The plastic mold structure mainly includes a concave mold with variable cavity composed of a concave mold combined base plate, a concave mold assembly and a concave mold combined clamping plate, and a punch with variable core composed of a punch combined base plate, a punch assembly, a punch combined clamping plate, a cavity cutting assembly and a side cutting combined plate.

In order to improve the properties of plastics, various auxiliary materials, such as fillers, plasticizers, lubricants, stabilizers and colorants, should be added to the polymer in order to become plastics with good properties.

1. 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 plastics, people often regard resin as a synonym for plastics. 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 an unprocessed original polymer. It is not only used to make plastics, but also used as raw material for coatings, adhesives and synthetic fibers. In addition to a small part of plastics containing 100% resin, the vast majority of plastics need to add other substances in addition to the main component resin.

2. Filler

Fillers, also known as fillers, can improve the strength and heat resistance of plastics and reduce costs. For example, the addition of wood powder to phenolic resin can greatly reduce the cost, make phenolic plastic one of the cheapest plastics, and significantly improve the mechanical strength. Fillers can be divided into organic fillers and inorganic fillers, the former such as wood powder, rags, paper and various fabric fibers, and the latter such as glass fiber, diatomite, asbestos, carbon black, etc.

3. Plasticizer

Plasticizers can increase the plasticity and softness of plastics, reduce brittleness and make plastics easy to process and shape. Plasticizers are generally high boiling organic compounds that are miscible with resin, non-toxic, odorless and stable to light and heat. Phthalates are the most commonly used. For example, in the production of PVC plastics, if more plasticizers are added, soft PVC plastics can be obtained. If no or less plasticizers are added (dosage < 10%), rigid PVC plastics can be obtained.

4. Stabilizer

In order to prevent the synthetic resin from being decomposed and damaged by light and heat in the process of processing and use, and prolong the service life, a stabilizer should be added to the plastic. Commonly used are stearate, epoxy resin, etc.

5. Colorant

Colorants can make plastics have various bright and beautiful colors. Organic dyes and inorganic pigments are commonly used as colorants.

6. Lubricant

The function of lubricant is to prevent the plastic from sticking to the metal mold during molding, and make the plastic surface smooth and beautiful. Common lubricants include stearic acid and its calcium magnesium salts. In addition to the above additives, flame retardants, foaming agents, antistatic agents, etc. can also be added to plastics.