recycling resins with filler 1

[loughnane]

How involved does recycling resins with filler become?

The specific instance where this came up was calcium carbonate-filled polypropylene, but I'm also intrigued in more conventional fillers such as glass.

for that matter, what about blended thermoplastics (PC/ABS, PC/PBT, etc.)

..looking over the question I see it has several degrees of freedom, but I haven't been able to find any solid resources, so if anyone could help point me in the right direction it would be much appreciated.

Chris Loughnane - Product Design

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[patprimmer]

It depends a bit on what you mean by recycling, what you mean by plastic and what you mean by filler.

By recycling you will get best value if it is is done with a stream dedicated to one material type and grade. Everything gradually goes downhill from there.

I will presume you mean thermoplastics and will exclude thermosets from consideration as they severly limit options.

I will consider Fillers and additives and reinforcements separately.

Additives substantially change properties with only small add rates and change properties other than flex mod or tensile. Recylclability is greatly varied depending on their thermal stability.

Fillers normally have a very low aspect ratio and do not reinforce most physicals. In fact they often diminish them. They can generally be recycled as per unfilled grade.

Reinforcements normally have a higher aspect ratio and are degraded by recycling as the reinforcement media is cut into smaller parts during granulating. This decreases their reinforcement effect as it decreases aspect ratio. The degree varies greatly with conditions.

Regards
Pat
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[Demon3]

Calcium carbonate has no effect on the excellent recyclability of PP. As an isotropic filler it increases modulus, slightly decreases yield strength, slightly increases HDT. In PP homopolymer impact resistance increases. In PP copolymer it decreases.

Talc (higher aspect ratio type), mica, wollastonite increase modulus more than calcium carbonate but only in the direction in which the fibers or platelets are aligned. Increase yield strength but again, only in the direction of the fibers, plates. Increase HDT more than isotropic fillers. Decrease impact resistance.

Glass fiber more effective than platy and short fiber fillers mentioned above.

I give webinars on this every year. I won't advertise them here but you could find them should you wish to.

Calcium carbonate is a great filler for PP in cost : performance. Does not cause warpage whereas all the other fillers do. Also, when recycled the properties are retained whereas plates and fibers are broken down and lose their aspect ration and reinforcement effect with each recycling.

Chris DeArmitt PhD FRSC CChem