Plasticizer, also known as a plasticizer, is a widely used polymer material additive in the industry. Adding this substance to plastic processing can increase plasticity without affecting the essential characteristics of the polymer. It can improve the elongation, flexibility, and flexibility of plastics, but the hardness, modulus, softening temperature and embrittlement temperature will decrease. So what are the reasons that affect the plasticization of plasticizers, do you know?
1. The role of plasticizers
• Lower the glass transition temperature of the polymer.
● Change the structure of the polymer to make the plasticized material soft.
●Increase the elongation of the polymer and reduce the tensile strength.
●Increase the toughness of the polymer and improve the impact resistance.
●Improved low-temperature performance.
2. The main factors affecting plasticization
●Intermolecular forces of polymers
When a plasticizer is added to a polymer, the interaction force between plasticizer molecules and between plasticizer and polymer molecules has a great influence on plasticization. This interaction is mainly van der Waals force and hydrogen bond force, and van der Waals force includes three kinds of dispersion force, inductive force and orientation force.
(1) Van der Waals force
▶ The dispersion force exists between all polar or non-polar molecules, and it is the suction force generated by the interaction with the tiny instantaneous dipoles, which makes the dipoles close to the opposite poles adjacent to each other, but only in the non-polar state. In the system, its dispersion force occupies the main position.
▶When a molecule with a dipole induces an induced dipole in an adjacent non-polar molecule, the molecular attraction between the induced dipole and the intrinsic dipole is called the inductive force. The inductive force is particularly strong for aromatic compounds. The plasticizing effect of polystyrene with low molecular weight esters is mainly inductive.
▶When polar molecules are close to each other, due to the inherent dipole orientation, a force is generated between the molecules, which is usually called an orientation force. The interaction between ester plasticizers and PVC is a representative example.
(2) Hydrogen bond
Hydrogen bonding is a relatively strong interaction bond, and its existence will prevent the insertion of plasticizer molecules into polymer molecules. The denser the hydrogen bonds are distributed along the polymer molecular chain, the more difficult the corresponding plasticizer molecules are inserted, Therefore, the plasticizer is required to have a strong effect similar to that of the polymer molecules. When the temperature increases, the effect of hydrogen bonds will be weakened due to the thermal motion of the molecules hindering the orientation of the polymer molecules.
●The crystallinity of the polymer
It is much more difficult for plasticizer molecules to insert into crystalline regions than into amorphous regions. Because the free space between polymer chains in the crystalline region is small. A plasticizer is a non-solvent plasticizer if its molecules can only insert into the amorphous regions of a partially crystalline polymer. If the molecules of the plasticizer can be inserted into both the amorphous region and the crystalline region of the polymer, the plasticizer is a solvent-based plasticizer, the so-called primary plasticizer.
The above is the relevant content about the reasons that affect the plasticization of plasticizers. I hope that it will be helpful after reading it. In summary, the main factors affecting the plasticization of plasticizers are the intermolecular force and polymerization of polymers. When the plasticizer is added to the polymer, the interaction force between the plasticizer molecules and between the plasticizer and the polymer molecule will have a great influence on the plasticization effect.