Application of polymer plasticizer in PVC

Application of polymer plasticizer in PVC

Application of polymer plasticizer in PVC

(1) PVC/polyester plasticizer

Polyester plasticizer is a kind of polymer plasticizer with earlier application. It is mainly obtained by condensation reaction of dibasic acid and dihydric alcohol. There are adipic acid polyester and phthalic anhydride polyester, etc., and the molecular weight is about 3000. It is not only resistant to extraction, not easy to migrate, but also can reduce the migration of small molecular plasticizers in soft PVC. Polyester plasticizers improve the processing performance of PVC and are suitable for oil, water and solvent resistant plastic products such as leather, toys, medicine and food industries. When applied in soft PVC, the addition amount can reach 70%.

The relative molecular weight and branching degree affect the plasticizing effect of polyester plasticizer. As the relative molecular weight of polyester plasticizer increases, the glass transition temperature of soft PVC decreases, and the plasticizing effect, heat resistance and solvent resistance increase. The increase in the degree of branching of the polyester plasticizer also improves the heat resistance of the flexible PVC.

PVC/polyester plastisol system, the appropriate addition amount of polyester (polytrimethylene adipate, PPA) is 50-70 parts by mass, and the thermal stability of the plastisol is better under this condition. At present, the "wet-on-wet" technology is widely used in the coating process of automobile production. In order to avoid the extraction of plasticizers by organic solvents, the traditional small-molecule plasticizer system of PVC/polyester plastisol can be selected , which can achieve good results. The shear strength of PVC/DOP/filler plastisol can also be improved when end-capped polyurethane is used as a plasticizer additive .

(2) PVC/LNBR

Liquid nitrile rubber is a copolymer of butadiene and a small amount of acrylonitrile, which is synthesized by free radical emulsion polymerization. The earliest varieties without functional groups and random functional groups, and later dominated by terminal functional groups, such as hydroxyl-terminated liquid nitrile rubber (HTBN), carboxyl-terminated liquid nitrile rubber (CTBN), mercapto-terminated liquid nitrile rubber (MTBN) and Amino-terminated liquid nitrile rubber (ATBN), etc. When the rubber with terminal functional groups is cured, the functional groups at the molecular ends participate in cross-linking, so that the cross-linking network of the vulcanizate does not contain free chain ends, and the relative molecular mass between the cross-linking points is larger than that of ordinary rubber, and the structure is regular. , no short chains , so the flexibility is very good. The domestic brands are mainly Lanzhou Petrochemical's liquid nitrile-26, liquid nitrile-40 and carboxyl liquid nitrile, and the mass fraction of combined acrylonitrile is 23%~27%, 30% respectively ~40%, 30%~35%.

Adding LNBR instead of phthalic acid small molecule plasticizer to PVC paste resin can make plasticized polyvinyl chloride material with good solvent resistance and oil resistance. The extraction rate is extremely low, and it can be used in industries that come into contact with food.

Liquid nitrile rubber makes up for the defect that solid nitrile rubber is not easy to mix with PVC paste resin, so it can be used to modify PVC foam. The tensile strength, elongation at break and hardness of PVC foamed plastics were greatly improved with 0-8 (mass parts) LNBR, but the foaming ratio decreased.

LNBR can improve the elasticity of PVC while replacing common plasticizers such as DOP, DBP, etc. Add LNBR to PVC/DINP (100/80) mixture to make films and test the mechanical properties. When the addition amount of LNBR is 20 parts, the elongation at break is doubled compared with that without addition, while the tensile strength does not decrease.