Release agent is a functional substance that lies between the mold and the finished product. Release agents have chemical resistance and are not dissolved when in contact with the chemical components of different resins, especially styrene and amines. Release agents also have heat resistance and stress resistance, and are not easily decomposed or worn; The release agent adheres to the mold without transferring to the processed parts, and does not hinder painting or other secondary processing operations. Due to the rapid development of injection molding, extrusion, rolling, compression molding, lamination and other processes, the amount of release agent used has also significantly increased. In theory, release agents have high tensile strength, making them less prone to polishing when in frequent contact with molded resins. This is especially true when there are frosted mineral fillers or glass fiber reinforcements in the resin. Release agents have chemical resistance and are not dissolved when in contact with the chemical components of different resins, especially styrene and amines. Release agents also have heat resistance and stress resistance, and are not easily decomposed or worn; The release agent adheres to the mold without transferring to the processed parts, and does not hinder painting or other secondary processing operations. The function of release agent is to smoothly separate the cured product from the mold, thereby obtaining a smooth and flat product, and ensuring that the mold is used multiple times. The specific principle of the release agent is as follows:
1. Polar chemical bonds interact with the surface of the mold to form a regenerable adsorption film;
2. The silicon oxygen bond in polydimethylsiloxane can be regarded as a weak dipole (Si+- O -). When the release agent spreads in a single orientation on the surface of the mold, the molecule adopts a unique extended chain configuration;
3. The free surface is covered by alkyl groups in a densely packed manner, and the demolding ability increases with the density of alkyl groups; But when the alkyl group occupies a large steric hindrance, the stretching configuration is limited, and the demolding ability will decrease;
4. The molecular weight and viscosity of the release agent are also related to its demolding ability. When the molecular weight is small, it has good spreading ability but poor heat resistance.
The specific performance requirements for release agents are as follows:
1. Demoulding properties (lubricity). When forming a uniform thin film with complex shapes, the dimensions are precise and error free.
2. Good demolding continuity.
3. The appearance of the formed product is smooth and beautiful, without the adhesion of dust caused by the application of sticky release agents.
4. Superior secondary processing capability. When the release agent is transferred to the formed object, it has no adverse effects on the processing materials such as electroplating, hot pressing molds, printing, coating, and bonding.
5. Easy to apply.
6. Heat resistance.
7. Pollution resistance.
8. Well formed, high production efficiency.
9. Good stability. When used in combination with additives and materials, its physical and chemical properties are stable.
10. Non flammable, low odor, low toxicity.
Classification of types of rubber release agents:
1. Rubber release agent: refers to a type of substance used to prevent rubber products from adhering to the surface of molds and to ensure smooth demolding without tearing. Spray or apply it onto the surface of the mold cavity during use to form an effective isolation layer. The main requirements for release agents are: they have certain thermal stability and chemical inertness, and do not corrode the surface of the mold cavity; Residual decomposition products under the surface of the mold cavity; Does not affect the color of the product, but can give it a good appearance and is non-toxic; Easy to configure and convenient to use.
2. Fluorine based release agent: Fluorine based release agents inherit the characteristics of fluorine-containing materials and can significantly reduce the surface energy of solids, making them difficult to wet and non stick, and difficult to dissolve with other substances, effectively solving the bonding problem between finished products and molds. When formulated as release agents, the amount of fluorine-containing compounds is extremely small. Suitable for thermosetting resins, thermoplastic resins, and various rubber parts, the surface of molded products is smooth and the secondary processing performance is excellent, especially suitable for demolding of fine electronic components.
3. Silicon based release agent: Organosilicon release agent is prepared from organosiloxane as raw material. Its advantages include good heat resistance, moderate surface tension, easy formation of uniform isolation film, and long release life. The disadvantage is that there is a layer of oily surface on the surface of the product after demolding, and the surface of the secondary processing label must be cleaned. Commonly used ones include silicone oil, silicone rubber, emulsified silicone oil, and silicone grease. Organic silicone release agent is currently the mainstream product in the mid-range market of rubber and plastic release agents, widely used in the processing of resins such as polyurethane, rubber, etc.
4. Wax (oil) series release agents are characterized by low price, good adhesion performance, but the disadvantage is mold pollution. Their main varieties include: ① industrial Vaseline, directly used as a release agent; ② Paraffin wax, directly used as a release agent; ③ Sulfonated vegetable oil, directly used as a mold release agent; ④ Printing and dyeing oil (Türkiye red oil, swire oil), add 0 to 100 parts of boiling water. The lotion made of 9~2 parts of printing and dyeing oil has better demoulding effect than soapy water; ⑤ Polyethylene glycol (with a relative molecular weight of 200-1500) is directly used for demolding rubber products.
