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How to choose additives?

How to choose additives?


Plastic additives, also known as plastic additives, are some compounds that must be added to improve the processing performance of polymers (synthetic resins) during molding processing or to improve the insufficient performance of the resin itself. For example, a plasticizer added to reduce the molding temperature of polyvinyl chloride resin and make the product soft. For example, in order to prepare light weight, anti vibration, heat insulation and sound insulation foam plastics, foaming agents should be added. The thermal decomposition temperature of some plastics is very close to the molding processing temperature, so they cannot be formed without adding heat stabilizer. Therefore, plastic additives play a particularly important role in plastic molding processing.


 A large class of additives used for plastic molding products, including plasticizer, heat stabilizer, antioxidant, light stabilizer, flame retardant, foaming agent, antistatic agent, mildew inhibitor, colorant and whitening agent, filler, coupling agent, lubricant, release agent, etc. Among them, colorants, brighteners and fillers are not special chemicals for plastics, but general-purpose matching materials.

The plastic formula design looks very simple on the surface, but it actually contains many internal links. In order to design a formula with high performance, easy processing and low price, many factors need to be considered when selecting additives. Select the appropriate additives according to the purpose to be achieved, and the additives added should give full play to their expected efficacy and meet the specified indicators. The specific selection range of additives is as follows:

Selection range of additives:

Toughening - select elastomer, thermoplastic elastomer and rigid toughening material;

Reinforcement - select glass fiber, carbon fiber, whisker and organic fiber;

Flame retardant - bromine (ordinary bromine system and environmental protection bromine system), phosphorus, nitrogen, nitrogen / phosphorus composite intumescent flame retardant, antimony trioxide, hydrated metal hydroxide;

Antistatic - various antistatic agents;

Conductivity - carbon (carbon black, graphite, carbon fiber, carbon nanotube), metal fiber and metal powder, metal oxide;

Magnetism - ferrite magnetic powder and rare earth magnetic powder include samarium cobalt (SmCo5 or Sm2Co17), neodymium iron boron (NdFeB), samarium iron nitrogen (SmFeN) and aluminum nickel;

Heat conduction - metal fibers and metal powders, metal oxides, nitrides and carbides; Carbon materials such as carbon black, carbon fiber, graphite and carbon nanotubes; Semiconductor materials such as silicon and boron;

Heat resistant - glass fibers, inorganic fillers, heat-resistant agents such as substituted maleimide and β Crystal nucleating agent;

Transparent - nucleating agent, for PP α Sorbitol series of crystal nucleating agent has the best effect;

Wear resistance - cobalt magnetic particles such as graphite, molybdenum disulfide and copper powder;

Insulation - calcined kaolin;

Barrier - mica, montmorillonite, quartz, etc

Matching of additives and plastics

Red phosphorus flame retardant is effective for nylon (PA), polyethylene terephthalate (PET) and polybutylene terephthalate (PBT);

Nitrogen based flame retardants are effective for Oxygenates, such as PA, PBT, pet, etc;

Nucleating agent has good effect on copolymerized polypropylene (PP);

The heat-resistant modification of glass fiber has good effect on crystalline plastics and poor effect on amorphous plastics;

Carbon black filled with conductive plastic has good effect in crystalline resin;The additives with the same component have different forms, which have a great impact on the modification.

Particle size of additives

① Effect of particle size of additives on mechanical properties

The smaller the particle size, the better the tensile strength and impact strength of the filling material;

② Effect of particle size of additives on flame retardancy

The smaller the particle size of flame retardant, the better the flame retardant effect. For example, the smaller the particle size of hydrated metal oxide and antimony trioxide, the less the addition to achieve the same flame retardant effect;

③ Effect of particle size of additives on color matching

The smaller the particle size of the colorant, the higher the coloring power, the stronger the covering power and the more uniform the color;

④ Effect of particle size of additives on electrical conductivity

Taking carbon black as an example, the smaller its particle size is, the easier it is to form a network conductive path to achieve the same conductive effect, and the amount of carbon black added is reduced. However, like colorants, the particle size also has a limit value. The particle size is too small, easy to aggregate and difficult to disperse, and the effect is not good.

Surface treatment of additives

After the surface treatment of all inorganic additives, the modification effect will be improved. Especially the filler is the most obvious, and others include glass fiber, inorganic flame retardant, etc.

Aluminate coupling agent 

The surface treatment is mainly based on coupling agent and compatibilizer, such as silane, titanate and aluminate, and the compatibilizer is maleic anhydride grafted polymer corresponding to the resin.

Introduction to specific additives

(1) Plasticizer.

Plasticizers are a kind of low volatile organic compounds that can be miscible with polymers to a certain extent. They can reduce the viscosity of polymer melt, glass transition temperature and elastic modulus of products. The mechanism is based on the weakening of the attraction between polymer chains by plasticizer molecules.

Phthalate esters are the main body of plasticizers, and their output accounts for about 80% of the total output of plasticizers. Dioctyl phthalate (DOP) is the most important variety. 

Plasticizers with small production scale include esters of adipic acid and sebacic acid (with good cold resistance), phosphate esters (with flame retardant effect), epoxy oil and epoxy esters (with synergistic effect with heat stabilizer), trimellitic acid ester and pentaerythritol ester (with good heat resistance), chlorinated paraffin (auxiliary plasticizer and flame retardant plasticizer), phenyl alkyl sulfonate (auxiliary plasticizer).

(2) Heat stabilizer.

The main function of heat stabilizer is to prevent thermal degradation during processing and aging of products during long-term use. The larger amount is the heat stabilizer of PVC and vinyl chloride copolymer. The dosage of heat stabilizer is about 2% in soft products and 3% ~ 5% in hard products.

The main categories of heat stabilizers are basic lead salts, fatty acid soaps, organic tin, organic auxiliary stabilizers and composite stabilizers.

① Basic lead salts (i.e. basic lead salts) such as tribasic lead carbonate and dibasic lead phosphite. It was first used and is still widely used at present. It has good heat resistance, electrical insulation and weather resistance, low price, but it is toxic, opaque and poor dispersion.

② Fatty acid soap. Mainly cadmium, barium, calcium, zinc and magnesium salts of stearic acid and lauric acid. Cadmium soap and barium soap, calcium soap and zinc soap are usually used together to produce synergistic effects. Cadmium soap has great toxicity, barium soap also has certain toxicity, but calcium soap and zinc soap are non-toxic.

③ Organotin. Organotin is the fastest growing category recently. It has good transparency, and many varieties have outstanding heat resistance and weather resistance. It is an essential heat stabilizer for hard transparent products. Isooctyl dimercaptoacetate and di-n-octyl tin are the most widely used non-toxic stabilizers.

④ Phosphite and epoxy compounds. As an auxiliary stabilizer, it is often used as a component of composite stabilizer. Composite stabilizers include general cadmium barium (zinc), sulfide resistant barium zinc, non-toxic calcium zinc and Organotin Complexes, which are mostly liquid.

Grafted polyethylene wax

(3) Antioxidants.

At room temperature and high temperature, most polymers will have automatic oxidation reactions with different speeds, which will cause yellowing, degradation and strength reduction of plastics. Substances that can inhibit or delay this reaction can be called antioxidants.

In 1918, phenols were used to inhibit the oxidation of rubber. In the 1930s, the first varieties of modern antioxidants such as alkyl phenols and p-phenylenediamine came out one after another. Although the amount of antioxidant in plastics is small (0.1% ~ 1.0%), it is an important assistant for large tonnage plastics such as polyolefin, styrene resin, polyvinyl chloride, polyamide and polyacetal. In the rubber industry, antioxidant is still used to be called antioxidant.

Antioxidants for plastics are mainly phenolic main antioxidants and auxiliary antioxidants such as THIODIPROPIONATE and phosphite.

The main antioxidant, also known as chain terminator, its function is to capture active free radicals generated in oxidative degradation, so as to interrupt the chain degradation reaction. Its representative varieties are 2,6-di-tert-butyl-4-methylphenol (antioxidant 264) and tetra [3 - (3 ', 5' - di-tert-butyl-4-hydroxyphenyl) propionic acid] pentaerythritol ester (antioxidant 1010).

Auxiliary antioxidant, also known as peroxide decomposing agent, is used to decompose the intermediate products of oxidative degradation into non free radical products.

Lauryl THIODIPROPIONATE and dioctyl phosphite are the most commonly used auxiliary antioxidants. Main and auxiliary antioxidants are usually used together to play a synergistic effect.

(4) Light stabilizer.

Plastics and other polymers absorb ultraviolet energy, which can initiate automatic oxidation reaction and lead to degradation. This process is called photooxidation or photoaging, and the substances that can inhibit or delay this process are called light stabilizers.

Plastics and other polymers absorb ultraviolet energy, which can initiate automatic oxidation reaction and lead to degradation. This process is called photooxidation or photoaging, and the substances that can inhibit or delay this process are called light stabilizers. Light stabilizers are mainly used for polyolefins, especially polypropylene. Polyvinyl chloride, polycarbonate and polyester also use a small amount of light stabilizer, with an amount of about 0.1% ~ 0.5%.

(5) Flame retardant.

Flame retardants are a kind of additives to inhibit the flammability of polymers. Most of them are compounds of group V, VII and III elements in the periodic table of elements; Especially phosphorus, bromine, chlorine, antimony and aluminum compounds.

Flame retardants can be divided into additive type and reactive type. Additive flame retardants are mainly phosphate esters and halogenated phosphate esters, halogenated hydrocarbons, antimony oxide, aluminum hydroxide, etc. Advantages are easy to use, strong adaptability. However, due to the addition of 10% ~ 30%, often affect the performance of plastics. Reactive flame retardants are actually monomers containing flame retardant elements, so they have little effect on the properties of plastics. Common reactive flame retardants, such as halogenated anhydride for polyester, tetrabromobisphenol A for epoxy resin and phosphorus containing polyol for polyurethane, etc. 

(6) Foaming agent.

Foaming agents are divided into physical foaming agents and chemical foaming agents. Chemical foaming agents are divided into inorganic foaming agents and organic foaming agents. They are named because they are heated to gasify or decompose into gas in the polymer, resulting in bubbles in the polymer. Physical foaming agents are mainly chlorinated hydrocarbons or fluorochlorinated hydrocarbons, such as trichlorofluoromethane, trichlorotrifluoroethane, etc. It is mainly used for producing polyurethane foam. The main type of chemical foaming agent is Azodicarbonamide (foaming agent AC).

(7) Antistatic agent.

The volume resistivity of polymer is generally as high as 1010 ~ 1020 Ω· cm, which is easy to accumulate static electricity and cause danger. Antistatic agents are mostly surfactants, which can make the plastic surface hydrophilic to water. Ionic surfactants also have conductive effect, so they can make static electricity leak in time. According to the use method, antistatic agents are divided into external antistatic agents and internal antistatic agents. The external antistatic agent is a dilute solution of 0.5% ~ 2.0%, which is used to coat the surface of plastic. The internal antistatic agent is additive, and the dosage varies from 0.1% to 3.0%. Cationic surfactants, such as ammonium salt, quaternary ammonium salt and alkyl imidazoline, are commonly used antistatic agents in plastics.

Qingdao Sainuo Chemical Co., Ltd. We are manufacturer of PE wax, PP wax, OPE wax, EVA wax, PEMA, EBS, Zinc/Calcium Stearate…. Our products have passed the REACH, ROHS, PAHS, FDA testing. 

Sainuo rest assured wax, welcome your inquiry!



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