Heat Shrink Tube Process (I）

First, a plastic pipe of appropriate size is made. Then, through irradiation, its molecular structure changes (cross-linking), endowing it with a "memory effect". Finally, it is heated to expand to a larger size and cooled to set. When reheated, it will shrink back to its original size.
Core principle: "Memory effect"
The "memory effect" of Tuoyan heat shrink tubing stems from the cross-linking process of its polymer materials. Untreated thermoplastic will melt when heated. However, after cross-linking, chemical bonds are formed between the molecular chains, creating a three-dimensional network structure and transforming the material into a thermosetting plastic. This means that when it is heated again, it will not melt but contract back to the shape set when it was cross-linked.
Detailed production steps
Step 1: Basic blending and extrusion molding
Raw material preparation: The main raw materials are various high-molecular polymers, the most common of which are polyolefins (such as polyethylene PE, polyvinyl chloride PVC). In addition, there are also special materials such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and ethylene-tetrafluoroethylene copolymer (ETFE), to meet the requirements of different temperature resistance and chemical corrosion resistance.
Mixed ingredients: Mix the base polymer resin with various additives, for example:
Masterbatch: Provides color.
Flame retardant: Endows heat shrink tubing with flame retardant properties (such as UL-V0 grade).
Plasticizer: Increases the flexibility of materials.
Stabilizer: Enhances anti-aging and anti-ultraviolet performance.
Extrusion molding: Feed the mixed raw material particles into the extruder. The raw materials are heated, melted and plasticized in the extruder, and then extruded through a ring-shaped die (die) to form a thick-walled plastic pipe with precise dimensions. This is the initial form of the heat shrink tube. At this point, it does not yet have the property of heat shrinkage.
Step Two: Key step - Molecular cross-linking
This is the most crucial step in endowing heat shrink tubing with "memory function". There are mainly two crosslinking methods:
High-energy electron beam irradiation crosslinking (the most mainstream method) :
Pass the extruded plastic pipe through a device of an electron accelerator.
The high-energy electron beams emitted by the equipment are like countless tiny bullets, bombarding the molecular chains of the plastic tubes and breaking their chemical bonds.
These broken bonds will reconnect with each other, forming a three-dimensional network structure (cross-linked structure) that spans the molecular chain. This process is like connecting a bunch of parallel noodles (linear molecules) haphazardly with many small toothpicks (cross-linking bonds) to form a solid network.