Help you summarize the commonly used additives in plastics

Plastic additives, also known as plastic additives, are compounds added to polymers (synthetic resins) to improve their processing properties or to improve the properties of the resin itself. The main function is to improve the process performance of the polymer, optimize the processing conditions, improve the processing efficiency and improve the performance of the product, and improve the use value and life of the product. For example, in order to reduce the molding temperature of polyvinyl chloride resin, to make the product soft and added plasticizer; Another example is the foaming agent added for the preparation of foam plastics with light weight, earthquake resistance, heat insulation and sound insulation; The thermal decomposition temperature of some plastics is very close to the molding processing temperature, and it cannot be formed without adding heat stabilizer. Therefore, plastic auxiliaries occupy a particularly important position in plastic molding processing. Additives used in plastic molding processing include heat stabilizers, plasticizers, antioxidants, light stabilizers, flame retardants, blowing agents, antistatic agents, colorants and whiteners, fillers, coupling agents, lubricants, release agents, etc.

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1. Heat stabilizer

Heat stabilizer is mainly used for polyvinyl chloride and its copolymer, polyvinyl chloride in the hot processing process, before reaching the melting flow there is a small amount of molecular chain break and release hydrogen chloride, and hydrogen chloride is a catalyst to accelerate the chain reaction of molecular chain break, so do not exclude just decomposed hydrogen chloride will make the polymer chain continue to crack into low molecular compounds, As a result, plastics such as polyvinyl chloride cannot be processed. Adding appropriate alkaline substances to PVC can immediately neutralize the decomposed hydrogen chloride to achieve the purpose of stabilizing PVC.

Commonly used heat stabilizers are divided into primary stabilizers and auxiliary stabilizers:

Main stabilizer: Mainly salts and soaps containing heavy metal cations such as lead, calcium, cadmium, zinc, barium, aluminum, lithium and strontium

Among them, lead sulfate and lead stearate are the most widely used.

Auxiliary stabilization: The main ring oxidizes oil and esters, and they also have a certain function as plasticizers



2. Antioxidants

Antioxidants are a class of chemicals that, when present in small amounts in a polymer system, can delay or inhibit the oxidation process of the polymer, thereby increasing the service life of the polymer. Commonly used plastic antioxidants are generally divided into five categories according to their molecular structure and mechanism of action: hindered phenols, phosphite esters, thioides, compounds and hindered amines (HALS).



3. Uv absorbent

Polymers can be photodegraded by ultraviolet radiation. Ultraviolet absorber is a kind of chemical substances that can absorb ultraviolet light or reduce ultraviolet transmission, it can convert energy, convert high energy ultraviolet light into the form of heat or non-destructive longer light waves to release energy, so as to protect polymers from ultraviolet damage.

Uv absorbers can be divided into the following categories according to their chemical structure: salicylate esters, phenylketones, benzotriazole, substituted acrylonitrile, triazines and hindered amines.



4. Light masking agent

The light shielding agent is a kind of material which can absorb the light wave harmful to the polymer, and then convert the light energy into heat energy to scatter or reflect the light wave, so as to play a shielding effect on the polymer. The main light shielding agents are carbon black, zinc oxide, titanium dioxide, zinc barium white and other black or white substances that can absorb or reflect light waves.