In order to improve the properties of plastics, it is necessary to add various auxiliary materials, such as fillers, plasticizers, lubricants, stabilizers, colorants and so on, in order to become good plastics.
1. Synthetic resin synthetic resin is the main component of plastics, and its content in plastics is generally 40% - 100%. Because of its high content, and the nature of resin often determines the nature of plastic, so people often regard resin as a synonym for plastic. For example, PVC resin and PVC plastic, phenolic resin and phenolic plastic are confused. In fact, resin and plastic are two different concepts. Resin is a kind of raw polymer, which is not only used in the manufacture of plastics, but also the raw material of coatings, adhesives and synthetic fibers. In addition to a small part of plastics containing 100% resin, the vast majority of plastics, in addition to the main component resin, also need to add other substances.
2. Filler filler also known as filler, it can improve the strength and heat resistance of plastics, and reduce the cost. For example, the cost of phenolic resin can be greatly reduced by adding wood powder, which makes phenolic resin one of the cheapest plastics, and can significantly improve the mechanical strength. The fillers can be divided into organic fillers and inorganic fillers, the former such as wood flour, rags, paper and various fabric fibers, and the latter such as glass fiber, diatomite, asbestos, carbon black, etc.
3. Plasticizers plasticizers can increase the plasticity and softness of plastics, reduce brittleness, and make plastics easy to process. Plasticizers are usually organic compounds with high boiling point, which are miscible with resin, nontoxic, odorless, light and heat stable, and phthalate esters are the most commonly used. For example, in the production of PVC plastics, soft PVC plastics can be obtained by adding more plasticizers, while rigid PVC plastics can be obtained without or less plasticizer (dosage < 10%).
4. In order to prevent the synthetic resin from decomposition and damage by light and heat in the process of processing and using, and prolong the service life, the stabilizer should be added into the plastic. Commonly used are stearate, epoxy resin and so on.
5. Colorants colorants can make plastics have a variety of bright and beautiful colors. Organic dyes and inorganic pigments are commonly used as colorants.
6. The function of lubricant is to prevent the plastic from sticking to the metal mold during molding, and to make the surface of plastic smooth and beautiful. Commonly used lubricants are stearic acid and its calcium magnesium salt. In addition to the additives mentioned above, flame retardant, foaming agent and antistatic agent can also be added into the plastics.
