×
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

Question about Plastic Thermal stability

Question about Plastic Thermal stability

Question about Plastic Thermal stability

(OP)
I am designing a plastic enclosure for electronics.  I selected a PBT with no glass fiber reinforcement for the prototype, since it should be very predictable dimensionally.

The process engineer has raised concerns about the part "moving" when heated to 90C for 10 minutes.  

My thoughts are if the plastic was held in place it would not "move".  

What properties in the data sheet should I be looking at to get it's thermal stability, and how high a temperature it is reliably able to survive?

I have a Valox 357 PBT;
it lists on the data sheet,
Melt Flow 250C
Deflection Temp @ 0.46MPa, 135C
Deflection Temp @ 1.8MPa, 98C
Vicat Softening point 134C
UL RTI, Mechanical without impact 140C

Are any of these numbers I should be looking at?  

RE: Question about Plastic Thermal stability

Quote (ryandias):

The process engineer has raised concerns about the part "moving" when heated to 90C for 10 minutes.  

My thoughts are if the plastic was held in place it would not "move".
2thumbsup I'm willing to bet good money the process engineer gave you a confused look when you replied with that...

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Question about Plastic Thermal stability

(OP)
Ok,

Sorry my description was not amazing.  By move, I meant that the internal stresses in our "prototype" tooling injection molded part, pulled the room temperature straight sides and left them slightly curved.  Approximately 1mm over a 50 mm length.

I think the plastic in it's softened state (90C), let the internal stresses in the part alter it's shape slightly.

The process engineer thinks that the plastic is not suitable at all.

RE: Question about Plastic Thermal stability

(OP)
Thanks.

But back to the original question.

What properties on the datasheet would predict the dimensional stability of a part made of resin X?

I felt that the;
Melt Temperature,
Vicat Softening point,
Deflection Temperatures,
were good indications of how the part would mold.  Is there a better specification?  or am I looking at the correct properties?

RE: Question about Plastic Thermal stability

The property you are after is not normally quoted in data sheets. It is more likely in technical bulletins or literature with extensive data on properties.

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