Plastic auxiliaries are chemicals added to improve the processability and performance of the resin. There are more than a dozen types of plastic auxiliaries commonly used. With the increase in the number of plastics, the expansion of use and the continuous improvement of processing technology, the types and types of auxiliaries are also increasing.
Plastic additives are added during the processing and use of plastic films. Because some of the resin or film products do not have the inherent performance to meet the requirements of their processing technology. Adding auxiliaries only needs to change their processability; while some materials have better processing performance, but the performance of the products does not meet ours. Requirements, it is also necessary to add additives to change its product performance. Of course, these two effects are mutually reinforcing, sometimes for the purpose of achieving both.
Here we first introduce additives that can change the performance of plastic packaging films.
General requirements for additives
compatibility
In general, the additive only has good compatibility with the resin, so that the additive can exist in the film for a long time, stably and uniformly, and effectively perform its function. If the compatibility is not good, the "migration" phenomenon easily occurs. Performance in the liquid additive is "sweating", showing "blooming" phenomenon in solid additives. But sometimes when the film is less stringent, it can still allow its lack of compatibility, such as the compatibility between the filler and the resin is not good, but as long as the filling of the small particle size, it can still meet the performance requirements of the film, of course, if Treating it with a coupling agent or a surfactant will give fuller play to its function. However, some auxiliaries such as an opener, an antistatic agent, etc., which improve the surface properties of the film, are required to have a slight mobility so that they function on the surface of the film.
Durability
Durability requires that the auxiliaries remain in the film for a long time with little or no loss. The loss of auxiliaries is mainly through three routes: volatilization, extraction and migration. This is mainly related to the molecular weight of the auxiliary, the solubility in the medium and the solubility in the resin.
Adaptability to processing conditions
Some resin processing conditions are more severe, such as high processing temperature, this time should consider whether the choice of additives will be decomposed, additives on the processing equipment for corrosion.
The use of film for the control of additives
Different applications of the film have certain requirements for the odor, toxicity, weather resistance, thermal properties of the additives. For example, plastic bags containing foods are non-toxic because they are different from the additives used in plastic bags for general packaging.
Synergistic action and phase reaction in adjuvants
In the same resin system, some of the two auxiliaries will produce a "synergistic effect", that is, more than a single auxiliaries with a single function. However, if it is not properly formulated, some auxiliaries may produce “phase interactions,†which will impair the function of each auxiliaries and even render certain auxiliaries ineffective. This should be particularly noted, such as carbon black and amines or phenols. The use of antioxidants can produce antagonistic effects.
Plastic packaging film commonly used performance additives
Plasticizers and heat stabilizers
Plasticizers, as the name suggests, increase the plasticity of materials, that is, they are added to the resin. On the one hand, the fluidity of the resin is increased during molding, and the processing performance is improved. On the other hand, the flexibility and elasticity of the resulting film can be increased. .
The thermal stabilizer is an additive added for the purpose of improving the thermal stability of the resin. Mainly used for the processing of polyvinyl chloride and vinyl chloride copolymers.
Plasticizers and heat stabilizers are mainly used for the processing of PVC products. The function and use of these two additives will be introduced separately.
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