1. Cover film Most of the jelly, cold drinks, yogurt, f […]
1. Cover film
Most of the jelly, cold drinks, yogurt, fruit milk and other foods available on the market are packed in plastic cups and bottles, and the cups and bottles are sealed with a film. Some requirements can be uncovered, while others do not.
The unsealed heat seal layer is generally used for packaging of milk, fruit milk, etc. The cup or bottle body is basically made of high-density polyethylene (HDPE) resin as a raw material. The inner layer material only needs to be made of the same material as the cup body (bottle body).
On the one hand, it must have a good seal strength, and on the other, it must have a detachable performance. For this special requirement, the choice of heat seal layer is very important.
The material with both functions is modified EVA.
EVA-ethylene-vinyl acetate copolymer has good adhesion to polypropylene and polystyrene, but it has a different molecular structure from polypropylene and polystyrene. When heat sealing and bonding, the two resins cannot be completely Diffusion, penetration and fusion together.
Only the cohesive force with obvious interface can be formed. Therefore, the modified EVA is used as the heat sealing layer of the cover film, which not only has sufficient heat sealing strength, but also has easy peelability.
2. Special heat sealing material
In the packaging of special occasions, nylon vacuum bags, composite vacuum bags, high transparent vacuum bags, large-size vacuum bags, anti-static vacuum bags, large-size vacuum bags will use some special heat-sealing materials, such as ionic polymers , EAA (ethylene-acrylic acid copolymer), EEA (ethylene-ethyl acrylate), EMAA (ethylene-methacrylic acid), etc.
These special materials need to be imported from developed countries such as Europe, America, and Japan. However, with the rapid development of my country's national economy, the requirements for packaging materials are becoming higher and higher. The application of these special heat-sealing materials is more and more extensive.