What is heat shrinkable material and structure

Heat shrinkable material is the material that shrinks and deforms after heating. If it is cold, it is a thick tube. When heated, it can shrink into a thin tube and adhere to the surface of the attached object, so as to ensure the insulation of the object or the corrosion protection of the metal surface. If the material is a film, use this to package food, and the film material shrinks and wraps the food tightly after heating, so that the food is isolated from the air and plays a role in keeping fresh.

Ordinary polyethylene pipes are not heat-shrinkable. Polyethylene is polymerized by ethylene monomers. The molecular formula of ethylene monomers is H2C = CH2. Under the polymerization conditions, the double bond of each ethylene monomer molecule is opened, and several molecules are polymerized to form a high molecular weight polyethylene. The polyethylene plastic we usually see is composed of linear molecules polymerized by ethylene monomers stacked together.

However, under the action of radiation, polyethylene plastics will produce chemical bonds between linear molecules. This is radiation crosslinking. The greater the radiation dose, the greater the degree of crosslinking. As a result of radiation crosslinking, the polyethylene plastic has changed from a linear structure to a network structure, that is, a three-dimensional structure. The newly generated material has a wonderful "memory effect". For example, the pipe can be enlarged and then cooled to form a thick pipe. This pipe can be restored to the original diameter of the plastic pipe before expansion as long as it is heated, so it is called a "memory effect" material.

The tube made of heat-shrinkable polyethylene material can be conveniently used to protect the joints of cables and optical cables, and the protection of metal pipe rods. The heat-shrinkable material can be prepared not only as a radially shrinkable heat-shrinkable tube, but also as a warp and weft bi-directional shrinkable plastic film, which can be used in packaging, protecting items, etc. The magical heat-shrinkable material brings more extensive applications to people's lives and industrial and agricultural production.

什么是热缩材料及结构

热缩材料就是该材料经加热以后即收缩变形。如冷时是一个粗管，当加热以后可以收缩成细管，并紧贴在其附着的物体表面，从而可保证物体的绝缘或保证金属表面的防腐。如果材料是薄膜，用此包装食品，一经加热即膜材料收缩紧包住食品，使食品空气隔绝，起到保鲜作用。

普通的聚乙烯管子并不具有热收缩性。聚乙烯是由乙烯单体聚合而成，乙烯单体分子式是H2C=CH2，在聚合条件下，每个乙烯单体分子的双键打开，若干个分子聚合成高分子的聚乙烯呈线性状。我们平时所看到的聚乙烯塑料就是由乙烯单体聚合的线性分子堆积在一起构成的。

但是聚乙烯塑料在射线作用下，线性分子间就会产生化学键，这就是辐射交联，辐射剂量越大，交联度就愈大。辐射交联的结果使聚乙烯塑料由线状结构变成网状结构即立体结构。新生成的材料有奇妙的“记忆效应”。例如管材可扩粗，然后冷却定形成粗管，这种管子只要再受热即可恢复到扩管前塑料管的原管径大小，所以称它为“有记忆效应”的材料。

热收缩聚乙烯材料制备的管子，可以方便地使用来保护电缆、光缆的接头，金属管杆的保护等方面。热收缩材料不仅仅可制备成径向收缩的热缩套管，同时还可制备成经纬双向收缩的塑料膜，它可用在包装，保护物品等方面。神奇的热收缩材料，给人们生活和工农业生产带来更广泛的应用。