×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

30% Glass filled Nylon 6; can I use it in water?

30% Glass filled Nylon 6; can I use it in water?

30% Glass filled Nylon 6; can I use it in water?

(OP)
I have some elements molded from a Firestone Nylon 6 CG430-203. I use them in a machine that uses a conveyor type belt to screen solids out of influent water channels. I have had issue with tightness and stiffness in the belt and I believe it is due to water absorption.
I need help with information on this material water absorption and desorption rates.
How much will the material grow when submersed in water and how long will it take to absorb water and how long will it take to dry out and come back to its dry size?

RE: 30% Glass filled Nylon 6; can I use it in water?

Unfilled nylon 6 typically absorbs about 3% water in air with an average humidity and about 9% if stored at 100% RH.

At 3% moisture content it expands about 1%

At 3%  moisture the flex mod is reduced by about 70% and the elongation increases by about 300% although elongation also depends largely on molecular weight and nucleation.

30% glass fibre drastically reduces the effect of the moisture uptake. The %age moisture will be the same for the nylon content only so it becomes 2% and 6% moisture uptake.

At one molecule thick the moisture uptake to equilibrium is virtually instant, however the moisture travels quite slowly through the nylon. The rate depends on concentration gradient and temperature, but for a thick moulding can take months to equalise to the core of the moulding, however most alteration to properties occur before full equalisation of moisture content.

I have data somewhere I could dig up, but reputable raw material suppliers should be able to provide extensive data taking several variables into account.

Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
 

RE: 30% Glass filled Nylon 6; can I use it in water?

(OP)
Pat, thank you for your help. My molded part has various thicknesses, the area I am looking at is a cylindrical boss that has a 1-1/2" OD, 1" ID and is approx 1/4" thick.
In reponse to my on site issue I dropped two elements into a pail of water; at this time they have been submerged for about 20 hours and I have seen little dimensional change.
As for desorption, on site my belt had been out of the water about three days and I did not see a change back to the original dimensions.
Would this be typical rates based on your experience?

RE: 30% Glass filled Nylon 6; can I use it in water?

Yes. At 1/4" wall section, significant size changes will take quite a few weeks or even months if it is cold. At 100 deg C it could change to days or even hours.

Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
 

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources