Plastic additives, also known as plastic additives, are compounds that must be added to polymers (synthetic resins) to improve their processing properties or to improve the performance of the resin itself.
The addition of additives can promote the processing of plastics to improve the processing, physical and chemical properties of the base material and increase the physical and chemical properties of the base material.
Today we will learn about the classification of plastic additives and take stock of the different plastic additives.
Unsaturated double bonds in plastics are attacked by oxygen atoms, heat and light and cause breakage to produce free radicals, which cause a chain reaction that breaks molecular chains or forms chain cross-links, resulting in reduced strength or brittleness of the finished plastic product. The function of antioxidants is to delay the decomposition of plastics due to oxidation and extend the life of plastic products.
Antioxidants used in the plastics industry can be differentiated according to their function as follows
(1) Oxidation chain reaction inhibitors
Such as Alkyl phenol、Butylated hydroxytoluene 、Aromaticamines、Phenyl-B-Naphtylamine、Alkyl quinone、Alkylene bisphenol、Alkyl phenolthioether、Phenyl salicylate etc.
(2) Peroxide decomposer
Such as Liu alcohol acute sulfide system、Thio propionate ester、Organic phosphites etc.
(3) Heavy metal inactivators
Such as amides, hydrazides, aromatic amine compounds, etc.
The main function of antistatic agents is to impart electrical conductivity to plastics so that they do not accumulate static electricity due to friction. Commonly used antistatic agents include quaternary ammoniumsalt, amines, fatty acid esters and sulphonated wax.
There are three main types of foaming agents for plastics.
(1) nitrogen, carbon dioxide, and air, directly pressed into the plastic melt to make foaming.
(2) volatile liquids such as butane, pentane, petroleum ether, difluorodichloromethane, etc., after warming that is volatile expansion, and make the plastic body foaming, the common polystyrene foam that belongs to this type.
(3) decomposition of chemical blowing agent, this type of blowing agent is generally a solid powder, they are heated that is decomposed to release gas (usually nitrogen or carbon dioxide), and make the plastic cell-like structure, and reduce weight.
This type of foaming agent is mostly organic azo compounds, such as azodicarbonamide, azobisisobutyro-nitrile (AIBN for short). The main plastics used for foaming are: ABS, PS, PVC, PU, EVA, PE, PP, etc.
When plastics with flame retardants are exposed to flame, they inhibit the spread of flame and prevent the formation of smoke on their own, and when the flame is removed the burning stops.
The principles of flame retardants used in plastics can be divided into three broad categories.
(1)Reactive incombustible agents can react with oxygen to form an inert gas, shrouded around the burning material, reducing the oxygen content of the burning material to end the purpose of combustion. Where the combustion can produce CO, CO2, NH3 and halogen compounds, such as PVC, PU foam, polyester or epoxy resin, etc. are selected for this method.
(2) Non-reactive flame retardant is a compound containing halogen, phosphorus, nitrogen or boron, when combustion occurs, it can decompose an inert material, cloaked in plastic combustion material on the surface, forming a layer of barriers to isolate the outside oxygen, to achieve the purpose of flame resistance.
(3) containing water oxides such as alumina incombustible agent encounter combustion, can release water gas, absorb the heat of the combustion process, so that the temperature around the burning material to reduce the spread of flame inhibition, to prevent the formation of smoke.
Lubricant can be divided into internal lubricant and external lubricant, the main function of internal lubricant is to improve the internal fluidity of resin, reduce the internal friction between resin molecular chains, such as fatty acid lipids (stearic acid monoglycerides); external lubricant in reducing the adhesion of resin to processing machinery, and improve the smooth surface of the product easy to release, such as HoechstWax.
Impact modifiers are usually special resins that are added by way of compounding to improve the impact resistance of plastics. Impact modifiers often affect the heat resistance, flowability or processability of the plastic and must chosen with care.