In the past few years, with the ecological disaster caused by the discarded plastic products, the plastics industry has experienced fear and confusion. However, under the main efforts of legislators and environmental organizations, the plastics industry is trying to explore various ways of producing controlled-life plastic products. Such products can be degraded into non-toxic, low-molecular-weight fragments through natural processes. As with any technology in its early stages, people are skeptical about whether they can control the degradability of plastics and ask a lot of questions. However, these initial issues, such as whether the degraded plastic can be completely degraded, the possible impact on the environment, and how to match with the recycling system, have already had satisfactory responses.
Degradation mechanism
The main mechanism of degradation can be thermal degradation, photooxidative degradation, hydrolytic degradation, chemical degradation, mechanical degradation, or biodegradation. These degradations cause various reactions within the polymer, such as random bond-breaking reactions, cross-linking reactions, side chain group removal reactions, depolymerization reactions, melting reactions and substitution reactions, and the like. The goal of industrial development of plastic degradation has been focused on two aspects. First, it begins with sunlight or ultraviolet (UV), and it is called light degradable. First, it begins with the biological action of microorganisms, such as fungi, bacteria, or algae, and it is called biological. degradation. The photodegradation process eventually led to the formation of a large amount of exposed base (as measured by the Tantric Index) in the plastic. These talks turned again and greatly accelerated biodegradation. Research shows that when the base is exposed, it can be oxidized to nucleic acids. The oxidized nucleic acid is quickly metabolized by microorganisms into CO2 and water.
The corresponding additive can accelerate the degradation process through these two reaction mechanisms. Biodegradable Additives Adding an additive made from corn starch can promote the biodegradation of the plastic surface, usually adding 6 to 15% (by concentration) of the final product to the additive. A large number of biodegradation processes occur at concentrations close to 50%. However, as the percentage concentration of starch increases, the physical properties also decrease. The binding of starch granules is crucial because these starch granules promote the intrusion of microorganisms when the polymer material is buried under the proper conditions of the soil. The price of starch additive is around US$1.05/lb, and the cost of low density polyethylene, linear low density polyethylene, high density polyethylene or high molecular weight high density polyethylene film will increase by 8-20%. At present, some companies have developed degradable plastics that use starch additives. These companies include: AgriTech Industries, St. Lawrence Starch and ADM. A family of fully degradable plastics that are completely different from the above types are already on the market, namely "natural polymers" such as polyhydroxybutyrate developed by ICI and "bio-plastic" starch developed by Warner-Lambert. Adding photodegradable additives containing single-component vinyl ketone polymer additives accelerates the natural degradation of plastics. When this additive is added to the base plastic polyethylene or polystyrene, the proportion thereof is required to add 5 or more additives per 100 parts of polyethylene or polystyrene. This type of additive is suitable for plastics that are required to be exposed outdoors for about three months to degrade.
The second photodegradable additive is an organic chelated metal salt such as calcium stearate or iron stearate. These additives can enhance the UV effect, so that the plastic rapidly degrades under sunlight. Other octanoate or benzophenone compounds are available from the following companies: Enviromer, DOW Chemical, DU Pont, unio Carbide, Ampacet, Princeton Polymers, Atlantic Internal Group and Rhone-Poulenc, among others. The third category of photodegradable additives uses Scott-Gilead's patented technology. The method is to mix a stabilizer and an accelerator in a one-component masterbatch. These additives can be used for LDPE, HDPE, HMW-HDPE, PP. This technology can precisely control the start time of photodegradation reaction. Once the induction period (between 2 weeks and 12 months, time is different. During which the film strength does not change) ends, the plastic rapidly and automatically accelerates the irreversible degradation reaction. The final concentration of masterbatch is 2%. This additive is particularly useful when making agricultural cover films. It can also be used to make garbage bags, fertilizer bags and retail products bags.
Plastigone Technologies supplies this additive. Photodegradable plastics, which have been degraded by sunlight, will continue to degrade when they are buried underground and have suitable environments (such as water, oxygen, and microorganisms). If this suitable environment is in a landfill, photodegradable plastics will degrade as completely as biodegradable plastics and other organics. However, the landfill site is in a dry and anaerobic environment, and organic matter will not have any degradation reaction. People OJ often intentionally build this kind of dump to prevent subsidence and the occurrence of biogas, seepage of sewage and other ills. Various tests have been conducted using various types and colors of pigment inks in combination with degradation promoting additives. However, the general rules for the accelerated degradation of pigments and additives have not yet been explored to predict which pigments can promote degradation. Because some pigments can speed up this process, some pigments may slow down the process. The concentration of the pigment in the film, the chemical composition (especially the metal compound), and the opacity or the degree of light and thickness of the film may all affect the photodegradation speed of the plastic. The price of photodegradable additives ranges from $1.35/lb to $3.2/lb, and the percentage reduction may vary from 2-6%. Mixed additives Some manufacturers mix photodegradable components with biodegradable components (for example, an organometallic complex oxidizing agent and starch granules) to produce a faster degradation. The product without losing its physical properties, but the use of pure biodegradable additives will have the opposite result. In these products, starch does not participate in the initial degradation process. Garbage bags, fertilizer bags and retailer bags can be made using this blended additive. The price range of mixed photodegradable additives is 1. US$50/lb to US$2.00/lb is produced by manufacturers Ampacet and St. Courtesy of Lawrence Starch. Regulations and Inspections There are more than 250 federal, state and local regulatory provisions in the United States concerning the manufacture, sale and disposal of plastics. Some states also provide that only degradable plastics can be used to make certain retailer bags, such as plastic carrying bags.
A Florida regulatory requirement (the law was effective in 1990.1.1) that plastics must be degraded within 120 days (according to ASTM's stringent test standards), and their degradation products were subjected to acute and chronic toxicity tests, respectively, to obtain non-toxic proof. ASTM's D-20 Plastics Committee has set up a D-20.96 sub-agency. This chapter will introduce the standard definition of degradable plastics, testing procedures and environmental toxicity assessment methods. According to ASTM D-882-83: If the plastic becomes brittle, ie, the elongation at break is 5% or less, it can be confirmed as "degradable plastic." The photodegradability test method is: ASTM D-1435-85: outdoor weathering test; ASTM D-4364-84: accelerating outdoor weathering test using enhanced natural light; ASTM D-2565-89: win arc light exposure instrument; ASTM D-4329-84: Fluorescent UV (Q plate type).
For the photodegradation and toxicity of biodegradable plastic degradation products, universal tests have been carried out. In addition, the long-term and short-term toxicity of photodegradable agricultural coatings to soil, groundwater, and growing plants is also examined. The U.S. Food and Drug Administration (FDA) has nothing to do with the packaging of degradable plastics in food packaging. Recycling Recyclable biodegradable plastics are mainly used for packaging materials. Waste was rolled up and thrown into the heap of human waste. At present, these waste materials have not yet been economically recycled and reused. Photodegradable plastics can enter clean recycling systems along with clean waste plastics. Because standard stabilizers or antioxidants are used during processing, any degradation additives present will be inactivated. The final product recycled by plastic is a bulk product that has no UV absorption capability. Biodegradable plastics with a high percentage of starch content may not be easily regenerated with other used mixed plastics.
Degradation mechanism
The main mechanism of degradation can be thermal degradation, photooxidative degradation, hydrolytic degradation, chemical degradation, mechanical degradation, or biodegradation. These degradations cause various reactions within the polymer, such as random bond-breaking reactions, cross-linking reactions, side chain group removal reactions, depolymerization reactions, melting reactions and substitution reactions, and the like. The goal of industrial development of plastic degradation has been focused on two aspects. First, it begins with sunlight or ultraviolet (UV), and it is called light degradable. First, it begins with the biological action of microorganisms, such as fungi, bacteria, or algae, and it is called biological. degradation. The photodegradation process eventually led to the formation of a large amount of exposed base (as measured by the Tantric Index) in the plastic. These talks turned again and greatly accelerated biodegradation. Research shows that when the base is exposed, it can be oxidized to nucleic acids. The oxidized nucleic acid is quickly metabolized by microorganisms into CO2 and water.
The corresponding additive can accelerate the degradation process through these two reaction mechanisms. Biodegradable Additives Adding an additive made from corn starch can promote the biodegradation of the plastic surface, usually adding 6 to 15% (by concentration) of the final product to the additive. A large number of biodegradation processes occur at concentrations close to 50%. However, as the percentage concentration of starch increases, the physical properties also decrease. The binding of starch granules is crucial because these starch granules promote the intrusion of microorganisms when the polymer material is buried under the proper conditions of the soil. The price of starch additive is around US$1.05/lb, and the cost of low density polyethylene, linear low density polyethylene, high density polyethylene or high molecular weight high density polyethylene film will increase by 8-20%. At present, some companies have developed degradable plastics that use starch additives. These companies include: AgriTech Industries, St. Lawrence Starch and ADM. A family of fully degradable plastics that are completely different from the above types are already on the market, namely "natural polymers" such as polyhydroxybutyrate developed by ICI and "bio-plastic" starch developed by Warner-Lambert. Adding photodegradable additives containing single-component vinyl ketone polymer additives accelerates the natural degradation of plastics. When this additive is added to the base plastic polyethylene or polystyrene, the proportion thereof is required to add 5 or more additives per 100 parts of polyethylene or polystyrene. This type of additive is suitable for plastics that are required to be exposed outdoors for about three months to degrade.
The second photodegradable additive is an organic chelated metal salt such as calcium stearate or iron stearate. These additives can enhance the UV effect, so that the plastic rapidly degrades under sunlight. Other octanoate or benzophenone compounds are available from the following companies: Enviromer, DOW Chemical, DU Pont, unio Carbide, Ampacet, Princeton Polymers, Atlantic Internal Group and Rhone-Poulenc, among others. The third category of photodegradable additives uses Scott-Gilead's patented technology. The method is to mix a stabilizer and an accelerator in a one-component masterbatch. These additives can be used for LDPE, HDPE, HMW-HDPE, PP. This technology can precisely control the start time of photodegradation reaction. Once the induction period (between 2 weeks and 12 months, time is different. During which the film strength does not change) ends, the plastic rapidly and automatically accelerates the irreversible degradation reaction. The final concentration of masterbatch is 2%. This additive is particularly useful when making agricultural cover films. It can also be used to make garbage bags, fertilizer bags and retail products bags.
Plastigone Technologies supplies this additive. Photodegradable plastics, which have been degraded by sunlight, will continue to degrade when they are buried underground and have suitable environments (such as water, oxygen, and microorganisms). If this suitable environment is in a landfill, photodegradable plastics will degrade as completely as biodegradable plastics and other organics. However, the landfill site is in a dry and anaerobic environment, and organic matter will not have any degradation reaction. People OJ often intentionally build this kind of dump to prevent subsidence and the occurrence of biogas, seepage of sewage and other ills. Various tests have been conducted using various types and colors of pigment inks in combination with degradation promoting additives. However, the general rules for the accelerated degradation of pigments and additives have not yet been explored to predict which pigments can promote degradation. Because some pigments can speed up this process, some pigments may slow down the process. The concentration of the pigment in the film, the chemical composition (especially the metal compound), and the opacity or the degree of light and thickness of the film may all affect the photodegradation speed of the plastic. The price of photodegradable additives ranges from $1.35/lb to $3.2/lb, and the percentage reduction may vary from 2-6%. Mixed additives Some manufacturers mix photodegradable components with biodegradable components (for example, an organometallic complex oxidizing agent and starch granules) to produce a faster degradation. The product without losing its physical properties, but the use of pure biodegradable additives will have the opposite result. In these products, starch does not participate in the initial degradation process. Garbage bags, fertilizer bags and retailer bags can be made using this blended additive. The price range of mixed photodegradable additives is 1. US$50/lb to US$2.00/lb is produced by manufacturers Ampacet and St. Courtesy of Lawrence Starch. Regulations and Inspections There are more than 250 federal, state and local regulatory provisions in the United States concerning the manufacture, sale and disposal of plastics. Some states also provide that only degradable plastics can be used to make certain retailer bags, such as plastic carrying bags.
A Florida regulatory requirement (the law was effective in 1990.1.1) that plastics must be degraded within 120 days (according to ASTM's stringent test standards), and their degradation products were subjected to acute and chronic toxicity tests, respectively, to obtain non-toxic proof. ASTM's D-20 Plastics Committee has set up a D-20.96 sub-agency. This chapter will introduce the standard definition of degradable plastics, testing procedures and environmental toxicity assessment methods. According to ASTM D-882-83: If the plastic becomes brittle, ie, the elongation at break is 5% or less, it can be confirmed as "degradable plastic." The photodegradability test method is: ASTM D-1435-85: outdoor weathering test; ASTM D-4364-84: accelerating outdoor weathering test using enhanced natural light; ASTM D-2565-89: win arc light exposure instrument; ASTM D-4329-84: Fluorescent UV (Q plate type).
For the photodegradation and toxicity of biodegradable plastic degradation products, universal tests have been carried out. In addition, the long-term and short-term toxicity of photodegradable agricultural coatings to soil, groundwater, and growing plants is also examined. The U.S. Food and Drug Administration (FDA) has nothing to do with the packaging of degradable plastics in food packaging. Recycling Recyclable biodegradable plastics are mainly used for packaging materials. Waste was rolled up and thrown into the heap of human waste. At present, these waste materials have not yet been economically recycled and reused. Photodegradable plastics can enter clean recycling systems along with clean waste plastics. Because standard stabilizers or antioxidants are used during processing, any degradation additives present will be inactivated. The final product recycled by plastic is a bulk product that has no UV absorption capability. Biodegradable plastics with a high percentage of starch content may not be easily regenerated with other used mixed plastics.
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