Not to be confused with polyvinyl acetate
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Polyvinyl alcohol (PVOH, PVA, or PVAl) is a water-soluble synthetic polymer. It has the idealized formula [CH2CH(OH)]n. It is used in papermaking, textile warp sizing, as a thickener and emulsion stabilizer in polyvinyl acetate (PVAc) adhesive formulations, in a variety of coatings, and 3D printing. It is colourless (white) and odorless. It is commonly supplied as beads or as solutions in water.[3][4] Without an externally added crosslinking agent, PVA solution can be gelled through repeated freezing-thawing, yielding highly strong, ultrapure, biocompatible hydrogels which have been used for a variety of applications such as vascular stents, cartilages, contact lenses, etc.[5]
Although polyvinyl alcohol is often referred to by the acronym PVA, more generally PVA refers to polyvinyl acetate, which is commonly used as a wood adhesive and sealer.
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PVA is used in a variety of medical applications because of its biocompatibility, low tendency for protein adhesion, and low toxicity. Specific uses include cartilage replacements, contact lenses, and eye drops.[6] Polyvinyl alcohol is used as an aid in suspension polymerizations. Its largest application in China is its use as a protective colloid to make PVAc dispersions. In Japan its major use is the production of Vinylon fiber.[7] This fiber is also manufactured in North Korea for self-sufficiency reasons, because no oil is required to produce it. Another application is photographic film.[8]
PVA-based polymers are used widely in additive manufacturing. For example, 3D printed oral dosage forms demonstrate great potential in the pharmaceutical industry. It is possible to create drug-loaded tablets with modified drug-release characteristics where PVA is used as a binder substance.[9]
Medically, PVA-based microparticles have received FDA 510(k) approval to be used as embolisation particles to be used for peripheral hypervascular tumors.[10] It may also used as the embolic agent in a Uterine Fibroid Embolectomy (UFE).[11] In biomedical engineering research, PVA has also been studied for cartilage, orthopaedic applications,[12] and potential materials for vascular graft.[13]
PVA is commonly used in household sponges that absorb more water than polyurethane sponges.[citation needed]
PVA may be used as an adhesive during preparation of stool samples for microscopic examination in pathology.[14]
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Polyvinyl acetals are prepared by treating PVA with aldehydes. Butyraldehyde and formaldehyde afford polyvinyl butyral (PVB) and polyvinyl formal (PVF), respectively. Preparation of polyvinyl butyral is the largest use for polyvinyl alcohol in the US and Western Europe.
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Unlike most vinyl polymers, PVA is not prepared by polymerization of the corresponding monomer, since the monomer, vinyl alcohol, is thermodynamically unstable with respect to its tautomerization to acetaldehyde. Instead, PVA is prepared by hydrolysis of polyvinyl acetate,[3] or sometimes other vinyl ester-derived polymers with formate or chloroacetate groups instead of acetate. The conversion of the polyvinyl esters is usually conducted by base-catalysed transesterification with ethanol:
The properties of the polymer are affected by the degree of transesterification.
Worldwide consumption of polyvinyl alcohol was over one million metric tons in .[7] Large producers include Kuraray and Sekisui Specialty Chemicals, while mainland China has installed a number of very large production facilities in the past decade[clarification needed] and currently accounts for 45% of world capacity.
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PVA is an atactic material that exhibits crystallinity. In terms of microstructure, it is composed mainly of 1,3-diol linkages [&#;CH2&#;CH(OH)&#;CH2&#;CH(OH)&#;], but a few percent of 1,2-diols [&#;CH2&#;CH(OH)&#;CH(OH)&#;CH2&#;] occur, depending on the conditions for the polymerization of the vinyl ester precursor.[3]
Polyvinyl alcohol has excellent film-forming, emulsifying and adhesive properties. It is also resistant to oil, grease and solvents. It has high tensile strength and flexibility, as well as high oxygen and aroma barrier properties. However, these properties are dependent on humidity: water absorbed at higher humidity levels acts as a plasticiser, which reduces the polymer's tensile strength, but increases its elongation and tear strength.
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Polyvinyl alcohol is widely used, thus its toxicity and biodegradation are of interest. Tests showed that fish (guppies) are not harmed, even at a poly(vinyl alcohol) concentration of 500 mg/L of water.[3]
There are several different grades of PVA depending on the degrees of polymerization and hydrolysis, which will affect their physical and chemical properties as well as their biodegradability.[3] Aqueous solutions of PVA degrade faster, which is why PVA grades that are highly water-soluble tend to have a faster biodegradation.[15] Not all PVA grades are readily biodegradable, but studies show that high water-soluble PVA grades such as the ones used in detergents can be readily biodegradable according to OECD screening test conditions.[16]
Orally administered PVA is relatively harmless.[17] The safety of polyvinyl alcohol is based on some of the following observations:[17]
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In today's world, where there is a growing concern about the impact of plastic waste on the environment, eco-friendliness has become a top priority. PVA or Polyvinyl Alcohol is a water-soluble synthetic polymer that is gaining popularity due to its eco-friendly nature. In this article, we will explore what PVA is, its properties, and its eco-friendliness.
What is PVA?
Polyvinyl alcohol (PVA) is a water-soluble synthetic polymer that is produced by the partial hydrolysis of polyvinyl acetate. It is a colorless and odorless solid, and it is commonly used in various industries, such as paper, textiles, adhesives, coatings, packaging, and more.
PVA is known for its excellent film-forming properties, which makes it a popular choice for coatings and packaging films. It is also used as a binder in paper and textiles and as an adhesive in a range of applications. Additionally, PVA can be modified with different additives to improve its properties, such as its strength, water resistance, and flexibility.
PVA is a non-toxic and biodegradable material, which makes it an eco-friendly choice for many applications. However, its biodegradability depends on the conditions of the environment in which it is disposed, and it may take a long time to decompose in certain conditions.
Is polyvinyl alcohol the same as PVA glue?
Polyvinyl alcohol (PVA) and PVA glue are related but different substances. PVA glue, also known as white glue or school glue, is a water-based adhesive that contains polyvinyl acetate (PVA) as its main ingredient. PVA glue is commonly used in arts and crafts, woodworking, and other applications where a strong, flexible, and water-resistant bond is needed.
PVA is not an adhesive like PVA glue and does not have the same bonding properties. Instead, PVA is valued for its biodegradability and other physical and chemical properties. While both PVA and PVA glue contain PVA polymer, they are formulated differently and serve different purposes.
What is PVA commonly used for?
PVA's unique properties make it useful in a variety of applications, including paper coatings, adhesives, textiles, and films. It is also commonly used in the food packaging industry due to its oxygen barrier properties, which help to preserve the freshness of the packaged products.
Polyvinyl alcohol (PVA) is also sometimes used in laundry detergent as a water-soluble film that dissolves during the wash cycle to release other active ingredients in the detergent. This type of PVA film is called a "unit dose" or "single dose" film, and it is used to improve the convenience and efficiency of laundry detergent by providing pre-measured amounts of detergent that dissolve quickly in water.
How eco-friendly is PVA?
One of the key benefits of PVA is its biodegradability and water solubility. When exposed to moisture and microorganisms, PVA breaks down into non-toxic components, making it a more sustainable alternative to traditional plastics. However, PVA is not completely biodegradable and can take several months to break down under the right conditions.
Compared to other plastics, PVA has a relatively low environmental impact. It is non-toxic and does not release harmful chemicals when it degrades. However, it still requires energy and resources to produce, and its biodegradability is not perfect.
According to Michigan State University, "We don't always have to sacrifice what's easy for what safe for our health and best for the environment. PVA ingredients are an excellent example of an ingredient positively transforming industries."
However, it is important to note that some countries have regulations in place regarding the disposal of PVA products to prevent environmental pollution. For example, in the European Union, PVA is subject to the Waste Framework Directive, which sets out rules for waste management and disposal to protect human health and the environment. The Directive requires that PVA products be disposed of in a way that minimizes their impact on the environment, such as through composting or in dedicated waste treatment facilities. It is possible that some countries may adopt stricter regulations or bans on PVA in the future if concerns arise about its environmental impact.
Recommended products with and without PVA
Despite its downsides, PVA is still a sustainable solution. There are several eco-friendly laundry detergents and dish soaps that contain PVA, which can help to reduce plastic waste. Additionally, there are other sustainable packaging options available, such as biodegradable plastics made from plant-based materials.
Several companies, such as Dropps, TruEarth, and Kind Laundry, have recognized the importance of reducing plastic waste and promoting sustainability by adopting PVA-based packaging for their laundry detergents. These companies are taking a step in the right direction by offering eco-friendly alternatives to conventional plastic packaging.
However, there are PVA-free options available, such as Meliora Laundry Detergent, which uses biodegradable paper packaging and natural ingredients.
Consumer choices play a crucial role in reducing plastic waste. By choosing products that contain PVA or other sustainable alternatives, we can help to minimize the environmental impact of our daily lives.
Making Informed Choices for a Sustainable Future
In conclusion, PVA is an encouraging development as a sustainable solution. It has unique properties that make it useful in a variety of applications, and its biodegradability and water solubility make it a more sustainable alternative to traditional plastics. However, it is not a perfect solution, and there are still downsides that we need to be aware of. As consumers, we can make a difference by choosing products that are more sustainable, and by advocating for more eco-friendly solutions in the products we use every day.
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