Injection Molding: Two-Layer Light-Barrier Preforms For PET Milk Bottles

White PET preforms with black inner layer block out light while saving on expensive pigment.

Related Suppliers

At the Drinktec beverage technology show this month in Munich, Germany, Netstal (U.S. office in Florence, Ky.) will present two-layer Prelactia light-barrier PET preforms for milk products and drinks with a long shelf-life (up to six months for milk). These preforms consist of a 1-mm inner layer of gray PET, which is overmolded with a 1.4-mm white outer skin. This approach is said to provide an improved light barrier—blocking nearly 100% of visible light—while cutting the use of expensive, UV-blocking titanium dioxide white pigment by two-thirds.

The molding system is a Netstal PET-Line 2400-4000/1000 240-metric-ton hybrid machine with two-stage screw/plunger injection and a second injector in an “L” position. The side injector first molds the gray inner layer, then the main injector overmolds the white outer skin. At the show, the 32 + 32 cavity mold for 17-g, 0.5L preforms will by supplied by Molmasa of Spain. The core plate shuttles up and down to transfer preforms between the two molding stations. A top-entry robot removes the preforms to a post-cooling station above the clamp. A second robot transfers the cooled preforms to a belt conveyor that carries them down to floor level. Overall cycle time is 9 sec.


  • Best Methods of Molding Undercuts

    Producing plastics parts with undercuts presents distinct challenges for molders.

  • The Business Advantage of Sustainability

    Companies promote their sustainability commitment in various ways, but beneath the promises and promotional materials should be a true corporate commitment to sustainability goals that provide meaningful environmental, economic, and social benefits.

  • How to Dry PET for Container Applications

    PET is extremely hygroscopic, highly moisture sensitive, and one of the toughest challenges to dry. Here are the basic principles of doing it right for rigid packaging applications