How To Select Additives for Plastics

Before processing any plastic material, once the polymer is selected, the next critical step is choosing the appropriate additives and determining their dosage. The correct selection of plastic additives directly impacts processing efficiency, product performance, and service life. Four major considerations should be taken into account when selecting additives:

1. Compatibility with the Polymer
Compatibility refers to the ability of the additive to blend uniformly with the polymer without phase separation or precipitation. Additives must remain stably present in the final product over time to be effective. Therefore, additives with good compatibility with the polymer should be chosen whenever possible. However, each additive has a limited compatibility range with any given polymer. Beyond this range, the additive may precipitate.

2. Adaptability to Processing Conditions
If the polymer must be processed under high temperatures for extended periods, the chosen additives must withstand such conditions. For example, polypropylene is processed at relatively high temperatures, so stabilizers that do not decompose or volatilize at such temperatures should be selected. Similarly, heat-resistant, non-fading colorants are necessary. Even for the same polymer, different processing methods may require different additives.

3. Maximizing Synergistic Effects
A single plastic product often contains multiple additives that can interact with each other. When properly combined, these additives may enhance each other's effects, known as a synergistic effect. For example, mixing the UV absorber 2-hydroxy-4-octyloxybenzophenone with the antioxidant tris(nonylphenyl) phosphite produces a significant enhancement in performance. Conversely, when additives are mismatched and reduce each other's effectiveness, it results in an antagonistic effect. For instance, using carbon black with amine-based antioxidants in polyethylene can weaken the stabilizing effects of both.

4. Restrictions Based on Product Use
The intended use of the plastic product often restricts the choice of additives. Products that come into contact with humans—especially those used for food packaging or medical applications like blood bags—require non-toxic additives. For products frequently exposed to oil or water, additives should be chosen that are resistant to extraction by these substances.

NANJING HAISI is professional manufacturer of Plastic Extruder Machine, we supply Twin Screw Extruder, Single Screw Extruder, Plastic Recycling Extruder, Two Stage Extruder, Lab Scale Extruder, Mixing and Feeding Machine, Cooling and Pelletizing Machine, Crushing Machine and so on.