Symphony Environmental Technologies : Successful farm trial for oxo-film

Technical Paper

September 2013

PEMBROKE MULCHING FILM TRIAL

West Orielton Farm, Pembrokeshire

1. Introduction.

The trial was arranged to demonstrate that Symphony's d2w controlled-life plastic film can remain intact as a cover for a growing potato crop for the 10 week period required by the farmer, and that it will subsequently degrade.

The film is required to protect the plants in the early stages of growth and is designed to degrade rapidly once the plants are established, so that the film, contaminated with earth and vegetable matter, does not have to be removed and disposed of, and so that the film will instead degrade then biodegrade on and in the soil, leaving no harmful residues.

2. Materials.

The oxo-biodegradable additive and films for the trials were produced at Symphony's Telford experimental facility on 22nd May 2012.

Two oxo-biodegradable films were produced with Symphony's d2w masterbatch:

1. DG12-05-a masterbatch based on a manganese catalyst
2. DG12-06-a masterbatch based on a cobalt catalyst.

The masterbatches were produced on a Rondol 24mm twin-screw laboratory compounder.

The masterbatches were incorporated at 1% w/w in a pre-blended polymer mixture of 75% LDPE (Total 1022FN24) and 25% LLDPE (Sabic 118W), and blown into film.

The film (with a nominal thickness of 35µm) was blown on a 20mm single screw Rondol laboratory extruder fitted with a 40mm diameter die. A lay-flat film ca. 130mm wide was produced and cut into a centre-fold sheet prior to opening out and winding onto a cardboard core. The final sheet width was ca. 260mm. The film was clear and un-pigmented, as requested by the farmer.

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3. Outdoor exposure- field trial on site.

The films were not exposed to uv light before being laid on 27th July 2012 on the surface of the field used for growing potatoes in the presence of the farmer, Mr. Walter Simon, and of representatives of the Environment Agency Mr. Ged Davies, Mr. Brian Klass and Ms. Liane Bacon, and of Mr. Michael Stephen, a Director of Symphony Environmental Ltd. The samples were lifted by the farmer from the trial site in late September 2012 and returned to Symphony on 29th September.

Observation showed that the cobalt DG12-06 film had shown the greatest degree of degradation, and this was confirmed on laboratory examination of the returned film samples. The DG12-06 film sample was brittle (too weak to test mechanically) whilst the DG12-05 sample retained some elasticity.

The DG12-06 film had therefore performed as expected by the farmer.

Timescale can be adjusted by modifying the formulation of the d2w additive.

4. Analysis of films from field trials.

The molecular-weight of the samples returned from West Orielton Farm was determined by high temperature Gel Permeation Chromatography (GPC). The results are tabulated below.

Table 1: Gel Permeation Chromatography analysis of film residues

Sample ref.	Mw	Mn	Intrinsic Viscosity
DG12-05 Unaged	125,100	19,400	1.07
DG12-05 Aged		17,800	0.93
DG12-06 Unaged	143,600	17,500	10.6
DG12-06 Aged	36,900	6,200	0.42

The molecular weight (Mw) of the DG12-06 film had therefore fallen by ca. 75%

The DG12-05 film did not show a reduction in molecular weight under the conditions in which it had been exposed, and the DG12-06 film was therefore better suited to this particular application.

5. Further outdoor exposure.

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The materials returned from the Pembroke site were further exposed outdoors at a site in Telford, Shropshire, in order to observe any further reduction of the molecular weight through oxidation.

A frame was constructed to contain the two films so that they were exposed side by side. The exposure was started on 1st November 2012 (Figure 1). Plastic crop-protection netting (mesh size: 15mm x 20mm) was placed over the materials, to reduce losses due to the wind.

Figure 1: Exposure of films at Telford site- 1st November 2012.

Film DG12-05 is on the left of the central dividing bar and film DG12-06 is on the right.

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After 4 further months of outdoor exposure, film DG12-06 had disintegrated, and film DG12- 05 was still intact. Figure 2 shows the condition of the films on 1st March 2013.

Figure 2: films exposed at Telford site- 1st March 2013.

Film DG12-05 is on the left of the central dividing bar and film DG12-06 is on the right.

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By August of 2013, Film DG12-05 had also disintegrated.

Figure 3 shows the condition of the films on 16th August 2013.

Figure 3: Exposure of films at Telford site- August 2013.

Film DG12-05 was on the left of the central dividing bar and film DG12-06 was on the right.

6. Laboratory evaluation of films.

6.1 Thermal aging.

Thermal ageing of unexposed samples of both films was carried out in a Memmert UFE 600 fan-assisted oven at a temperature of 70ºC in accordance with ASTM D5510 Procedure B. Samples of the films were withdrawn every 96 hours and their carbonyl optical density (COD) determined by FT-IR spectroscopy. The COD is a technique for monitoring degradation which charts the accumulation of carbonyl break-down compounds in the polymer structure.

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