A wide variety of additives are used in plastic molding to modify the properties of the base plastic and achieve specific functionalities in the final product. These additives can be broadly categorized into the following groups:

1. Fillers and Reinforcements:

• Fillers: These are inert materials added to reduce the cost and weight of the final product, improve dimensional stability, and sometimes enhance certain mechanical properties. Examples include calcium carbonate, talc, clay, and silica.
• Reinforcements: Unlike fillers, reinforcements significantly improve the strength, stiffness, and other mechanical properties of the plastic. Glass fibers, carbon fibers, and aramid fibers are common examples.

2. Plasticizers:

• These additives increase the flexibility and workability of the plastic, making it easier to process and mold. They are commonly used in products like hoses, cables, and shoe soles.

3. Stabilizers:

• These additives protect the plastic from degradation caused by factors like heat, light, and oxygen exposure. They prevent the plastic from becoming brittle, cracking, or losing its color over time.

4. Colorants:

• Pigments and dyes are added to give the plastic its desired color. Pigments are insoluble particles that disperse throughout the plastic, while dyes are soluble and color the plastic itself.

5. Antioxidants:

• These additives combat the negative effects of oxidation, which can cause the plastic to degrade and lose its properties. They are particularly important for plastics exposed to sunlight or high temperatures.

6. Antimicrobials:

• These additives help prevent the growth of mold, mildew, and bacteria on the plastic surface. They are used in applications where hygiene is crucial, such as medical devices and food containers.

7. Flame Retardants:

• These additives are incorporated into the plastic to make it more resistant to fire and slow down the spread of flames. They are used in various applications where fire safety is a critical concern.

8. Processing Aids:

• These additives improve the flow characteristics of the plastic during molding, making it easier to fill the mold cavity and reducing the risk of defects. Examples include lubricants and mold release agents.

9. Antistatic Agents:

• These additives reduce the buildup of static electricity on the plastic surface, which can attract dust and dirt or cause electrical discharges. They are used in electronics and other applications where static buildup is undesirable.

10. Biodegradability Enhancers:

• As environmental concerns grow, additives are being developed to promote the biodegradability of plastics. These additives help break down the plastic into harmless components by microorganisms in landfills or compost environments.

The specific types and combinations of additives used in plastic molding depend on the desired properties of the final product, the type of plastic being used, and the intended application.