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The Differences Between Thermoforming and Cold Forming Blister Pack

01/02/2014

Blister packs are commonly used as unit-dose packaging for pharmaceutical tablets, capsules etc. The primary component of a blister pack is a cavity or pocket made from a formable film, usually a thermoformed plastic or cold formed aluminum film. This usually has a lidding seal of aluminum foil. Using different packaging materials and principles of forming, Blister Packs may be divided into three types：aluminum/plastic (thermoforming) blister pack, aluminum/aluminum (cold forming) blister pack and aluminum/plastic/aluminum blister pack.

Aluminum/plastic blister pack：adopts thermoforming plastic and lidding material of aluminum foil. The thermoforming plastic film is guided though a heating station on the blister machine. The temperature of the heating plates (upper and lower plates) is such that causes the plastic to soften and become pliable. The warm plastic then arrives in a forming station where a large air pressure will form the blister cavity from a forming mold. The blister is cooled so that the plastic becomes rigid again and maintains its shape when removed from the mold. After the medicine is filled into the cavity, the plastic film arrives in the sealing station to be sealed with a lidding material of aluminum foil.

The advantages of thermoforming blister pack:

  1. The most basic material for the forming web is PVC or Polyvinyl Chloride, for ease of thermoforming and low cost.
  2. The product can be visually examined through the transparent plastic. The fault blister card can be rejected vie the inspecting camera or naked eyes.
  3. Because the cavity or pocket contain the item snugly, it can adopt the universal feeder which consists of circular brushes and planetary agitators that sweep the products into blister pockets. Parts are not required for different formats. This feeder is noted for its low cost and ease of operation.

The disadvantages of thermoforming blister pack:
The protective properties are not strong because of the PVC’s poor barrier against moisture and oxygen ingress.
Not suitable for light-sensitive drugs because of the transparency of PVC.

Aluminum/aluminum blister pack: adopts cold forming aluminum film and lidding material of aluminum foil. In this case, an aluminum-based laminate film is simply pressed into a mold by means of a stamp. The aluminum will be elongated and maintain the formed shape. After the filling, the formed aluminum film arrives in the sealing station to be sealed with lidding aluminum foil.

The advantage of cold forming blister pack：
The use of aluminum offers a nearly complete barrier for moisture，light and oxygen, allowing an extended product expiration date.

The disadvantages of the cold forming blister pack:

  1. The slower speed of production compared to thermoforming;
  2. The package is opaque, making the inspecting system, which rejects the faulty blister card, complicated and costly.
  3. The cost of cold forming aluminum film is higher than PVC.
  4. The larger size of the blister card (aluminum cannot be formed with near 90 degree angles) increases the material cost.
  5. Because the cavity or pocket is larger than the drug, the feeder should be dedicated. this increases the cost and difficulty of operation.

Larger size of the cold forming blister pack compared to thermoforming blister pack.

Aluminum/plastic/aluminum blister pack: adds one tropical aluminum forming station and a second sealing station to allow the aluminum/plastic (thermoforming) blister package to be sealed with formed tropical aluminum again.
The advantages：

  1. Because the item is filled in thermoformed pockets or cavities, it can adopt the universal feeder, resulting in low cost and ease of operation.
  2. The inspecting camera can detect the faulty blister card easily, because of the transparency of thermoforming plastic.
  3. The tropical aluminum film has the same property as cold forming aluminum film, which offers a nearly complete barrier for water，light and oxygen.
    The disadvantages:
  4. The use of tropical aluminum film increases the cost.
  5. Adds one tropical aluminum forming station and a second sealing station making the machine longer than the standard blister machine.

Strip Pack: The difference between a strip pack and a blister pack is that a strip pack doesn’t have thermoformed or cold formed cavities; the strip pack is formed around the tablet or capsule when it is dropped to the sealing area between sealing moulds.
Advantage:
The Al/PE laminated film has the same protective property as cold forming aluminum film, that perfectly protects the medicine from moisture，light and oxygen.
Disadvantages:
Slower speed of production compared to thermoforming blister pack;
Because it doesn’t have pre-formed cavities, the packaging area for each item is larger than the blister pack.

Different size between strip pack, cold forming blister pack and thermoforming blister pack
Jornen Machinery Co., Ltd

02-01-2014