Corvaglia launches one-piece hot-fill cap

Almost all plastic caps for products hot-filled in PET bottles are made from temperature-resistant polypropylene and are fitted with a separate liner.

Since 2005, Corvaglia and Gatorade (Pepsi) in Mexico worked together to develop a one-piece cap in high-density polyethylene (HDPE) that addressed caps with a tendency to deform when subjected to elevated temperatures and to ensure a leak-proof seal at ambient temperatures.

A slight overpressure in the bottle usually occurs after filling and as the temperature falls a slight vacuum is created.

PET and PE also shrink at different rates, which can possibly lead to so-called "micro leakage", especially at the critical phase between the over-pressure and the partial vacuum.

This also opens up the possibility of the contents becoming contaminated by bacteria.

Both companies have therefore used a newly-developed geometry the two-start 38mm cap.

When the cap has been screwed onto the bottle, it showed sufficient pre-tension to form a seal, which is actually reinforced by the distortion of the cap under vacuum.

This solution for a one-piece HDPE cap therefore allows cost savings in comparison with the previous PP cap and separate liner.