Heat seal face blister pack ( blister-to-card )
Within the various options available in the range of blister packaging, heat seal blister packs are by far the most commonly used type worldwide. The reason for this is obvious. Heat seal blisters consist of only two pieces of material, a single piece of board and a blister. Heat seal blister packs are therefore very economically to produce. The board of which the blister card is produced is coated with a layer of heat seal coating. Generally there are two main types of coatings in use to produce heat seal cards. These are water-based heat seal coatings and solvent based heat seal coatings. With today’s advanced technologies most coatings are suitable to seal both, PET blisters or PVC blisters, using the same coating.
In average the bond strength of solvent based coatings is better that the strength of water based coatings, but if all the guidelines for the use and processing are being respected, both types of coatings give good sealing results. Please pay attention to the producers warranty on heat seal blister cards. Once the production of the cards is ready, heat seal cards should not be kept in stock for a period longer than 6-12 months. In high humidity countries it is advisable to have the cards packed in such a way that moisture can not penetrate into the blister cards (plastic wrap around the cards before putting them in a outer box). Heat seal coatings are hygroscopic, meaning that they attract moisture. The disadvantage of moisture in the coating is that in the sealing process. Moisture in heat sealing cards causes undesirable air enclosures/ bad bonding spots in the area where the blister is being sealed.
The variety in heat seal cards and blisters is endless. The cards can be of any shape and size and the same goes for the blisters. Depending on the desired quality feeling, the thickness of the two materials can vary from very thick and strong to extremely light weight and thin.
First the blister is placed onto a bottom tray, than the product(s) are added to the blister. The blister card is placed between the spring loaded pins located in the bottom tray. Now the sealing cycle can start. During the heat seal cycle the blister is bonded (under heat and pressure) to the heat seal coating on the blister card.
Packaging is done on heat sealing machines. These machines apply heat and pressure during a prefixed period of time. A typical heating cycle seal takes approximately 2-5 seconds at a temperature of 130°-150° Celsius. Tooling is usually build up as following: The bottom tool is usually a aluminium or wooden tray with rubber and spring pins to position the blister and card. A typical top tool is a Teflon coated (or covered) aluminium heat sealing plate.
In case the blister pack is sealed through the back a generic top plate can be used for sealing. This is by far the most used option. (radiant heating). In case sealing takes place by applying heat directly on the flange of the blister a dedicated sealing tool is used. (impuls sealing). You can learn more about heat sealing radiant and impuls sealing machines by visiting http://www.blistermachines.com/
Availability: World wide many printing companies are producing heat seal cards. Please make your choice carefully and choose for quality suppliers. Numerous problems can occur in the heat sealing process, and worse, with packed products in the market. These problems are mostly the result of getting inconsistant quality of heat seal cards, but also from not having the right type or good quality heat sealing machines.