PET (Polyethylene terephthalate) vs PVC (Polyvinyl chloride)
Sustainability awareness in the packaging industry has driven a trend towards the use of PET components in visual packaging. PET is considered to be an environmentally friendly material with good clarity and structural integrity. When developing new products or switching existing products from PVC to PET there are a few things that should be considered to aid in providing desirable results:
DESIGN & TOOLING
Design and Tooling costs for new PET products are similar to tooling costs for PVC products; however, existing PVC tooling may not be compatible with PET materials. PET films form at a lower temperature than PVC so the lower level of heat limits the level of detail in finished parts. If too much heat is applied the material will “Blush”, indicating it has crystallized and will become brittle. PVC fractures when the knife strikes the plastic and PET requires the knife to cut all the way through to the striker plate. In some situations this may result in smaller tool sizes to accommodate the increase in cutting pressure required for cutting all the way through PET.
De-Nesting and Auto Feeding
PVC has a rough surface with a low COF (Coefficient of Friction) allowing excellent de-nesting and auto feeding characteristics with small amounts of silicone applied to the surface. PET has a much smoother surface and higher COF which requires the application of higher amounts of silicone to separate parts. The additional silicone could present challenges for some types of packaging such as clamshells with closure features and face seal blisters. Draft angles play an important role in separating parts as well. PET designs with draft angles less than 10 degrees can make it difficult to separate parts or auto feed using automated equipment.
PET and Heat Sealing
PET can be heat sealed on the same equipment used for PVC, however some applications will require specific grades with modifiers added that improve performance. It is important to communicate intended sealing method prior to starting new product development.