Biodegradable plastics have been advertised as one solution to the plastic pollution problem bedeviling the world, but today&#;s &#;compostable&#; plastic bags, utensils and cup lids don&#;t break down during typical composting and contaminate other recyclable plastics, creating headaches for recyclers. Most compostable plastics, made primarily of the polyester known as polylactic acid, or PLA, end up in landfills and last as long as forever plastics.
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University of California, Berkeley, scientists have now invented a way to make these compostable plastics break down more easily, with just heat and water, within a few weeks, solving a problem that has flummoxed the plastics industry and environmentalists.
&#;People are now prepared to move into biodegradable polymers for single-use plastics, but if it turns out that it creates more problems than it&#;s worth, then the policy might revert back,&#; said Ting Xu, UC Berkeley professor of materials science and engineering and of chemistry. &#;We are basically saying that we are on the right track. We can solve this continuing problem of single-use plastics not being biodegradable.&#;
Xu is the senior author of a paper describing the process that will appear in this week&#;s issue of the journal Nature.
The new technology should theoretically be applicable to other types of polyester plastics, perhaps allowing the creation of compostable plastic containers, which currently are made of polyethylene, a type of polyolefin that does not degrade. Xu thinks that polyolefin plastics are best turned into higher value products, not compost, and is working on ways to transform recycled polyolefin plastics for reuse.
The new process involves embedding polyester-eating enzymes in the plastic as it&#;s made. These enzymes are protected by a simple polymer wrapping that prevents the enzyme from untangling and becoming useless. When exposed to heat and water, the enzyme shrugs off its polymer shroud and starts chomping the plastic polymer into its building blocks &#; in the case of PLA, reducing it to lactic acid, which can feed the soil microbes in compost. The polymer wrapping also degrades.
The process eliminates microplastics, a byproduct of many chemical degradation processes and a pollutant in its own right. Up to 98% of the plastic made using Xu&#;s technique degrades into small molecules.
One of the study&#;s co-authors, former UC Berkeley doctoral student Aaron Hall, has spun off a company to further develop these biodegradable plastics.
Plastics are designed not to break down during normal use, but that also means they don&#;t break down after they&#;re discarded. The most durable plastics have an almost crystal-like molecular structure, with polymer fibers aligned so tightly that water can&#;t penetrate them, let alone microbes that might chew up the polymers, which are organic molecules.
Xu&#;s idea was to embed nanoscale polymer-eating enzymes directly in a plastic or other material in a way that sequesters and protects them until the right conditions unleash them. In , she showed how this works in practice. She and her UC Berkeley team embedded in a fiber mat an enzyme that degrades toxic organophosphate chemicals, like those in insecticides and chemical warfare agents. When the mat was immersed in the chemical, the embedded enzyme broke down the organophosphate.
Her key innovation was a way to protect the enzyme from falling apart, which proteins typically do outside of their normal environment, such as a living cell. She designed molecules she called random heteropolymers, or RHPs, that wrap around the enzyme and gently hold it together without restricting its natural flexibility. The RHPs are composed of four types of monomer subunits, each with chemical properties designed to interact with chemical groups on the surface of the specific enzyme. They degrade under ultraviolet light and are present at a concentration of less than 1% of the weight of the plastic &#; low enough not to be a problem.
For the research reported in the Nature paper, Xu and her team used a similar technique, enshrouding the enzyme in RHPs and embedding billions of these nanoparticles throughout plastic resin beads that are the starting point for all plastic manufacturing. She compares this process to embedding pigments in plastic to color them. The researchers showed that the RHP-shrouded enzymes did not change the character of the plastic, which could be melted and extruded into fibers like normal polyester plastic at temperatures around 170 degrees Celsius, or 338 degrees Fahrenheit.
To trigger degradation, it was necessary only to add water and a little heat. At room temperature, 80% of the modified PLA fibers degraded entirely within about one week. Degradation was faster at higher temperatures. Under industrial composting conditions, the modified PLA degraded within six days at 50 degrees Celsius (122 F). Another polyester plastic, PCL (polycaprolactone), degraded in two days under industrial composting conditions at 40 degrees Celsius (104 F). For PLA, she embedded an enzyme called proteinase K that chews PLA up into molecules of lactic acid; for PCL, she used lipase. Both are inexpensive and readily available enzymes.
&#;If you have the enzyme only on the surface of the plastic, it would just etch down very slowly,&#; Xu said. &#;You want it distributed nanoscopically everywhere so that, essentially, each of them just needs to eat away their polymer neighbors, and then the whole material disintegrates.&#;
The quick degradation works well with municipal composting, which typically takes 60 to 90 days to turn food and plant waste into usable compost. Industrial composting at high temperatures takes less time, but the modified polyesters also break down faster at these temperatures.
Xu suspects that higher temperatures make the enshrouded enzyme move around more, allowing it to more quickly find the end of a polymer chain and chew it up and then move on to the next chain. The RHP-wrapped enzymes also tend to bind near the ends of polymer chains, keeping the enzymes near their targets.
The modified polyesters do not degrade at lower temperatures or during brief periods of dampness, she said. A polyester shirt made with this process would withstand sweat and washing at moderate temperatures, for example. Soaking in water for three months at room temperature did not cause the plastic to degrade.
Soaking in lukewarm water does lead to degradation, as she and her team demonstrated.
&#;It turns out that composting is not enough &#; people want to compost in their home without getting their hands dirty, they want to compost in water,&#; she said. &#;So, that is what we tried to see. We used warm tap water. Just warm it up to the right temperature, then put it in, and we see in a few days it disappears.&#;
Xu is developing RHP-wrapped enzymes that can degrade other types of polyester plastic, but she also is modifying the RHPs so that the degradation can be programmed to stop at a specified point and not completely destroy the material. This might be useful if the plastic were to be remelted and turned into new plastic.
The project is in part supported by the Department of Defense&#;s Army Research Office, an element of the U.S. Army Combat Capabilities Development Command&#;s Army Research Laboratory.
&#;These results provide a foundation for the rational design of polymeric materials that could degrade over relatively short timescales, which could provide significant advantages for Army logistics related to waste management,&#; said Stephanie McElhinny, Ph.D., program manager with the Army Research Office. &#;More broadly, these results provide insight into strategies for the incorporation of active biomolecules into solid-state materials, which could have implications for a variety of future Army capabilities, including sensing, decontamination and self-healing materials.&#;
Xu said that programmed degradation could be the key to recycling many objects. Imagine, she said, using biodegradable glue to assemble computer circuits or even entire phones or electronics, then, when you&#;re done with them, dissolving the glue so that the devices fall apart and all the pieces can be reused.
&#;It is good for millennials to think about this and start a conversation that will change the way we interface with Earth,&#; Xu said. &#;Look at all the wasted stuff we throw away: clothing, shoes, electronics like cellphones and computers. We are taking things from the earth at a faster rate than we can return them. Don&#;t go back to Earth to mine for these materials, but mine whatever you have, and then convert it to something else.&#;
Co-authors of the paper include Christopher DelRe, Yufeng Jiang, Philjun Kang, Junpyo Kwon, Aaron Hall, Ivan Jayapurna, Zhiyuan Ruan, Le Ma, Kyle Zolkin, Tim Li and Robert Ritchie of UC Berkeley; Corinne Scown of Berkeley Lab; and Thomas Russell of the University of Massachusetts in Amherst. The work was funded primarily by the U.S. Department of Energy (DE-AC02-05-CH), with assistance from the Army Research Office and UC Berkeley&#;s Bakar Fellowship program.
Manufacturing #biodegradable garbage bags involves a complex production process that includes several stages. Basically, the production process is very similar to our traditional plastic #garbagebags and #carrierbags.
Here is a detailed description of the typical production process for biodegradable garbage bags and plastic garbage bags:
1. Material Selection:
The selection of the appropriate biodegradable plastic resin is a critical step in determining the characteristics of garbage bags. In the case of traditional #trashbags, High-density polyethylene (HDPE) is often chosen for its strength and durability, while low-density polyethylene (LDPE) is preferred for its flexibility.
However, at UPPBIO, we prioritize #sustainable solutions and customize our approach based on our clients' market demands.
At UPPBIO, we offer a range of biodegradable materials to meet our client's specific needs. We carefully select raw biodegradable materials, such as plant-based #PLA (Polylactic Acid) or enzyme-based bioplastics. These materials not only provide the necessary functionality but also offer a more environmentally friendly alternative to traditional plastics.
We also incorporate recycled plastic resins whenever possible according to the client&#;s requirements. The incorporation of #recycledplastics in our production process aligns with our goal of creating eco-friendly garbage bags that minimize #environmental impact.
2. Resin Preparation:
To initiate the production process, biodegradable plastic resins in pellet form are carefully chosen and fed into a hopper. The pellets are then transferred into an extruder, which consists of a heated barrel with a rotating screw. Inside the extruder, the pellets are heated, melted, and mixed to form a homogeneous molten mass.
The color of garbage bags is typically achieved by incorporating colorants during this step. How the color of garbage bags is created?
Select Color Masterbatch First. Then mix the color masterbatch with the base resin like plant-based resin in specific proportions. This ensures the colorant is evenly distributed throughout the plastic material.
3. Film Extrusion:
The molten plastic is extruded through a flat die, resulting in a continuous tube of #bioplastic film. The diameter and thickness of the #film are determined by the size and shape of the die. Cooling mechanisms, such as air or water, are employed to solidify the molten plastic and maintain its desired properties.
The film extrusion process is pivotal in determining the quality and attributes of the extruded plastic film. The core components of a Film Extrusion machine comprise the Hopper, Barrel, Screw, Die, Cooling Mechanism, and Take-Up System.
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At UPPBIO, we prioritize the utilization of professional and high-end film extrusion machines to ensure the exceptional quality required to meet our client's needs. These machines are equipped with advanced core parts that have been meticulously designed and engineered to optimize the extrusion process.
4. Bag Forming:
The printed #biobased plastic film passes through a series of rollers and folders, which fold it into a continuous tube with overlapping edges. Heat is applied to seal the edges together, creating a bottom seal for the bags. Simultaneously, the top portion of the tube remains open for later filling.
5. Printing:
The biodegradable plastic film may undergo a printing process to incorporate brand logos, product information, or graphics. Flexographic or rotogravure printing techniques are commonly employed. Flexographic printing uses flexible rubber or photopolymer plates, while rotogravure printing involves engraved cylinders. Ink is transferred onto the film through these plates or cylinders, resulting in high-quality and durable prints.
At UPPBIO, we can customize your own printing with a custom logo or other information. We have our own printing machines and also work with some sub-contracted printing companies to meet different clients&#; demands.
6. Cutting and Sealing:
In the bag-making machine, the continuous tube of plastic film is fed into a cutting and sealing section. Sharp blades or rotary cutters precisely cut the tube into individual bag lengths, while simultaneously sealing the sides to create the bag shape. Advanced machines incorporate sensors to ensure accurate cutting and sealing.
At UPPBIO, we recognize that different types of garbage bags require specific bag-making machines to ensure precise cutting and sealing processes. Our manufacturing capabilities enable us to produce a diverse range of garbage bags with varying styles and functionalities.
We offer a wide selection of garbage bags, including #flattop garbage bags, star-sealed garbage bags, #drawstring garbage bags, extra large heavy-duty garbage bags, small #pet poop bags, and medical #wastebags.
7. Handle Attachment (Optional):
cutting the handle
drawstring handle making
If desired, plastic garbage bags can be equipped with handles to facilitate easy carrying and disposal. Various techniques are employed for handle attachment, such as heat sealing, die-cutting, or attaching pre-made handles. Heat sealing involves applying heat and pressure to affix handles to the bags, while die-cutting creates slots through which handles can be inserted.
8. Quality Control:
Quality control measures are implemented throughout the production process. Inspections are conducted to ensure proper sealing, accurate dimensions, and consistent printing quality. Random samples may be collected and subjected to tests for properties like tensile strength, puncture resistance, and film thickness. Defective bags are rejected or rectified to maintain high-quality standards.
At UPPBIO, we prioritize the highest standards of quality throughout the entire production process. Rigorous quality control measures are implemented to ensure that our garbage bags meet and exceed customer expectations. We have established comprehensive quality control protocols to monitor various aspects of production, ensuring that every bag leaving our facility meets stringent quality standards.
9. Packaging and Distribution:
Once the #biodegradablegarbagebags have passed quality control checks, they are packaged in suitable quantities, such as rolls or stacks. Packaging materials may include cardboard boxes, plastic bags, or shrink wrapping, depending on the intended distribution and market requirements. Labeling and barcoding are applied to facilitate identification and inventory management.
This comprehensive description provides a more detailed overview of the production process for biodegradable garbage bags, incorporating additional techniques and steps involved in each stage.
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&#;&#;&#;&#;&#;&#; is a leading manufacturer specializing in producing an extensive selection of biodegradable and #compostable bags to meet various needs and requirements. The range of #bags includes options for different usages, such as food waste disposal, shopping, and packaging.
UPPBIO's eco-friendly products are popular in various countries, including the United States, Mexico, France, German, Italy, the UK, etc.
We take pride in using cutting-edge biodegradable materials to create eco-friendly products that are 100% compostable. Our products are ready for certification from renowned organizations such as BPI and TUV Austria, ensuring that our products meet global quality standards.
At UPPBIO, we are committed to providing sustainable and reliable packaging solutions that benefit both our customers and the environment.
Contact us at sales@uppbio for more details about biodegradable bags.
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