Thermoforming is the production process that shapes plastic film into the cavities of a blister pack using heat and a mold. The plastic is heated until pliable, pressed into the mold cavity, and cooled back to solid form. The whole cycle takes seconds. It's the most common cavity-forming technique in pharma packaging globally.
How thermoforming differs from cold forming
Cold forming uses pressure alone to shape an aluminum-aluminum laminate, no heat. The result is a cavity with significantly higher moisture and light barrier than any thermoformed plastic, at higher cost and slower line speed.
The choice between the two is dictated by API stability:
- Stable formulation? Thermoformed PVC, cheap and fast.
- Moderate moisture sensitivity? Thermoformed PVDC-coated PVC.
- High moisture or light sensitivity? Cold-formed Alu-Alu.
Most pharma blister packs are thermoformed because most APIs don't need Alu-Alu's barrier protection.
Common thermoformed pharma materials
PVC. Most common, cheapest, easy to thermoform, basic moisture barrier.
PVDC-coated PVC. PVC with a barrier coating laminated on. Better moisture barrier than plain PVC. Common for moderately sensitive APIs.
ACLAR. Polychlorotrifluoroethylene laminate. High moisture barrier and light-resistant. Used for hygroscopic and photosensitive APIs that don't quite need Alu-Alu.
PETG, APET. Used for medical device trays. Clear, strong, easy to thermoform into custom cavity shapes for surgical instruments and infusion sets.
The thermoforming process step by step
A roll of plastic film feeds into the thermoformer. The film passes through a heating station that softens it. A mold descends, sometimes with vacuum assist, and presses the softened film into cavity shape. The film cools rapidly, locking in the geometry. The formed strip continues to the filling station.
Modern pharma thermoformers run 200-400 cavities per minute. The whole forming step takes a couple of seconds per cavity.
When thermoforming is the wrong choice
Three cases:
- Hygroscopic, light-sensitive, or oxygen-sensitive APIs that need Alu-Alu cold forming.
- Heat-sensitive products where even brief exposure to thermoforming temperature is a stability risk (rare, but real for some biologics).
- Medical devices that need custom cavity shapes incompatible with standard thermoforming tooling.
For everything else, thermoforming is the default and works well.
If you're scoping thermoformed packaging
The decision starts with stability data, ends with cavity tooling. We run thermoforming across PVC, PVDC, ACLAR, and PETG/APET for medical device trays. Send us the brief if you want a thermoforming spec for a new product.
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