GB/T 35795-2017Biodegradable mulching film for agricultural use (English PDF)

1 Scope

China's national standard for biodegradable agricultural mulch film. It specifies the terms and definitions, the classification, the technical requirements, the test methods and the inspection rules. Plastic mulch is one of the most effective things a farmer can do to a field: it warms the soil, conserves moisture, suppresses weeds and can advance a harvest by weeks. China uses more of it than anywhere else in the world, and the consequence is one of the country's most serious agricultural problems. Conventional polyethylene mulch is thin, it tears, and recovering it from a field is uneconomic, so it is ploughed in - and it accumulates, year on year, until the residue interferes with root growth, water movement and germination. Biodegradable film is the way out, provided the degradation is real. That is the burden this standard carries: it must distinguish a film that genuinely mineralises in soil from one that merely fragments into pieces too small to see, which is worse than the problem it claims to solve.

This Standard specifies requirements, test methods, inspection rules, marks, packaging, transport and storage of biodegradable mulching film for agricultural use. This Standard is applicable to biodegradable mulching film for agricultural use that uses one or more resins in aliphatic polyesters, aliphatic-aromatic copolyesters, carbon dioxide-epoxy copolymers, and other biodegradable polymers that have biodegradation characteristics as main compositions, that it is allowed to add appropriate proportion of biodegradable natural polymer materials such as starch and cellulose, as well as other inorganic fillers and functional additives without environmental hazards to formulation, that is produced by processes such as blow molding or casting.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

GB/T 1037, Test method for water vapor transmission of plastic film and sheet - Cup method

GB/T 1040.1, Plastics - Determination of tensile properties - Part 1: General principles

GB/T 1040.3, Plastics - Determination of Tensile Properties - Part 3: Test Conditions for Films and Sheets

GB/T 2828.1, Sampling procedures for inspection by attributes - Part 1: Sampling schemes indexed by acceptance quality limit (AQL) for lot-by-lot inspection

GB/T 2918, Plastics - Standard atmospheres for conditioning and testing

GB/T 6672, Plastics film and sheeting - Determination of thickness by mechanical scanning

GB/T 6673, Determination of Length and Width of Plastics Film and Sheeting

GB/T 15337, General rules for atomic absorption spectrometric analysis

GB/T 16422.1, Plastics - Methods of the exposure to laboratory light sources - Part 1: General guidance

GB/T 16422.2-2014, Plastics - Methods of exposure to laboratory light sources - Part 2: Xenon-arc sources

GB/T 19276.1, Determination of the ultimate aerobic biodegradability of plastic materials in an aqueous medium - Method by measuring the oxygen demand in a closed respirometer

GB/T 19276.2, Determination of the ultimate aerobic biodegradability of plastic materials in an aqueous medium - Method by analysis of evolved carbon dioxide

GB/T 19277.1, Determination of the ultimate aerobic biodegradability of plastic materials under controlled composting conditions - Method by analysis of evolved carbon dioxide - Part 1: General method

3 Terms and definitions

For the purposes of this document, the following terms and definitions apply.

3.1 biodegradable materials Materials that are degraded by the presence of microorganisms in nature under conditions such as soil and/or sand, and/or under specific conditions such as composting conditions or anaerobic digestion conditions or aqueous culture fluids, and eventually completely are degraded into carbon dioxide (CO2) or/and methane (CH4), water (H2O) and mineralized inorganic salts of elements contained therein and new biomass

3.2 biodegradable mulching film for agricultural uses; biodegradable mulching film Sample condition adjustment shall be in accordance with GB/T 2918. Temperature is 23°C ± 2°C. Adjustment time is not less than 4h. Perform test under such conditions, excluding appearance, net mass deviation.

6.3 Thickness deviation According to GB/T 6672, use thickness measuring meter of which accuracy is 0.001mm to measure. Calculate limit thickness deviation according to formula (1). Calculate average thickness deviation according to formula (2). Where, Deltad - Limit thickness deviation, in millimeters (mm); dmax or min - Actually-measured maximum or minimum thickness, in millimeters (mm); d0 - Nominal thickness, in millimeters (mm). Where, d - Average thickness deviation, %; dn - Average thickness, in millimeters (mm); d0 - Nominal thickness, in millimeters (mm).

6.4 Limit width deviation According to GB/T 6673, use measuring tape or steel ruler of which accuracy is 1mm to measure. Calculate limit width deviation according to formula (3). Where, Deltaw - Limit width deviation, in millimeters (mm); wmax or min - Actually-measured maximum or minimum width, in millimeters (mm); w - Nominal width, in millimeters (mm). d max or min w max or min

6.10 Heavy metal content When testing heavy metal content, perform microwave digestion to sample through high-pressure system. Then use atomic absorption spectrophotometer to test according to GB/T 15337.

6.11 Biodegradability Determine organic component (volatile solid content) according to Method A in GB/T 9345.1. Measurement temperature is 650°C. Use any method in GB/T 19277.1, GB/T 19277.2, GB/T 19276.1, GB/T 19276.2, GB/T 22047 to perform biodegradability test. In arbitration inspection, use GB/T 19277.1.

6.12 Artificial weathering performance Sample preparation and treatment are in accordance with GB/T 16422.1. Age 3 pieces for each kind of sample. Extract individual sample from aged large sample to test. Take average value of three samples. Determinations for nominal strain of initial fracture of sample and nominal strain of fracture after exposure are in accordance with 6.7. Test method is in accordance with GB/T 16422.2-2014. Irradiation method uses Method A. Irradiance is narrow band (340 nm)

0.51 W/(m2nm). Temperature control uses black mark thermometer. Exposure cycle uses cycle number 1. Test duration is 100h.

7 Inspection rules

7.1 Batching Biodegradable mulching films for agricultural use are inspected and accepted in batches. One batch refers to products of continuous production of 50t from same formula and same specification. If continuous production is one week but production is less than 50t, one batch shall refer to one-week production.

8 Marks, packaging, transport, storage