Replacement for Pebax 7233 - Extruded Tubing

[StorageMan]

Hello,
I am looking for a substitute for the Pebax 7233SP we presently use (but not available because of the 'Force Majure' declared by Arkema).

We have tried Hytrel 7246 and Hytrel 6356 and neither were able to work for our application (extruded tubing with strength and flexibility).
The Hytrel 7246 issue is that the extruded Hytrel 7246 tube cannot retain air, as it starts coming out of the extruder the proper size; then shortly it becomes wider out of the extruder (expanding) larger and larger until it ‘pops/cracks’, then goes back to the proper size. We’ve tried increasing and decreasing the extruder temp and adjusting the pull rate, but it keeps happening.
The Hytrel 6356 did not expand and ‘pop/crack’ like the 7246 but it pulsed narrow and wide (did not keep shape) and the extruded product was also not very strong/stiff (it was mushy/rubbery).

The 7233SP has strong UV properties but we don’t need that aspect.
It is a Shore D 69, that is extruded as a clear tube. It is rigid/strong (hard to kink), yet quite flexible.

I have contacted other companies about Riteflex, Grilamid and Styroflex but no one has stepped-up to offer a recommendation.

Any help would be appreciated.

Thanks.

 

[MikeHalloran]

Doesn't a tube extruder need a gas connection in the central plug in order to put air in the center of the product? The reported behavior suggests a malfunction in the assumed precision air regulator feeding that connection, e.g. that its relieving function is not working well.





Mike Halloran
Pembroke Pines, FL, USA

 

[Pud]

Hytrel is a polyester based TPR - do you have the capability to dry it down to the recommended moisture level?

Generally, no degradation of the polymer or imperfections
in the molding or extrusion occur if the
moisture content is less than 0.10%, the maximum
moisture specification for all grades of Hytrel.
When dry polymer is subjected to 50% relative
humidity, 0.10% moisture increase occurs in about
2 hr, whereas at 100% relative humidity, it occurs
in less than 1 hr (see Figure 7). Therefore, pellets
so exposed should be redried before use.
When drying Hytrel, dehumidified air ovens are
recommended. Effective drying with such ovens
takes place in 2–3 hr at 100°C (212°F) or overnight
at 70°C (158°F).* Drying ovens without dehumidifiers
may be used but will require 4–6 hr or more,
depending on the quantity being dried. Even then,
these ovens may not be adequate during periods of
high humidity.
* It is critical to ensure that the dehumidifying medium is dry prior to
the drying of Hytrel.

If you have done the above (note the bold type), then contact Du Pont

Cheers
Harry
(Another Du Pont victim!)

http://www.tynevalleyplastics.co.uk