What is Crosslinking? Radiation induces the crosslinking of polymers. Polymers, or Plastics, are made of thousands of very long chains of molecule. Crosslinking is the bonding together of these long chains. When crosslinking occurs, these strings are bonded to each other in multiple places forming larger multi-chain molecules.
What are the benefits of Crosslinking?
When polymer chains are not crosslinked, the chains have the ability to slide past each other when exposed to various elements. This can include; heat, abrasion, or chemical solvents. The crosslinks lock all of the polymer chains together so they no longer have the freedom to rearrange themselves. For an example, if you were to use non crosslinked wires under the hood of a car, an environment full of drastic temperature changes, oils and chemicals, the wires’ insulation would break down and essentially fall off, exposing the bare wire. This is because, in the harsh environment of being near a running engine, the polymer chains can warm up and slide past each other, or oils and chemicals can work their way in between the polymer chains. This would result in fires or damage to your vehicles delicate electronics. If those same wires were crosslinked, the polymer chains would all be stuck together, so the warmth of the engine, or the grease and oil near the engine would not be able to separate the polymer chains, and the insulation would not break down.This locking together of molecules is the origin of all the benefits of crosslinking including:
Increased Tensile Strength
Increased Creep Resistance
Increased Form Stability
Resistance to Deformation
Resistance to Abrasion
Resistance to Solvents
Resistance to Stress Cracking
Electrons are a proven, versatile, and economical method of enhancing the physical and chemical characteristics of many materials commonly used as insulation.
What is Polymer Degradation? Polymer degradation is the opposite of crosslinking. When the electron from an E-beam hits a molecule, with a higher dose than that needed for crosslinking, it can break the molecular bonds. This is useful in a number of areas. For example, PTFE (polytetraflouroethylene) is an excellent engineering thermoplastic with great properties. It is most known for its very low friction, and almost slippery feel. This low friction characteristic makes it a great lubricant for high quality inks. However, ink would not be able to flow from a pen or a print cartridge very easily if it had high molecular weight polymer chains in it, so it needs to ground into a fine powder. However, because it is a great engineering thermoplastic, the does not grind into a powder easily (its fractures and gets very stringy). With the electron beam, the PTFE can be treated at a dose that will actually break down the material. This degradation of the PTFE shortens and breaks apart the polymer chains so that can be easily ground into a fine powder, yet still have its good properties.Another example of this would be the treatment of chemically contaminated water. Treating this water will break the molecular bonds in some complex chemicals converting them into simpler non-hazardous chemicals.During E-Beam processing, crosslinking or degradation can occur, however it depends on the chemical makeup of the material, and the dose (or amount of beam) the material is exposed to.
What is Sterilization? The E-beam inactivates microbes either by causing microbial death, as a direct effect of the destruction of a vital molecule, or by an indirect reaction. This is the same mechanism as Gamma radiation, and the dose required is the same.Electron beam is very popular for sterilizing medical components. Currently food processing is becoming more popular. E-beam will destroy e-coli, salmonella and a host of other contaminates that are found in foods.
What is Cold Pasteurization? Cold Pasteurization is the destruction of microorganisms and is similar to sterilization. (See Sterilization)
What is Vulcanization?
Vulcanization is a process used in manufacturing rubber. It is similar to crosslinking.
Many tire manufacturers use E-beam. They are able to reduce raw material, improve yields, and refine tire specifications.
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