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.
Introduction to release agent:
Release agent is an interface coating used on the surface of two objects that are easily adhered to each other, which can make the surface of the object easy to detach, smooth, and clean.
Release agents are widely used in various molding operations such as metal die casting, polyurethane foam and elastomer, glass fiber reinforced plastics, injection molding thermoplastics, vacuum foam sheets and extruded profiles. In molding, sometimes other plastic additives such as plasticizers may seep out onto the interface, and a surface remover is needed to remove it.
Theoretical basis of release agent:
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 specific working principle of 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.
Classification of release agents:
1. Classified by usage:Internal release agent, external release agent;
2. Classified by lifespan:Conventional release agent, semi permanent release agent;
3. Classified by Form:Solvent based release agent, water-based release agent, solvent-free release agent, powder release agent, paste release agent
4. Classified by active substance:
① Silicon series—— Mainly composed of silicone compounds, silicone oil, silicone resin methyl branched silicone oil, methyl silicone oil, emulsified methyl silicone oil, hydrogen containing methyl silicone oil, silicone grease, silicone resin, silicone rubber, and silicone rubber toluene solution.
② Wax series—— Plants, animals, synthetic paraffin; Microcrystalline paraffin; Polyethylene wax, etc.
③ Fluorine series—— The best isolation performance, minimal mold pollution, but high cost PTFE; Fluororesin powder; Fluororesin coatings, etc
④ Surfactant series—— Metal soap (anionic), EO, PO derivatives (non-ionic)
⑤ Inorganic Powder Series—— Talc, mica, clay, white clay, etc
⑥ Polyether series—— Polyether and fat mixture, heat-resistant and chemically good, often used in certain rubber industries where silicone oil is restricted. The cost is higher than that of silicone oil series.
5. Other
Water containing release agent with masking agent: fix water molecules with masking agent. Durable release agent: silicone oil+silicone resin system, with more than 800 cycles of multi-layer composite release agent: halogenated hydrocarbon film+polyethylene release agent+polyvinyl alcohol release agent. Aromatic polysulfone release agent for mold treatment. Halogen containing polyether release agent: reduce vapor pressure, increase decomposition temperature, and will not cause charged contact. Carbonylsilane release agent: internal release, improve adhesion to water-based ink surface. Reactive release agent: after coating, it undergoes chemical reaction to form a film and adheres to the mold surface. The above are some representative release agents, which have their own characteristics and can be used according to their applications. For example, it is used as a back treatment agent, peel off paper, anti adhesive agent (for power poles, telephone boxes, signs, etc.) for fiber adhesive tapes, and anti pollution agent (for inner and outer wall coatings, vehicles, roadblocks, road barriers, etc.) to prevent residual adhesion around adhesives.
