ASTM D6954-04  

The scope of the project is to assess the degree of physical property losses of polymers by a thermal oxidation process and determine the rate of aerobic biodegradation of the submitted test product as well as its ecological impact in the defined applications and disposal environments after degradation. This method is divided into three tiers, whose goals and objectives are outlined in the following headings.  

3.1 Tier 1-Heat Aging of Oxidatively Degradable Plastics

The goal of Tier 1 is to evaluate the extent of molecular weight loss resulting from thermal oxidation of test material using ASTM D5510-94（2001）. The test material is incubated in a Forced-Ventilation or Gravity-Convection Oven at a temperature not exceeding 20℃ from the end use and maintained at a relative humidity level for a defined period of time (depending on rate of fragmentation). Before and after exposure, the following analyses are performed on the test material: molecular weight, polydispersity index, mass of volatiles, and % gel. Weight loss will also be determined upon termination of the oxidation process. 

All observations and conditions (time, temperature, and humidity) will be recorded on a daily basis.  

UV light exposure can be an alternative route for oxidation testing in Tier 1. 

Inquire for more details regarding pricing for UV exposure. 

3.2 Tier 2-Biodegradability Testing 

The goal of Tier 2 is to determine the degree and rate of aerobic biodegradation of a test material from Tier 1 using ASTM D5338-98(2003). In this method, the test material is incubated with a compost inoculum and the percentage of biodegradability is obtained by determining the percent of conversion of carbon in the test material to carbon in the form of CO₂ in the gas phase. The inoculum can be derived from several sources ranging from commercially operated compost facilities to yard/plant matter compost. The aerobic decomposition occurs under high-solids conditions with weekly mixing of the contents to provide optimum contact between inoculum and test material and to keep the entire contents of the vessel aerobic for the duration of the test. 

ASTM D5338-98(2003) requires a setup of three replicates of each of the following: the test product, a blank that contains inoculum only, a negative control that contains polyethylene in the same form as the test material, and a positive control of thin-layer chromatography cellulose. Air (CO₂ free) will be fed to the reactors at a constant flow rate to allow accurate determination of CO₂ level in the exhaust air, and the amount of CO₂ converted from organic carbon in the test material will be calculated based on the blank reactor systems. 

Reactor vessels will be incubated in the dark or in diffused light at 58℃±2 for a maximum of 180 days.  The incubation time may be extended until gas production is not significantly greater than that of the blank during one week, or until 70% of the positive control has been degraded.  Carbon dioxide gas concentrations will be measured regularly throughout the study (at least daily) using a Ba (OH)₂ scrubbing
solution in the exhaust of the reactors. The following analyses will also be conducted on the inoculum:  pH, volatile fatty acids, percent of dry solids, percent of volatile solids, total Kjeldahl nitrogen, and ammonia nitrogen. Total organic carbon and volatile solids content of the test product will be determined prior to test initiation. 

Calculations will be performed according to the method to determine the overall percent biodegradability of the product. 

3.3 Tier 3-Toxicity Testing

The goal of Tier 3 is to evaluate the ecological impact of the test material in the final disposal medium after oxo-biodegradation testing. ASTM D6954 recommends several terrestrial and aquatic toxicity tests for determining the effect a product has on plant and animal life. 

ASTM E1440:Determines possible toxicity effects on aquatic invertebrates. Inoculum from biodegradation testing is extracted with water and filtered. One day aquatic toxicity test with Rotifer brachionus is performed. Testing is recommended if final disposal medium is aquatic in nature. 

Plant Germination:Determines possible toxicity effects on plant germination. Inoculum from biodegradation testing (before and after) is extracted with water and filtered. Various dilutions of the supernatant are prepared. Cress seed germination is compared to that of a prepared blank.  Testing is recommended if screening processing additives are used at 1% or less in the plastic. 

OECD 207:Determines possible toxicity effects on terrestrial invertebrates. Inoculum from biodegradation testing used at 65% dry solids. Inoculum applied to soil containing earthworms.  Weight change and survival are measured over the course of three months. Testing is recommended if final disposal medium is soil (very common). 

OECD 208:Determines possible toxicity effects on plant growth. Inoculum from biodegradation testing used at 65% dry solids. Generally, three plant species (two dicots, one monocot) are tested in a homogenized mixture of soil and inoculum. Plant emergence survival and growth are evaluated over the course of approximately one month. Recommended is final disposal medium is soil (very common).

Additional testing includes pH, metals analysis, and ability to hold and percolate water. All three analyses are performed before and after oxo-biodegradation testing. 

4.0 Reporting and Deliverables  

Xiamen Botest Business Services Co., Ltd will issue a report of the initial analysis within 15 business days of test completion. Should the remaining tests be performed, the final report with quality control review will be issued within 30 working days of test completion. The report will include all necessary information per method requirements.