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Caps and Closures: Functions and Aesthetic Considerations

Caps and closures help safeguard products from microbes, premature degeneration and damaging UV light – protection that is particularly crucial for the food, beverage, medical and pharmaceutical sectors.

Additives not only provide protection, they can also be designed to complement a product’s or package’s aesthetic appeal.

Common Functional Additives for Caps and Closures

To effectively seal a bottle or container and provide the right level of protection for the contents, caps and closures may require one or more functional additives. Some of the most widely used include:

  1. Antimicrobial additives: Antimicrobial properties are especially important in the medical and pharmaceutical industries. For instance, antimicrobial caps help to reduce the risk of infection in catheter tubes.
  2. Antioxidant additives: Like any other plastic, caps and closures can degrade over time, which affects the seal on the package. Medicine and supplement bottle caps often use antioxidant additives to guard against degradation.
  3. UV stabilizers: Exposure to ultraviolet light from sunlight and some artificial lighting can break down plastics. UV light also causes plastics to lose aesthetic properties, fading colors and yellowing whites.
  4. Impact modifiers: Impact modifying additives increase closure elasticity and strength, so a bottle will remain intact if dropped or struck by another object.
  5. Anti-static additives: Some products, including electrical components, are affected by static electricity. Some medical applications require anti-static additives as well, including inhalers and spacers for inhalers.
  6. Mold release additives: Caps and closures are manufactured by injection and blow-molding processes. Mold release additives prevent them from sticking to the machinery so the product line can keep moving.
  7. Nucleating agents: Liquid polymers used in molding have to crystallize for production to move forward. Nucleating agents help caps and closures cool faster and retain their stability after cooling.
  8. Antiblock and slip additives: Without slip additives, plastics tend to experience friction when in contact with other plastics. These additives reduce the tackiness of polymers, allowing caps and closures to be used (opened) more easily.

Common Aesthetic Additives

Functional additives play a large role in the production process. Aesthetic additives make caps and closures make the plastic visually appealing and reinforce the product’s brand.

Manufacturers have a wide selection of aesthetic additives at their disposal when designing and producing plastic caps and closures:

  1. Compounds: Manufacturers can save time on production by using pre-colored resin compounds ready for the mold.
  2. Concentrates and masterbatches: Manufacturers who already have the resin they need for their caps and closures can use color concentrates and masterbatches to achieve a desired look.
  3. Liquid color: For manufacturers that want low cost, easy to use color additives with superb color consistency, liquid color can be mixed via highly customizable, automated dispersion systems.
  4. Clarifying agents: Some polymers, particularly polypropylene, can become hazy during the molding process. Clarifying additives reduce the hazing effect.
  5. Optical brighteners: Optical brightening additives make whites whiter and colors more colorful, and even facilitate florescence under black light.
  6. Matting agents: A frosted or matte finish can impart a luxurious feel.
  7. Toners: Toners clarify color, either making the color more neutral or sharpening it.

Plastics Color Corporation, Polymer Additives, and Caps and Closures

Plastics Color Corporation offers a range of functional and aesthetic additives suitable for caps and closures. PCC’s Microblok® solves the antimicrobial needs of packaging manufacturers. LiquiSol® achieves desired polymer colors quickly at a reasonable cost and Ultrabatch™ provides explosively bright colors through standard-sized masterbatch pellets.

To learn more about our wide variety of plastic additive products, please fill out the form at the bottom of this page.

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