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The Science Behind PVOH

What is PVOH?

Polyvinyl alcohol (PVOH) is a very long molecule comprised of repeating chemical units. It’s made from just carbon, hydrogen, and oxygen atoms. It's commonly used everyday by consumers in various ways. Applications include everything from eye drops and food (health supplements) to medication capsules and textiles (water soluble fishing nets). Sounds simple right?  Not so fast.

How is it made?

PVOH is made via a two-stage reaction process. The process starts with the basic starting molecule, called vinyl acetate, comprised of 3 simple atoms (carbon, hydrogen and oxygen.) In the first reaction step, vinyl acetate is reacted with itself at high temperature and pressure so that it polymerizes to form polyvinyl acetate. 

And what's that you ask?... well we know it as white glue, like the stuff you used in grade school.

Now, the "glue" goes through one more process (hydrolysis) where it is reacted with water to create the PVOH we use for the water-soluble membrane on our pods. 

Why hydrolysis matters.

Hydrolysis is essentially a chemical reaction in which water is used to break down the bonds of a particular substance. This is where it gets complicated. 

As with most polymer types, PVOH can be made to take many shapes and forms to give it different mechanical properties. The degree of hydrolysis here is very important as it dictates the level of water solubility of the end product. High-hydrolysis PVOH is very water resistant and does not break down easily - think sturdy fishing nets. 

Low/mid-hydrolysis PVOH on the other hand is very water soluble - that's what we use! There are many uses for these films outside of laundry and home care. 

How is PVOH used?

There are many uses for these films outside of laundry and home care. As a matter of fact, PVOH film such as that used in our pod membrane is used and sold in the US as part of edible foods and personal consumer products. For example, the film is currently used in nutritional supplements and has been the subject of an US FDA GRAS (Generally Recognized As Safe) notice as an edible substance. It is widely used in personal care products like hand soaps and shaving cream

Not all PVOH is created equal.

Because of this, at Dropps we know that not all PVOH is created equal. The polymer class may have the same name but the actual materials being manufactured and sold can be very different. The PVOH we use is listed on the EPA's CleanGredients database. We engineer all of our products with the safety of you, your family, and the planet as our top priority.

What happens in the wash?

Our pod membrane fully dissolves when mixed with water in your machine.

What happens next?

Washing machine drains are fed by an electric pump, which moves water from inside the cleaning drum, through a flexible drain hose on the underside of the machine, into the water drain, and out into your home sewer system where it makes its way out of the house. After the pod membrane dissolves in your washer it enters the water stream and micro-organisms (including bacteria, yeasts, and fungi) that commonly exist in water treatment plants eat the monomers for breakfast, lunch, and dinner.

INTERESTED IN LEARNING MORE?

A significant body of work, citing over 190 peer-reviewed papers, supports this mechanism: 

Chiellini, E., Corti, A., D'Antone, S., Solaro, R., Progress in Polymer Science, 2003, 28, 963-1014.

AND 50+ MORE INDEPENDENT PEER-REVIEWED SCIENTIFIC PAPERS INCLUDING:

Gross R.A., Kalra B., “Biodegradable polymers for the environment.” Science, 2002, 297, 803-807.

Solaro R., Corti A., Chiellini E., “Biodegradation of PVOH with different molecular weights and degree of hydrolysis.” Polymers for Advanced Technologies, 2000, 11, 873-878.

Schonberger H., Baumann A., Keller W., “Study of microbial degradation of polyvinyl alcohol (PVA) in wastewater treatment plants.” American Dyestuff Reporter, 1997, 8, 9-18.

Wheatley Q., Baines F., “Biodegradation of PVOH in wastewater.” Textile Chemist and Colorist, 1976, 8, 28-33.

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