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In addition to using renewable raw materials, emission of greenhouse gases during production is also lower. Because carbon dioxide is consumed during the growth of corn, the net greenhouse gas emission of the overall PLA production process can even be considered negative.
Ongoing studies on the use of alternative carbohydrate sources, such as agricultural and household wastes, even suggest that PLA production can lead to a decrease in overall solid waste.
PLA is a thermoplastic , meaning it will turn into a liquid in its melting point of to Celsius. A nifty feature of thermoplastics is that they can be heated, set upon cooling, and reheated again to form other shapes without any degradation.
In contrast, a thermosetting plastic such as epoxy or melamine can only be heated and molded once, but the resulting product can no longer be reheated as it will just burn.
This property of PLA makes it a desirable material for recycling. PLA can be broken down to its original monomers by a thermal de-polymerization process or by hydrolysis.
The resulting monomer solution can be purified and used for subsequent PLA production without any loss of quality.
Should a material made from PLA be incinerated, no toxic fumes will be generated. The ease with which PLA melts makes it a material that is easy to work with.
However, this also renders PLA unsuitable for high temperature applications such as containers made for holding hot liquids. A material made from PLA may even show signs of getting soft or deforming on a hot summer day.
PLA packaging material has been found to be more permeable to moisture and oxygen compared to other plastics, which may result in faster food spoilage.
Applications where toughness and impact resistance are critical may also be inappropriate for the more brittle PLA.
PLA can be processed via extrusion, injection molding, casting, blown film, thermoforming, and fiber spinning to form useful and versatile products.
It is typically available in the market as thin films for thermoforming, plastic pellets for injection molding, or 3D printable filaments.
A variety of colors of PLA is available. Sturdier versions of PLA have been developed by mixing different PLA isomers, resulting in higher melting temperature higher by 40 to 50 Celsius and increased mechanical strength.
This improved version has seen a wide array of applications, such as microwavable containers and engineering plastics. Short-term applications such as food containers, water bottles, and disposable cutlery are a popular use for PLA.
A PLA film shrinks upon heating, making it a desirable material for shrink wrap. Remarks from firms that use PLA as material for food packaging indicate the preference for PLA due to increased aesthetics, better printability, good resistance to grease and oils, and reduced issues in taste and odor transfer.
PLA is widely used in the medical field due to its ability to degrade into non-toxic lactic acid. Medical implants such as screws, rods, pins and mesh have been made using PLA.
PLA can be extruded into thin fibers with significant mechanical strength. These PLA fibers have been used to manufacture casual sports apparel, upholstery material, hygiene products, and diapers.
Specifically, PLA is widely used in fused filament fabrication 3D printing , where PLA solids are encased in plaster-like mouldings to form moulds that can be filled with molten metal.
The development of cheaper and more environment friendly processes by which PLA is made should result in the decrease of its price in the market, leading to its more widespread application.
This will be further aided by a growing environmentally conscious consumer base. Issues with permeability, brittleness, and low melting temperature will have to be addressed by further research, but it is safe to say that PLA will continue to substitute petroleum-based plastics for pharmaceutical and food packaging materials in the future.
In , in terms of volume the market demand for polylactic acid was I do not think you can call PLA biodegradable.
It is compostable but not biodegradable. This is not readily found in the environment and therefore, the ease at which PLA can degrade in the environment is low.
Only degradation through microorganism can be defined as biodegradable. PLA can degrade quickly under the right conditions, specifically heat and hydrolysis, however, both are not immediately found in nature so a PLA bag left in soil can take nearly as long to degrade as a conventional plastic bag.
Certain studies have alluded to the fact that PLA may degrade faster and fully in the marine environment. If we continue to call PLA biodegradable, we risk leading consumers astray and allowing more plastics to enter our environment, leading to increased litter and destruction of biodiversity.
In , PLA had the second highest consumption volume of any bioplastic of the world,  although it is still not a commodity polymer. Its widespread application has been hindered by numerous physical and processing shortcomings.
The name "polylactic acid" does not comply with IUPAC standard nomenclature, and is potentially ambiguous or confusing, because PLA is not a polyacid polyelectrolyte , but rather a polyester.
The monomer is typically made from fermented plant starch such as from corn , cassava , sugarcane or sugar beet pulp.
Several industrial routes afford usable i. Two main monomers are used: lactic acid , and the cyclic di-ester, lactide. The most common route to PLA is the ring-opening polymerization of lactide with various metal catalysts typically tin octoate in solution or as a suspension.
The metal-catalyzed reaction tends to cause racemization of the PLA, reducing its stereoregularity compared to the starting material usually corn starch.
Another route to PLA is the direct condensation of lactic acid monomers. This reaction generates one equivalent of water for every condensation esterification step.
The condensation reaction is reversible and subject to equilibrium, so removal of water is required to generate high molecular weight species.
Water removal by application of a vacuum or by azeotropic distillation is required to drive the reaction toward polycondensation.
Molecular weights of kDa can be obtained this way. Even higher molecular weights can be attained by carefully crystallizing the crude polymer from the melt.
Carboxylic acid and alcohol end groups are thus concentrated in the amorphous region of the solid polymer, and so they can react.
Molecular weights of — kDa are obtainable thus. Use of stereospecific catalysts can lead to heterotactic PLA which has been found to show crystallinity.
The degree of crystallinity, and hence many important properties, is largely controlled by the ratio of D to L enantiomers used, and to a lesser extent on the type of catalyst used.
Apart from lactic acid and lactide, lactic acid O -carboxyanhydride "lac-OCA" , a five-membered cyclic compound has been used academically as well.
This compound is more reactive than lactide, because its polymerization is driven by the loss of one equivalent of carbon dioxide per equivalent of lactic acid.
Water is not a co-product. The direct biosynthesis of PLA similar to the poly hydroxyalkanoate s has been reported as well.
Another method devised is by contacting lactic acid with a zeolite. Due to the chiral nature of lactic acid, several distinct forms of polylactide exist: poly- L -lactide PLLA is the product resulting from polymerization of L , L -lactide also known as L -lactide.
PLA is soluble in solvents, hot benzene , tetrahydrofuran , and dioxane. In the latter case, PDLA acts as a nucleating agent , thereby increasing the crystallization rate [ citation needed ].
Several technologies such as annealing ,    adding nucleating agents, forming composites with fibers or nano-particles ,    chain extending   and introducing crosslink structures have been used to enhance the mechanical properties of PLA polymers.
Polylactic acid can be processed like most thermoplastics into fiber for example, using conventional melt spinning processes and film.
PLA has similar mechanical properties to PETE polymer, but has a significantly lower maximum continuous use temperature. The tensile strength for 3-D printed PLA was previously determined.
PLA can be solvent welded using dichloromethane. PLA is soluble in a range of organic solvents. If the filament is soaked in a small amount of ethylacetate, it will dissolve and can be used to clean 3D printing extruder heads or remove PLA supports.
Other safe solvents to use include propylene carbonate , which is safer than ethylacetate but is difficult to purchase commercially.
Pyridine can also be used however this is less safe than ethylacetate and propylene carbonate. It also has a distinct bad fish odor. PLA is used as a feedstock material in desktop fused filament fabrication 3D printers e.
This is known as "lost PLA casting", a type of investment casting. PLA can degrade into innocuous lactic acid, so it is used as medical implants in the form of anchors, screws, plates, pins, rods, and as a mesh.
This gradual degradation is desirable for a support structure, because it gradually transfers the load to the body e.
PLA can also be used as a decomposable packaging material, either cast, injection-molded, or spun.
In the form of a film, it shrinks upon heating, allowing it to be used in shrink tunnels. It is useful for producing loose-fill packaging, compost bags, food packaging, and disposable tableware.
In the form of fibers and nonwoven fabrics , PLA also has many potential uses, for example as upholstery , disposable garments, awnings , feminine hygiene products, and diapers.
Thanks to its bio-compatibility and biodegradability, PLA has also found ample interest as a polymeric scaffold for drug delivery purposes.
Racemic and regular PLLA has a low glass transition temperature, which is undesirable. It has a wide range of applications, such as woven shirts ironability , microwavable trays, hot-fill applications and even engineering plastics in this case, the stereocomplex is blended with a rubber-like polymer such as ABS.
Such blends also have good form stability and visual transparency, making them useful for low-end packaging applications. Pure poly-L-lactic acid PLLA , on the other hand, is the main ingredient in Sculptra , a long-lasting facial volume enhancer, primarily used for treating lipoatrophy of cheeks.
Progress in biotechnology has resulted in the development of commercial production of the D enantiomer form, something that was not possible until recently.
Transparent PLA. PLA is degraded abiotically by three mechanisms: . The degradation rate is very slow in ambient temperatures.
PLA samples of various molecular weights were degraded into methyl lactate a green solvent by using a metal complex catalyst. PLA also be degraded by some bacteria, such as Amycolatopsis and Saccharothrix.
A purified protease from Amycolatopsis sp. From Wikipedia, the free encyclopedia. Biodegradable polymer. CAS Number. Solubility in water.
Tea bags made of PLA. Peppermint tea is enclosed. Play media.