Some plastics are simple resins themselves, such as polyethylene, polystyrene, etc., known as single-component plastics. Some plastics contain other auxiliary materials, such as plasticizers, stabilizers, colorants, various fillers, etc., in addition to synthetic resin, which is called multi-component plastic.
Stabilizers
We all know that in the process of processing, storage and use of plastic products, under the action of light, heat and oxygen, the aging phenomenon of fading, brittleness and cracking will occur. In order to delay and stop the aging phenomenon, stabilizers must be added. Mainly used to prevent thermal aging, called heat stabilizers; mainly used to prevent oxidative aging, called antioxidants; mainly used to prevent light aging, called light stabilizers, they are collectively known as stabilizers. Today’s best performance plastic stabilizer is methyl tin heat stabilizer (referred to as 181), on the hard polyethylene (PVC) calendering, extrusion, injection molding and blow molding are very effective. Because of its high safety, it is especially used in food packaging and high definition rigid polyethylene products, and it is also commonly used in plastic doors and windows, water pipes, and decorative materials to replace other highly toxic plastic heat stabilizers. It has been widely used in the United States, Europe, and Japan. In recent years, 181 methyl tin heat stabilizer in China began to be used in large quantities.
Plastic additives
Plastic additives in plastics to add additives in order to improve processing performance, improve the use of efficiency and reduce costs. Auxiliaries in plastics with a small proportion of the material, but the quality of plastic products has a great impact. Different types of plastics, due to molding and processing methods and different conditions of use, the types and amounts of additives required are different. The main additives are the following categories.
Plasticizers
Plasticizers can increase the softness, extensibility and plasticity of plastics, reduce the flow temperature and hardness of plastics, and facilitate the molding of plastic products. Commonly used are benzodicarboxylic acid esters, sebacate esters, chlorinated paraffins, etc.
Flame retardant
Additives that can improve the flame resistance of plastics are called flame retardants. Most of the plastics containing flame retardants have self-extinguishing properties, or slow down the burning rate. Commonly used flame retardants include antimony oxide and compounds of aluminum and boron, halides and phosphate esters, tetrachlorobenzenedicarboxylic anhydride, tetraauromedicarboxylic anhydride, etc.
Lubricant
Lubricant is a substance added to improve the mold release and surface finish of the products when plastic is heated and molded. Commonly used lubricants are: stearic acid and its salts, paraffin wax, synthetic wax, etc.
Reinforcing materials and fillers
In many plastics, reinforcing materials and fillers occupy a considerable proportion, especially reinforcing plastics and calcium plastic materials. The main purpose is: to improve the strength and rigidity of plastic products, generally adding a variety of fiber materials or inorganic substances. The most commonly used reinforcing materials are: glass fiber, asbestos, quartz, carbon black, silicate, calcium carbonate, metal oxides, etc.
Antistatic agent
Antistatic agents play a role in eliminating or reducing static electricity generated on the surface of plastic products. Most antistatic agents are electrolytes, and they have limited compatibility with synthetic resins, so that they can migrate to the plastic surface to achieve the role of moisture absorption and elimination of static electricity.
Foaming agents
Plastic blowing agents are low molecular organic compounds that can be vaporized at a certain temperature, such as dichlorodifluoromethane; or organic compounds that decompose into gases when heated. These gases remain in the plastic matrix will form a number of fine foam structure of the foam. Commonly used are azo compounds, nitroso compounds, etc.
Colorants
Colorants are used for coloring plastics. Mainly play a beautifying and finishing role. About 80% of plastic products are made into final products after coloring.
