The DLG QUALITY MARK test seal is awarded to agricultural equipment that has passed a comprehensive DLG usability test. A DLG usability test is carried out to independent and recognized test criteria. The DLG QUALITY MARK test provides a neutral assessment of the essential features of the product, from performance capability and animal welfare, to stability, occupational and functional safety. These tests are performed in the lab and under a range of operating conditions and rate how the test candidate performs during practical testing on the farm. The specific test conditions and procedures are defined by an independent test commission and described in a test framework which also defines the parameters for evaluation. The test conditions and procedures as defined are revised on an ongoing basis so they reflect what is acknowledged by the current state of the art and to the latest scientific findings and agricultural insights and requirements. The tests are performed in accordance with procedures that allow an objective assessment based on reproducible results. After a product has passed the test, a test report is produced and published and the quality mark is awarded to the product.
The DLG QUALITY MARK test consists of technical measurements that are carried out on test stands and at the lab on the one hand and of performance tests that are carried out in the field on the other. In this test, the roll length of the film was measured on the test stand. The lab tests included strain, elongation and tensile strength at break, puncture force and tear growth force, relaxation behaviour, cling, oxygen permeability and weathering resistance. All tests were carried out in accordance with the DLG test programme on linear low-density polyethylene stretch film (PE-LLD) as dated November 2017.
The green 25 µm Agriflex silage stretch film was tested at the lab for its mechanical, physical, chemical and aging properties and roll length. Ease of handling was assessed in a practical test.
|Parameter tested||Test result||DLG requirement|
|The Agriflex stretch film (green, 25 µm) is suitable for wrapping silage bales.||suitable|
|Film length and width measured on the test stand were identical with the manufacturer information.||
≥ rated length |
≥ 98 % rated width
|Roll length at 1,500 m rated length||1,541 m||≥ rated length|
|Roll length at 1,800 m rated length||1,836 m||≥ rated length|
|The average thickness is 0.025 mm.||0.022 ≤ d ≤ 0.029 mm|
|The stretch film has a green colouring and is free of waviness and pores.||uniform colouring; free of waviness and pores|
|Strength when new, mechanical properties|
|Tension at 65 % longitudinal stretch||10.5 N/mm²||≥ 10 N/mm²|
|Tension at 70 % longitudinal stretch||10.6 N/mm²||≥ 10 N/mm²|
|Elongation at break||
longitudinal 431 % |
crosswise 561 %
|≥ 400 %|
|Tensile strength at break||
longitudinal 27.1 N/mm² |
crosswise 23.3 N/mm²
|≥ 10 N/mm²|
|Puncture resistance at 80 % stretch||24.1 N from inside; 22.4 from outside||≥ 10 N|
|Tear growth force||longitudinal 2.4 N||≥ 1.8 N|
|Relaxation behaviour||loss of force after 0.1h at 80 % stretch:|
|longitudinal 26.7 %||≥ 40 %|
|Adhesive force||0.05 N||≥ 0.05 N|
|at 0.2 bar 1765 cm³/(m² · d) in 24 h||≤ 1800 cm³/(m² · d)|
|Tensile strength after aging/weathering resistance|
|Elongation at break||longitudinal 401 %||≥ 350 %|
|Loss relative to force in new condition||longitudinal 7.0 %||≥ 30 %|
Description and technical data
The product is a green, 25 µm thick stretch film made of linear low-density polyethylene (PE-LLD Cast). The film roll is packed in a cardboard box to protect them from damage during transport.
The suitability, usability and applications of the stretch film were assessed in practical use.
The width of the film is measured with a calibrated tape measure. The roll length is measured on a film roll test stand with the film not pre-stretched.
The thickness of the film is measured to DIN 53370:2006-11, Method P at + 23 °C.
The film is visually inspected for uniform colouring, waviness and pores.
Tensile strength and mechanical properties
Critical parameters for determining tensile strength and the mechanical properties of stretch film are tension, elongation at break, tensile strength at break, puncture force, tear growth force, relaxation behaviour and adhesive force.
Longitudinal tension at 65 % stretch on square bales and at 70 % stretch on round bales and elongation at break and tensile strength at break (both longitudinally and crosswise) are tested to DIN EN ISO 527-3:2003-07 at +23 °C and at a rate of 500 mm/min. The type of the sample is Type 2; the extent of deformation is measured between two marks and in new condition.
The puncture force (at 80 % stretch) is measured to DIN EN ISO 12236 : 2006-11 using a 12.5 mm diameter mandrel with a 60 ° chamfer tip.
Tear growth force is measured to DIN ISO 34-1 : 2004-07, method B, procedure (b).
The relaxation behaviour (drop of force after 6 min at 80 % stretch) is measured to DIN EN ISO 527-3 : 2003-07.
Adhesive force is measured in a peeling test; inside surface to outside surface; unstretched at +23 °C;
specimen width is 50 mm; 50 mm/min test rate.
Oxygen permeability is measured on unstrained film and on a single-layer wrap to DIN 53380-3 : 1998-07; oxygen at +23 °C and 0.2 bar.
Aging and weathering resistance
Weathering is tested according to DIN EN ISO 4892-2, Procedure A.
Continued quality monitoring by DLG
The quality of the product is monitored annually as part of the DLG monitoring programme. In addition, the manufacturer is required to monitor their internal production processes for quality assurance.
The green 25 µm Agriflex stretch film is suitable for wrapping silage bales. The film performed well during a field application in the 2017 season.
The length and width as measured were identical with the manufacturer information. The roll length as measured was 1,541 m (75 cm width) and 1,836 m (50 cm width).
The mean thickness was determined as 0.025 mm. The thinnest measurement was 0.025 mm; the thickest reading was 0.025 mm. These measurements comply with the requirements for average film thickness and are within the permissible range of deviation from the mean value.
The film has a green colouring and is free of waviness and pores.
Tensile strength and mechanical properties
Longitudinal tension at 65 % was 10.5 and at 70 % stretch it was 10.6 N/mm² (minimum level for each stretch is 10.0 N/mm²).
The longitudinal elongation at break was 431 %; the transverse elongation at break was 561 %.
Both percentages exceed the required minimum elongation of 400 %.
The longitudinal tensile strength at break was 27.1 N/mm², the transverse tensile strength at break was 23.3 N/mm² which is higher than the required minimum of 10.0 N/mm². The puncture force at 80 % stretch was 24.1 N when applied from the inside and 22.4 N when applied from the outside of the film (the minimum puncture force was 10.0 N each time). The longitudinal tear growth force was 2.4 N, hence better than the minimum 1.8 N.
The longitudinal relaxation (the loss of force after 0.1 h at 80 % stretch) was 26.7 %, which is less than the required maximum relaxation of 40 %.
The adhesive force was 0.05 N and reaches the required minimum of 0.05 N for film with integral adhesive particles.
As a result, the film complied with all requirements as to tensile strength and mechanical properties.
The oxygen permeability (one layer, unstretched) at 0.2 bar was 1,765 cm³/(m² · d) which is less than the tolerated maximum ceiling of 1,800 cm³/(m² · d) in 24 h.
Aging and weathering resistance
After simulating a one-year exposure to natural weathering by applying 2,000 MJ/m², the longitudinal elongation at break was 401 % (minimum requirement is 350 %). This translates into a 7.0 % reduction of its resistance to break when elongated. This results compares to a permissible reduction of 30 % of the new film and proves that the film is resistant to weathering.
The criteria tested in this DLG Quality mark test assess the mechanical, physical and aging characteristics of the green 25 µm Agriflex stretch film on the test stand, at the lab and in the field. The green 25 µm Agriflex stretch film meets all test requirements in all criteria tested.
Manupackaging Deutschland GmbH,
Value Park Bau Z 20,
DLG TestService GmbH, Gross-Umstadt location
The tests are conducted on behalf of DLG e.V.
DLG test scope
DLG quality seal “The DLG testing scheme for linear low-density polyethylene stretch film (PE-LLD)”
Date of issue 11/2017
Special tests carried out at
SKZ – Testing GmbH, Friedrich-Bergius-Ring 22, 97076 Würzburg
Kunststoff-Zentrum in Leipzig gGmbH, Erich-Zeigner-Allee 44, 04229 Leipzig
Farm inputs and consumables
DLG Test Commission
Stefan Wolf, 63110 Rodgau Weiskirchen
Willi Schüler, 64395 Brensbach Wallbach
Dr. Hansjörg Nußbaum, LAZBW Aulendorf, 88326 Aulendorf
Dr. Klaus Hünting, VBZL Haus Riswick, 47533 Kleve
Dipl.-Ing. Udo Dengel, SKZ – Testing GmbH, 97076 Würzburg
Head of Department
Dr. Michael Eise
Dr. Harald Reubold *