Tag Archives: pollution

Plastic replacements: some new conSQUIDerations

Posted on March 27, 2019 by | 3 comments

The amount of plastic that has been produced to date now exceeds 8300 million metric tonnes (Mt). To put this into perspective, the average blue whale weighs approximately 180 Mt, thus 46 million blue whale’s worth of plastic has been produced since humans started commercializing plastics in 1950. Our society had become extremely dependent on plastic products and synthetic (petroleum- based) textiles which cause serious consequences such as microplastic and microfiber pollution as I’ve discussed in previous blog posts.

Figure 1. Size reference for blue whales. Wikipedia Commons

Bioplastics have more recently taken the stage as a potential avenue for replacing petroleum-based plastics. Biologically based polymers have structural elements such as helices, β-turns, β-sheets and coils which provide structural integrity and resilience and can replicate the desirable polymeric interactions in plastics. Additionally, a lot of new material is being developed based on the protein polymers that are naturally occurring in biological systems (including ourselves).

Figure 2. Fibrous protein polymers have molecular architecture that can include (i) helices and coils, (ii) β-turns and β-spirals, and (iii) β-sheets. Source

Video 1. SRT- coated fabrics that self-heal in water.

Squid ring teeth (SRT) are an especially promising candidate for making functional fibres and films due to its strength, conductivity and self-healing properties. The SRT are located inside the suction cups of the tentacles of squids and are composed of a naturally occurring protein complex. Fortunately, it is not necessary to harvest squid to obtain the SRT proteins as they can be biosynthetically produced since having their genome sequenced. The SRT-inspired monomer is repeated to create a polymeric chain and the resulting protein that is produced is named accordingly as tandem repeat (TR) proteins.

Figure 3. The Squid ring teeth of a giant squid. Wikipedia Commons

Figure 4. Optical images of squid ring teeth (SRT) and the six common squid species they originate from. Source

Films produced with SRT proteins consist of disordered domains that provide elasticity and flexibility to the materials in addition to ordered domains such as β-sheets that provide mechanical strength. One study designed four TR proteins denoted as TR-nX where X was the number of repeat units within the molecule. They measured the mechanical force of these four TR proteins and found that the ultimate strength of the protein’s scale linearly, with TR-n25 reaching an ultimate strength of 40 MPa. As seen in Figure 4 below, there is a limitation of the study due to sample size. The error bars of the TR-n12 and TR-n25 overlap, so it is not possible to say there is a statistically significant difference from each other.

Figure 4. Mechanical testing of fully hydrated TR proteins (inset shows 1/n dependence) Source

Additionally, SRT protein films have been suggested as a potential solution to the issues related to the release of microfibers into the water from washing. A cloth made from polyester was coated with an SRT protein film and was found to dramatically increase the cloths resistance to abrasion (and microfiber release) compared to cloths that were not coated with SRT protein films.

While there is still a lot of further research to be done, SRT-based proteins are a promising avenue for making our world a little bit less plastic.

~Isla

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Photoactivated Self-healing Copolymers- It’s Lit

Posted on March 25, 2019 by | Leave a comment

A scratch on your car may no longer need a trip to the auto-shop. Simply applying heat or light could remedy this issue. This idea could soon be a reality using vitrimers, a new class of plastics that have thermal and chemical stability, but can also be self-healing on a small scale and fully recyclable on a larger scale.

Taylor Wright from Dr. Wolf’s group at UBC. Source

In 2018, at the University of British Columbia, Taylor Wright under the supervision of Dr. Michael Wolf investigated the photoactive self-healing properties of vitrimeric copolymers.

Photoactive materials undergo physical and chemical changes in response to illumination. The development of responsive materials to both heat and light were explored for the first time through the incorporation of functional molecular groups into the polymeric backbone of these systems.

Wright and Wolf’s focus on the molecule’s response to light also offered a new aspect into vitrimeric research compared to the previous studies, that exclusively focused on the vitrimers’ response to heat.

Figure 1. Comparison of thermoplastics and thermosets upon heating. Source

So what exactly are vitrimers? Vitrimers are a new class of polymeric material that was first created in 2011 by a Polish physicist, Dr. Ludwik Leibler. By combining characteristics of thermosets and thermoplastics, Leibler was able to develop a material that is strong and durable, yet moldable and recyclable.

Thermoplastics are made of plastics linked by intermolecular forces. They can be easily molded and shaped under heat, then cooled down to produce the final structure. This allows for ease when it comes to processing. Additionally, this property allows them to be recycled to produce new products.

Conversely, thermosets involve irreversible cross-linking, connecting the backbones of the polymer chains with molecular bridges. This results in enhanced chemical and heat resistance, making the material less susceptible to stress-cracking. However, due to their cross-linked bonds, these materials do not melt upon exposure to heat,  unable to remold and recycle.

Vitrimers combine the best properties of both materials; structural integrity is improved through cross-linking, as well as self-healing and fully recyclable properties.

Figure 2. The molecular structure of the photoactivated vitrimeric copolymer created by Wright and Wolf. Source

As seen above in Figure 2, the vertical wiggly line splits the system into the two unique parts that make this a copolymer. The left side shows the aromatic anthracene molecule that crosslinks into a dimer in response to UV radiation.  The amine on the right side behaves like a more traditional vitrimer and responds to heat to form reversible exchanges.

Originally, their aim was to create a single polymeric system that responds to both heat and light simultaneously. However, during their research, they found that amines directly bonded to the anthracene molecules simply do not engage in the bond exchange process. They believed the electronics of the ring alters the behaviour of the molecule in comparison with non-aromatic amines.

Studying the photodimerization and thermally exchangeable functionalities of the copolymer based on the vinylogous urethane vitrimer, the self-healable properties can be seen in the video above. Self- healing polymers are a class of materials that enable the repair of micro-scale damage in the coating, ultimately restoring the passive state of the metal substance.  This enables reprocessability or longer lifetimes in cross-linked polymeric materials. The systems containing anthracene undergo self-healing through reversible reactions, allowing monomers and polymer chains to link and unlink.

Figure 3. Polymer sample, P2, mounted on a glass slide. A scratch from a razor blade can be observed. Source

Wright and Wolf tested the modification of surface properties by using a razor blade to scratch a polymer sample (that Wright denoted as P2), that was mounted on a glass slide. By using optical microscopy, the scratches were observed as dark lines crossing the sample, as seen below in Figure 4. The scratches were seen to decrease in width and ultimately close during heating through a series of expansions and contractions of the material, which can be seen in the video above.

Figure 4. Optical microscope image of (a) sample P2a initial scratch, (b) P2a after heating (c) sample P2b initial scratch, (d) and (e) P2b after heating. Black scale bar is 300 μm. Source

These specific Wright and Wolf vitrimeric copolymers will not be scaled up for commercial use, due to the difficulties of incorporating the two components of the copolymer together. However, the general idea of vitrimeric materials has “almost limitless applications”. For example, they can be incorporated into products that have a long lifetime, such as shipping materials and plastic stadium seats which can be recycled into new products once they start to deteriorate.

Additionally, Wright is currently working on vitrimers that start as a viscous liquid, much like thermoplastics, that can be easily molded and processed. This possible advancement will provide more flexibility with processing the starting material and ease in the synthesis process.

~Brina, Isla and Taiki (Group 4)

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Polyester Suits: a Fashion and Environmental Faux Pas

Posted on March 7, 2019 by | 7 comments

Although polyester suits are no longer a fashion statement like they were in the ’70s, polyester and other synthetic materials such as nylon are still very popular materials used to make clothes due to their accessibility, durability and cost-effectiveness. Polyester, nylon and acrylic fibers are among the most popular synthetic fibers on the market. As their name would imply, synthetic fibers are manmade, synthesized fibers and are petroleum-based products.

Figure 1: The manufacturing process of synthetic nylon fibers. Source: Japan Chemical Fibers Association

One of the advantages and appeals of synthetic fibers is that they can be made using recycled materials. This recycled material can be old polyester materials themselves or can even be old plastic water bottles or other recyclable plastic products. There are many companies actively working to use recycled materials to make their apparel and while this may seem beneficial and an excellent solution to fully utilize plastic products to their full potential, it may actually be a double-edged sword. More people could be inclined to use plastic products, as they would assume that the plastic will be recycled properly. Unfortunately, that is not often the case. Not all the plastic products on the market are recycled responsibly and instead can contribute even more to the growing plastic pollution and microplastic issue as mentioned in my previous post. But even when plastic IS effectively recycled to make new fabric, there still is another hidden micro problem, a microfiber problem.

Figure 2: The cycle of synthetic polyester apparel made from recycled materials. Source: Japan Chemical Fibers Association

The video above outlines the not so micro issue surrounding microfibers.

Essentially, every time you wash a piece of clothing made of synthetic materials, tiny fibers or pieces of plastic, called microfibers are released. These microfibers are a type of microplastic since they are essentially micro pieces of plastic. It causes an issue due to the microfibers being too small and bypassing the filters in both our washing machines and at water waste treatment sites.

Figure 3: The estimated amount of fibers released from every wash for three synthetic fibers commonly used in the textile industry. Source for data.

This study estimates the amount of microfibers released (in mg) after the first five washes of 6 kg (the weight of a typical load of laundry) of three different types of commonly used synthetic materials. Figure 4 illustrates the data from their study. While looking at this data, it can be concluded that after the first five washes, the number of microfibers released decreases. However, other studies conclude the opposite—that the amount of microfibers released actually increases the more that the clothing items are washed due to the degradation of the product and the loss of structural integrity.

Figure 4: The amount of fibers (in mg) released from washing 6 kg of synthetic material. Source for data.

So, what can be done to mitigate the amount of microfibers entering our waterways and contributing to the alarming microplastics issue? Some studies suggest implementing better, higher quality filters in waste treatment plants and found them to be extremely effective at trapping these microfibers, decreasing the amount of microplastics entering waterways by 98%. Additionally, there have been other suggestions that include using proteins found in squids to make a biomaterial that can be used to make fabrics. The simplest solution, however, is to just be more conscientious about the products you purchase. By looking for products that have blends of both synthetic and natural fibers not only can recycled materials be incorporated, but also the integrity of the fabrics is improved to prevent less microfiber shedding, leading to the best of both worlds.

~Isla

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Hydroelectricity: A Temporary Band-aid

Posted on January 28, 2019 by | Leave a comment

Global temperature averages are increasing at abnormal rates. Sea levels are rising, ice caps are melting, and nature is dying. Almost all governments and scientists worldwide have been looking for solutions to impede the fate that humanity is heading towards. One of the ways is through using a cleaner energy source such as hydroelectricity.

In the past two decades, hydroelectricity has become more popular as a substitution for fossil fuel powered energy production. Its claim to fame was that it was a clean way to generate electricity; it was a viable solution for the future as climate change started to become a mainstay in the news. Initial studies had hydroelectricity being almost emission free!

Vattenfall Study for Carbon Emissions of Fossil Fuels, Renewables, Nuclear. Source: Wikimedia Commons

However, hydroelectricity was also declared a part of the greenhouse gas problem.

When thinking about producing electricity using water, one would think of it as being a clean and renewable process. It’s water! People bathe in it and drink it. How can it be dirty?

Unlike coal, a non-renewable resource which takes millions of years to form, the water isn’t being burned or used up. However, like coal , it is not clean (albeit to a much lesser extent).

Clean water for drinking. Source: kisspng

The basics of hydro-power is that water is pumped through a turbine to induce spinning. This motion activates a generator, producing the electricity which has become so important in daily life. The dirty part comes from the carbon emissions generated during construction and passively during the hydroelectric dam’s lifetime.

Typical hydroelectric dam. Source: United States Geological Survey (USGS)

Throughout the building process, many carbon sinks will be destroyed as trees and plants will be chopped down. This reduces the overall carbon dioxide that can be stored while releasing the carbon dioxide back into the atmosphere. Not to mention the habitats and the environments near the power plants that are destroyed at the same time.

Hydroelectric dam construction by China. Source: Giorgio Taraschi / Al Jazeera

However, it’s not just during the initial construction that hydroelectric power is unclean. Plants and other living things are able to grow in these bodies of water.  All living things that die and decompose in the waters produce methane, carbon dioxide, and nutrients. The nutrients in turn help other living organisms grow, thus continuing the cycle. When thought about in this manner, the hydroelectric dams become carbon emission generators.

In its current state, hydroelectricity is not a clean source of power. Nevertheless, it is a viable alternative to fossil fuels as we transition to better solutions. There is hope in the future that hydro-power becomes one of these solutions. Companies are still innovating and working towards a setup that is gentler on the environment while still providing adequate amounts of electricity.

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Microplastics No Longer a Micro Issue

Posted on January 27, 2019 by | Leave a comment

You wake up in the morning and then press snooze on your alarm clock one more time before groggily dragging yourself out of bed to the bathroom. Quickly you brush your teeth with your electric toothbrush, then hop in the shower and lather yourself with the bottle of that fancy body wash with the microbeads in it. In the kitchen, you grab the lunch you made from the prepackaged salad mix before heading out the door. Now in your car, you turn some knobs on the dashboard to play some music on your way to work or school. In case you have lost count, you have already encountered half a dozen plastic products and it isn’t even 9 AM yet.

Polymerization of ethylene to form polyethylene
Source: Image © Eugbug

Plastics are the result of taking petrochemical monomers (such as ethylene) and converting them to long chain polymers. This is done through a process called polymerization which is relatively easy and cheap to do. Another process, called photo-oxidation occurs as a result of exposure of these long-chain polymers to UV radiation (from the sun) and oxygen (in the air). Essentially, this process causes plastics to become brittle and in combination with the elements (wind and water abrasion), causes the degraded plastics to break into minuscule pieces. When these pieces are between 0.1 and 1000 μm in size, they are referred to as microplastics.

How microplastics are produced and introduced into the food cycle. Roy Cooper/The National

Due to plastics being such a cheap and omnipresent resource, there has been little incentive to recycle such products, leading to an accumulation of plastic waste in landfills and the world’s oceans. It is tragic to see seawater bodies filled with plastic, but only recently has it come into light that these microplastics are starting to make their way into our own bodies too. While seemingly obvious, microplastics have been reported in seafood, but they are also found in fertilizers and in common food items such as beer, sugar and salt. One study from last year found microplastic particles in 17 salt brands from 8 different countries. Additionally, atmospheric fallout of microplastics has also been reported, so it’s very possible we have already been inhaling and consuming microplastics.

A (a) polyisoprene/polystyrene, (b) polyethylene, and (c) pigment (phthalocyanine) fragment. Image (d) is a nylon-6 filament. Source

So what can be done to mitigate the amount of plastic that is becoming ocean waste and effectively microplastics? Our daily lives and plastic products have become too intertwined to even entertain the thought of completely banning plastics worldwide. Fortunately, there have already been movements to ban especially harmful products such as microbeads found in many skin products. But, some effective steps that everyone can implement into their routines are to reduce the use of single-use plastics such as plastic straws or plastic grocery bags. The issue with single-use or “disposable” plastics is that they are difficult to recycle and thus only contribute to plastic waste. Additionally, choosing products that have less plastic packaging is also a viable way to lessen your plastic consumption. Lastly, whenever possible, recycle your plastic products so your plastic water bottle can become a new plastic water bottle and not the microplastics in our food.

The following video is a collaboration between BBC Earth Lab and Exeter University and shows how microplastics can make it through the food chain and potentially onto our plates.

~Isla

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