PVOH with David Edwards18 June 2019
In a recent interview, Matthew Rogerson spoke with David Edwards to learn more about his technology, PVOH. As the industry gears towards more sustainable solutions we discuss the credentials of the material, and how it has so much more to offer the industry.
What is PVOH?
Poly(vinyl alcohol) (PVOH, PVA, or PVAL) is a water-soluble synthetic polymer. It has the idealized formula [CH2CH(OH)]n. It is white (colourless), odorless and non-toxic.
It is usually supplied as a powder, granules, or pellets, or sometimes as a solution in water.
What are its current uses?
PVOH is safe and environmentally friendly. It is used in many household, medical and personal care applications, including laundry and detergent packets, food packaging, textile yarns, paper products, unit-dose pharmaceuticals, “artificial tears” used to treat dry eyes and even contact lens lubricant.
Food grade versions of water-soluble film can be used to package pre-measured quantities of rice, pasta, cocoa, seasoning and nutritional supplements.
Other grades of film are used in manufacturing processes such as a mold-release film in the production of solid surface countertops and reinforced composites.
What is its potential, where could it be used?
The extraordinary and diverse properties of water-soluble PVOH make the potential of this polymer virtually limitless if moisture exposure can be controlled until point of use. This is substantiated by the year on year increase in patent activity.
The uses of PVOH are often governed by the polymer’s properties:
- Excellent gas barrier/oxygen barrier
- Film is inherently static dissipative (barrier bags for electronics sensitive to ESD)
- Barrier to oils, grease and solvents (allowing unit-dosing and packaging of materials that would destroy other plastics)
- Solubility in water: unit dosing of agricultural chemicals, swimming pool and spa chemicals, detergents, personal care items (shampoo, conditioner, soap, body wash, hair bleach, lotions – sometimes as concentrates that can be used as “refills” and home-mixed with water), pre-measured foods or supplements that are mixed or cooked in water
- Controlled solubility: laundry bags in hospitals used to hold contaminated laundry triggered to dissolve at washing temperatures
- Printability: requires no corona treatment
- Odour and perfume barrier: cosmetic unit dosing
- Polymer is injection and blow mouldable: can be used in pharmaceutical capsules for human or animal ingestion, a non-animal-derived gelatin replacement
- Biodegradability: paper-making, adhesives, coatings, water-soluble labels, etc.
Why is it such a good candidate for sustainable packaging?
PVOH in solution simply breaks down into carbon dioxide and water when consumed by any of 55 acclimated organisms found in municipal wastewater treatment or activated sludge. In most water-soluble applications, such as laundry unit dose, the polymer is readily or inherently biodegradable as measured by OECD 301B test criteria.
PVOH is currently used in the recycling of paper and board and is actually added to the slurry to enhance the process. Because of its solubility, it does not contaminate recycling streams for other materials as it is removed during the rinsing process.
How can it be used to support other polymers and reduction in plastics waste?
For example, PVOH can replace other barrier polymers to enhance the overall biodegradability of composite packaging. PVOH also combines well with paper and corrugated packages to provide an internal vapor barrier or to dissipate static electricity. Water soluble labels made from PVOH can be attached as labels to other plastic materials such as plastic bottles and be simply washed off at the end of the bottle’s life. The labels are also biodegradable in municipal wastewater.
Are there limits to the materials potential? What can it not do, what are its weaknesses?
Though the solubility of PVOH is adjustable (speed, temperature, etc.), exceedingly high humidity or exposure to water prior to its intended use may present some difficulties.
Additionally, the cost of PVOH compared with other plastic materials can be as much as 2x higher. However, given the current concerns regarding plastic waste, the benefits of PVOH increasingly justifies the price premium.
What are some of the other considerations that make PVOH such a potentially game-changing solution?
The packaging industry (worth around £970 billion) is traditionally conservative when it comes radical change and innovation. In the last few years, however, the global plastic pollution situation has brand owners looking for innovative new materials, delivery systems and commercial models. Consumers have shown a willingness in some instances to pay a premium for more sustainable products.
There has never been a more exciting time and opportunity for polymers that can disappear after use or can be utilised with other plastics, paper, corrugated and other materials to facilitate recycling.
Why is it not used more extensively?
Water-soluble PVOH manufacturing is complex and requires considerable investment and know-how to produce the resins that demonstrate the desired characteristics. In the last five years, the world has seen unprecedented development of new applications of this remarkable polymer substantiated by the high patent filing activity.
What are its functional and ancillary abilities (coating/ barrier/print/formulation)?
PVOH-based materials have high flexibility in their formulation. Not only can PVOH films be coated, laminated, and printed, they can also contain many types of functional additives, including enzymes and fragrances, for example.
What makes PVOH such a versatile material?
The polymer has incredible mechanical properties, including high tensile strength and elongation. It is colorless, odorless and non-toxic. It exhibits excellent gas and odor barrier properties. It acts as a barrier to oil, grease and solvent. In contact with water, it completely dissolves. It’s solubility speed and temperature can be adjusted. In municipal wastewater treatment, PVOH biodegrades. It emits no toxins when combusted.
It is one of the few materials that does not require corona treatment when printed. The material is inherently static dissipative which is a huge benefit in conversion operations and can be used to protect electronics against Electro Static Discharge (ESD).
At a time when the world wants to ban or drastically reduce plastic packaging, PVOH provides a real alternative since in many applications, there is no plastic to recycle or dispose. The material is already accepted by regulatory authorities for food, medical and pharmaceutical applications as well as bureaus of land management for application to soil.
Why is it good as a sustainable material?
Water-soluble PVOH is colorless, odorless and non-toxic. It is solubilizes in water and biodegrades in wastewater treatment. When used in combination with other materials, it does not contaminate the recycling stream.
What happens when it is combined with a less compostable or recyclable material?
This would depend on the precise application, but in general this would not seem to make a lot of sense. The ideal applications are as unit dose whereby the package disappears upon use or in combination with materials that intended to be recycled. In certain instances, one might imagine applications where it can be used to replace single-use plastic items that have recently been banned, but significant work would need to be done to create the right degree of solubility and a complementary end-of-life scenario to dissolve the product and dispatch it through the municipal waste-water stream.
Can it be microwaved? Cooked, steam vented, ovenable?
Generally, no, except in instances where the intention is for the film to disappear in the process. For example, PVOH films embedded with seasonings are used in commercial cooking operations where it is desirable to add a consistent measure of flavorings to each food item during the preparation process. The film dissolves and the seasonings remain.