I don't know if this is a dumb question, but does the effectiveness of the Kevlar in chaps diminish over time?
Not all chaps have 'Kevlar' - there are a variety of protective materials used. Regardless, it is those fibrous mats inside that get tangled in the chain and drive sprocket, and stall out the chain. Note that they are
not '
cut-proof', or even '
cut-resistant'; they just stall out the saw. But they do this very quickly, so the chain has less time to work on cutting you. It may still cut through your chaps, and maybe your jeans, and maybe part of your leg. But without chaps, there is nothing to keep it from going, and going, and going. . . So they likely reduce the severity of a cut. They don't prevent it, and they should not be thought of as 'armor'.
When the cutter snags the protective fibers, it pulls them out of the mat all the way from the top to the bottom. If you look closely, there should be no sewing or seams that penetrate the mat, preventing this, only seams around the edges, outside of the protective mat. So, if you have snagged the mat once, you are reducing the protection all along that leg, not just at the same place. If you cut just the outside fabric, it is OK to sew or duct tape the tear, as long as you don't snag the inside material. Once you have hit the mat, it has done its job, and it's time to replace them. Save them for safety demos if you want by wrapping them around a log.
Some of the protective fibers can be damaged by certain types of washing. Never use bleach, which degrades Kevlar and some other fibers. I hand wash mine flat in the bathtub, or folded over in the laundry tub, if they are particularly dirty. Otherwise, just brush off the dirt and maybe hand spot the surface. Some types of oils or chemicals may also degrade the fibers. *'As always, read the recommendations from the manufacturer of your chaps'*.
There might be some aging issues as well. I got a perfectly good pair along with a used saw once, but they were dated '1985', and I just did not have confidence in them, so I used them for a safety demo at a GTG (caution, they can really jam a nose sprocket - use a hard nose bar if you have one!).
Philbert
http://www.fs.fed.us/t-d/pubs/pdfpubs/pdf04512324/pdf04512324dpi300.pdf
http://www.labonville.com/Chap-Specifications-Care_ep_55.html
