Basic properties of plasticizers

Plasticizers are substances that make the resin easier to process and the products softer after being mixed with polyvinyl chloride resin. However, in reality, not all substances with this property can be used as plasticizers. The necessary conditions for being a plasticizer are:

1. Good compatibility with polymers

Plasticizers must have good compatibility with polyvinyl chloride resins.

2. Lowering the melting point

Polyvinyl chloride is a microcrystalline polymer with a crystallinity of 10~20%. The melting point of polyvinyl chloride crystals is above 200℃, which is one of the reasons that harm the processability of polyvinyl chloride. One of the functions of plasticizers is to lower the melting point of this microcrystal, lower the processing temperature, and facilitate processing and molding. The smaller the interaction constant between the plasticizer and the resin, the greater the reduction in melting point, the better the miscibility of the plasticizer and the resin, and the easier the processing.

3. Softness

The biggest purpose of adding plasticizers to polyvinyl chloride is to make polyvinyl chloride soft. Adding plasticizers to polyvinyl chloride will lower the glass transition temperature of polyvinyl chloride and make soft polyvinyl chloride plastics become rubbery near room temperature. The effect of lowering the glass transition temperature is generally called plasticization.

The mechanism of plasticization can be explained mainly from the following three aspects:
(1) Due to the solvation effect of plasticizers between the polar groups of polyvinyl chloride, the intermolecular forces of polyvinyl chloride are weakened;
(2) The distance between polyvinyl chloride molecules is increased, which weakens the intermolecular forces of polyvinyl chloride;
(3) Dilution effect.