Biodegradable plastics are one of the important contents of the current research in the polymer material community, and their degradation performance directly affects the arable soil, safety and crop growth. For this reason, various domestic industries are actively promoting the use of biodegradable plastics instead of non-degradable plastics.

Especially after the National Development and Reform Commission's opinion on strengthening plastic pollution control was released in February this year, the development and application of degradable plastics have become more important. At the same time, experts from agriculture, chemical and environmental protection industries, consumer groups and consumers have been questioning the degradability and safety of degradable plastics and biodegradable plastic products sold in the market.

Tableware made of biodegradable plastic (or compostable degradable plastic), with novel and environmentally friendly materials, is used by a large group of people, from infants and children to the elderly, plus the product way involves personal safety, which is more concerned by the society and consumers.

How to distinguish biodegradable plastic and compostable degradable plastic?

Biodegradable Plastics

Biodegradable plastics are plastics that degrade under the action of microorganisms naturally present in nature, such as soil/sand, or under special conditions such as composting, anaerobic digestion, moisture incubation, etc. They degrade under the action of naturally present microorganisms and eventually degrade completely into carbon dioxide (CO2), methane (CH4), water (H2O) and mineralized inorganic salts of the elements contained and new biomass. According to the technical requirements of GB/T20197 "Definition, Classification, Marking and Degradability Requirements of Degradable Plastics", the biodegradation rate of biodegradable plastics should be greater than 60%.

Compostable degradable plastics.

Due to the biological reaction process, compostable degradable plastics can be degraded and disintegrated, and eventually completely decomposed into carbon dioxide (CO2), water (H2O) and mineralized inorganic salts of the elements it contains and new biomass, and the heavy metal content, toxicity test and residues of the finally formed compost should be in accordance with the relevant standards. At the same time, the biodegradation rate of plastics should be above 60%.

As can be seen from the definition, the degradation principles of the above two materials are basically the same, mainly the degradation of plastics caused by the action of microorganisms, and the decomposition of materials into small molecules and new biomass. The above two materials are referred to as "biodegradable plastics" in the following.

The current application.

In this regard, the state will implement a licensing system for plastic tableware. Monopolymer PLA (polylactic acid) can be used to make tableware products made of biodegradable materials. The reality is that in physical stores and e-commerce platforms, you will see a variety of tableware products, such as "biodegradable," "compostable and degradable," "environmentally safe products" "green" and other promotional or advertising terms, bowls, plates, lunch boxes, dinner plates, etc. are marked. Many consumers, especially young people from environmentally conscious families, are more eager to buy such products, and the products are highly regarded and sought after by the market.

The main components and logo.

biodegradable utensils

In terms of tableware products currently on the market, the raw material components are mainly: PLA + starch (corn, cassava), PLA + rice husk and other fully biodegradable mixtures, such as PLA + starch (corn, cassava), PLA + rice husk; PLA + rice husk, etc., labeled biodegradable plastic containing biomass, such as polypropylene + starch, polypropylene + rice husk fiber, etc..

Inconsistent labeling of commodity descriptions. Can use microwave, there are signs marked with signs, no signs marked microwave; there are signs indicating the maximum temperature of tableware use, there are signs do not indicate the use of temperature; individual signs marked migration, such as in 70 ℃ 2h, 4% acetic acid, water migration in 70 ℃ 2h conditions, the vast majority do not mark the migration conditions and migration.

Degradability.

In theory, PLA + a variety of biological materials such as starch, bamboo powder, rice husk powder and other products made from the material should be all mixed into the raw material, in nature under the action of microorganisms, can be completely degraded into elements and inorganic salts.

Polypropylene PP, melamine MF and other biomass mixed with biomass such as corn, tapioca starch, bamboo flour, rice husk, etc. Biomass in nature can be degraded, but non-degradable plastics such as PP and MF are not degradable. The use of plastic + biomass can essentially serve to reduce the use of plastic, reduce plastic pollution, and at the same time can reduce the cost of products.

Now, the tableware containing biomass materials sold in the market, claiming "biodegradable" "fully biodegradable" "compostable degradation" is mostly just propaganda. According to GB/T20197 standard, can be called biological (composting) degradable materials, its biodegradation rate or composting biodegradation rate ≥ 60%, but the products sold on the market can hardly provide the corresponding test or experimental data.

Application safety

High temperature resistance

The microwave oven test found that: when the microwave oven power reached 500W, 3min heating, pure PLA, PLA + starch (bamboo powder), PLA + bamboo powder and other materials made of tableware products have occurred melting (see Figure 1); polypropylene + starch tableware appeared foam, deformation situation. When 300W,3min conditions, tableware heating is completed, tableware are deformed and become soft. When 200W,3min, after the heating was completed, the tableware was slightly softened and the deformation was not obvious.

Mobility.

The products were significantly precipitated in 50℃, 70℃, 4% acetic acid for 24h, and the precipitate precipitation increased with the increase of soaking times. The total amount of migration clearly exceeded the national limited food safety standard. The product is made of dense amine + biomass, which will precipitate melamine and formaldehyde under certain conditions.

From the above, the tableware containing biomass materials, must be indicated on the product whether it can be used in the microwave oven, product use temperature, conditions of use, use period and other information to guide consumers and ensure the safety of use. Conversely, such tableware such as long-term misguided, misuse, will cause greater harm to human health, especially the health of infants and children, the elderly.

Posted by: wiwili at 09:56 AM | No Comments | Add Comment
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