upvc pipe tests.

[devarajan]

Hello!
i am producing Upvc pipes as per IS standards using compounds having maximum 5phr filler and still unable to pass the Pressure test and sometimes reversion tests also. The machines are italian and german twin screw extruders.
Can someone give me some practical solutions to overcome these problems?

[Skip]

Sounds like the PVC material exiting the die is too cold?? perhaps not fully fused??-----what is the exit melt temperature of PVC?? Should be in the 185-190C range. Is the material "cheesy" (partially fused) at the vent?
If you can disclose your formulation, along with extrusion conditions of heats, RPMs, flood or starve feeding, amps, etc. as well as the type of pipe (thin wall, heavy wall)----I'll try to offer some help.

(What do you mean by "reversion" test----I've not heard that term before)

[devarajan]

Dear Mr.Skip,
Thanks for reply.
The tests i am talking about is Heat reversion test on uPVC pipe as per the BS standards 3505.
The formulation is Resin + 2.6phr stabilizer(one pack), 0.3phr External Lubricant, 5phr filler.
The temp profile is 165Deg. to 180Deg in the barrel and 170 to 180 in the die head.higher temperature at the die exit only increases the surface glossiness but creates more waviness on the inside of the pipe.
Wall thickness is 8mm on a 12" Cl. B pipe.
Output is 380kph which is 95% of the extruder rated max. o/p.
The sizing water temp is 20Deg.
My problem is inconsistency in the test results.
I wish to know the critical parameters to get a consistant pass result in the tests.
Regards,
devarajan.

[apathetic]

Edit ~L