stabilizers and mechanism by Type

A plastic heat stabilizer by category
Is a kind of heat stabilizers to prevent or reduce the polymer in the course of processing by heat degradation or crosslinking, extend the period of
Aggregate material life additives. Stabilizers commonly be divided into categories according to the plastic flame retardant  main component base, fatty acid soaps,
Organic tin compounds, composite heat stabilizer and pure organic compounds.
1) base heat stabilizers: base with stabilizers is the "base" of the lead salt of inorganic and organic acids, such stability
Agent has excellent heat resistance, weather resistance and electrical insulation properties, low cost, poor transparency, toxicity, usually in the amount of 0.5%
~ 5.0%. (Source Global polyurethane network) 2) fatty acids heat stabilizers: These heat stabilizers is defined by the root fatty acid composition of the compounds with metal ions, also known as gold
Is a soap heat stabilizers, radical, and its performance and the kinds of metal ions, the general amount of 0.1% to 3.0%.
 3) Organic tin-based heat stabilizer: These heat stabilizers may be unstable PVC and chlorine atoms in the molecule to form a ligand,
And in ligand organotin carboxylate group and a chlorine atom substitution unstable. Such thermal stabilizers are stability characteristics
High transparency, heat resistance, deficiencies are more expensive.
 4) composite heat stabilizer: This class is the base class of heat stabilizers or metal soap-based compound to a liquid or solid
And organic tin-based compound, wherein the metal salts of calcium - magnesium - zinc, barium - calcium - zinc, barium - zinc and barium - cadmium;
Commonly used organic acids such as organic acids, naphthenic acid, oleic acid, benzoic acid and salicylic acid.
 5) Organic compound heat stabilizers: These thermal stabilizers may be used alone except for a few primary stabilizer (mainly nitrogen-containing organic
Compounds), but also includes high boiling polyols and phosphite, often with metal phosphite stabilizer and used, can improve the composite
Materials, weatherability, transparency, and improve the surface color.
2PVC heat stabilizer mechanism
1) absorption and HCL, inhibit its catalytic automatically. Such stabilizers include lead salts, organic acids, metal soaps with
Organotin compounds, epoxy compounds, phenol salts and metal thiolate salt. They can react with HCL, inhibition PVC de HCL response.
 2) replacement of PVC molecules suppress unstable allylic chlorine atoms off the PVC. Such as organic tin stabilizer unstable molecules of PVC
Chlorine atoms given ligand binding, the ligand, a chlorine atom with an unstable organotin substitution.
3) the addition reaction of a polyene structure, a large conjugated system damage formation and reduce coloration. Unsaturated acid salts or esters containing
There is a double bond, with PVC molecules conjugated diene double bond addition reaction, thereby undermining its conjugate structure, inhibit discoloration. 4) to capture free radicals and prevent the oxidation reaction. Such as adding phenolic heat stabilizers can block off the HCL, is due to the original phenol given H
Sub-radical degradation of PVC macromolecules with radical coupling reaction with O2 to form a substance can not be, and has a thermal stability.
Such thermal stabilizers may have one or several functions of both.
 Ideal PVC heat stabilizer should be a multi-functional substance, or a mixture of some materials, they are able potassium soap  to achieve the following
Functions: First, replacement lively, unstable substituent; second absorption and neutralization evolved in PVC processing HCL, HCL eliminated
Autocatalytic degradation; Third, neutralize or catalytic effect on the degradation of the passivation of metal ions and other harmful impurities; Fourth
Through various forms of chemical reactions can block the continued growth of the unsaturated bond, inhibiting degradation coloring; Fifth preferable to ultraviolet radiation
Protective shielding effect. Generally, heat stabilizers based on their performance with the use of a special, used alone is very rare, and large
Some varieties of a powder, some of which are highly toxic chemicals. For ease of use, to prevent dust poisoning, reduce toxic substances or replaced by non-toxic substances, at home and abroad in recent years developed many kinds of composite stabilizer, for example, the world famous German brand composite stabilizer Bear series, the United States, Germany, Japan, Netherlands and other countries or organotin compound organotin stabilizers have considerable market share in China. Therefore, efforts to promote the application developed in China with high efficiency, low cost, no dust pollution and non-toxic or low toxicity of new composite stabilizer, is the urgent need for the development of the plastics industry. 3PVC processing required heat stabilizer principle analysis
 PVC is the first ideal structure - tail structure-CH2-CHCl-CH2-CHCl-, is quite stable. But so far the PVC synthesis method can not be like synthetic butadiene rubber, as the role of catalyst in Jigger so there are rules for orientation cis butadiene polymerization is a free radical polymerization of vinyl chloride random polymerization, in addition to its stable First - tail structure, as well as the first - the first structure-CH2
-CHCl-CHCl-CH-, tail - tail structure-CHCl-CH2-CH2-CHCl-; generate a coupling disproportionation vinyl Results CH2 = CH-CHCl
-CH2-structure and  organic pigments allyl chloride-CH2-CH = CH-CHCl-CH2 and so on.
Generated in the PVC synthetic allyl chloride, chlorine and tertiary carbon double bond in its molecular chain structure instability, unstable cis
Sequence is: PVC within the molecular chain allyl chloride> tertiary carbon Chlorine> terminal allyl chloride> sec chlorine. PVC processing is easily degraded but because
The PVC molecular chain structure, there is instability factors, such modification not be stabilized, and its decomposition temperature is about 130 ℃, but
PVC resin to be processed into useful articles, molding temperature to above 190 ℃. Therefore, you must add to its junction heat stabilizer
Improved structure for stabilization. Four types of heat stabilizers heat discoloration Comment
Ideal thermal stabilizer should also absorb HCL, remove the active site, the addition of a conjugated polyene chain, from the destruction of carbenium
Sub-salt, to prevent the auto-oxidation and other functions, without generating a catalytic degradation of PVC products. The actual heat stabilizer due to
Has a different function and behave in a different thermal stability characteristics, can be divided into early-type, long type, intermediate type and versatile