What is the role of plasticizers? What is the mechanism of action?
In the eyes of the chemical industry, additives are always a supporting role. But experienced engineers and technicians know that without good additives with, the quality of the material is difficult to be improved. In the production of plastics, plasticizers, as common additives, play an important role. lONGCHANG CHEMICAL provides a detailed introduction to the role of plasticizers.
Plasticizers are low volatile substances added to plastics in order to improve plasticity and increase their flexibility.
The main role of plasticizers is to weaken the intermolecular forces of the polymer, reduce the melting temperature and melt viscosity, improve its molding and processing properties, in the use of temperature range, giving plastic products flexibility and a variety of other necessary properties.
The plasticizing effect is caused by the weakening of the aggregation between the macromolecular chains in the polymer material. The insertion of plasticizer molecules between polymer molecular chains weakens the forces between polymer molecular chains and as a result increases the mobility of polymer molecular chains and reduces the crystallinity of polymer molecular chains, thus increasing the plasticity of the polymer. Specifically, the plasticizer molecules inserted between the polymer molecules, weakening the intermolecular forces, thereby achieving plasticization purposes.
Plasticizers are usually high boiling point, low volatile liquid, or low melting point solid, most of its molecules have polar and non-polar parts.
The polar part is often composed of polar groups, and the non-polar part is alkyl with a certain length and volume. The polar groups are mainly ester groups, chlorine atoms and epoxy groups.
Compounds containing different polar groups have different characteristics, such as phthalate esters have good compatibility, plasticizing effect and comprehensive performance; phosphate esters and chlorides have flame retardancy; epoxides and dipentaerythritol esters have good heat resistance; aliphatic dibasic acid esters have excellent cold resistance; phenyl alkyl sulfonate esters have good weather resistance; citrate esters and acetyl citrate esters have antibacterial properties, etc.
The molecular weight of plasticizers mainly affects durability, plasticizing efficiency and compatibility. To get good durability, the molecular weight of plasticizers should be more than 350, and molecular weight of more than 1000 polyester and benzene polyacid esters (such as trimellitate) plasticizers have very good durability, they are mostly used in wire and cable, automotive interior decorative products and some so-called permanent plasticized products.
Plastic with the ideal plasticizer should have: good compatibility with the resin, high plasticizing efficiency, durability, cold resistance, stability, insulation; non-toxic; excellent processability, flame retardant, and inexpensive and easy to obtain.