Effect of plasticizer on PVC film

Plasticizer is an important chemical additive that can improve the plasticity and strength of plastics and other materials. Compared with traditional chemical plasticizers, this oil-based bioplasticizer has natural environmental protection characteristics, good thermal stability, high plasticization efficiency, and can be used in the production of PVC processing enterprises to reduce energy consumption and costs and improve production efficiency. Today, the editor will introduce the relationship between PVC film performance and plasticizers

The addition of plasticizers can reduce the interaction between PVC molecular chains, reduce the glass transition temperature, flow temperature and melting point of microcrystals in PVC plastics. Plasticizers can improve the plasticity of resins, make products soft, and have good low temperature resistance.

The influence of plasticizers on PVC film

The performance of PVC film materials has developed different changes due to the different plasticizers used by enterprises, and the mutual influence relationship between film performance and plasticizer chemical knowledge structure. When the film technology is required to have certain special properties, it is very important to determine the film formula, and some national requirements for films are sometimes contradictory.

If it is difficult to make a good cold-resistant and flame-resistant film, and if oil resistance is also required, using various known plasticizers still cannot meet the requirements. Therefore, we must choose a plasticizer in an appropriate proportion and learn from each other to make up for the defects of various plasticizers to meet the requirements of use.

The plasticizer content of PVC soft film is generally 18-45%. When the amount of plasticizer as a processing aid is less than 18%, a special phenomenon can be observed, that is, the film at this content is not softer than the pure PVC rigid film but more brittle. Its impact strength and cold resistance are lower than those of pure PVC hard film. This phenomenon may be due to the small amount of plasticizer, and it is impossible to “eliminate” the polarity of PVC molecules.

Films with a plasticizer content of less than 18% to 20% are mostly not made of pure PVC, but brittle and impact-resistant PVC. Films containing more than 45% plasticizer are difficult to manufacture, have extremely low strength, high elongation, high viscosity, and are rarely produced.

The higher the plasticizer content in the film, the more obvious the impact on the film performance. In order to achieve the same softness, if different plasticizers are used, the amount of addition is also different. When comparing different films, films with the same hardness are often used as the benchmark, rather than films with the same plasticizer content.

According to the different uses and processing technology approaches of the enterprise, we also need to make our own choices for the resin model. The combination management method of PVC resins and various additives of different product models is designed because of the PVC formula we often say now.

Principles for the selection of PVC plasticizers

1. Compatibility of PVC plasticizers and resins

Compatibility refers to the compatibility when two or more substances are mixed, and the compatibility at the molecular level. Usually PVC plasticizers only have good compatibility with resins. After the plasticizer is mixed with the resin, the PVC plasticizer can be retained in the product for a long time and stably. They have good compatibility, high plasticizer content, good product flexibility, long service life, no seepage or segregation, low volatility, and can effectively maintain its good functions.

Generally speaking, according to market rules, the more similar the polarity, the easier it is for plasticizers to dissolve each other, and good solubility can be achieved by forming a uniform mixed management system. The parameter of dielectric constant is used to analyze and judge the compatibility of plasticizers.

2. Adaptability of PVC plasticizers to processing conditions

Some resins have high requirements for processing conditions. When the processing temperature is high, it is necessary to consider whether the PVC plasticizer will decompose or need to be flame retardant, and whether the PVC plasticizer is corrosive to the equipment. The plasticizer added during the molding process will deteriorate, and the plasticizer will not have a destructive effect on the substrate.

3. Durability of PVC plasticizers

PVC plasticizers are combined by volatilization, migration, extraction, etc., which is related to the molecular weight of PVC plasticizers, solubility in the medium, and solubility in the resin.

4. Migration learning rate of PVC plasticizers

The migration rate of PVC plasticizers has a large correlation with temperature. The migration coefficient is proportional to the thermodynamic temperature. The thermodynamic temperature is linear and accelerates with increasing temperature. Generally, the initial migration rate is fast, and as the migration rate decreases, the linear relationship between the migration time and the square root of the migration concentration gradually tends to balance. Therefore, the migration of polyvinyl chloride plasticizers changes over time.

5. Synergistic and antagonistic effects of PVC plasticizers

Sometimes two PVC plasticizers will produce a “synergistic effect”, which is much greater than the effect of using PVC plasticizers alone. However, improper dosage may lead to “antagonism” between the two plasticizers, weakening their respective effects, and even making some additives ineffective.