Polyethylene in Food Packaging Technology. I. The Effect of Chain Structure on Heat Sealing

In recent years, the use of polymers in the packaging industry has increased significantly due to their excellent advantages over conventional materials. In the meantime, polyethylenes (PE) have become one of the most important options in the manufacture of polymer food packaging, due to high structural diversity, low cost, easy processability, and flexibility in the design and chain architecture and their effect on the control of polymer engineering properties. The aim of this article is to introduce the heat sealing process of polymer films with an emphasis on polyethylene polymer as well as methods and mechanisms related to this process. In the heat-sealing process study, the diffusion phenomenon of tangled chains through the interface and the effect of chain structure on improving the adhesion strength and increasing the heat-sealing capability of polyethylene films were studied. Understanding the factors affecting the chain diffusion phenomenon, by controlling these factors, the strength of the interface during the heat-sealing process can be increased, which leads to improvement the adhesion of the two polymers to each other. Also, different methods of modifying the structure of polyethylene chains and placing different side groups on the chain were introduced. Hyper branching in the polymerization stage, hyper branching using high-energy rays, and hyper branching in the reactive melt mixing state using free radical generators are the three main methods for changing the structure of polyethylene chains. Each of these methods has its advantages and limitations, and different methods are used according to the desired properties of the polymer.