The heat shrinkable material is that the material shrinks and deforms after being heated. If it is a thick pipe when it is cold, it can shrink into a thin pipe when it is heated, and stick to the surface of the object to which it adheres, so as to ensure the insulation of the object or the corrosion protection of the metal surface. If the material is film, once the food is heated, the film material shrinks tightly to wrap the food, so that the air of the food is isolated, and the fresh-keeping function is played.
Ordinary polyethylene pipes do not have heat shrinkability. Polyethylene is polymerized from ethylene monomers. The molecular formula of ethylene monomers is H2C = CH2. Under the polymerization condition, the double bond of each ethylene monomer molecule is opened, and several molecules polymerize into polyethylene with linear properties. The polyethylene plastic we usually see is made up of linear molecules polymerized by vinyl monomers.
However, under the action of radiation, the linear molecules of polyethylene will produce chemical bonds, which is radiation crosslinking. The greater the radiation dose, the greater the crosslinking degree. The result of radiation crosslinking makes the polyethylene plastic change from linear structure to network structure, that is, three-dimensional structure. The new material has a wonderful "memory effect". For example, the pipe can be expanded and then cooled to form a thick pipe. As long as the pipe is heated again, it can be restored to the original pipe diameter of the plastic pipe before expansion, so it is called a "memory effect" material.
The pipes made of heat shrinkable polyethylene can be used conveniently to protect the joints of cables, optical cables, metal pipe rods, etc. The heat shrinkable material can not only be used to prepare the heat shrinkable sleeve with radial shrinkage, but also be used to prepare the plastic film with longitudinal and latitudinal shrinkage. It can be used in packaging, protection and other aspects. Miraculous heat shrinkable materials have been widely used in people's life, industry and agriculture.