×
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

PTFE BEHAVIOUR

PTFE BEHAVIOUR

PTFE BEHAVIOUR

(OP)
We have recenty done some work laminating 4 mils of PTFE film to roughened (240 grit) copper plates in a high temperature press (380 deg C). When we cut the now laminated product from 3'X3' sheets into panels of 1'X1' with a saw the edge of the panel show excellent adhesion between the copper and the PTFE. However further in the panel ~1/4" the bond is poor and it is easy to peel the film from the copper plate. If the product is left for 2 weeks the bond further in towards the centre improves. This improvement is accelerated if the product is baked unsupported in an oven for a number of hours above 100 deg C. Can anyone explain this phenomenon . Is there a stress relieve occurring within the material due to cold flow of ptfe, is the bake of the material relieving this stress ?.

RE: PTFE BEHAVIOUR


When designing components made of PTFE, the relatively high degree of thermal expansion must be taken into consideration:
20-100 °C:  = 16 · 10-5 1/K
20-200 °C:  = 23 · 10-5 1/K

Recordings of the coefficient of linear expansion  reveal two conspicuous transitions:

At 19°C there is a conversion within the crystal phase (<19°C triclinic, > 19°C hexagonal), which corresponds to a significant increase in thermal expansion.
At app. 327°C there is even higher unsteadiness, i.e. the crystal melting point

The following chart depicts the correlation between temperature and thermal expansion.

0

Regards,

Peter P

RE: PTFE BEHAVIOUR

Frank
If it is correct to assume that by the edges you are referring to the original sheet edges and not the newly cut edges then I suspect the problem is due to some gas evolving during the bonding process. It is likely to be most apparent towards the centre and least apparent on the edges.

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