Which Additives Used For Clear Plastic?

In today’s world, we are surrounded by several clear or transparent plastic materials that make products more attractive as well as portable to use over traditional glass. From the water bottles we carry to the health-caring medical devices, clear plastics have become an indispensable part of our everyday life. However, raw material is not naturally clear. Manufacturers use some types of additives to make plastics transparent. In this article, we’ll explore what the clear plastic is and the different types of additives that come in with that function.

1. When Is A Plastic Called “Clear Plastic”?

*When is plastic called “clear plastic”?*

Transparency fundamentally involves an intricate relationship between light and the polymer chains that make up plastic. When light encounters these chains, it interacts in a complex way, sometimes passing through unimpeded and other times being scattered or absorbed. This interaction ultimately affects how transparent the plastic is.

So, how do we determine the clarity of a material? There is a method that scientists call the ‘refractive index’, which measures how much light is refracted, or bent when passing through a substance. A material is transparent if it allows light rays through without deflection or scatter. The less light has to bend through a substance, the clearer it is. In contrast, a semi-crystalline polymer has the thousands of crystallites that form its regular structure that diffract light rays, making it opaque. This property is linked to the degree of regularity with which its molecules are structured and is one that many plastics naturally have.

A number of factors can throw a wrench into plastic transparency, such as crystallinity, scattering, manufacturing, degradation, surface, etc. The available materials for see-through plastics include polycarbonate, acrylic, PETG, and PVC.

2. A List Of Additives For Clear Plastic

2.1. Clarifying agents

Clarifying agents are substances that are added to a liquid in order to eliminate or decrease the concentration of one or more undesired components in order to improve the liquid’s clarity. They promote the formation of smaller, more uniform crystals within the plastic. These smaller crystals scatter less light, leading to improved transparency. Others, like optical brighteners, actually absorb ultraviolet light and re-emit it as visible light, effectively brightening the plastic and enhancing clarity.

Some types of common clarifying agents such as:

Polyethylene glycol: A material helps reduce friction and improve the flow properties of the plastic, leading to better transparency.
Optical brighteners: These additives absorb UV light and re-emit it as visible light, improving brightness and clarity.

2.2. Surface modifiers

Surface modifiers show the function of creating a smooth and allowing light to pass through unimpeded. It is helpful for transparency, and the visual appeal of the plastic product.

There are some surface modifiers that manufacturers usually use including:

Fluorinated compounds: They add a layer with low surface energy, much like silicones, but deliver better resistance to chemicals.
Nanoparticles: These tiny particles can smooth out small flaws and make the surface very clear.

2.3. Nucleating agents

Nucleating agents function like tiny seeds scattered throughout the plastic. They offer a “platform” for spherulite formation, promoting them to form earlier and grow smaller and more uniform. This leads to a significant reduction in light scattering, which is the main reason behind a cloudy appearance.

Nucleating agents are most widely used in polypropylene (homo- and random co-polymers), where they provide three main benefits: property enhancement, improved molding productivity, and increased transparency. Some commonly used nucleating agents to clear plastic include:

Talc: This additive is used in polypropylene and polyethylene.
Sodium benzoate: This is a food additive that can be applied to numerous plastic products.
Calcium stearate: A fatty acid salt is used in PVC plastic.

2.4. Polymer processing aids (PPAs)

*Polymer processing aids (PPAs) for plastic*

The processing-aid additives are materials added to the polymer to lower the friction between plastics and machines during production. This results in fewer air bubbles getting trapped and fewer surface defects appearing, helping a more transparent final product.

Here are some of the PPAs that are widely used in industrial plastics:

Fluoropolymers: These additives are highly effective lubricants providing a slippery surface that allows the molten polymer to flow smoothly.
Organic phosphates: These offer good thermal stability and are widely used in polyolefins.
Silicones: These are particularly useful for reducing die swell and improving surface finish.

2.5. Anti-fog additives

In many plastic applications, especially food packaging films, fogging causes loss in content visibility, and therefore in product attractiveness, as well as accelerating product quality deterioration.

Anti-fog additives prevent the condensation of water on the surface of a clear plastic film. Surfactants in anti-fog additives modify surface tension. In plastic products, chemical compounds migrate to the surface and change the interaction between water and plastic surface to decrease surface tension, therefore, it prevents creating drops and allows more effective light transmission.

2.6. UV stabilizers

UV stabilizers are chemically formulated to absorb UV light’s energy, thus minimizing the contact between the plastic surface and the UV rays. This prevents the formation of free radicals, which are the main culprits behind yellowing, brittleness, and reduced transparency.

There are at least 3 types of UV stabilizers to clear plastic including:

Absorbers: They help absorb UV light, which may be absorbed by chromophores, and change the harmful UV radiation into harmless infrared radiation or heat.
Quenchers: It is also called light stabilizers. They work by quenching molecules that are over-excited during the UV absorption and transfer the energy absorbed into heat.
HALS (Hindered amine light stabilizers): When UV rays are exposed to plastics leading free radicals are formed, it then traps them, thus preventing them from doing any damage to end-products.

2.7. Optical brightener

Optical brightener additive is used to increase light reflectivity, and clear plastic thereby improving end-products to meet aesthetic requirements and maintain the appearance of plastics over time. It works by absorbing ultraviolet (UV) light and re-emitting it as visible blue light. This process effectively reduces yellowing and enhances the brightness and whiteness of the plastic material, making it more visually appealing.

3. Conclusion

In conclusion, maintaining transparency in plastics plays an important role in diverse applications. It involves the use of various additives, each playing a specific function. By carefully selecting and combining these additives, manufacturers can address numerous challenges related to light transmission, surface smoothness, and protection against degradation. This ensures that plastic not only meets aesthetic and functional requirements but also maintains its quality and performance over time.

4. About EuP Egypt’s Additives

EuP Egypt is a leading manufacturer and provider of high-quality and unique plastic raw materials and additives products, catering to a diverse range of industries to help enterprises optimize production costs and improve the competitiveness in the market.

We not only are one of the leading filler masterbatch manufacturer, but also bring a range of plastic additives, including:

Our additives can help end-products achieve the required mechanical and aesthetic properties, leading to improved durability and longevity. Don’t hesitate to contact us now! We will help you choose the right additive type and usage rate to create the final product according to your requirements.