Blister Packaging|Pharmaceutical Packaging

Blister packaging is one of the most common and widely used packaging in pharmaceutical industries for tablets, capsules, pills, or lozenges. Blister packaging is a type of packing in which the product is placed in pockets or cavities and is protected by a covering. Blister pack is also known as Through Pack (PTP) because we can remove the product by pushing it through the covering or lidding foil and it is used for unit-dose packaging in most of the countries of the word but in the USA it is used for physician samples or OTC  and remaining doses are dispensed by bulk plastic containers.

Advantages of Blister Packaging

Advantages of  Blister packaging are as follow,

Protection

Blister packaging Protect the product from 

• Humidity
• Gases
• Temperature
• Light

Light Weight

Blister packaging is lightweight as compared to other packaging like glass bottles and plastic bottles.

Intact

Blister packs provide the option to remove only one dose which is to be taken so other products are intact inside sealing and are protected from exposure to the environment and chances of product contamination are minimised.

Tamper Resistance

Blister packaging provides tamper resistance.

Cost 

The cost of blister packaging is low as compared to glass and it meets regulatory requirements

Components Of Blister

Following are components of a blister

1. Cavity Forming Film/Foil
2. Lidding Foil
   

1.Cavity Forming Film

• Cavity forming film or foil is a material that is used to form pockets or cavities.
• In pockets or cavities product is placed.

Method Of Cavity Formation

Pockets or cavities can be formed by two methods

• By Application Of Heat
• By Application Of Pressure

Types of Cavity Forming Films

Based on the method of manufacturing of pockets following type of forming films are used

• Thermoforming Film (By Heat)
• Cold Forming Film (By Pressure)

Thermoforming Film

Thermoforming films are used to form pockets or cavities by application of heat.

Procedure

• For cavity formation by using thermoforming foil, the roll of foil is unwound and passes over the heating plates.
• Heat softens the foil.
• This softened foil is then passed over the forming station or cavity plate.
• Air Pressure is applied from the lower forming plate which pushes the soft forming film in the dies of the upper forming plate and pockets or cavities are formed.
• This is then cooled by circulating water below the plates so the soft sheet becomes rigid and pockets are not deformed.
• The product is fed in the pockets and is sealed by the lidding material.

Materials Used For Thermoforming Cavities

Following materials are used for thermoforming cavities.

• PVC
• PVDC
• PVDC
• PTCE
• COC
  

 

• PVC
• PVC is polyvinyl chloride and it is the most widely used material as a thermoforming film.
• It can easily be softened by heat and form good pockets to retain product
• It is cost-effective.
• In pharma PVC used do not have any plasticizer so it is also known as rigid PVC or RPVC.
• The rigidity of PVC is such that we can easily push our product from the pockets by applying little pressure with the thumb.
• In pharma, PVC is used having a thickness of 200 microns to 300 microns.

Disadvantages of PVC

• Even though it is a commonly used material for blister formation in pharma, its barrier property for moisture and oxygen is low.
• Water Vapor Transmission Rate (WVTR) of a PVC sheet having a 250-micron thickness is  3g/m²/day  and it is measured at the following conditions
  • Temperature 38°C
  • Relative Humidity 90%

• The Oxygen Transmission Rate OTR is 20 ml/m²/day.
• The barrier property of PVC can be increased by coating the PVC with the Following.
  • PVDC
  • PCTFE
  • COC
• Pigments or UV filters can also be used on PVC sheets.

PVDC

PVDC is polyvinylidene chloride and is used to enhance the barrier properties of PVC for Moisture and oxygen penetration.

PVDC is applied as an aqueous coating over the PVC.

The weight of PVDC is expressed as grams per square meter or gsm.

The strength of the barrier depends upon the weight of the coating material applied over PVC.

It is a less costly method to enhance the barrier properties of PVC.

 PVDC coated films are available in two forms

• Duplex Form
• Triplex Form

Duplex Form

• Duplex forms contain PVDC and PVC as PVC/PVDC.
• The weight of coating layers and WVTR, OTR  in the duplex are as follow ranging from
• PVC 250-micron PVDC 40 gsm having WVTR 0.65 g/m 2/d and OTR 1.0 cc/m²/d.
• PVC 250-micron PVDC 120 gsm having WVTR 0.25g/m²/d and OTR 0.1 cc/m²/d
  

Triplex Form

• Triplex forms contain PVC/PE/PVDC.
• PE is polyethene.
• In triplex form, PE is in between PVC and PVDC.
• PE forms a flexible layer between rigid PVC and PVDC and helps to form deep cavities.
• The triplex form is used where very deep cavities are required to form by heat.
• The weight of coating layers in a triplex is the same as in duplexes  with the addition of the PE layer and are as follow ranging from
  • PVC 250 micron 
  • PE      25 micron
  • PVDC 40 gsm 

to

• • PVC   250 micron 
  • PE       25   micron
  • PVDC 120 gsm

PCTFE

• It is a polychlorotrifluoroethylene.
• It is laminated over PVC to enhance its barrier properties.
• 15 micron to 150 micron PCTFE film is used for lamination of 250 micron PVC films.
• It also exists as duplex and triplex form 
• The duplex form is PVC/PCTFE.
• Triplex form is PVC/PE/PCTFE/.
• PCTFE films have the least Water vapour permeation.
• It is the most expensive film available for thermoforming blisters.

COC

• COC is a cyclic olefin copolymer.
• COC is used to provide a barrier for moisture in combination with PE or Polypropylene PP.
• COC differs from PVC because it consists of hydrogen and carbon and does not contain chlorine or other halogens.

Cold forming Film/Foil

• Cold forming films are used to form pockets or cavities by application of pressure.
• In cold forming, the film or sheet passed over the forming station.
• In this forming station, the upper plate has Teflon punches which press the foil or sheet in pockets of the lower plate with high pressure.
• When the pressure has released the pockets of foil are formed.
• The product is fed in the pockets and is sealed by the lidding material.

Advantage

Cold forming foil provides more protection to the product.

Disadvantage

• In Cold forming blisters, products are not visible to consumers.
• Machine Speed is slow for cold forming blister formation.
• Usually, the size of cold forming blisters is large so a large secondary pack is required.
• The cost of cold forming foil is high as compared to thermoforming foil.
• Cold forming blisters may damage if not handled well.
  

Materials For Cold Forming Cavities

Aluminium foil is used for cold forming cavities.

2.Lidding Foil

Lidding foil is used to form a covering over the cavities or pockets.

• Lidding foil forms a protective sealing over the forming foil.
• Usually, thin aluminium foil of thickness 18-25 micron is used.
• The inner side of the lidding foil which faces towards the product has a heat sealing coating to form a sealing bound with forming foil on heating.
• The outer or upper side of the lidding foil has a printed pattern and may contain product identification marks.
• The ink used for printing should be Stable at high temperature and should not fade.
•  Ink used should comply with FDA guidelines.

The following pattern of lidding foil may be used 

•  Push Through 
•  Child Resistance
•  Peel Off