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Nine Most Commonly Seen Additives in Plastics

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Reinforcing materials and fillers

In many plastics, reinforcing materials and fillers occupy a considerable proportion. In order to improve the strength and rigidity of plastic products or reduce production costs, various fiber materials or inorganic substances are added. The most commonly used reinforcement materials are: glass fiber, asbestos, quartz, carbon black, silicate, calcium carbonate, metal oxides, etc.

Coupling agent

Coupling agent refers to a class of substances that can improve the interface properties between fillers and polymer materials. Usually there are two functional groups in the molecular structure of the coupling agent: one can chemically react with the polymer matrix or have good compatibility; the other can form chemical bonds with the inorganic filler. For example, silane coupling agent, the general formula of which can be written as RSiX3, where R is an active functional group that has affinity and reactivity with polymer molecules, such as vinyl, chloropropyl, epoxy, methacryloyl, amine and mercapto, and X is an alkoxy group that can be hydrolyzed, such as methoxy, ethoxy, etc. At present, organosilane is the most widely used coupling agent, and organotitanate is a more efficient coupling agent.

Cross-linking agent

Crosslinking agents are mainly used in polymer materials (rubber and thermosetting resins). Because the molecular structure of the polymer material is a linear structure, the strength is low when it is not cross-linked and it’s easy to break. A network structure is formed, which improves the strength and elasticity of the rubber. The crosslinking agent used in the rubber is mainly sulfur, and an accelerator is added. The general cross-linking agent mostly refers to organic peroxide. For instance, dicumyl peroxide can be used as the cross-linking agent for polyethylene.

Foaming agent

Foaming agent is a kind of substance that can make rubber and plastic in a liquid or plastic state to form a microporous structure. According to the mechanism of action, foaming agents can be divided into physical foaming agents and chemical foaming agents. Physical foaming agent is a type of compound that relies on the change of its physical state during the foaming process to achieve the purpose of foaming; while chemical foaming agent will thermally decompose at a certain temperature to generate one or more gases to foam the polymer.

Nucleating agent

Nucleating agent is suitable for incomplete crystalline plastics such as polyethylene and polypropylene. By changing the crystallization behavior of the resin, it can speed up the crystallization rate, increase the crystallization density and promote the miniaturization of the grain size, so as to shorten the molding cycle, improve the transparency and surface of the product.


Colorants are insoluble in common solvent chemicals. To obtain ideal coloring properties, the pigments need to be uniformly dispersed in the plastic by mechanical methods. Inorganic pigments have excellent thermal stability and light stability, low price, but relatively poor tinting strength and high relative density. In contrast, organic pigments have high tinting strength, bright color, complete color spectrum, and low relative density. Colorants mainly include masterbatches and optical brighteners. Masterbatch is a kind of aggregate prepared by uniformly loading super-constant pigments or dyes in resin. Its basic composition includes: pigments or dyes, carriers, dispersants, additives. Fluorescent whitening agent is a fluorescent dye, and can be classified into several sub-categories, including carbocyclics, triazinylaminostilbene, stilbene-triazoles, benzoxazoles, furans, benzofurans and benzimidazoles, 1,3-diphenyl Base-pyrazoline, coumarin, naphthalimide and others.

Antibacterial agents

With the continuous enhancement of people's safety awareness, more and more people begin to buy antibacterial plastic products. Antibacterial agents are used in antibacterial plastics. Antibacterial agents refer to chemical substances that can keep the growth or reproduction of certain microorganisms, such as bacteria, fungi, yeast, algae and viruses, etc., below a necessary level for a certain period of time. Antibacterial agents are substances with bacteriostatic and bactericidal properties.

Flame retardant

The additives that slow down the combustion performance of plastics are called flame retardants. Most of the plastics containing flame retardants are self-extinguishing or have the effect of slowing down the burning rate

Antistatic agent

Any object has its own electrostatic charge, which can be negative or positive. The accumulation of electrostatic charges affects or even harms life or industrial production. Chemical substances that guide/eliminate the accumulated harmful charges so that they do not cause inconvenience or harm to production or life are called antistatic agents. Antistatic agents generally have the characteristics of surfactants, and have both polar groups and non-polar groups in structure. The commonly used polar groups are: anions of carboxylic acid, sulfonic acid, sulfuric acid, phosphoric acid, cations of amine salts, quaternary ammonium salts, and -OH, -O- and other groups. The commonly used non-polar groups, namely, lipophilic groups or hydrophobic groups, include alkyl groups, alkaryl groups, and the like. Antistatic agents can be of five basic types: derivatives of amines, quaternary ammonium salts, sulfates, phosphates, and derivatives of polyethylene glycols.

Alfa Chemistry is chemical supplier that provides a comprehensive range of stabilizers, including antioxidant, flame retardant, heat stabilizer, light stabilizer, mould inhibitor, optical brightener, plasticizer, and synthetic auxiliary. All can be used as additives for plastics.

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