Degradability inspection method of degradable plastics

Degradability inspection method of degradable plastics

Time:2021-12-25

Recycling and disposal of plastics after waste has become a hot spot, but it is difficult for plastics to be completely recycled. How to manage and dispose of waste plastics is a worldwide concern. Plastic recycling technologies include material recycling (mechanical recycling, chemical or monomer recycling, biological or organic recycling) and energy recycling (heat, steam or electrical energy as substitutes for fossil fuels and other fuel resources). In addition, some hard-to-recycle plastics, such as fishing gear, agricultural coverings, and water-soluble polymers, often leak into the environment from the closed garbage disposal recycling system; some products used in the ocean are made of plastic ( Such as fishing gear), these products are sometimes lost or intentionally placed in the marine environment; the products or packaging materials sent to the composting facility should be biodegradable (biodegradable) as much as possible. The use of biodegradable plastics is a valuable recyclable option (biological or organic recycling). Therefore, the use of biodegradable materials is one of the effective ways to solve such environmental problems. It is important to determine the possible biodegradability of these materials and to obtain indicators of their biodegradability in the natural environment.

Today, we have reorganized and compared the relevant information on the “degradation performance test methods, test principles, degradation cycles and scope of application of different degradable plastics”, in order to allow more readers to clearly understand the relevant testing standards and standards in the field of degradable plastics. Require.

Comparison of test methods for the degradation performance of different degradable plastics, test principles, degradation cycles and application scope

This article will analyze and compare the types of degradable plastics, based on standard numbers, standard names, test principles, degradation cycles, and scope of application to readers.

Degradability inspection method of degradable plastics

Degradation of freshwater environment

GB/T 19276.1 Determination of the final aerobic biodegradability of materials in aqueous culture medium. The method of measuring the oxygen demand in a closed respirometer is used.

Test principle:
Use aerobic microorganisms to determine the biodegradation rate of materials in an aqueous system. The test mixture contains an inorganic culture medium, test materials with an organic carbon concentration ranging from 100 mg/L to 2 000 mg/L (the only source of carbon and energy), and activated sludge or compost or activated soil suspension Of the culture medium. This mixture is stirred and incubated in a sealed flask in the respirometer for a certain period of time, and the test period cannot exceed 6 months. Use a suitable absorber above the flask to absorb the released carbon dioxide and measure the biochemical oxygen demand (BOD). The level of biodegradation is calculated by the ratio of biochemical oxygen demand (BOD) and theoretical oxygen demand (ThOD), expressed as a percentage.
Degradation cycle: 180 days

Scope of application:
Natural and (or) synthetic polymers, copolymers or their mixtures;
Plastic materials containing additives such as plasticizers, pigments or other compounds;
Water-soluble polymer.

GB/T 19276.2 Determination of the final aerobic biodegradability of materials in aqueous culture medium. The method of measuring the released carbon dioxide is adopted.

Test principle:
Use aerobic microorganisms in an aqueous system to determine the biodegradation rate of test materials. The test mixture contains an inorganic culture medium, test materials with an organic carbon concentration ranging from 100 mg/L to 2 000 mg/L (the only source of carbon and energy), and activated sludge or compost or activated soil suspension Of the culture medium. The mixture is stirred in the test flask and passed through to remove carbon dioxide air. The test period depends on the biodegradability of the test material, but cannot exceed 6 months. The carbon dioxide released when the microorganisms decompose the material can be measured by a suitable method. The degree of biodegradation is calculated by the ratio of the amount of carbon dioxide released and the theoretical amount of carbon dioxide released (ThCO2), expressed as a percentage.
Degradation cycle: 180 days

Scope of application:
Natural and (or) synthetic polymers, copolymers or their mixtures;
Plastic materials containing additives such as plasticizers, pigments or other compounds;
Water-soluble polymer.

GB/T 32106 Determination of the final anaerobic biodegradability of plastics in aqueous culture broth by measuring biogas products

Test principle:
This standard is to determine the biodegradability of plastics in an aqueous culture medium under anaerobic conditions. First, the digested sludge is washed before use to make it contain a very small amount of inorganic carbon (IC) and diluted to a total dry solid concentration of 1 g/L to 3 g/L. Incubate the test materials and digested sludge with an organic carbon (OC) concentration of 20 mg/L~200 mg/L in a closed container at a temperature of 35 ℃ ± 2 ℃ under anaerobic conditions for a period of time (usually no more than 60 days) . Under this condition, the test material will biologically decompose into carbon dioxide (CO2) and methane (CH4). The production of CO2 and CH4 will cause the pressure or volume of the test container to increase, so the release can be obtained by measuring the increase in pressure or volume. The amount of biogas. The percentage of the above total carbon converted into biogas and inorganic carbon and the total carbon contained in the test material itself (which can be calculated by measurement or molecular formula) is the biodegradation percentage of the test material.
Degradation cycle: 60 days

Scope of application:
Natural and (or) synthetic polymers, copolymers or their mixtures;
Plastic materials containing additives such as plasticizers, pigments or other compounds;
Water-soluble polymer.

Compostable and degradable


Compostable for industrialization GB/T 28206

GB/T 19277.1 Determination of the final aerobic biodegradability of materials under controlled composting conditions. Method for measuring released carbon dioxide. Part 1: General method

Test principle:
This method is used to determine the final aerobic biodegradability and disintegration degree of the test material under simulated intense aerobic composting conditions. The inoculum used is from a stable, mature compost, if possible, from the compost of the organic matter in municipal solid waste. The test material is mixed with the inoculum and introduced into the static compost container. In this container, the mixture undergoes intense aerobic composting at a specified temperature, oxygen concentration and humidity. The test period does not exceed 6 months. In the process of aerobic biological decomposition of test materials, carbon dioxide, water, mineralized inorganic salts and new biomass are the final biological decomposition products.
During the test, continuously monitor and regularly measure the carbon dioxide produced by the test container and the blank container, and accumulate the amount of carbon dioxide produced. The ratio of the actual amount of carbon dioxide produced by the test material in the test to the theoretical amount of carbon dioxide that the material can produce is the biodegradation percentage.
Degradation cycle: 180 days

Scope of application:
Organic polymer materials such as plastics

GB/T 19277.2 Determination of the final aerobic biodegradability of materials under controlled composting. Method for measuring released carbon dioxide. Part 2: Determination of carbon dioxide released under laboratory conditions by gravimetric method

Test principle:
The purpose is to use a small reactor to determine the final biodegradability of the test material. By controlling the humidity, oxygen permeation rate and temperature of the compost container, the biodegradation rate of the test material under the condition of decomposed compost was determined and calculated. The test material is a mixture of inoculum from decomposed compost and inert material such as sea sand. By comparing the amount of carbon dioxide released with the theoretical amount of carbon dioxide released (ThCO2), the biodegradation rate of the material (expressed as a percentage) is obtained. The test ends when the biodegradation reaches a plateau. The standard time for termination is 45 days, but the test can also last up to 180 days.
Degradation cycle: 45 days; the longest can be 180 days

Scope of application:

Natural and/or synthetic polymers, copolymers and their mixtures;
Plastics containing additives such as plasticizers and pigments;
Water-soluble polymer
Under the experimental conditions, the material that does not inhibit the activity of microorganisms in the inoculum.

GB/T 19811 defines the degree of disintegration of plastic materials under the conditions of composting pilot test

Test principle:
This standard is used to determine the degree of disintegration of plastic materials in aerobic composting tests under defined pilot conditions. The test methods specified in this standard can be used to determine the impact of test materials during the composting process and the quality of the compost obtained, but they cannot be used to determine the aerobic biodegradability of test materials. The test materials are mixed with fresh biomass waste in a precise ratio and placed in a defined composting environment. Microbial populations that are ubiquitous in nature naturally trigger the composting process, usually after about 12 weeks. The disintegration of the test material was evaluated by the ratio of the amount of test material fragments on the 2 mm test sieve to the total dry solids.
Degradation cycle: 12 weeks; or the actual cycle of composting

Scope of application:
Organic polymer materials such as plastics

OECD 208 Phytotoxicity test requirements

Test principle:
It aims to assess the potential effects of chemicals on the germination and growth of seeds. In the evaluation of compostable plastics, it is mainly to evaluate the eco-toxicity evaluation of compost after biodegradable materials are composted. During the experiment, the average survival rate of germinated seedlings reached at least 90%;
Degradation cycle: plant growth time

Degradable by soil

GB/T 22047 Determination of the final aerobic biodegradability of plastic materials in soil Use the method of measuring the oxygen demand in the airtight respirometer or measuring the released carbon dioxide

Test principle:
This standard specifies the method for determining the final aerobic biodegradability of plastic materials in the soil by measuring the oxygen demand in the airtight respirometer or the amount of carbon dioxide released. The biodegradation rate is calculated by the ratio of the biochemical oxygen demand (BOD) and the theoretical oxygen demand (ThOD) or the ratio of the amount of carbon dioxide released and the theoretical amount of carbon dioxide released (ThCO2), and the result is expressed as a percentage.
Degradation cycle: 180 days

Scope of application:
Natural and/or synthetic polymers, copolymers and their mixtures;
Plastics containing additives such as plasticizers and pigments;
Water-soluble polymer
Under the experimental conditions, the material that does not inhibit the activity of microorganisms in the inoculum.

Marine environment degradation

ISO 18830 Plastics. Determination of the final aerobic biodegradability of non-floating plastic materials at the seawater sedimentation interface. Method by measuring oxygen consumption in a closed respirometer


Test principle:
Plastic products are directly discarded or flow into the pelagic area (free water) with fresh water. Then, affected by material density, tides, ocean currents, and ocean folds, they may sink to the sub-coast and reach the surface of the seabed. Many biodegradable plastics with a density greater than 1 tend to sink to the seafloor. From the surface (the interface with seawater) to the deep layer, the state of the sediments changes from aerobic to anoxic to anaerobic, showing a sharply changing oxygen gradient. This standard specifies a test method to determine the degree and rate of aerobic biodegradation of plastic materials at the seawater sedimentation interface at the junction of seawater and seabed by measuring the oxygen demand in a closed respirometer. The determination of aerobic biodegradation can also be achieved by measuring the amount of carbon dioxide released. This method is a simulation of the habitat environment of different seawater sedimentation areas in the ocean under laboratory conditions, such as the benthic zone (light zone) that can be irradiated by sunlight called the sub-coastal zone in marine science. The level of biodegradation is calculated by the ratio of biochemical oxygen demand (BOD) to theoretical oxygen demand (ThOD), expressed as a percentage.
Degradation cycle: 2 years

Scope of application:
Non-floating plastic material

ISO 19679 Plastics-Determination of the final aerobic biodegradability of non-floating plastic materials at the seawater sedimentation interface. Method by measuring the release of carbon dioxide

Test principle:
This standard specifies a test method for measuring the amount of carbon dioxide released to determine the degree and rate of aerobic biodegradation of plastic materials when they deposit on the seawater sedimentation interface on the marine sandy sediment at the junction of seawater and the seabed. This method is also applicable to other solid materials. Use appropriate analytical methods to determine the carbon dioxide released during microbial degradation. The biological decomposition rate of the material (expressed as a percentage) is obtained by the ratio of the amount of carbon dioxide released to the theoretical amount of carbon dioxide released (ThCO2).
Degradation cycle: 2 years
Scope of application:
Non-floating plastic material

ISO 22404 Plastics-Determination of the ultimate aerobic biodegradability of non-floating materials exposed to marine sediments Method by analysis of released carbon dioxide

Test principle:
A laboratory test method used to determine the degree and rate of aerobic biodegradation of plastic materials. The biodegradation rate is determined by measuring the amount of CO2 released by plastic materials when they come into contact with marine sediments from the sandy tidal zone. Use appropriate analytical methods to measure the carbon dioxide released during microbial degradation. The biodegradation rate is determined by the ratio of the amount of carbon dioxide released and the theoretical amount (ThCO2), expressed as a percentage.
Degradation cycle: 2 years
Scope of application:
Non-floating plastic material

Anaerobic digestion and degradation of sludge

Determination of the final anaerobic biodegradation rate of materials in the GB/T 38737 plastic controlled sludge digestion system Using the method of measuring the released biogas

Test principle:
Provides a method to evaluate the anaerobic biodegradability of plastics in a controlled sludge anaerobic digestion system, the solid content of the system is not more than 15%. This system is more common in sludge sewage, livestock manure or garbage disposal plants. This method aims to determine the conversion rate of organic carbon in materials into biogases such as carbon dioxide (CO2) and methane (CH4).
Degradation cycle:
The test period is generally 60 days. The test period can be shortened or extended until it reaches the stable stage of decomposition, but not more than 90 days.

Scope of application:
Natural and/or synthetic polymers, copolymers and their mixtures;
Plastics containing additives such as plasticizers and pigments;
Water-soluble polymer
Under the experimental conditions, the material that does not inhibit the activity of microorganisms in the inoculum.

High solid anaerobic digestion and degradation

Determination of the final anaerobic biodegradability of GB/T 33797 plastics under high solids composting conditions. Method of analyzing and determining the release of biogas

Test principle:
Provides a method for evaluating the biodegradability of plastics under anaerobic conditions by measuring the amount of biogas released under high solids anaerobic digestion conditions. This method simulates typical anaerobic digestion conditions with municipal organic solid waste. The test material was exposed to the inoculum of household waste treated by anaerobic digestion in the test room. Anaerobic decomposition occurs in an environment with high solids content (total dry solids content greater than 20%) and is left unmixed. This test method is used to determine the carbon content in the test material and its conversion into carbon dioxide and methane percentage.
Degradation cycle:
At 15 days, if the biodegradation phenomenon is still obvious at 15 days, the culture period can be extended until the biodegradation of the test material reaches a plateau.

Scope of application:
Organic polymer materials such as plastics

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