STRETCH AND SHRINK FILM | MATERIALS


its FSP600 can identify gels in the film. This was used – integrated into a W&H Filmex II line – to compare virgin films with those containing 30% and 50% PCR.


Other potential defects include black specks, contamination, die lines and oil stains – which can have different sources. One way of reducing defects was to inject liquid anti-oxidant into the repelletiser at the same time as processing the resin and PCR. Similarly, Dover Chemical said the reduction of gels was critical to allow the production of thinner films that use recyclate. Here, a Doverphos LGP-12 was used as a phosphite stabiliser. The chemical is a liquid phosphate that is not derived from alkylphenols. It is highly soluble in polyolefins. “Phosphites are sacrificial additives that protect the polymer and other additives throughout the process,” said Shawn Cook, technical manager for plastic additives at Dover Chemical. He said that, after introduc- ing the stabiliser, films con- tained no gels of 1600 microns or larger.


Higher stability Lucio Baccaro, of market development at Sabic Europe, said that embedding polypropylene (PP) into the stretch film structure can help to improve load stability. Trends for stretch film include: greater circular-


ity; stiffer and thinner films; and load-securing and pallet stability, he said. A way to boost stability was to add PP to the


formulation, he said. This helps to reduce goods damage, use less plastic per pallet and wrap more efficiently – due to less downtime. One project saw the production of a five-layer


film that included two grades of its Supeer LLDPE around 10% of its 621P random PP. This patented film was produced in collaboration with machinery manufacturer SML. Using the PP leads to a higher holding force – to


improve stability – plus a higher elongation than for the pure LLDPE grade. It also raises tear resistance, meaning less downtime, fewer breakages and higher efficiency. “End users and brand owners can use less plastic per pallet, have a more reliable wrapping process and comply with sustainability pledges,” he said.


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Innovation front Gavin Lewis, innovation lead at UK Research and Innovation (UKRI), pointed to several of the organisation’s projects that address sustainability. One, in collaboration with Interface Polymers, involves compatibilization, recycling and surface modification of olefin films. Here, Polarfin diblock copolymers – introduced via coating or additive masterbatch – can enhance the polarity of the surface of olefin films. Trials using small quantities of Polarfin showed improvements in compatibilis- ing waste films contaminated with labels and tape, allowing far higher process tolerance. It can also compatibilise polyamide in olefin films with zero gels.


“Coating olefin substrates with Polarfin allows printing, painting and high levels of adhesion using standard adhesive products,” said Lewis. A second project, CO-


tooClean (with Nextek) uses a supercritical CO2


process for


food-grade recycled films. It boasts high-performance decontamination and oil


removal. There is no need for water, drying or toxic chemicals, he said. The project also studied the removal of inks


and fatty oils from films. Oils and inks are key obstacles to the recycling of plastic films, and results from the study are very encouraging, he said. n The next Stretch and Shrink Film conference takes place in Charleston, USA on 29-30 November 2023. The next events in Europe takes place in Valencia, Spain on 23-25 April 2024. For more details, contact Pranita Nangia on +1 610 478 0800 (pranita.nangia@amiplastics.com).


CLICK ON THE LINKS FOR MORE INFORMATION: � www.amiplastics.com � www.plasticsrecyclers.eu � https://recyclass.eu � www.siigroup.com � www.lantech.com � www.saica.com � www.itene.com � www.ocsgmbh.com � www.wh.group � www.doverchem.com � www.sabic.com � www.ukri.org � www.kuraray.com � www.smscor.com


July/August 2023 | FILM & SHEET EXTRUSION 35


Left: UKRI’s COtooClean project uses supercritical CO2


process in


the recycling of plastic films


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