Shrink wrapping is the best form of packaging. The molecules in the material are stretched and then it is heated and made to shrink around the product being packed. The two types of shrink wrapping done are: transit and display.
Shrink wrapping for transit is cheaper. This involves the use of a sleeve sealer and polyethylene film. Polyethylene is strong and has sufficient thickness so that the product can be wrapped easily and tightly. The slip can be changed to suit the product being wrapped. Once the article is wrapped, it is moisture proof and it cannot be tampered with. Individual packs like doors and machinery can benefit from this type of packing. The films can be colored and printed as well. However, polyethylene is not good for coloring because of its consistency. In being colored, it may retain dust and turn cloudy. If you like colored films, there are other display films available that have the same tensile strength as polyethylene. Only the cost of these is higher.
Display shrink wrapping is not meant for wrapping food. It is meant for wrapping things like rolls of wall paper where the product gets an overall wrap. A two dimensional flat bag is packed around the product and then sealed.
PVC was used in the past. It is easiest to shrink. When it is used, deposits of hydrogen chloride gas and carbon settle on the sealer. With proper ventilation, these disappear. Lately, polyolefin has been used instead of PVC and it sure has its benefits. PVC hardens in cold weather and softens in warm weather. This does not happen with polyolefin. PVC has to be stored at normal room temperature while polyolefin tolerates any temperature.
An L Sealer with center folded film is used for shrink wrapping products. The L sealer can be manual, semi or fully automatic. Combined seal and shrink machinery is the best. These are called the chamber machines.
Flow wrappers have the highest speed. No matter what method of shrink wrapping you use, the basic features always remain the same.
Polyolefin is used for shrink wrapping pizzas and eggs. However, it cannot help to store the food longer. Other materials that shrink are used to prolong the life of a food product.
Shrink wrapping is constantly being improved on because they are not complicated in any way. Polyolefin will improve as the days go by.