The Application of Cold Stamping Aluminum Hard Sheets in Pharmaceutical Blister Packaging
The aluminum-plastic blister packaging for pharmaceuticals, referred to as PTP packaging, involves heating the packaging material to form or cold stamping to create cavities suitable for tablets, capsules, etc. The drugs are then filled into these cavities, and a heat-sealable aluminum foil coated with a suitable heat seal layer is used to seal it, forming unit packaging.
Advantages of Aluminum-Plastic Blister Packaging
Aluminum-plastic blister packaging offers many advantages, making it widely used in the pharmaceutical packaging field and becoming the primary packaging form for tablets and capsules.
| Advantages | Description |
| Accurate Dosing | Each drug is independently packaged, ensuring that patients receive an accurate single dose, avoiding medication errors. |
| Portability | Individual packaging makes it easier to carry drugs, allowing patients to use them conveniently anytime. |
| Medication Safety | The independent packaging design enhances medication safety and reduces the risk of cross-contamination. |
| Excellent Protection Performance | Effectively prevents external environmental influences on the drugs, protecting their quality. |
| High Production Efficiency | Fast production speed and high automation improve production efficiency. |
| Cost Effectiveness | Compared to traditional packaging, it has lower costs and strong economic benefits. |
| Lightweight and Easy to Transport | The packaging is lightweight, making transportation easier and reducing logistics costs. |
Typically, aluminum foil is used as the covering material for pharmaceutical blister packaging, while the blister substrate is generally made of polyvinyl chloride (PVC) hard sheets. However, with the development of the pharmaceutical industry, this traditional packaging method has gradually exposed some shortcomings.
Limited Barrier Performance: The barrier performance of PVC hard sheets is relatively poor, making it difficult to ensure that the drugs maintain their quality throughout their shelf life.
Advantages of Cold Stamped Hard Sheets
To address the insufficient barrier performance of conventional blister packaging, cold stamped hard sheets have been developed. This new type of packaging offers the following advantages:
| Advantages | Description |
| Innovative Manufacturing Process | Cold stamped hard sheets use a stamping process, replacing the traditional vacuum forming method. |
| Material Upgrade | Cold stamped hard sheets can utilize pure aluminum composite materials as the blister substrate. |
| Excellent Barrier Performance | The use of high-strength aluminum foil provides cold stamped hard sheets with significant advantages in blocking water vapor, oxygen, and light, outperforming other materials. |
Cold stamped hard sheets enhance the effectiveness of drug packaging in protecting drug quality, meeting the increasingly stringent packaging performance requirements of the pharmaceutical industry.
Structure of Cold Stamped Hard Sheets
Cold stamped hard sheets typically consist of three functional layers: a surface support strength layer, a middle aluminum foil barrier layer, and an inner heat-seal layer. The surface support layer can be printed with the desired colors or patterns, and the layers are bonded together using adhesives to form a composite film as a whole.
| Layer | Material | Properties and Requirements |
| 1. Surface Support Strength Layer | Biaxially Oriented Nylon Film (BOPA) | Smooth and Flat |
| Good Transparency | ||
| High Mechanical Strength | ||
| Excellent Impact Resistance | ||
| Wear and Puncture Resistance | ||
| Alternative Materials: Biaxially Oriented Polyester Film (BOPET) or Biaxially Oriented Polypropylene Film (BOPP) | Used in shallow drawing applications to reduce costs | |
| 2. Intermediate Aluminum Foil Barrier Layer | High Strength Alloy Aluminum Foil | Strong Barrier Properties |
| Provides Strength Support | ||
| Resistant to Draw Stretching | ||
| Typical Thickness: 45 μm | ||
| Shallow Drawing Can Be Reduced to 30 μm | ||
| Special Deep Drawing Can Be Increased to 70 μm | ||
| 3. Inner Surface Heat Seal Layer | Polyvinyl Chloride (PVC) Sheet | Heat Sealing Capability |
| Internal Plasticization and Lubrication | ||
| High Impact Resistance | ||
| Typical Thickness: 60 μm | ||
| High Rigidity Can Be Increased to 100 μm | ||
| In Special Cases, PP, PE, PET, or Surlyn Can Be Used |
Production Process Requirements for Cold Stamping Formed Hard Sheets
The surface support strength layer, aluminum foil barrier layer, and inner surface heat seal layer in the cold stamping formed hard sheets are bonded together using adhesive to form a composite material. To ensure that the cold stamping formed hard sheet does not delaminate or break under strong impact forming forces, the choice and application of the adhesive are crucial. Generally, the adhesive bond strength between the aluminum foil and the surface support strength layer and heat seal layer should exceed 8N/15mm after bonding.
Common Issues and Process Solutions for Cold Stamping Formed Blister Packaging
Although cold stamping formed blister packaging has a good appearance and high barrier performance, this product exhibits many characteristics that differ from other packaging materials during use, often resulting in the following issues: during the forming of the cold stamping hard sheets, cracks and pinholes may occur in the aluminum foil on the blister cavities, and sometimes delamination can happen between the composite film layers.
1. Quality Issues of Cold Stamping Formed Hard Sheets
Scratches and Cracks: The outer nylon film of cold stamping formed hard sheets is prone to scratches, which can lead to the breakage of the aluminum foil and nylon film. Scratches may occur during production or use and are difficult to detect with the naked eye.
Solution: Ensure that the rollers of the production equipment are flexible, and regularly inspect and clean the equipment to avoid scratches caused by foreign objects. Additionally, maintain a dry environment to prevent moisture absorption by nylon, which can lead to material separation.
Moisture Absorption Issue: Moisture absorption by nylon may lead to the separation of aluminum foil and nylon film, reducing the forming rate.
Solution: Store cold stamping formed hard sheets in a dry environment to prevent moisture absorption.
2. Defects in Stamping Die Design
Material and Design of the Die: The choice of die material and geometry can affect friction and stress distribution during the stamping process.
Solution: Preferably use polytetrafluoroethylene (PTFE) dies due to their low friction coefficient, which effectively reduces the risk of aluminum foil cracking and layer separation.
Die Shape: The design of the die head also affects the forming results; smooth die heads look aesthetically pleasing but have poor stamping resistance, while stepped die heads allow for uniform stretching.
Solution: Use computer software to design the optimal die head shape based on the drug shape to avoid excessive localized stress.
3. Improper Control of Stamping Process
Stamping Depth and Speed: Excessively deep or fast stamping can lead to aluminum foil rupture.
Solution: Adjust the stamping depth to minimize it, ensuring that the aluminum foil operates within its stretch limit.
Effects of Preheating: Preheating can improve PVC forming, but excessive temperatures may reduce the composite strength of aluminum foil and nylon film.
Solution: Select an appropriate preheating temperature based on the characteristics of the equipment and materials.
4. Poor Heat Sealing
Insufficient Thickness of the Heat Seal Layer: Inadequate sealing points may lead to gas leakage.
Solution: Increase the thickness of the PTP aluminum foil heat seal layer and determine the design parameters of the sealing points through experimentation.
5. Deformation Issues
Impact of Deformation: Stamped hard sheets may deform after stamping, affecting heat sealing effectiveness and packaging positioning.
Solution: Ensure the rigidity of the materials and reasonable design of the die while optimizing tension control of the equipment.
Quality Inspection
For ordinary transparent PVC blister packaging, due to the relatively low barrier properties of PVC, the impact of pressure marks at sealing points on the drug's shelf life is minimal and can be assessed visually.
However, the double aluminum foil blister packaging of cold stamping formed hard sheets, while airtight, can have pressure penetrations at sealing points that significantly affect packaging barrier properties and the drug's shelf life. Due to their opacity, pressure penetrations at sealing points are difficult to inspect. To ensure product quality, in addition to strengthening production process controls, it may be advisable to increase the thickness of the PTP aluminum foil. Typically, the thickness of PTP aluminum foil is 20μm, but for cold stamping formed hard sheets, it is recommended to use 25μm or, for high-demand products, 30μm aluminum foil to improve barrier performance.
