FAQ for Optimizing Your Products with Polymer Crosslinking of Wire & Cable
What is Crosslinking?
By crosslinking, polymer chains are linked together in a pattern called cross-links. With certain thermoplastics, the setting up of chemical links between molecular chains occurs. When extensive, crosslinking makes an infusible super molecule of all the chains.
The phenomenon of crosslinking involves primary bonds between polymer chains creating a three-dimensional network.
Crosslinking plastics, utilizing e-beam processing, creates excellent property improvements. The greater the degree of crosslinking, the greater the rigidity of the material, the less soluble, and less it responds to remelting. In short, ionizing radiation produced by the beam breaks bonds within molecules; when the bonds reform in a beneficial way, it is “crosslinking.”.
How it Works
The process involves accelerating a beam of electrons to near light speed. It then passes through a scan chamber, and transitions into a curtain of electrons. Materials moving through the chamber on a high-speed conveyor system are showered with these high-energy electrons. These electrons penetrate the material with a precise, predetermined dose and–depending on the material being processed and the dose that is being applied–several different effects occur. Electron beam processing effectively and efficiently creates beneficial changes in material properties and performance.
E-beam crosslinking for wire, cable and tubing does not require any additives, does not generate hazardous chemical by-products, nor require the extensive cure time needed for other chemical crosslinking methods. E-beam is energy efficient, and the minimal amount of exposure time helps ensure high throughputs.
Heavy Wall Cable - higher tensile strength and improved thermal resistance gives you an improved product above your competitor’s. E-BEAM has the capability to crosslink any length, diameter, and gauge cable.
PEX Pipe Tubing - Polyethylene crosslinked (PEX) tubing boosts thermal resistance up to 180 F over the standard 140 F of uncrosslinked polyethylene. With both freezing and extreme heat resistance, plumbing with PEX pipe has become extremely common.
Heat Shrink Tubing - with the ability to improve resistances against abrasions, cracking, and fatigue, crosslinked tubing protects wiring like no other heat shrink product on the market.
Why it Matters to You:
In polyethylene, a bond with a hydrogen atom is broken, allowing the carbon backbone of the molecule to join with another carbon backbone of an adjacent molecule. The final result is an increase in the molecular weight of the polymer, imparting beneficial properties such as:
- No harmful chemicals and environmentally friendly process
- Increased tensile and impact strength
- Increased creep resistance
- Increased durability
- Improved abrasion resistance
- Improved environmental stress crack resistance
- Improved barrier properties
- Increased material strength & stability
- Resistance to chemical solvents
- Shrink memory
E-beam Crosslinking: can be done without heat and processing is fast, controllable and in many cases more economical than thermal and/or chemical crosslinking.
A simple way of demonstrating the effects of crosslinking by E-beam is to place one irradiated sample of polyethylene tubing and one un-irradiated sample in an oven, as seen here:
After 30 minutes at 200°C :
Can you guess which sample has been irradiated? The sample on the left clearly has a higher operating temperature, due to crosslinking that occurred during e-beam processing.
What Kinds of Crosslinking Systems are Available?
For the wire and cable industry, three major crosslinking systems are available:
• E-beam (irradiation) crosslinking
• C.V. (continuous vulcanization)
• Silane (moisture) crosslinking