Moisture Conditioning of Nylon

[alex45]

Looking for advice on moisture conditioning nylon from anyone who has experience with the process in industrial setting for production parts (this is not for testing). I am looking not for why, but more how. To offer some rough numbers:

144/parts/day
smaller fuel tanks - 27"x26"x7" & 24"x19"x12"
Would like parts to reach equib. in 24 hrs (wishful)


I am looking for possible methods. Also what not to do, and is the 24 hr period feasible.

Thank You,
Alex

 

[patprimmer]

What is the section thickness.
What is the type of nylon.
Is it glass filled, nucleated, lubricated etc.
Will water spotting be an issue.
Are you looking for dimensional stability or toughness.
If toughness, how tough. Just a bit better than dry as moulded, or a lot better.

Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
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[Pud]

A search on web gave many sites with info:

e.g.

http://www.vydyne.com/pages/pdfs/moist_cond.pdf

Might be all you need but many more.

I (dimly) recall that boiling parts in (i think) a sodium acetate solution of a certain (unknown) strength will give equilibrium quickly without causing saturation. Perhaps one of the sites (or Pat!) may have the info?

Rgds


Harry

 

[patprimmer]

I have a draw full of info on conditioning of nylon.

The reason the draw is full, and the reason for my questions is that the subject has MANY variables, some of which have an extreme effect. i.e. The impact strength of a typical nucleated lubricated injection moulding grade of nylon 6 can have a 300% increase in impact strength when dry as moulded is compared to fully and properly conditioned to standard conditions.

Also, putting dry as moulded very thick extruded rod into boiling water to accelerate conditioning can result in enough expansion of the surface only, to create internal stresses high enough to crack the material.

Increasing temperature increases the rate of conditioning dramatically, but also increases rate of hydrolysis.

The rate of absolution of water onto the surface is virtually instantaneous, but the diffusion through the nylon is extremely slow at room temperature.

Nylon 6 anneals at about 60 deg C in water, but needs about 180 deg C (from memory) to anal in air. This annealing process causes shrinkage, but the simultaneous water absorption causes swelling, so the final dimension once equilibrium is reached throughout the moulding is different, depending on whether the moulding is conditioned above or below 60 deg C

I never heard about the sodium acetate thing before, but I can't think how it might work. I would need to dig out some old inorganic chemistry books to review a few things and think about it.



Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Pud]

hi folks,

I suppose the easiest(?) way to solve the problem would be to use an impact modified nylon which will have good toughness as moulded anyway.

The (small) additional cost may well be recovered by the removal of the conditioning operation.

(The sodium acetate(?) thing was in a technical brochure issued by a company called BIP (UK) who no longer make Nylon. I know I have it - just been "archived" in the office somewhere!)


Rgds

Harry

 

[patprimmer]

Impact modified nylon still changes dramatically in some properties on absobtion of moisture

Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.