MATERIALS | AGRICULTURAL FILM
properties were vital to total impermeable film (TIF) – which helps to reduce the use of fumigants by ensuring that it is not lost to the environment after dosing.
Methyl bromide, for instance, is used as a fumigant but is an ozone-depleting substance. For this reason, its use must be limited. Balemans showed a seven-layer TIF structure, incorporating a middle layer of EVOH. “The EVOH layer should be less than 10% of the total structure to have good mechanical proper- ties,” he said. Tests by the University of California Davis, for
Above: Kuraray said that its high barrier film has been used to improve the performance of silage film
include ‘biomass’ – which typically varies between 10 and 40%. “The purpose of lab testing is to show the
inherent nature of the material to biodegrade under a given set of conditions,” he said. He also pointed out that ‘non-biodegradable’
film leaches into the soil: a conventional LDPE mulch film has a maximum accumulation level of 463kg per hectare after 10 years. Downgauging the film actually increases accumulation, he said. In comparison, a biodegradable film would build up a maximum accumulation level of 463kg per hectare, after two years. BASF, whose biodegradable PLA-based Ecovio is commonly used in agricultural mulch film, has also looked at soil accumulation. The company has used a range of analytical techniques – including NanoSIMS, to assess the incorporation of polymer carbon into the soil, and Cavity Ring Down Spec- troscopy (CRDS) to track 12C and 13C-carbon dioxide. “There is a strong stakeholder demand to know
the fate of materials introduced into the soil,” said Andreas Kuenkel, vice president of biopolymers research at BASF in Germany. In addition, he said BASF could differentiate between biodegrading microbes and other soil microbes by seeing which ones actually grow on the polymer. “Fungi is the most potent degrading micro-
organisms in the soil,” he said. The team has identified more than 150 species in soil that play a role in biodegradation.
Barrier performance As well as retaining moisture, plastic film can also help to retain other species – such as fumigants and other chemicals. Frank Balemans, senior regional technical sales manager at Kuraray, told delegates how barrier
16 FILM & SHEET EXTRUSION | April 2018
instance, showed that TIF helped to keep methyl iodide soil retention levels at 2,000ppm after 180 hours – where it was around 100ppm for standard LDPE film after the same period. In a similar way, high barrier films can be used to
improve the performance of silage film – prevent- ing the degradation of feed such as wet corn. It can also prevent mould, infestation and aroma loss in harvest such as grains. The company has demonstrated a proof of concept high barrier storage bag, to store corn for five months. It was conducted in Indonesia using plastic liners inside a woven PP bag. Another TIF, from Arkema, was similarly used for
crop fumigation. Here, the fumigant was dimethyl disulphide (DMDS) – a natural substance found in brassicas and onions, that is an alternative to methyl bromide. Arkema’s film also uses EVOH – in a seven-layer structure – and includes a photo- catalyst (titanium dioxide) that speeds up the decomposition of DMDS.
Fighting UV Kompuestos of Spain has developed a green- house film that fights the detrimental effects of UV light. Its PEUV7001 is an anti-UV masterbatch that is an alternative to either UV absorbers or UV scavengers. Instead, it uses 20-30nn inorganic particles to reflect and absorb UV light. It is transparent to visible light – which is vital to plant growth – and does not migrate, said the company. In addition, it retains its mechanical properties
after UV ageing, said Kompuestos. The company has also developed anti-IR film which helps to control greenhouse temperatures. Its PEIR1000 incorporates an engineered inorganic additive – sized optimally, to ensure maximum translucency – which helps it to reduce greenhouse temperatures by as much as 6°C. This helps to reduce thermal stress and enhance plant growth. “Greenhouses could use this film all year round – in summer, to keep the interior cooler, and in
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