Analysis of nine plastic additives

1, antioxidant

The function of antioxidants is to delay the decomposition of plastics due to oxidation and prolong the life of plastic products. The antioxidants used in the plastics industry can be distinguished by function:

(1) Oxidative chain reaction inhibitors: such as alkylphenol, butylated toluene (abbreviated as BHT), aromatic amines, phenyl-B-amine-resistant, alkane-p-quinone, alkenyl bisphenol, alkylphenol thioether , salicylic acid benzene refers to.

(2) Peroxide decomposition agent: such as a sulphur thioether system, a thiopropionate, an organic phosphite compound, a disulfide sulfonate or the like.

(3) Heavy metal inactivating agents: such as amidates, urethanes, aromatic amine compounds, and the like.

2, antistatic agent

The main function of the antistatic agent is to impart conductivity to the plastic so that it avoids the accumulation of static electricity due to friction. Common antistatic agents include quaternary ammonium salts, ethoxylated amines, fatty acid esters and sulphonated waxes.

3, foaming agent

There are three main types of foaming agents for plastics:

1 nitrogen, carbon dioxide, and air, directly pressed into the plastic melt to foam;

2 volatile liquids such as butane, pentane, petroleum ether, difluoromethylene chloride, etc., volatilize and expand after heating, and foam the plastic body, which is a common type of polystyrene foam;

3 Decomposable chemical blowing agents, which are generally solid powders which, when heated, liberate gases (usually nitrogen or carbon dioxide), which cause the plastic to produce a cellular structure and reduce weight. Most of such blowing agents are organic azo compounds such as azobisformamide and azobisisobutylation (abbreviated as AIBN). Foamed plastics mainly include: ABS, PS, PVC, PU, ​​EVA, PE, PP, etc.

4, flame retardant

When the plastic added with the flame retardant is exposed to the flame, it can suppress the spread of the flame and prevent the formation of smoke. When the flame is removed, the combustion will stop. The principle of flame retardant used in plastic can be roughly divided into three types:

(1) The reactive flame retardant can react with oxygen to form an inert gas, which is enveloped around the combustion product and reduces the oxygen content of the combustion product to achieve the purpose of terminating combustion. This method is used for CO, CO2, NH3 and halogen compounds, such as PVC, PU foam, polyester or epoxy resin.

(2) A non-reactive flame retardant is a compound containing halogen, phosphorus, nitrogen or boron. When combustion occurs, an inert substance can be decomposed and covered on the surface of the plastic burning object to form an obstacle. In order to isolate the outside of the oxygen, to achieve the purpose of fire resistance.

(3) When a flame retardant containing an aqueous oxide such as alumina is subjected to combustion, water vapor can be released to absorb the hot gas in the combustion process, so that the temperature around the combustion product is lowered to suppress the spread of the flame and prevent the formation of smoke.

5, lubricant

The slip agent can be divided into an internal slip agent and an external slip agent. The main function of the internal slip agent is to improve the internal fluidity of the resin and reduce the internal friction between the resin molecular chains, such as fatty acid lipids (stearate monoglyceride); The external slip agent reduces the adhesion of the resin to the processing machine and improves the smoothness of the surface of the product.

6, impact modifier

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

7, plasticizer

Most synthetic resins have plasticity, but the plasticity is not the same. In order to make the resin easy to plasticize and impart softness to the product, some low molecular substances are generally added to the resin. These low molecular substances are called plasticizers. Plasticizers are liquid or low melting materials and should have good miscibility with the resin. Commonly used plasticizers are phthalic acid esters, aliphatic dibasic acid esters, phosphate esters, chlorinated paraffins, and the like.

8, coloring agent

The colorant-containing additive added to the material to beautify and decorate the plastic is called a colorant.

9, filler

It is added to the plastic compound to reduce the cost, and sometimes it can also improve the physical properties of the plastic. The relatively inert substance such as hardness, stiffness and impact strength is called filler. The most commonly used fillers are clays, silicates, talc, carbonates, and the like.