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Significance and Use
5.1 This guide is a sequential assembly of extant but unconnected standard tests and practices for the oxidation and biodegradation of plastics, which will permit the comparison and ranking of the overall rate of environmental degradation of plastics that require thermal or photooxidation to initiate degradation. Each degradation stage is independently evaluated to allow a combined evaluation of a polymer’s environmental performance under a controlled laboratory setting. This enables a laboratory assessment of its disposal performance in, soil, compost, landfill, and water and for use in agricultural products such as mulch film without detriment to that particular environment.
5.2 The correlation of results from this guide to actual disposal environments (for example, agricultural mulch films, composting, or landfill applications) has not been determined, and as such, the results should be used only for comparative and ranking purposes.
5.3 The results of laboratory exposure cannot be directly extrapolated to estimate absolute rate of deterioration by the environment because the acceleration factor is material dependent and can be significantly different for each material and for different formulations of the same material. However, exposure of a similar material of known outdoor performance, a control, at the same time as the test specimens allows comparison of the durability relative to that of the control under the test conditions.
1.1 This guide provides a framework or road map to compare and rank the controlled laboratory rates of degradation and degree of physical property losses of polymers by thermal and photooxidation processes as well as the biodegradation and ecological impacts in defined applications and disposal environments after degradation. Disposal environments range from exposure in soil, landfill, and compost in which thermal oxidation may occur and land cover and agricultural use in which photooxidation may also occur.
1.2 In this guide, established ASTM International standards are used in three tiers for accelerating and measuring the loss in properties and molecular weight by both thermal and photooxidation processes and other abiotic processes (Tier 1), measuring biodegradation (Tier 2), and assessing ecological impact of the products from these processes (Tier 3).
1.3 The Tier 1 conditions selected for thermal oxidation and photooxidation accelerate the degradation likely to occur in a chosen application and disposal environment. The conditions should include a range of humidity or water concentrations based on the application and disposal environment in mind. The measured rate of degradation at typical oxidation temperatures is required to compare and rank the polymers being evaluated in that chosen application to reach a molecular weight that constitutes a demonstrable biodegradable residue (using ASTM International biometer tests for CO2 evolution appropriate to the chosen environment). By way of example, accelerated oxidation data must be obtained at temperatures and humidity ranges typical in that chosen application and disposal environment, for example, in soil (20 to 30°C), landfill (20 to 35°C), and composting facilities (30 to 65°C). For applications in soils, local temperatures and humidity ranges must be considered as they vary widely with geography. At least one temperature must be reasonably close to the end use or disposal temperature, but under no circumstances should this be more than 20°C away from the removed that temperature. It must also be established that the polymer does not undergo a phase change, such as glass transition temperature (Tg) within the temperature range of testing.
1.4 The residues resulting from the oxidations are then exposed to appropriate disposal or use environments in standard biometric test methods to measure the rate and degree of biodegradation (Tier 2).
1.5 The data generated under Tier 1 evaluation and the determined time for the biodegradation in the chosen environment (Tier 2) allow ranking relative to other polymers evaluated under similar environmental conditions with this guide. The degree and time for biodegradation should be consistent with ASTM International methods, and any residues from the intermediate oxidation stage and from biodegradation must be shown to be environmentally benign and not persistent (Tier 3).
1.6 It is cautioned that the results of any laboratory exposure in this guide cannot be directly extrapolated to actual disposal environments; confirmation to real world exposure is ultimately required as with all ASTM International standards.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
D883 Terminology Relating to Plastics
D3826 Practice for Determining Degradation End Point in Degradable Polyethylene and Polypropylene Using a Tensile Test
D3987 Practice for Shake Extraction of Solid Waste with Water
D5071 Practice for Exposure of Photodegradable Plastics in a Xenon Arc Apparatus
D5208 Practice for Fluorescent Ultraviolet (UV) Exposure of Photodegradable Plastics
D5272 Practice for Outdoor Exposure Testing of Photodegradable Plastics
D5338 Test Method for Determining Aerobic Biodegradation of Plastic Materials Under Controlled Composting Conditions, Incorporating Thermophilic Temperatures
D5510 Practice for Heat Aging of Oxidatively Degradable Plastics
D5526 Test Method for Determining Anaerobic Biodegradation of Plastic Materials Under Accelerated Landfill Conditions
D5951 Practice for Preparing Residual Solids Obtained After Biodegradability Standard Methods for Plastics in Solid Waste for Toxicity and Compost Quality Testing
D5988 Test Method for Determining Aerobic Biodegradation of Plastic Materials in Soil
D6002 Guide for Assessing the Compostability of Environmentally Degradable Plastics
D6400 Specification for Labeling of Plastics Designed to be Aerobically Composted in Municipal or Industrial Facilities
E1440 Guide for Acute Toxicity Test with the Rotifer Brachionus
Other StandardsORCA Guidelines for the Evaluation of Feedstock for Source Separated Biowaste Composting and Biogasification Available from ORCA, Avenue E. Mounier 83, Box 1, Brussels, Belgium B-1200.
ICS Number Code 83.080.01 (Plastics in general)
ASTM D6954-04(2013), Standard Guide for Exposing and Testing Plastics that Degrade in the Environment by a Combination of Oxidation and Biodegradation, ASTM International, West Conshohocken, PA, 2013, www.astm.orgBack to Top