TWIN SCREW EXTRUDERS | MACHINERY


extruder maker Comac. It sees co-rotating twin- screws becoming especially popular in recycling of flakes obtained from post-consumer PET bottles, as well as for recycling materials from industrial polyolefin-based moulded waste.


Adding value According to Charlie Martin, President of Leistritz Extrusion in the US, says twin screw compounding technologies offer unique opportunities to repro- cess post-industrial and post-consumer recycled materials. “When utilised in a thoughtful way, the co-rotating intermeshing twin screw extruder can transform recycled materials into value-added products and parts,” he says. Martin points out the need for removing foreign contaminants such as metals – close-meshing twin-screws are not amenable to such off-spec materials, he notes dryly – and there is also the challenge of getting sometimes fluffy materials into the system, so a crammer may be required. “The feed system is critical,” he says. One example of the use of twin-screw com- pounding for post-industrial recycling highlighted by Martin enabled a customer to convert fractional-


melt HDPE scrap from production of film into injection moulding material. The equipment was used to modify the MFI from 0.4 g/10 min to 2.2 g/10 min by what he calls “purposeful degrada- tion.” The extruder set-up involved the use of high-energy-input neutral and reverse kneading elements to maximise the energy imparted by the screws, high screw speeds (more than 800 rpm),


Above: This Leistritz twin-screw extruder is fitted with a crammer feeder


SOLVED ODOR & VOLATILES Turn Your Obstacles into Opportunities


Struktol engineered odor and volatile control additives can help you solve “smelly” problems. From high odor/volatile feed streams in recycled applications to strict odor/VOC specifications in automotive and packaging applications – these problems can be solved by adding a small amount of our unique solutions.


Your Application + Struktol Additives = Odor & Volatiles


Learn more at 4struktol.com or email plastics@struktol.com


IMAGE: LEISTRITZ


VOC / Odor Reducers


Odor Neutral izers


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