Reducing delamination in PS/PS foam coextruded profile
Reducing delamination in PS/PS foam coextruded profile
(OP)
I'm currently trying to extrude a thin profile consisting of a low-density foamed PS core material with a coextruded PS layer (foamed or compact) on top to improve compressive strength.
Core is extruded at approx. 167°C, coextruded layer between 190 and 200°C.
What we see is that the top layer can easily be peeled off by hand. Since we are in a very subjective market we need to improve the interaction between both layers. My guess is the temperature of the foamed core is holding this back, plus the lack of cross-linking in polystyrene.
Are there additives that can improve the adhesion between the layers? Does anyone else have experience with a similar problem?
Thanks in advance
Core is extruded at approx. 167°C, coextruded layer between 190 and 200°C.
What we see is that the top layer can easily be peeled off by hand. Since we are in a very subjective market we need to improve the interaction between both layers. My guess is the temperature of the foamed core is holding this back, plus the lack of cross-linking in polystyrene.
Are there additives that can improve the adhesion between the layers? Does anyone else have experience with a similar problem?
Thanks in advance





RE: Reducing delamination in PS/PS foam coextruded profile
Another problem may be a weak boundary layer. That's when low molecular weight additives migrate to the surface and prevent the chains from entangling. Effectively you can have for example a waxy layer there of calcium stearate, anti-static or other additive. Reduce that by minimizing such additives as much as possible.
Chris DeArmitt PhD FRSC CChem
RE: Reducing delamination in PS/PS foam coextruded profile
Only additive used is a talcum-based nucleating agent which is distributed fairly evenly across the melt judging by the narrow cell size distribution we get.
I've played around with the composition of the coex layer without significant results.
Temperature might be the decisive factor but we tried coextrusion in a different extruder where the foam is fully formed before coextruding and the grafting was much better. Even though core temp was 150°C, coex temp around 175.
RE: Reducing delamination in PS/PS foam coextruded profile
Regards
Pat
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RE: Reducing delamination in PS/PS foam coextruded profile
RE: Reducing delamination in PS/PS foam coextruded profile
In the case of HIPS you have lots of surfactant too.
Chris DeArmitt PhD FRSC CChem
RE: Reducing delamination in PS/PS foam coextruded profile
Also, from our calculations the coextruded layer seems to be stretched elongationally due to shear forces.