Nowadays, medicine blister packaging machines mostly use PVC plastic films as packaging materials. The principal advantages of PVC are the low cost and the ease of thermoforming. The main disadvantages are the poor barrier against moisture ingress and oxygen ingress; moreover PVC has a negative environmental connotation due to its chlorine content. PVDC features high barrier but also high cost. In recent years, blister forming materials such as PP and PET have been developed worldwide, but their processability and productivity are much poorer than PVC films. Moreover, its usage requires upgrading of current Blister Packaging Machines.
PVC/PE composite films discussed in this paper are made by combining PVC and PE films. PE films are used inside in direct contact with the packaged products to avoid their direct contact with PVC and at the same time ensure heat-sealing property of PTP aluminum foils and PE. Currently, PVC/PE composite films are mainly used for packing containers of small liquid dosage including oral solutions, household chemicals and suppositories with mature production technology. However, as PVC/PE composite films are forming materials, their application in blister packaging machines with aluminum foils as covering material is rare.
This paper will explore in terms of theoretical testing and practical application such parameters as thermal sealing strength, barrier and tightness of PVC/PE composite materials and study the feasibility of their application in blister packaging
Test material and method
PVC/PE composite film
PVC/PE composite films are 0.3 mm in thickness, in which PE is 0.05 mm and PVC is 0.25 mm.
PTP (Push-Through-Pack) aluminum foil
Hot-melt adhesive mainly made of water-borne polyurethane and polyolefin will replace traditional VC adhesive in the bonding layer.
One Blister Packaging Machine
Take some PVC/PE composite film samples, cut them into required size and perform oxygen permeance and water vapor permeance tests.
Thermal sealing strength test
Evenly cut two pieces of 100 mm × 260 mm PVC/PE composite film and PTP aluminum foil samples, thermally seal their gluing layer with the Blister Packaging Machine at the temperature of 150 °C ± 5 °C and pressure of 0.4 MPa for 1 s; put them at room temperature for 12 h, cut them into 15 mm in width with a sampler and pull off to test at an angle of 180° with a universal tensile testing machine.
Take a roll of PVC/PE composite film and PTP aluminum foil respectively and test their operation effect on the Blister Packaging Machine; take care to adjust their rolling
direction to keep PE layer of PVC/PE composite film and gluing layer of PTP aluminum foil in touch; load disk type simulations into the feeder for packaging test after heat-sealing temperature stabilizes (test of 15,000 sheets in 3 groups).
Transport samples of 60 boxes (200 sheets/box) from a low-altitude area from a high-altitude and low-pressure area; take 30 sheets, keep them under the pressure of 0.08 MPa for 30 s and check for water ingress.
Test result and analysis
Influence of PVC/PE composite films on blister barrier
Composite packaging materials for medicines must have high barrier. Aluminum foils in blisters are metal material and their barrier is much higher than PVC/PE composite films. Therefore, the overall barrier property of the blister package depends upon that of PVC/PE composite films. Test result indicates that oxygen permeance of 30 m3/(m2.24h.0.1MPa) and water vapor permeance of 2.5 g/(m2.24h) have been met (refer to YBBO0212005 PVC films for solid drugs).
Thermal sealing strength conformance
In addition to barrier, thermal sealing strength and tightness of blister packages have direct impact on product protection performance. Test result shows that the thermal sealing strength is 9.5 N/15 mm, compliant to the standard requirement of ≥ 7 N/15 mm.
Forming heating temperature and heat-seal temperature
PVC/PE composite films have different materials at both sides, therefore they have different softening temperature. During test, adjustment should be made to the top and bottom heating plates, which means reducing top heating temperature for PE side and increasing bottom heating temperature for PVC side.
After replacing VC with polyolefin adhesive as PTP aluminum foil heat-seal adhesive, friction factor of aluminum foil increases, which requires smaller fraction factor and more flexible movement of all PTP aluminum foil guide rollers on the Blister Packaging Machine. Meanwhile, it is detected during test that heat-seal temperature of PTP aluminum foils using polyolefin adhesive is slightly higher than that of traditional PVC and PTP aluminum foils.
Key parameters of PVC/PE composite films and PTP aluminum foils are found to be compliant to standards. Since PE layer is used in contact with products now instead of PVC layer, they are safer than PVC films.
After actual operation test on the Blister Packaging Machine, it is proved that blister packages made with PVC/PE composite films and PTP aluminum foils are technically fit for practical application and therefore mass production is possible.
Since PE materials are used in PVC/PE composite films, an additional composition process is required. Thus, the problems of increased cost and reduced transparency due to use of PE have to be considered during practical application.