MATERIALS | STRETCH AND SHRINK FILM


polymer – such as LLDPE – during processing or in use. In LLDPE, a primary anti-oxidant (to protect the product long-term) might be phenolic-based; a secondary anti-oxidant (used as a process stabi- liser) is typically phosphite-based. SI says that its Weston 705T secondary anti-


oxidants have high solubility in PE, with almost no blooming or plate-out. They are highly reactive with peroxide, and protect against thermal oxidation. In one example, Srabotic cited its use in LLDPE


Above: SI says its Evercycle products help to raise


sustainability


l Make sure that film labels are provided with a water soluble/water releasable adhesive (to ensure label separation);


l If printing is required, minimise it – and use polyurethane-based inks rather than those based on nitrocellulose;


l Blending PE with EVA is fine, but keep the VA% as low as possible (less than 5%); and,


l Use only workhorse additives and limit their presence (so avoid bio-, photo-, oxo-degradable additives).


Film improvement Matej Srabotic, senior market development man- ager for polymer solutions at SI Group, explained how the company’s phosphite anti-oxidant can enhance PE and recycled-PE film properties. An antioxidant’s main job is to protect the


resin, where it can provide higher melt flow protection and protection against discoloration – with a lower yellowness index, for instance, compared to previous SI grades. It also exhibited a much lower gel count in cast film. In a second example, to assess its performance


in stretch film, a line from W&H was used t cast a film using a 3m-wide die, line speed of 400 m/min and throughput of nearly 1500 kg/h. Films were tested on Highlight and ESTL testing machines. The film stabilised with Weston 705T showed a higher elongation at break and tear resistance, lower gel levels in industrial stretch wrap film (using 1% masterbatch) and one-third the level of plate-out compared to an earlier grade. Die build-up was also reduced. A different anti-oxidant was also used to boost the performance of PCR-based stretch film. Here, a similar film was produced – using 1% Evercycle LD-104P – and tested. This boosted the perfor- mance of the film – with a lower gel count and higher mechanical properties.


Asian expansion in stretch and shrink film


Earlier in the year, AMI organised a similar stretch and shrink film event in Bangkok, Thailand – with speakers covering topics from film grades and new machinery to the importance of quality control. Expansion in stretch and shrink film production is expect- ed to be driven by growth in Asia. Hiroshi Koyama, manager of technical services at Kuraray Asia Pacific, told delegates that ethylene vinyl alcohol (EVOH) can make a key contribution towards greater sustain- ability. For one, it is recyclable – which can


often be done at the same time as recycling the base polyolefin up to a certain level. Several projects – includ- ing a sorting test at Tomra, and a


30


RecyClass project – are assessing ideal conditions for recycling EVOH within flexible film waste. The material can also be applied to


standard processes, such as blown and cast film extrusion.


“It is applicable to conventional


co-extrusion and orientation process- es,” he said. This includes its use in oriented


films, which typically boast a higher strength than non-oriented film. Addition of the EVOH layer can lead to the creation of ultra-high barrier films. It has been used in various applications, including packaging for powdered milk and for meat. Bio-based materials can also help to boost sustainability. Siwarutt


FILM & SHEET EXTRUSION | July/August 2023


Boonyarattanakalin, assistant innova- tion director at SMS in Thailand, said the company is using thermoplastic starch-based material as an alterna- tive to conventional resins. Its advantages include composta- bility and bio-based content com- bined with good mechanical and physical properties. SMS’ Tapioplast range is derived from cassava and complies with standards including those of the US Food & Drug Admin- istration (FDA). n The next edition of Stretch and Shrink Film in Asia is in Bangkok again, on 27-28 February 2024. For more details, contact Koos Ahmed (koos.ahmed@amiplastics.com) on +44 (0) 117 314 8157.


www.filmandsheet.com


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IMAGE: SI GROUP


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