Plastic additives are some compounds that must be added to improve the processability of polymers (synthetic resins) or to improve the performance of the resin itself.

The addition of additives can promote plastics to improve the processability, physical and chemical properties of the substrate and increase the physical and chemical properties of the substrate.

Antioxidant

Unsaturated double bonds in plastics are attacked by oxygen atoms, heat and light to cause breakage and produce free radicals, which cause chain reaction to break molecular chains or form chain crosslinks, leading to reduced strength or brittleness of plastic products. The function of antioxidants is to delay the decomposition of plastics due to oxidation and prolong the life of plastic products.

Antioxidants used in the plastic industry can be divided into:

Oxidation chain reaction inhibitor

For example, alkyl phenol, butylated toluene (BHT), aromatic amines, phenyl-B-Naphtylamine, alkyl quinone, alkylene bisphenol, alkyl phenol thioether, phenyl salicylate, etc.

Peroxide decomposing agent

Such as lauryl alcohol sulfide series, Thio propionate ester, organic phosphites, disulfide series, etc.

Heavy metal deactivator

Such as amides, hydramides, aromatic amine compounds, etc.

Antistatic agent

The main function of the antistatic agent is to give the plastic conductivity, so that it can avoid the accumulation of static electricity caused by friction. Common antistatic agents include quaternary ammonium salt, amine ethoxide, fatty acid esters and sulfonated wax.

Blowingagent

There are three main types of foaming agents for plastics:

Nitrogen, carbon dioxide and air are directly pressed into the plastic melt for foaming;

(2) Volatile liquids, such as butane, pentane, petroleum ether, difluorodichloromethane, etc., will volatilize and expand after the temperature rises, making the plastic body foam. Common polystyrene foam is of this type;

(3) Decomposition chemical foaming agent, which is generally solid powder, will decompose and release gas (usually nitrogen or carbon dioxide) when heated, so that the plastic will produce cellular structure and reduce weight.

Flame retardant

When the plastics added with flame retardant are exposed to the flame, they can inhibit the spread of the flame and prevent the formation of smoke. When the flame is removed, the combustion will stop.

The principles of flame retardants used in plastics can be roughly divided into three categories:

(1) Reactive type flame retardant can react with oxygen to form inert gas, which can be shrouded around the combustor to reduce the oxygen content of combustor, so as to terminate combustion. This method is applicable to all combustion products that can produce CO, CO2, NH3 and halogen compounds, such as PVC, PU foam, polyester or epoxy resin.

(2) Non Reactive type flame retardant is a compound containing halogen, phosphorus, nitrogen or boron. When burning, it can decompose into an inert substance and cover the surface of plastic combustor to form a barrier to isolate oxygen from the outside world to achieve the purpose of flame resistance.

(3) When encountering combustion, the flame retardant with water oxides such as aluminum oxide can release water vapor, absorb the hot gas in the combustion process, reduce the temperature around the combustor, inhibit the spread of flame, and prevent the formation of smoke.

Lubricant

The lubricant can be divided into internal lubricant and external lubricant. The main function of the internal lubricant is to improve the internal fluidity of the resin and reduce the internal friction between the resin molecular chains, such as fatty acid lipids (stearic acid monoglyceride); The external lubricant can reduce the adhesion of resin to processing machinery and improve the smoothness of product surface for easy demoulding, such as HoechstWax.

Impact modifier

The impact modifier is usually a special resin added by mixing to improve the impact resistance of plastics. Impact resistant modifiers often affect the heat resistance, fluidity or processability of plastics, and must be carefully selected.

Plasticizer

Most synthetic resins have plasticity, but the plasticity is different in size. In order to make the resin easy to plasticize and give the product flexibility, some low molecular substances are generally added to the resin, which are called plasticizers. Plasticizer is a liquid or low melting point substance, which should have good compatibility with resin. Common plasticizers include phthalate esters, aliphatic dibasic acid esters, phosphate esters, chlorinated paraffins, etc.

Coloring agent

It refers to the additive containing pigment added to materials for beautifying and decorating plastics, which is called colorant.

Filling material

It is added to the plastic batch to reduce the cost and sometimes improve the physical properties of the plastic, such as hardness, stiffness and impact strength. The relatively inert materials are called fillers. The most commonly used fillers are clay, silicate, talc, carbonate, etc.