally in solid form, therefore, they must be designed in accordance with the system to be used. Since there are no hydrophilic groups in wax-based mold release agents, they must be used by dissolving them in an organic solvent or by creating an emulsion medium in the presence of an emulsifier. However, these mold release agents are difficult to use by dissolving them in an organic solvent at low temperatures. Because at low temperatures, it is not possible to dilute the paraffin and apply it to the surface equally, and it may leave residues on the surface. This may also require a mechanical cleaning process after use. At the same time, paraffin can cause safety and health problems because it is flammable and volatile. This type of mold release agent is mostly used in the concrete industry. Using it by forming a molten paraffin emulsion in the presence of an emulsifier has high separation properties, is more environmentally friendly due to the absence of volatile organic compound (VOC) emission, and the surfaces remain clean after use [2, 4].
Free fatty acid mold release agents are used as lubricants and release agents. Free fatty acids are formed as a result of the reaction of glycerol and oils. They can be used by dissolving in solvents such as alcohol and water or mixing directly with the resin. They are easy to use, low cost, and environmentally friendly. In addition to their high separation ability, they can improve the processing properties of materials due to their lubricating effect [4, 8, 9]. “Thus, the release and processing properties of thermoplastic elastomers such as SBR, EPDM, butadiene rubber, acrylate rubber, epichlorohydrin, and thermoplastic elastomers can be effectively improved in order to obtain optimum economic efficiency. Used in many other elastomers, it has also been found to improve the flow of the rubber in the mold cavity, reduce operating temperatures and shorten the production cycle time of the product.”[4].
The most suitable mold release agents for the application area with different activities and properties can be developed by using one or more of the above-mentioned types of release agents. Process conditions, mold type and properties, chemical and physical properties of the product to be released from the mold are important in the selection of mold release agents. After choosing the appropriate mold release agent, there are a few issues that need to be considered in the use of mold release agents. First of all, it is important to distribute the mold release agents evenly on the mold surface on which they are applied. If it is not well dispersed on the mold surface, the separating surface between the product and the surface cannot be fully formed and it will be difficult to remove the product from the surface properly so that both the mold and the product can be damaged. If mold release agents are used excessively, deterioration may occur on the skin of the product that is desired to be separated from the surface. Correct use of release agents is as important as choosing the appropriate release agent for the product specifications and production process to ensure high performance.
References
[1] Michael J. Owen, “Release Agents”, Encyclopedia of Polymer Science and Technology (2001).
[2] Lammerting, Helmut. "Release Agents." Ullmann's Encyclopedia of Industrial Chemistry (2000).
[3] Mould releases – an overview, Reinforced Plastics,Volume 52, Issue 7, 2008, Pages 32-34,
[4] Liang, Bo, Ye Yang, and Junping Li. "Research progress of water-based release agents." MATEC Web of Conferences. Vol. 358. EDP Sciences, 2022.
[5] Bob Goss, The effective use of mould release agents, Reinforced Plastics, Volume 48, Issue 8, 2004, Pages 24-26
[6] Chung, Sungil, et al. "Evaluation of micro-replication technology using silicone rubber molds and its applications." International Journal of Machine Tools and Manufacture 43.13 (2003): 1337-1345.
[7] Zhang, Jiayao, et al. "Synthesis, structure and properties of non silicone release agents based on poly (vinyl n-octadecyl carbamate)." Progress in Organic Coatings 173 (2022): 107168.
[8] Barnat-Hunek, Danuta, and Małgorzata Szafraniec. "Influence of Biodegradable Release Oils on the Physical and Mechanical Properties of Light-Colored Architectural Concrete." Materials 14.16 (2021): 4630.
[9] Wu, Fucheng, et al. "Study on synthesis and demolding performance of polyethylene glycol fatty acid mold release agents." Polymers for Advanced Technologies 32.10 (2021): 4061-4069.
Authors: Beste TATLISES Date: November 2022
