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


PVC tubing bonding

PVC tubing bonding

PVC tubing bonding

We have experienced some cracks in the PVC tubing asembly. After investigation, we have the hypothesis that this craks in the joints could come from a non correct extrusión process temperatures, since the tubing appears to have very high shrinkage rates (9-10%). Have anybody experienced the same issues? Thanks for your help.

RE: PVC tubing bonding

First, if the cracks are very straight and run the length of the tube, they may be poorly formed weld lines cause by spider legs. Second, PVC must have proper fusion to get good mechanical strength The PVC powder is crystalized, and those crystals must complete melt during processing. If they do not, the material will be brittle. This can be determined by analyzing the extrusion with DSC.

Rick Fischer
Principal Engineer
Argonne National Laboratory

RE: PVC tubing bonding

Thanks Rick for your help. Tubing cracks appears when we use ciclohexanone in the joints with diferent parts. These craks are in the edge of the parts where cyclohexanone has contacted and are not in the lengh but in the wide. Could these cracks be related with an non correct extruxion process?

José Luis Zafrilla
Plant Technical Manager in Grifols

RE: PVC tubing bonding

Is this the first time you've used cyclohexanone to bond this material? Have you done this successfully in hte past? If so, has anything changed? New extruder? New resin supplier? Different material for the other part?

Rick Fischer
Principal Engineer
Argonne National Laboratory

RE: PVC tubing bonding

The only change is the plastic screw extruder. There are no changes in the material neither in the parts. He have used always ciclohexanone since we are bonding PVC.

Thanks Rick

RE: PVC tubing bonding

Is there another solvent you could try, not as a process change, but as a diagnostic exercise.

So you are saying its a new screw in an existing machine? Was this done to replace a worn screw, i.e. new screw has same specs as old screw, or is the new screw of a different design?

Is this rigid PVC or plasticized? My limited experience is with rigid. If this is rigid PVC, you could check your material properties by running a tensile test and comparing elongation to values from the resin supplier. If you have a piece of tube from the previous screw, run tensile on that and compare to the new stuff. If your testing produces a stable neck and draws out, your material is not too bad. If you cant get a good tensile specimen, run an Izod impact test. If you suspect process temperature issues, you should be looking to see if your material has undergone complete gelation. There are many papers dealing with this, one is below.


Rick Fischer
Principal Engineer
Argonne National Laboratory

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!


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close