Tag Archives: biodegradable

No more butts: biodegradable filters a step to boot litter problem.


Robertson, R, W Thomas, J Suthar and D Brown. 2012.  Accelerated degradation of cellulose acetate cigarette filters using controlled-release acid catalysis. Green Chemistry http://ds.doil.org/10.1039/C2GC16635F.


Synopsis by Marty Mulvihill and Wendy Hessler, Aug 14, 2012


Every year over 6 trillion cigarettes are manufactured globally. Approximately 99 percent have a filter tip. After the cigarette is smoked, the used filter is called a butt and is thrown out. When littered, cigarette butts often take years to break down.

Most filters are made using cellulose acetate fibers. More than 2 billion pounds of cellulose acetate is produced every year to meet the world demand for filters. To make it, acetic anhydride is added to cellulose fibers made from wood or cotton. The reaction creates a type of plastic that provides a stronger, more rigid filter.

By itself, cellulose fibers degrade naturally in the environment. Cellulose acetate plastic degrades very slowly.

The slow degradation, along with indoor smoking bans, mean increasingly large numbers of cigarette butts are found in public places, including parking lots, parks and beaches every year. Cigarette waste is the number one reported item collected during beach clean-ups, according to the Ocean Conservancy. In some coastal towns as many as 1 in 10 cigarette butts end up polluting the waterways.

The discarded butts are more than just an eyesore. The filters contain chemical residue from the tobacco. The residue can be toxic to marine animals. Cigarette butts are commonly found in the stomachs of dead shore birds.

One way to decrease the litter would be to create cigarette filters that degrade quickly. Previous attempts used plant-based products like cornstarch, hemp, flax or cotton. One brand of biodegradable filter, Greenbutts, incorporates plant seeds that would germinate after disposal. To date, cigarette manufacturers have not widely adopted alternative filters.

The demand for degradable filters may increase as states – including New York – consider levying taxes on non-biodegradable cigarette filters. In response, there is renewed interest to make cigarette filters degrade faster.

What did they do?

A group of chemists wondered if a cellulose acetate plastic filter could be converted back into natural, degradable cellulose after it was used. If so, the cigarette butts should degrade much more quickly.

They guessed that small amounts of acid added to the filter should speed the degradation process.

First, they measured the degradation rate of cellulose acetate using a wide range of acids with different strengths. Combinations of acids were also tested to find which worked best to make cigarette filters that retained their structure and function while degrading faster.

Next, they created an effective additive based on which acids worked best. The additive needed to be acidic, non-toxic and allow the cigarette to burn normally. To find one, they looked to acids common in food, including citric acid, phytic acid and vitamin C (ascorbic acid), as well as stronger mineral acids not commonly considered safe food additives.

The new filter design was tested. A smoking machine “smoked” the cigarettes, and the butts were left outside and monitored.

What did they find?

In the first tests, the butts exposed to water and a small amount of acid broke down faster than those not exposed to acid. Strong acids worked best to efficiently speed the degradation of the cellulose acetate fibers. In particular they found that sulfuric acid was the most effective catalyst.

Sulfuric acid, however, is not safe to put into cigarette filters. The researchers devised a way to generate the stronger acid only after the cigarette was smoked. The smoker would not be exposed to any additional harmful compounds, and the filter would degrade more quickly.

To make the acid additive, the researchers combined safer chemicals – cellulose sulfate, citric acid and phytic acid – into a tablet. When the tablet got wet, these ingredients mixed and released small amounts of sulfuric acid that degraded the filter material. The tablets were coated with ethyl cellulose and cellulose acetate to shield the acid precursors from premature exposure to water.

After 14 days outside, the butts containing the acid tablet were more acidic and tested positive for the presence of sulfuric acid, while the control butts remained unchanged. At the end of the 90-day trial, the new filters were considerably more degraded than the controls. Unfortunately they had not degraded as much as expected based on the laboratory experiments.

What does it mean?

Small amounts of strong acid increase the degradation rate of the cellulose acetate fibers found in cigarette butts. Although the idea worked in principle, the outside trials did not live up to the promise of the laboratory results.

The research is important because it is a step towards making a truly degradable and functional cigarette filter. This research shows how green chemistry can improve existing technology. The researchers designed the new filters for degradation while making safer chemical choices. This approach will ultimately minimize waste and hopefully prevent some of the toxic exposures to birds and other wildlife.

Under laboratory conditions, the acid converted the filter plastic into a biodegradable material within 30 to 60 days, depending on temperature. The food grade acids and materials generated the strong acid only after the cigarette had been smoked. These preliminary results indicate that acidic additive in the filter could reduce the time it takes for cigarette butts to degrade in the environment.

Several problems will need to be resolved before large manufacturers could adopt the use of acid tablets in cigarette filters. The filter’s effectiveness – improved degradation and materials safety of materials – will need to be quantified in clinical and environmental trials. This will take more research to design and incorporate the acid precursors into the filter body.

Cost and performance are also issues. The acid materials must be incorporated into cigarettes at a low cost without harming the performance of the product.

Researchers will llkely pursue this technology as well as other approaches to a biodegradable cigarette filter in an effort to reduce cigarette butt litter.


Clean Virginia Waterways and Longwood University. 2012. Cigarette butt litter. http://www.longwood.edu/cleanva/cigarettelitterhome.html.

Novotny, T, K Lum, E Smith, V Wang, and R Barnes. 2009. Cigarettes butts and the case for an environmental policy on hazardous cigarette waste. International Journal of Environmental Research and Public Health http://dx.doi.org/10.3390/ijerph6051691.

Ocean Conservancy. A rising tide of ocean debris, International Coastal Clean-up 2009 Report. http://www.oceanconservancy.org/pdf/A_Rising_Tide_full_lowres.pdf.

Register, K. 2000. Cigarette butts as litter: Toxic as well as ugly. Underwater Naturalist: Bulletin of the American Littoral Society http://www.longwood.edu/CLEANVA/ciglitterarticle.htm.


Green Chemistry at Virginia Tech Part I

Being a recent graduate of the University of Virginia, it is a little hard for me to write this article on all the innovation and leadership that is happening at Virginia Tech in the field of Green Chemistry (note: the two schools are notorious rivals). However, this is one topic on which I must concede: Tech just does it better.

To begin my series of Green Chemistry interviews with faculty and staff at Virginia Polytechnic Institute and State University (also known as Virginia Tech, VTech, and Tech), I interviewed Dr. Timothy Long. Dr. Long’s dedication to greener chemistry can be seen in both his teaching and in his research. I had the privileged opportunity to discuss his background, career at Tech, and plans for the future.

After receiving his PhD in chemistry, Dr. Long spent nine years in the chemical industry, where his passion for greener processes developed. He described: “they (industry) were very aware of green chemistry, motivated by economics and affordability.” Once exposed to this mentality, Dr. Long got passionate and wanted to see how to apply this mentality to his research and teaching. When he came to VTech twelve years ago he wanted a more sustainable way of doing things. He described: “I want to weave the principles of green chemistry into my teachings and research.”

A major contribution from Dr. Long’s lab is the more sustainable production of PSA (pressure sensitive adhesive used in many forms of tape and sticky notes). Previously, these compounds used petroleum-derived precursors that had terminal ester bonds. Dr. Long’s polyesters have that same ester bond but in the middle of the polymer. This structural change allows the compound to be made without solvent, while also allowing biodegradability. Killing two green chemistry birds with one stone.

Virginia Tech offers a course in green chemistry taught alternatively by Dr. Long and Dr. Etzkorn. It is a 4000 level class for undergraduates which caters to mainly to chemistry, biology, and business majors. Each semester the course has 45 students. The course takes an interdisciplinary approach to green chemistry as it integrates the science and concepts with society. It seeks to understand how chemistry is perceived in the wider community. While there is no green chemistry minor at Tech, the engineering school has a green engineering minor. Dr. Long also wants to make the green chemistry course mandatory for chemistry graduates. Currently he is submitting a proposal for a nanoscience degree at the University that would incorporate fundamentals of toxicology, essential for our upcoming chemists.

Dr. Long described the passion of Tech’s students to be more sustainable, commenting on their successful Earth Week each year and the increasing amounts of activity on campus. Tech is also hosting the World Polymer Conference next year – which is geared to making a more sustainable, healthy, and safer world.

AGC wishes Dr. Long success in all these ventures and applauds his success thus far.

Interview by: Mana Sassanpour, AGC

Shortcut converts common cellulose into useable parts.

Synopsis by Wim Thielemans, Sep 23, 2011

Long, J, B Guo, X Li, Y Jiang, F Wang, SC Tsang, L Wang and KMK Yu. 2011. One step catalytic conversion of cellulose to sustainable chemicals utilizing cooperative ionic liquid pairs. Green Chemistry http://dx.doi.org/10.1039/c1gc15597k.

A new one-step process blends a pair of specially selected solvents with cellulose, overcoming a big hurdle in the race to use the plant-based material as a reliable source of chemicals and fuels.

Pairing up a unique blend of specialized chemical solvents with plant cellulose has solved a looming problem for chemists grappling to find an efficient method to break apart naturally abundant cellulose.

The one-step process uses two ionic liquids to break cellulose down into its smaller chemical pieces and convert these pieces into useful chemicals. This is an important feat since cellulose is targeted as an alternative source for the chemicals and fuels currently derived from fossil fuels.

The results show for the first time that combinations of ionic liquids can be very useful in guiding more efficient chemical reactions that create less waste and more product. The findings are interesting because they show it is possible to combine several processing steps just by choosing the correct mixture of solvents.

Cellulose is a major part of plant cells and is the most abundant renewable material on Earth. Every year, plants, algae and some bacteria produce in excess of an estimated 100 billion metric tons. Cellulose is not a food and is a waste product of agriculture.

An enormous research effort is underway to understand how to use cellulose as a starting material for biofuel and chemical production in order to replace crude oil. In this process, cellulose – a long chain of identical chemical units – needs to be separated into the individual units.

The key challenge to convert cellulose into chemicals is its poor solubility – that is, it does not break up easily in liquids. Chemical reactions, though, require close contact between all the parts to work well. In 2002, researchers reported that some ionic liquids were very good at dissolving cellulose.

Ionic liquids are salts – a designation for chemicals made up of both a positively and a negatively charged component– that are liquid at low temperatures, unlike common salts such as table salt. Bulky positive and negative groups that make up the ionic salts hinder their packing into a solid crystal. Thus, they stay liquid to much lower temperatures – even room temperature.

In this work, Chinese researchers used a mixture of two ionic liquids. The first was chosen to dissolve cellulose. The second was chosen because it increases cellulose breakdown into its individual units, and further, into useful chemicals.

Under the right conditions, all the cellulose was broken down. The reaction products were also removed from the ionic liquid mixture by simply adding an insoluble solvent such as methanol or hexane. While there were a variety of different reaction products, up to 48.5 percent of the cellulose could be converted to a single product: 2-(diethoxymethyl)furan. This chemical, in turn, can be easily converted into a variety of other products useful for the chemical and pharmaceutical industries.

The choice of the solvent to extract the reaction products from the ionic liquid also allows researchers to select the reaction products that are recovered.

The ionic liquid mixtures were also reused. No real difference in performance and composition was noticed over 10 repeated reactions.

The researchers chose to dissolve cellulose first followed by a reaction to convert cellulose into smaller, more useful products. However, the results suggest the system is versatile and – depending on which ionic liquids are selected – could be extended to several reactions in a row. Ionic liquids will certainly hold some surprises in the future.

Read more science at Environmental Health News.


Can synthetic silk beat nature’s own?


Kinahan, ME, E Philippidi, S Koster, X Hu, HM Evans, T Pfohl, DL Kaplan and J Wong. 2011. Tunable silk: using microfluidics to fabricate silk fibers with controllable properties. Biomacromolecules http://dx.doi.org/10.1021/bm1014624.


Jul 09, 2011


A silkworm (Bombyx mori).

For the first time, people can do what only spiders and silkworms can do: spin silk fibers to specific specifications.

The new technique opens the door to customizing fibers to use in medicine, engineering and – of course – clothing. It relies on a special device to build silk protein chains that are then spun together into fibers with predicted and controlled strength, rigidity and width.

The researchers will continue to refine the method that may lead to a cheaper and more directed silk product than spiders and silkworms currently provide. The innovative method to make synthetic silk is explained in the journal Biomacromolecules.


Silk is a very attractive material for clothing and other textiles due its smooth, cool and comfortable qualities. Manufacturers also find silk tantalizing. Silk’s mechanical properties – it is as strong as steel yet six times lighter – and ecofriendliness – it is biocompatible and biodegradable – make it an attractive material for biomedical and engineering applications. In fact, silk is used for suture threads and in tissue grafts.

In all the world, only silkworms and spiders can make silk. A mysterious spinning process produces the strong threads that are weaved together into webs and cocoons. The animals make the unique silk protein and spin it together in just the right way to form a special structure that gives the fiber its desired properties. The invertebrates do this with apparent ease. More so, they can control its properties, depending on where and for what purpose the silk thread will be used.

Obtaining natural silk for consumer uses, then, comes with a set of problems. The properties of natural silk – its strength, width, length – is determined by the specific species of spiders and worms. Basically, people get what the animals produce. It is also expensive and laborious to keep the silk-producing creatures – normally silkworms – and harvest the product.

So, there is need for a rapid method to fabricate silk and control its mechanical properties. The first step in this process has already been solved. A variety of other organisms – ranging from bacteria to goats – have been genetically modified and can produce silk proteins. The type of silk protein can be easily varied. It can also be produced in large quantities. However, the second challenge of how to spin those proteins into fibers with the desired properties remains.

What did they do?

Researchers from Boston, Mass., and Göttingen, Germany, used a microfluidic device that mimics the silkworm glands by extruding silk proteins from an aqueous solution. The solid device is infused with two crossing channels similar to the thickness of a human hair. Liquids can flow through the channels, which come together to allow a very small point of mixing. Through one channel flows the aqueous silk protein solution. Through the two intersecting channels flows an acidic solution of polyethylene glycol. Where the two channels meet, the fluids mix. Polyethylene glycol is a benign molecule  – a polymer – that envelops the active drug ingredients and acts as a lubricant in a variety of medicines.

Several different flow speeds and ratios of silk protein to polyethylene glycol solution were tested. The ensuing mechanical properties of the spun fiber – such as strength, strain and stress failure – were measured.

What did they find?

The device created a single strand of silk fiber with very well-defined properties. The fiber’s properties were altered by varying the spinning conditions, such as flow speed and the speed with which the dry fiber was drawn out of the device.

A small amount of original material was required – as little as 50 microliters, which is about the volume of a drop of water. This makes it a very interesting tool to screen different processing parameters and determine their effects on the spun fiber properties.

The authors related the flow characteristics inside the device to the fiber’s mechanical properties – strength, rigidity – and the internal structure formed by the silk proteins inside the fiber. They were able to control the fiber diameter and fiber strength. They even could vary the diameter of the fiber as it was spun.

While they did not yet match the properties of natural silk in this work, the control they showed over properties is very promising.

What does it mean?

The researchers designed a device that can rapidly produce synthetic silk fibers from silk proteins. The spinning conditions are easily controlled to determine the effect on the properties of the spun fibers.

This new technique opens up the possibility to customize fiber properties so they be used for specific applications. Of several methods being investigated to produce synthetic silk, this one is closest to the natural process, so it offers a very clean method to produce silk fibers on a large scale. No real waste is generated, and the polyethylene solution can be recycled.

More generally, the process is an example of how green chemists can develop a clean manufacturing process straight away and avoid creating pollution problems right from the start.

This work has a great potential to improve understanding of how to make synthetic silk fibers and possibly make them stronger, softer, more stretchable or thinner than natural silk. Different silk proteins can be produced from bacteria, goats and other animals – or even synthetically in the lab – so it is now possible to study the effect of spinning conditions and variations on the silk fibers that are produced. The small starting volume reduces the amount of silk protein required making the tests cheaper and faster to run.

The authors investigated only two processing parameters, but their new device can easily be used to screen all others quite rapidly. The process will no doubt increase understanding of both synthetic and natural silk production.  More importantly, the device may produce better, designer silk fibers.


Silkworm information. Center for Insect Science Education Outreach. University of Arizona.

Novel, sugar-based surfactants more stable and sustainable.

Synopsis by Evan Beach and Wendy Hessler. Jan 12, 201

Foley, PM, A Phimphachanh, ES Beach, JB Zimmerman, and PT Anastas.  2011.  Linear and cyclic C-glycosides as surfactants. Green Chemistry http://dx.doi.org/10.1039/C0GC00407C.



Surfactants – the active ingredients in many household products, including cleaners and personal care products – are produced on the scale of millions of tons per year. In nearly every application, after a few minutes of use, they are rinsed with water either down the drain or directly into the environment.

Unsurprisingly, there have been harmful effects from such large-scale releases. When surfactants are slow to break down in the environment, problems range from unsightly foaming to toxic effects on aquatic organisms. Some of these chemicals – for example, the widely used nonylphenol ethoxylates – have been implicated in endocrine disruption. The term is used to describe substances that can alter hormone activity in the body.

There has been a push in recent years toward sugar-based surfactants because of improved biodegradability and lower toxicity. They are also derived from natural and renewable sources, adding another “green chemistry” benefit.

Sugar-based surfactants have been commercially available for more than a decade. Formulations of the alkyl polyglycosides (APGs) are used in a variety of consumer products for laundry, hair and skin care. On an ingredient label they are usually identified as a variety of “glucosides,” for example decyl glucoside or lauryl glucoside. The use of APGs is growing at a faster rate than petroleum-based surfactants.

However, chemists are trying to improve APGs. Many of the sugar-derived chemicals can fall apart when exposed to acids in water because the link between the water-loving and oil-loving ends of the APG molecules is vulnerable. Also, depending on the variety of the APG produced, the manufacturing process relies on high temperature and pressure and energy-consuming purification steps.

What did they do?

Researchers investigated a new process to make a stronger chemical bond in one particularly weak spot of sugar-based surfactant molecules. The researchers transformed a precursor chemical by treating it with a chemical mix that included alkyl aldehydes.

Several sugar derivatives with straight or cyclic tails were produced, depending on the conditions that were used to convert the intermediary chemical. The new chemicals were tested for surface tension and foaming and the results were compared to current APG surfactant performance.

The researchers showed that the new surfactants could be prepared in a two-step reaction under mild conditions, using only a minimum of solvent. It was not necessary to purify the products by column chromatography, a procedure that would consume large volumes of potentially hazardous solvents. This improves the prospects for producing the chemicals on a large scale.

The scientists show that the technical performance of the new surfactants is as good as existing APG technology. This was determined by measuring surface activity – how efficient the chemicals are at reducing the surface tension of water. It is important for surface tension to drop quickly with just a small amount of added chemical, for surfactant applications. The best chemical tested in the study worked at just 40 milligrams (the weight of a few grains of rice) per liter.

The researchers also explored the foaming properties of the new chemicals. Foaming is desirable for some personal care products like shampoos, but would be a disadvantage in laundry applications and some industrial cleaners. The Yale chemicals were low foamers compared to a conventional surfactant, sodium dodecyl sulfate (SDS). But when mixed with SDS, the resulting foam lasted longer. Thus they could be useful in either low- or high-foam formulations.

The biodegradability of the new chemicals was not measured, but U.S. Environmental Protection Agency software suggests that the changes made to improve acid stability will not affect how microbes disassemble the chemicals. The glucose end of the molecule contains many carbon-oxygen bonds that are common places for microbial attack. If the surfactants are made from long, straight-chain aldehydes, that should also provide bacteria with a familiar food source.

What does it mean?

The new sugar-based surfactants may offer more stable and sustainable varieties to use in consumer products. The novel chemicals are more stable under harsh conditions and work just as well in laboratory tests as the sugar-based surfactants currently used. In addition, their chemical production is a significant improvement over current methods in that it uses less resources and produces a wider array of chemicals with surfactant properties.

Evan Beach

This new family of sugar-based surfactants complements APGs that are already on the market. A wider variety of molecular structures means that manufacturers of green consumer products are more likely to come up with formulations that meet all the goals of function, performance, economy and low environmental footprint.

Replacing the weak spot in APGs with a sturdier alternative allows the sugar-based chemicals to be used in more applications. The two parts of the new molecule are linked with a bond between two carbon atoms instead of a bond between an oxygen and a carbon atom. The stronger carbon-carbon bond is unaffected by strong acid. That robustness could help in industrial applications and heavy-duty household formulations, for example acidic tile cleaners.

The new surfactants are made from glucose, which is widely found in nature. It is one of the components of table sugar and is the repeating chain unit in cellulose, which gives plants their supporting structure. Glucose acts as the water-loving part of the surfactant. The oil-loving part of the surfactant is made from aldehydes. Aldehydes are a diverse set of chemicals; some occur in nature and others are produced from petrochemicals. In this study, the aldehydes could be obtained by treating plant oils.

The researchers say their next step will be to explore algae as a possible source for all of the surfactants’ starting materials. The carbohydrate portion of algal biomass could provide the sugar, and algal oils could give the right kinds of aldehydes. Algae oils are particularly rich in carbon-carbon double bonds that can react with ozone to produce aldehydes. If that approach is successful, surfactant production could supplement algae-to-fuel technology.

Distinctions between biopolymers and bio-based polymers important (Media review).

Posted by Evan Beach at Nov 08, 2010 04:00 AM | Permalink

The origins of bio-based plastics need to be clarified in a Vancouver Business Journal article that highlights the use of the materials in industrial applications.

A recent story in the Vancouver Business Journal provides an overview of the challenges manufacturers face when trying to work with plastics that incorporate natural molecules – so-called bio-based plastics. Companies are exploring new ways to handle the raw materials and optimize the molding process.

The article draws attention to an important trend in the world of plastics and green chemistry, but could have been more precise in the language used when referring to the polymers involved. Polymers are large molecules made of smaller, repeating molecules that are chained together.

The reporter does a good job of explaining the difference between two major types of bio-based polymers: “biodegradable” and “compostable” polymers. The distinction can be important  when manufacturers or consumers choose an environmentally friendly disposal method for a particular material. International standards define a biodegradable polymer as one that breaks down into smaller fragments due to the action of bacteria and other microorganisms. To be “compostable,” a polymer must degrade completely into carbon dioxide, water, minerals and biomass; and it has to do this quickly without hurting the overall compost process.

He could have also clarified that biopolymers and bio-based polymers are different.  “Biopolymer” refers to polymers that occur in nature or are produced by biological action. Cellulose, starch, proteins and polyesters made by bacteria (known as PHAs) are examples of biopolymers.

Then there are the synthetic polymers – like polylactic acid (PLA). These materials usually biodegrade and are made from biological raw materials, but are prepared by chemical methods.  PLA is made up of small molecules found in nature, but the polymerization process is a human invention. Similarly, nitrocellulose, which was historically used in photographic film, is a chemically modified version of a natural material, but does not occur naturally. PLA and nitrocellulose would be more accurately referred to as “bio-based” or “bio-derived” polymers.

These distinctions may seem minute, but they help clarify for manufacturers, regulators and consumers to what extent a material is truly natural.

IBM, Stanford Unveil Green Chemistry Breakthrough

Scientists from IBM and Stanford University have unveiled discoveries that could lead to the development of new types of biodegradable, biocompatible plastics. The result of a multi-year research effort, the breakthrough also could lead to a new recycling process that has the potential to significantly increase the ability to recycle and reuse common PET and plant-based plastics in the future. Todays announcement may have sustainability implications across a wide range of industries including biodegradable plastics, plastics recycling, healthcare and microelectronics. IBM and Stanford scientists are pioneering the application of organocatalysis to green polymer chemistry, which represents a fundamental shift in the field. This discovery and new approach using organic catalysts could lead to well-defined, biodegradable molecules made from renewable resources in an environmentally responsible way.

See the YouTube video: Stanford & IBM on Green Chemistry and plastics.

Improved outlook for a biodegradable plastic.

Improved outlook for a biodegradable plastic.

May 12, 2010

Agarwal, S and C Speyerer. 2010. Degradable blends of semi-crystalline and amorphous branched poly(caprolactone): Effect of microstructure on blend properties. Polymer 51(5):1024-1032.

Synopsis by Evan Beach

A new way of concocting a promising “green” plastic called polycaprolactone (PCL) makes it clearer and more biodegradable – critical features for alternatives to PVC plastic or other conventional packaging materials.


PCL was transformed into a more transparent plastic when two different varieties of the same starting material were combined in the laboratory. The blends broke down faster when buried in a compost.  The results show that the new blends improve traits – transparency and degradability – necessary to develop PCL into a viable plastic product.

PCL degrades easily and thus has been studied for decades as an alternative plastic for use in agriculture, medicine, pharmacy, biomedical and as an environmentally friendly material for packaging. Because it has some disadvantages –  for example it cannot form a transparent film – it must be blended with other plastics in industrial applications.

PVC, like many other plastics, is not biodegradable, and therefore, it persists in the environment. PVC is rigid unless other chemicals are added to the formulation. Phthalates are among the most commonly used additives to make PVC flexible. Human health concerns have been raised about exposures when these chemicals migrate out of the plastic, especially effects on the male reproductive system.

Ironically, PVC is often chosen for blending with PCL because the two polymers can be mixed very easily. This takes away from the environmental benefits of PCL, since in the blended plastic, after the PCL degrades, the PVC persists just as it normally would on its own.

The new PCL plastic reported in this study does not use PVC. It can be fine-tuned so that the transparency increases from 8 percent to 45 percent and the plastic films break down much more quickly than ordinary PCL. The blends were less flexible and stretchy, but the researchers did not discuss whether the impact this would have on a potential packaging material.

The technique that led to the new plastic was a method of changing the structure of the PCL chain. Ordinary PCL and the new PCL contain the same repeating units, but the new PCL is not perfectly linear. It has branches, forcing the chains to take on a different overall shape. There are many different ways to make branched-chain PCLs, so more research could increase the number of options for manufacturers who want to use environmentally friendly plastics.