Release agent is a functional substance that lies between the mold and the finished product. It is a type of processing aid that prevents molded or laminated products made of rubber, plastic, elastomers, or other materials from sticking to the mold or other board surfaces, making it easy to detach. Due to the rapid development of processes such as injection molding, extrusion, rolling, molding, and lamination, the amount of release agent has also significantly increased.
Especially in recent years, the application of RIM (Reaction Injection Molding) technology has further promoted the development of release agents. There are many substances that can be used as release agents, such as metal soap, stearic acid, oleic acid, organic phosphite, silicone oil, silicone oil, coconut oil, vegetable oil, white wax, ultrafine fluoroplastic powder, and other fluorinated substances.
1.1 The Function of Release Agents During injection molding, plastics will generate two types of frictional forces: one is the internal frictional force between polymer molecules during polymer heating and melting, and the other is the external frictional force between polymer melt and the surface of the processing mold.
Due to the friction effect, the fluidity of the melt is easily reduced, resulting in adverse effects, such as poor processing performance, slow processing speed, difficulty in filling complex shaped molds in the product, rough surface of the product, lack of luster, and in severe cases, wrinkles and other defects. One effective way to overcome the two types of friction mentioned above is to add lubricants. The release agent we are referring to is actually an external lubricant. It can be added to mixed materials or applied to the surface of the mold during use. When applying release agent externally, the release agent forms a smooth and dense thin film on the surface of the mold, isolating it from the material being processed. This release agent film must be able to bond well with the surface of the mold, not easily detach or be damaged, but without any reaction or adhesion with the product, and can easily detach the molded product. Almost all release agents can be used as external release agents, but in recent years, the most commonly used external release agents are resins, polysiloxanes, petroleum products, and fluorinated polymers that can form tight and firm release films.
When added internally, during the demolding process, the demolding agent can precipitate from the inside and be evenly distributed on the surface of the plastic product, forming a lubricant film or vapor between the mold and the plastic product (to assist in demolding). Typical substances that can be used as internal additive release agents include metal soap and stearates, oleic acid, organic phosphites, silicone oil, and wax. Comparing the external
Mold Release agent with the internal mold release agent, it can be found that the internal mold release agent has a better effect (the mold will not scale and will also reduce the mold cleaning time), which can save the steps required for external mold release agent application (thus making the processing process more suitable for automation), and can also eliminate any possibility of mold damage caused by improper use. People who suggest using external release agents believe that using internal release agents will leave too many loopholes that can cause errors (too much or too little release agent mixed into the plastic can have adverse effects on its performance). When this type of release agent is dispersed on the plastic surface, it will hinder the second step of precision processing.
