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Wednesday, June 12, 2013

Radiation Crosslinking vs Chemical Crosslinking

     As more and more heat shrink manufacturers come into being in East Asia and in Eastern Europe, a question that comes up often is:  Is there really a difference between Radiation and Chemical Crosslinking?

     To that, I must shout a resounding YES!!  Here in our own shop, we've often gotten to play with chemically crosslinked products that were sent to us by foreign companies attempting to gain a foothold in the USA.  These products have always been markedly inferior to our own Covalence / Raychem products.  We've seen products that don't even return to their original shape (memory loss or inferior crosslinking), we've seen products with backing material that can actually be torn using only your fingers (low density polyethylene compound backing).  We've also seen products that; after sitting on our samples shelf collecting dust for a year or two; completely fall apart during installation (limited storage life). 

     One of the primary differences between these eastern European and eastern Asia heat shrink manufacturers is that they primarily utilize a chemical cross linking process to manufacture their heat shrinkable sleeves.  I came across an incredibly informative paper written by a Dr. Lewis A. Parks (here).  He (with much more knowledge and education about cross linking than I will ever have!) discusses in detail the difference between these two crosslinking techniques.  I will touch only on a few of the advantages and disadvantages he lists.  If you're looking for more in depth reading on this subject; please go read his entire paper!

Advantages of Radiation Crosslinking
  1. Many different types of compounds can be radiation crosslinked.  On the Covalence side, we've seen this with many different polyolefins and even some polypropylenes.  On the Raychem heat shrink side they do also focus on polyolefins, but they've also ventured into silicone rubbers, teflon, PVC, viton and other materials.
  2. Many different types of compounds can be radiation crosslinked.  On the Covalence side, we've seen this with many different polyolefins and even some polypropylenes.  On the Raychem heat shrink side
  3. Reliability.  Raychem Corporation began producing heat shrinkable technologies in the early 1970's. While that might make heat shrinkable sleeves sound like an ancient technology; the truth is that it means we've got 40+ years of proven, successful, reliable use history.  This really is an amazing fact that is often overlooked.  Since Covalence was originally part of Raychem Corp as the pipeline division (and Ultra-Tec), it also carries that incredible use history, even though the product name has changed.
  4. Radiation crosslinking is an efficient use of energy.  This is more and more important every year it seems.
  5. The process is cleaner, with the potential for no unwanted 'residuals' in the product. 
Disadvantages of Radiation Crosslinking
  1. The process of radiation crosslinking are not widely understood (that makes companies like Raychem and Covalence even more valuable due to their experience with this process).
  2. High capital cost.  It is expensive to purchase a large electron beam.  No real surprise there, to make a high quality product requires a fairly significant investment.  It requires years of commitment to learning the ins and outs of a technology.  It requires more than setting up a simple 'back yard crosslinking operation.'
 Advantages of Chemical Crosslinking  
  1. Low investment for set up.  Getting set up to perform chemical crosslinking is cheap and easy.
  2. It is a technique that is fairly easy to understand.
  3.  Can easily be done in small batches
Disadvantages of Chemical Crosslinking 
  1. More limited options in terms of compounds to work with
  2. Requires a relatively complicated compound design
  3. Compounds have a limited storage life
  4. Crosslinking is sensitive and can be difficult to control
  5. Potential for undesirable 'residuals' in the product
  6. High energy consumption
     So, the next time you're considering using a chemically crosslinked shrink sleeve, consider the fact that you're likely sacrificing significantly on performance.  The quote you've got probably looks pretty attractive.  You may see this as an opportunity to save a lot of money on your project.  Unfortunately, any money saved on the front end is likely to come back to haunt you 20 fold when you discover major corrosion problems 6 months, 12 months or 24 months down the road.  

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