Exploring the main components of plastic packaging materials

[Chinese Packaging News] Plastic is not a pure substance, it is made of many materials.

Among them, high-molecular polymers (or synthetic resins) are the main components of plastics. In addition, in order to improve the properties of plastics, various auxiliary materials such as fillers, plasticizers, lubricants, stabilizers, etc. must be added to the polymers. Colorants, etc., can become plastics with good properties.

1, synthetic resin

Synthetic resin is the main component of plastics, and its content in plastics is generally 40% to 100%. Because of its high content and the nature of the resin often determines the nature of the plastic, people often refer to resin as a synonym for plastic. For example, polyvinyl chloride resin is mixed with polyvinyl chloride plastic, phenolic resin and phenolic plastic. In fact, resin and plastic are two different concepts. Resin is a raw, unprocessed polymer that is not only used to make plastics, but also a raw material for paints, adhesives, and synthetic fibers. In addition to a very small percentage of plastics containing 100% of the resin, the vast majority of plastics, in addition to the main component resin, also need to add other substances.

2, filler

Fillers, also known as fillers, increase the strength and heat resistance of plastics and reduce costs. For example, the addition of wood flour to the phenolic resin can greatly reduce the cost, making the phenolic plastic one of the cheapest plastics, while also significantly improving the mechanical strength. Fillers can be divided into organic fillers and inorganic fillers, the former being wood flour, rags, paper, and various fabric fibers, and the latter being glass fibers, diatomaceous earth, asbestos, carbon black, and the like.

3, plasticizers

Plasticizers can increase the plasticity and softness of plastics, reduce brittleness, and make plastics easier to process and shape. Plasticizers are generally compatible with the resin, non-toxic, odorless, light and heat stable high-boiling organic compounds, the most commonly used phthalates. For example, in the production of PVC plastics, soft plastic PVC can be obtained by adding more plasticizers. If no plasticizer (less than 10%) is added, rigid PVC can be obtained. .

4, stabilizer

In order to prevent the synthetic resin from being decomposed and destroyed by the action of light and heat during processing and use, and to extend the service life, stabilizers must be added to the plastic. Stearate and epoxy resins are commonly used.

5, coloring agent

Colorants allow plastics to have a variety of bright, beautiful colors. Common organic dyes and inorganic pigments are used as colorants.

6, lubricant

The role of the lubricant is to prevent the plastic from sticking to the metal mold during molding and at the same time make the plastic surface smooth and beautiful. Commonly used lubricants are stearic acid and its calcium and magnesium salts.

7, antioxidant

Prevents plastics from being heated and oxidized during thermoforming or during high-temperature use, leaving the plastic yellow, cracked, etc.

In addition to the above additives, flame retardants, foaming agents, antistatic agents, etc. may also be added to the plastic to meet different requirements for use.