[Ski Dude]

Looking for ways to disolve nylon fibers to separate and recycle nylon.
Disolved nylon in concentrated HCl solution, and then precipitated by diluting w/ water.

1) Why does this work?  Does it chemically react with or destroy the nylon?

2) Why does dilution precipitate the nylon?  Is it STILL nylon, or a chloride salt?

[arnyk]

 [-NHCH2CH2CH2CH2CH2C-]n

There's Nylon 6/6.

It's a polymer made of hydrocarbons.  What kind of reaction do hydrocarbons undergo with HCl?  

H2C=CH2 + HCl --> H3C-CH2Cl

I may be forgetting a catalyst...but in your case the rx takes place in solution anyways.

[movies]

There are some carbonyls in there too, I'm pretty sure.  I think that nylon has amides bonding the two monomers together.

[HP]

Nylon(probably you mean polyamide6,6)may disolves in conc. H2SO4 or in formic acid. This is due to breaking intra and inter hydrogen bonds between amide bonds in the polymer chains. Ading H2O cause precipitation of the adid solutions due to reforming hydrogen bonds...

[Ski Dude]

Is this really DISSOLVING  (in the true sense) or just a SUSPENSION of fine nylon particles?

[HP]

Yes it its absolutely real disolving. Polymers are not monomer agregates as some years before some people has tought