According to the above mechanism, the structure of the plasticizer is preferably composed of polar and non-polar parts. The polar part is often composed of polar groups, and the non-polar part is usually composed of polar groups. The polar part is usually an alkyl group of a certain length. Polar groups commonly include energy groups, chlorine atoms, epoxy groups, etc. Compounds containing different groups have different characteristics. For example, phthalic acid has good compatibility, plasticizing effect, and comprehensive performance, and is often used as the main plasticizer.
Phosphate esters and vaporized compounds are flame retardant; epoxy compounds have good heat resistance; aliphatic dibasic acid esters have excellent cold resistance, etc. Of course, in addition to the polar groups of environmentally friendly plasticizers, the structure of other parts of the plasticizer molecule also has a great influence on the performance of the plasticizer.
Take vinegar plasticizers as an example. Esters containing aromatic ring structures have better compatibility than aliphatic esters, but their cold resistance is worse than aliphatic esters. The ring family is in the middle.
If the number of carbon atoms in the alkyl group is more than 4, the cold resistance gradually increases. The longer the carbon chain of the environmentally friendly plasticizer, the better the cold resistance; but the number of carbon atoms When it exceeds 12, the compatibility and plasticizing effect will decrease. The longer the carbon chain, the smaller the volatility and mobility. The plasticity and cold resistance of linear alkyl groups are good. As the alkyl branch increases, the cold resistance becomes worse and the plasticizing effect also decreases.
There is not much difference in the performance of plasticizers with ester-based structures. The number of ester groups is usually 2 to 3. Generally, there are more ester groups, and the mixability and transparency are good.
Compared with esters synthesized from primary alcohols, esters synthesized from secondary alcohols have poorer compatibility, plasticizing effect, cold resistance, and heat resistance.
In addition, the molecular weight of the plasticizer must be appropriate. If it is too small, the volatility will be high, and if it is too large, the plasticizing effect will be reduced and processing difficulties will occur. Better plasticizers have molecular weights generally between 300 and 500.
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