Ask the experts! These processors and consultants have been there and done that. Post your enigma now!


UBBFriend: Email This Page to Someone!
   Plastic processing forums for extrusion information and advice and for other feed screw applications.
  Extrusion, Twin Screw
  cpvc extrusion

Post New Topic  Post A Reply
profile | register | preferences | faq | search

next newest topic | next oldest topic
Author Topic:   cpvc extrusion
squeezeme
Member

Posts: 2
From:avon lake, oh usa
Registered: Apr 2003

posted April 28, 2003 02:19 PM     Click Here to See the Profile for squeezeme     Edit/Delete Message   Reply w/Quote
We are extruding a blend of PVC and CPVC using a twin screw extruder. We are experiencing black streaks on the surface of the profile. The streaks resemble pinking, however they can be wiped off easily. Also, they seem to be created by the sizer, not the die (profile appears clean when exiting the die, when sizer is closed and vacuum applied, the streaks appear.
Also, if I may ask two questions in one post, what are the preferred coatings for die and sizers (i.e. nickle, chrome, teflon, etc).
PLEASE HELP!
Thanks,
squeezeme

IP: Logged

farplast
Member

Posts: 1
From:sahab amman Jordan
Registered: Jun 2002

posted April 30, 2003 05:13 AM     Click Here to See the Profile for farplast   Click Here to Email farplast     Edit/Delete Message   Reply w/Quote
Hello,

WE ARE EXTRUDING CPVC PIPES ALL THE TIME WITHOUT ANY PROBLEM.ANY WAY THE BEST MATERIAL FOR DIES AND VACUME CALLIBRATOR WOUD BE HARD CHROME OR ss.
AS FOR THE STREAKS YOU ARE GETTING ,SINCE IT COMES OF EASY THAT MEANS IT HAS NOTHING TO DO WITH THE MATERIAL ,I AM SURE YOU WILL GET RID OF THIS BY COATING THE CONTACT SURFACE OF YOUR VACUME CALLIBRATOR WITH HARD CHROME.

------------------
farplast

IP: Logged

2beeps
Moderator

Posts: 43
From:Silver City, NM, USA
Registered: Jun 2001

posted April 30, 2003 09:20 PM     Click Here to See the Profile for 2beeps   Click Here to Email 2beeps     Edit/Delete Message   Reply w/Quote
Farplast makes a good point----is it possible
your sizing sleeve is aluminum??? Hot CPVC/PVC with tin mercaptide stabilizers may
form black/brown streaks due to metal sulfide
formation on the surface.

As you probably know already, the key to successful CPVC extrusion lies with the lube
balance. I always liked a good shot of AC629A
PE wax, along with the Ca Stearate and paraffin wax.

Skip

IP: Logged

squeezeme
Member

Posts: 2
From:avon lake, oh usa
Registered: Apr 2003

posted April 30, 2003 10:48 PM     Click Here to See the Profile for squeezeme     Edit/Delete Message   Reply w/Quote
Thank you both for your reply. We tried a chrome-plated die and found the chrome to flake off rapidly. We switched to a sub-micron diamond embedded nickle plating (high tech, huh?)and still saw the streaking, although the color of the steaks shifted from black to dark brown. We favor nickel due to it's chemical resistance.

We will look into the lube package and investigate your suggested additives.

Thank you both, again.
Tim

IP: Logged

All times are ET (US)

next newest topic | next oldest topic

Administrative Options: Close Topic | Archive/Move | Delete Topic
Post New Topic  Post A Reply
Hop to:

Contact Us | Feed Screw Designs

Powered by Infopop www.infopop.com © 2000
Ultimate Bulletin Board 5.45a