Hi There,
I have a nylon pivot which has suffered brittle failure in a bathroom environment. The peice is a hollow cylinder diameter 14mm with a 3mm wall. This peice cannot be made to fail with an impact loading either under a streight blow or with a twist. Are there any specific materials/cleaning products that might promote stress cracking in Nylon?
Thanks in advance
Mike Patching
Some shampoos or cleaning products, both of which contains soaps and surfactants, may stress-crack some nylons, but you would have to run tests on the specific nylon (6 or 6,6 or 6,12, etc.) and the specific stress-cracking agent.
If you have a magnifying glass you may want to look at the broken surface. Does the surface have many hair-like cracks, which is typical of most stress-cracking? Is there a void in the surface, indicating incomplete filling or a piece of contaminant fall out?
The other possible issue with some nylons is water absorption. Absorbed water can act like a plasticizers, making the nylon tougher. If the part broke when it was very dry (in the winter?) and since that time it re-absorbed some water, the part may be significantly tougher now.
Ernie
Go to the DSM Polymer, Ensinger-Hyde (A.L.Hyde) or Nytef websites and see if they have chemical resistant charts--look specifically for clorox, oils etc. Also, Nylon swells in the presence of moisture--which could cause cracking or failure if it's in a tight tolerance application.
Might consider Nylon 12 (low moisture absorption), Acetron GP (Delrin) or even UHMW which has better chemical resistance and no moisture absorption to speak of but not all the strength characteristics of the other two.
Let me know if this helps
Lyle
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