Heat Sealable Film
Most packaging films are heat sealed as an intermediate or final step to create a finished package. The goal of an integral heat seal is the same if you are using PE film for: vertical baggers, , horizontal flow wrap, , flexible laminations, , , , frozen foods and
To make a heat seal, the film must be melted together then allowed to cool down enough to become what is called crystalline, or solid. The three interdependent elements to heat-sealing are:
Think of it like a triangle:
There are two methods to measure the melting point of a film. They are Vicat softening point and DSC melting point. These measure the temperature at which a polymer begins to soften. They are different test methods, so they yield different results.
The softening point should not be confused with the seal initiation temperature (SIT) which is measured by a number of methods.
Copolymers such as lower the melting point and seal initiation temperature. Some but not all resins melt and seal much faster than PEVA.
A common mistake is to use too much heat and overcook the film if a seal is not easily achieved. Films with a low melting point/seal initiation temperature seal better with more cooling time, more pressure and less dwell time. The result is usually faster cycle speeds.
The enemies of good seals besides machine settings are contaminants inevitably encountered when heat sealing . While water does not usually interfere, blood, fat and especially powdered milk and cocoa powders in complete baking mixes can be frustrating.
To caulk and seal through these contaminants, a cheap general purpose homopolymer just wont do. We provide forgiving by including three or more resins with different sealing temperatures in films such as our 622 and IQF grades.
For more information on the types of sealing jaws, visit our page.
to end your frustration with heat sealing.