Skip to content 
Blister Pack Aluminum Foil: Correlation Between Heat Seal Strength and Drug Shelf Life
Blister packaging using aluminum foil is one of the most common and effective methods for protecting pharmaceutical products from moisture, light, oxygen, and contamination. A critical parameter in blister packaging is heat seal strength, which ensures the integrity of the seal between the aluminum foil and the blister base (usually PVC, PVDC, or Aclar). This article explores the relationship between heat seal strength and the shelf life of the packaged drug, highlighting key control factors and optimization strategies.
1. The Role of Heat Seal Strength in Blister Packaging
Heat seal strength refers to the force required to separate the aluminum foil from the base film after sealing. It is vital to ensure:
Leak-proof protection from environmental factors
Mechanical stability during transportation
Consistent opening behavior for patient usability
Insufficient seal strength can lead to micro-leakage, while overly strong seals may make the blister difficult to open or damage the product during opening.
2. Impact on Drug Shelf Life
Proper seal integrity directly affects the stability of pharmaceuticals by:
Preventing moisture ingress: Many APIs are hygroscopic and degrade upon exposure to humidity.
Shielding from oxygen: Oxidation-sensitive drugs require an airtight environment.
Avoiding contamination: Strong, uniform seals prevent microbial or particulate ingress.
Studies show that optimized heat seal parameters significantly improve long-term stability, especially for moisture- and oxygen-sensitive formulations such as effervescent tablets, antibiotics, and proton pump inhibitors.
3. Key Factors Influencing Heat Seal Performance
Several factors affect seal strength and packaging integrity:
| Factor | Description |
|---|---|
| Sealing Temperature | Too low: weak adhesion; Too high: blister distortion or material degradation |
| Dwell Time | Time the foil is in contact with the heated seal head; impacts bonding uniformity |
| Sealing Pressure | Controls adhesion force; insufficient pressure leads to uneven sealing |
| Surface Cleanliness | Any contamination can weaken seal strength and cause delamination |
| Lacquer Coating Type | Heat-seal lacquer formulation (e.g., PVC-based, vinyl-based) impacts bond strength and compatibility with base films |
4. Testing and Quality Control
Heat seal strength should be regularly tested according to standards such as:
ASTM F88 – Standard test method for seal strength of flexible barrier materials
USP <671> – Container performance testing
Accelerated stability studies – Simulating long-term storage conditions to predict shelf life
Additionally, visual inspection, leak detection (vacuum or dye ingress), and moisture vapor transmission rate (MVTR) testing provide critical data for verifying seal quality.
5. Optimization Tips for Better Shelf Life
Choose a heat-seal lacquer compatible with your blister substrate and drug type.
Maintain clean sealing surfaces in the packaging line.
Validate and monitor sealing parameters (temperature, pressure, time) during production.
Conduct periodic stability testing to ensure packaging maintains efficacy over the intended shelf life.
Conclusion
The heat seal strength of blister pack aluminum foil plays a decisive role in maintaining the integrity and extending the shelf life of pharmaceutical products. By optimizing seal parameters and understanding their correlation with drug stability, manufacturers can ensure reliable protection and compliance with global packaging standards. For moisture- or oxygen-sensitive drugs, achieving the right heat seal strength is not just a packaging detail—it’s a quality guarantee.
