Blister packaging for pharmaceuticals comes in various sizes and shapes — blister cavities, trays, and cartons of different dimensions depending on the packaged product. Some use backing substrates while others do not. Blister packaging machines also come in many types, and packaging methods vary. Despite these variations, the core blister packaging principles stay consistent. The typical process flow is:
Plastic sheet heating → Film forming → Product filling → Substrate covering → Heat sealing → Trimming
This process can be carried out using manual, semi-automatic, or fully automatic operation.
Pharmaceutical blister packaging involves large production volumes, relatively fixed product types, and strict safety and hygiene requirements. This makes automated packaging lines the preferred choice. In fully automatic operation, beyond completing packaging steps, processes such as printing, instruction leaflet insertion, and cartoning can be integrated into the packaging line to form a complete automated blister packaging production line.
Detailed Process Steps
(a) Roll plastic sheet unwinds and advances forward.
(b) Sheet is heated and softened, then formed into blisters using either pressure forming (compressed air) or vacuum forming (suction) inside a mold.
(c) Products are filled using an automatic feeding mechanism.
(d) Blister forming quality and fill accuracy are inspected. In automatic production lines, photoelectric detectors are commonly used — when a defective product is detected, a rejection signal is sent to a memory device, and after the cutting process is completed, the defective unit is automatically rejected.
(e) Roll substrate material is applied over the filled blisters.
(f) A plate-type or roller-type heat sealer bonds the blister to the substrate.
(g) Batch numbers and dates are printed on the back of the substrate.
(h) Individual packaging units are die-cut. The rejection device removes defective units after cutting, based on signals stored in the memory device.
(j) Instruction leaflets are inserted and units are cartoned — completing the saleable packaging unit.
II. Pharmaceutical Blister Packaging Materials
Pharmaceutical blister packaging primarily uses plastic sheets, substrate materials, heat-seal coating materials, and substrate printing inks.
1. Plastic Sheet Materials
Commonly used rigid plastic sheets for pharmaceutical blister packaging include PVC (polyvinyl chloride), PVDC (polyvinylidene chloride), and various composite materials. PVC rigid sheet is currently the most widely used.
Rigid PVC sheet offers good transparency and gloss. PVC sheet used for pharmaceutical packaging has stringent resin hygiene requirements — it must use non-toxic PVC resin, non-toxic modifiers, and non-toxic heat stabilizers.
PVDC has high molecular density, regular structure, and high crystallinity. It provides excellent gas sealing performance, outstanding moisture barrier properties, and good resistance to oils, chemicals, and solvents. Comparing materials of the same thickness, PVDC’s oxygen barrier performance is 1500 times that of PE, 100 times that of PP, and 100 times that of PET. Its water vapor and oxygen barrier properties both surpass PE. PVDC’s sealing performance, impact strength, and tensile strength durability meet the special requirements of pharmaceutical blister packaging. This makes PVDC one of the key future directions for blister packaging materials.
Composite rigid plastic sheets used in pharmaceutical blister packaging include PVC/PVDC/PE, PVDC/OPP/PE, and PVC/PE. For products requiring barrier properties and light protection, plastic sheet-aluminum foil composites such as PET/aluminum foil/PP and PET/aluminum foil/PE can be used.
2. Substrate Materials
Tablet and capsule blister packaging commonly uses coated aluminum foil as the substrate. The aluminum foil is made from 99% purity electrolytic aluminum through rolling. It has a highly dense metal crystal structure, is non-toxic and odorless, provides excellent light barrier properties, and offers exceptional moisture, gas, and aroma barrier capabilities — making it highly effective at protecting the packaged contents. It is widely used in pharmaceutical blister packaging.
The substrate surface should be clean and glossy with good printability, and must be able to firmly hold the heat-seal coating to ensure proper bonding between substrate and blister when the coating melts.
3. Heat-Seal Coating Materials
The heat-seal coating must be compatible with both the substrate and the blister. The heat-seal temperature should be relatively low to enable rapid sealing without damaging the blister film. Currently, pharmaceutical blister packaging uses two main types of heat-seal coating materials:
Single-component adhesives — primarily composed of natural or synthetic rubber, nitrocellulose, and acrylic esters. These are non-drying, heat-soluble, and provide a certain bonding strength.
Two-component adhesives — mainly polyurethane adhesives, offering good high and low temperature resistance, resistance to media erosion, and high bonding strength. These can bond multiple materials simultaneously and are widely used in substrate aluminum foil coating adhesives and various plastic film lamination processes.
Other commonly used heat-seal coating materials include solvent-resistant vinyl resins and water-resistant acrylic resins, both offering good gloss, transparency, and heat-seal performance.
4. Substrate Printing Inks
Considering the aluminum foil printing process and special requirements of pharmaceutical packaging, printing inks must have: good adhesion to aluminum foil; clear, durable printed text and graphics; good solvent release properties; heat resistance; excellent abrasion resistance and gloss; non-toxic pigments that do not contaminate the packaged pharmaceutical products; and practical viscosity that meets aluminum foil printing process requirements.
Two main categories of inks are used for substrate aluminum foil printing:
Alcohol-soluble polyamide inks — Polyamide resin has excellent adhesion to various materials, particularly suitable for printing polyolefin films. With good dispersion, gloss, flexibility, abrasion resistance, and solvent release, these are commonly used for gravure surface printing on treated LDPE, CPP, and OPP films. These inks offer good gloss, broad applicability, anti-blocking properties, and fast drying — making them suitable for pharmaceutical blister packaging substrate aluminum foil printing.
Vinyl chloride-vinyl acetate copolymer/acrylic resin-based specialty inks — These inks feature vibrant colors, high concentration, exceptional adhesion to aluminum foil, good transparency, and excellent metallic gloss reproduction from the aluminum foil. By adjusting the mixed solvent composition to suit aluminum foil surface printing requirements, these inks will see increasing application in substrate aluminum foil printing.
III. Pharmaceutical Blister Packaging Equipment
1. Equipment Components
Pharmaceutical blister packaging equipment is fundamentally similar to blister packaging equipment for other products and consists of the following main sections:
Heating Section — Uses heating devices to soften the plastic sheet for forming.
By contact method: direct heating (sheet contacts heater — fast but uneven, suitable for thin materials) and indirect heating (radiant heat — thorough and uniform but slower, suitable for all thicknesses).
By heat source: hot-air heating (high-temperature air jets directed at the sheet surface — lower efficiency, less uniform) and radiant heating (far-infrared heaters producing light radiation and high temperature — high efficiency, uniform).
Forming Section — Two forming methods are used:
Pressure forming — Compressed air blows the softened sheet against the mold, pressing it tightly against the mold cavity to form blisters. Uses flat plate molds, typically intermittent feed, but continuous feed is also possible. Produces good quality forming for both deep and shallow blisters.
Vacuum forming — Uses vacuum suction to draw the softened sheet against the mold cavity to form blisters. Molds are typically continuous-feed drum-shaped. Due to limited vacuum suction force and the geometric constraint of blister release from the drum, this method is only suitable for shallow blisters and thinner materials.
Filling Section — Quantitatively fills pharmaceutical products into formed blisters, typically using multi-lane automatic filling devices.
Heat-Sealing Section — Bonds the aluminum foil substrate material to the blisters. Available in flat plate type (for intermittent feed) and roller type (for continuous feed).
2. Equipment Classification
Blister packaging machines are classified by automation level into semi-automatic, automatic, and fully automatic production lines. Pharmaceutical packaging (for tablets, capsules, suppositories, etc.) primarily uses automatic packaging production lines, also known as PTP (Press Through Pack) automatic packaging lines.
These lines come in horizontal and vertical configurations, typically using multi-lane structures for high productivity and good packaging quality. They include inspection devices and defective product rejection mechanisms, and can integrate printing, instruction leaflet dispensing, and cartoning into the production line — making them comprehensive, fully-featured, and typical automated packaging production lines.
References
- Wikipedia: Blister Pack: Comprehensive overview of blister packaging technology, types, and applications
- ASTM D882 — Tensile Properties of Thin Plastic Sheeting: Standard test method relevant to PVC and PVDC blister film evaluation
- FDA: Pharmaceutical Quality Resources: U.S. FDA guidance on pharmaceutical packaging quality and GMP requirements
- Wikipedia: Polyvinyl Chloride (PVC): Material properties and applications of PVC in packaging
- ISO 15378 — Primary Packaging Materials for Medicinal Products: International standard for GMP requirements on pharmaceutical primary packaging