Plastics: A Close Look

 Created Nov 8 2012 – 1:00 AM Revised Aug 19, 2014 and April 20, 2018

Albatross at Midway Atoll Refuge by U.S. Fish and Wildlife Service Headquarters

There’s irony in having small bits of floatable plastic debris and larger chunks of trash in our oceans. Millions of years ago, many of the hydrogen and carbon atoms within these man-made polymers were part of marine life. Death, deposition and pressure simplified the organic molecules of the dead. Then a species that indirectly evolved from these oceanic ancestors accidentally stumbled upon a crude liquid. Eventually they learned to use not only its energy content but its building blocks. Some of these were linked into molecular chains that could be molded into any shape. But these chains proved to be resistant to the usual degradative action of bacteria and fungi. Coupled with one-time use, over-consumption and poor recycling, we have a problem on our hands as the plastic in oceans severely impacts wildlife.

We all curse plastic when it breaks and worry about its other drawbacks, which are amplified by human behaviour. But they do limit our use of other resources such as wood and metal.  Plastics chemists discovered the catalysts that made plastics more affordable and kept devising recipes in order to suit practical needs like placing side chains with hydroxyl groups on a contact lens polymer that could attract enough water to lubricate the eyes.

Yet perhaps because of the negative connotations of plastic, even chemistry professors writing organic chemistry textbooks for freshmen avoid the topic. The classic and otherwise excellent Organic Chemistry by Morrison and Boyd published between the late 1950’s and 70’s devoted only 8 of its 1183 pages to plastic. One could argue that the basics have to be covered adequately before one can understand how high temperatures can induce petroleum’s larger molecules to become free radicals, which with rapid cooling, convert into small, unsaturated hydrocarbons. One of those products, ethylene, is then polymerized into polyethylene which is used in wraps, squeeze bottles, disposable gloves, garbage bags and to weld cracks in kayaks.

But relative to how much space three recent popular organic chemistry textbooks devote to plastic, Morrison and Boyd wrote a thesis. And yet while sitting on a chair cushioned by polyurethane, I look around me and notice the acrylo-nitrile-butadiene-styrene(ABS)on my keyboard and mouse, two polyester backpacks on the floor and a polypropylene pot under my avocado tree. Students should learn how such ubiquitous substances are synthesized, and that they have different tensile strengths and varying resistance to substances like alcohols. And they should learn about the carbon footprint involved in producing such large quantities and the consequences of not recycling most of them.

On the internet there are still people worrying about bisphenol A (BPA) leaching out of plastic pots and getting into their herbs and marijuana. For starters, the production of plant pots does not use BPAs. The latter is associated with polycarbonate plastic found in DVDs , plastic helmets and other hard plastic products., some of which are labeled as code 7. In 2008, Health Canada banned BPA from plastic baby bottles and luckily the European Union followed suit as a precaution. The former also reassessed dietary exposure to the chemical and found that it was lower than what was previously estimated. They concluded that exposure to BPA through food packaging is not expected to pose a health risk to the general population, including newborns and young children. Other regulatory agencies in the United States, the European Union and Japan agreed with their analysis. The average exposure was 0.055 micrograms per kilogram of body weight per day. Not all concerns regarding BPA can be dismissed. Fish seem to be the most BPA-sensitive organisms. Depending on whose guidelines one examines, the predicted no-effect concentrations in freshwater range from 0.175 to 1.7 nanograms per milliliter or parts per billion(ppb). We also need more studies that look at the combined effect of various low level endocrine disruptors and other toxins in the environment.

While China’s economy has mushroomed in the last two decades, its short-lived plastic exports have found their way into the world’s still largest economy, the United States. At the same time, we’ve had computer, electronic game and phone revolutions, all of which have fed an exponential growth in the amount of plastic found in municipal waste. The only plastics that can be recycled economically so far, and in part only because China buys most of the refuse, are high density polyethylene(HDPE), polyethylene terephthalate (PET) and polystyrene. (recently China has refused some of Canada’s used plastic because of contamination.) Milk jugs are made of HDPE and PET is found in ziploc food storage bags, disposable water bottles, soft drink bottles and recently, vegetable packaging. The latter used to be code 6(polystyrene), which shrinks in the microwave when heated and is not as easily recycled.  in 2011, only 31% to 44% of Canadian homes had access to centres that could handle polystyrene, depending on the variety of that specific plastic.

Although more recycling can be done—the recycling rates for those two materials in the U.S. are only in the 30% zone—people have not warmed up to the 3 R’s“reduce” option. At least in theory, we could buy less plastic stuff when possible and drink tap water. To avoid plastic cups and cutlery at parties, spike the punch and get the guests to do the dishes. *
Such an approach does not have to negatively impact the economy. Money can be spent on non-plastic products and services and on paying down debt, which in the long run increases purchasing power.

The idea of biodegradable plastics is appealing. If they are produced on a global scale, however, there could be undesirable effects, especially if the raw materials are grown on land and not extracted from algae. The land needed for additional biomass could lead to deforestation, and then subsequent growth of crops won’t compensate for CO₂ released by decomposing trees and biodegradable plastic. One thing about conventional plastic: when not incinerated but kept in the home or in landfills, it does, at least for a century, keep petroleum’s carbon away from the atmosphere. And no one will throw away Canadian plastic $20s.

People often forget that we pay for packaging. If it’s good enough for stores to keep things visible and organized, why not do likewise?

* In the sixties throughout the 1980’s, a party with any combination of my 14 aunts was guaranteed to be free of plastic utensils.  After cooking a mind-blowing meal for 30 people, they were happy to chat among themselves and wash dishes faster and better than the average machine while the men played Italian card games —another activity with a low environmental impact :)—–the un-division of labour was terribly sexist, mind you!)

Sciences in the Mural of Life

Created Nov 8 2012 – 1:00 AM Revised Aug 19, 2014 and April 20, 2018

There’s irony in having small bits of floatable plastic debris and larger chunks of trash in our oceans. Millions of years ago, many of the hydrogen and carbon atoms within these man-made polymers were part of marine life. Death, deposition and pressure simplified the organic molecules of the dead. Then a species that indirectly evolved from these oceanic ancestors accidentally stumbled upon a crude liquid. Eventually they learned to use not only its energy content but its building blocks. Some of these were linked into molecular chains that could be molded into any shape. But these chains proved to be resistant to the usual degradative action of bacteria and fungi. Coupled with one-time use, overconsumption and poor recycling, we have a problem on our hands as the plastic in oceans severely impacts wildlife.

We all curse plastic when…

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From Playing Cards to Clover

If we keep looking at the same thing over a period of time with an uncritical, non-curious or distracted mind, attenuation sets in. And not only do our nervous systems tune out what’s commonplace, we also develop a false sense of history. We act as if things always were as they currently appear to be, and as if they will continue to be immune from flux.

Take playing cards as an example. If one was raised in North America and was not in contact with recent Spanish, Moroccan or Italian immigrants, it’s likely that the person has a fixed image of playing cards: 52 cards, 13 in each of four suits: clubs (clover), hearts, spades and diamonds with three of the cards being a king, queen and a jack.

The four suits of Neapolitan playing cards like those of other Spanish and Italian cards differ from French ones.  The former’s suits are far more similar to those of the first cards imported into Europe from Egypt in the 14th century. Pic by the author.

But these familiar cards are just one version, one that originated under the rule of  King Charles VI of France between 1380 and 1422. They continued to evolve a little later in the 15th century into their current forms which are neither unique nor static.  Take a tour of  cafes in Italy and you will see people playing with variations upon the theme of Italian-Spanish cards:  the king is still present, but there is a cavalier and a servant instead of the queen and jack, respectively. And there are only 40 cards with suits of clubs (large sticks), cups, swords and coins. These strike more of a resemblance to the first cards that were imported into Europe by Italian merchants around 1360. They discovered them while trading with Mamluks in Egypt. The cards had the same suits like those of contemporary Spanish and Italian cards, except that they featured a wand instead of a club.  Regional cards in Northeastern Italy still include a wand as a suit.

I often wondered why the word “club” is used for the clover leaf, one of the four suits of French cards. One hypothesis is that the suit was associated with commoners who grew clover alternately with their crops for fodder and in order to enrich the soil. But wooden clubs were also commoners’ weapon of choice, so the name “clubs” stuck to clover.

Clover is a legume whose roots include a mutualistic relationship between bacteria and plant cells.

The arrows point to white clover’s root- nodules, the site of nitrogen fixation by mutualistic bacteria. (The scale is in inches. 1 inch = 2.54 cm) Picture from NC State Extension Publications – NC State University

Thanks to bacterial enzymatic action, valuable nitrogen compounds are made from otherwise unusable nitrogen air molecules. In exchange, the bacteria receive shelter and sugars. Before many people developed the bad habit of adding herbicide to lawn grass, white clover seed  was often mixed with grass seed. Clover, when coexistent, helps grass by adding nitrogen compounds to the soil.

Like playing cards, not all clovers are alike. White clover is adapted to moist conditions. It should not be the only companion of lawn grass. Especially where grass grows on slopes where water drains easily, it makes more sense to grow bird’s foot trefoil. Scientifically known as Lotus corniculatus , it is another leguminous plant which does better in arid conditions and which will help abate dandelions. These unpopular relatives of the lettuce in turn out-compete grass when less water is available. A smaller legume with smaller yellow flowers, black medic, can do well in both moist and more arid soils. And of course there is a common origin to the genera of the bird’s foot (Lotus), to medic (Medicago) and to that of at least 238 Trifolium species, including red and white clover—-we see it in the similarity of leaflet shape, small pea-like flowers and to the all-important and welcome infection in their productive roots.

Clover and clover-like plants belonging to 3 different genera of the legume family: from left to right, Trifolium repens (white clover), Lotus corniculatus (bird foot’s trefoil) and Medicago lupulina (black medic). Just about all Trifolium species are bee-pollinated. All pics from wikipedia commons.

Their family Leguminosae evolved about 56 million years ago, 9 million years after large dinosaurs went extinct. A few million years later, their most important clades separated. From genetic analyses, it’s been determined that their evolution occurred quickly, reminiscent of  the way playing cards quickly branched out in Europe. And like the latter,  the 18000 species of legumes are now spread all over the planet. They are being used for food, oil, lumber, fiber, medicines, aesthetic purposes and not least of all, for a vital role in the Earth’s nitrogen cycle.

SOURCES:

Lavin, et al. 2004. Evolutionary Rates Analysis of Leguminosae Implicates a Rapid Diversification of Lineages during the Tertiary. Systematic Biology 54 (4): 530-549 http://sysbio.oxfordjournals.org/content/54/4/575.full

The Botanical Garden. Phillips and Rix

The Mediterranean and Mediterranean World. Francois Braudel

The four suits of a pack of cards www.theguardian.com/books/booksblog/2013/dec/04/books-advent-calendar-4-four-card-suits

Have you ever wondered why the symbols on playing cards are called…. http://www.brierfieldbridgeclub.org.uk/themes/Have%20you%20ever%20wondered.htm

Postscript:

Since I wrote this article I had a hard finding birds foot trefoil with orange, young petals. Finally saw some this week!

Fun With Shapes and Numbers

In the diagram below, in between two circles, each with a radius of 1 meter, three smaller circles are squeezed in, centred at C₁ , C₂ and C_3. If you imagine it was possible to continue drawing and squeezing in more circles until you had a billion of them, how much space would be left between the top of the smallest circle and point A? And what ubiquitous thing’s diameter is very close to that distance?

What could fit into the tiny space between point A and the smallest of a billion circles squeezed into the space between the two large circles, one of which is centered at B? Diagram by the author.

This is a variation of an old problem, and although the situation is often used as an example of a non-geometric series in calculus books, it could also be solved with some basic algebra and induction. And for that reason, versions of the puzzle have appeared in math competitions for bright kids who have yet to venture into calculus.

Let’s begin by solving for the radius of the first circle (the red one centered at C₁). If we come with expressions or numbers for all three sides,  we could apply the Pythagorean theorem to triangle ABC_1.

Notice that AC₁ ‘s length can simply be obtained by subtracting the radius of the red circle from the 1-meter length of the square’s side, which we obtain from the radius of the large, identical circles.

AC₁ = 1 – r₁.

Since AB² + AC₁ ² = BC₁ ²,  where the hypotenuse, BC₁ , is simply the sum of the radii, we obtain:

1² + (1 – r₁) ² = (1 + r₁) ²

Solving for r₁ yields  r₁ = ¹/₄ so the red circle’s diameter = d₁  = 2 * ¹/₄ =  ¹/₂ .

Not to bore you, we will walk through the steps only one more time to obtain the diameter, d₂, of the blue circle centered at C₂.

We add the red circle’s obtained diameter of  ¹/₂ to the radius of  the blue circle, r₂ , and then subtract the sum from 1 meter to obtain AC_2.

AC₂ = 1 – (¹/₂ + r₂ )=   ¹/₂ – r₂

Then we apply the Pythagorean theorem to the second triangle, ABC₂,

AB² + AC₂ ² = BC₂ ²,  or:

1² + ( ¹/₂ – r₂) ² = (1 + r₂) ²

1 + ¹/₄ – r₂ + r₂ ² = 1 + 2r₂ + r₂ ²

¹/₄ = 3r₂

r₂ = ¹/₁₂

so the blue circle’s diameter = 2 * ¹/₁₂ = d₂ = ¹/₆.

As promised, without going through the similar details, d₃ = ¹/₁₂ and for a fourth circle that we squeeze in, d₄ will be ¹/₂₀.

Now a pattern becomes apparent. For the diameter of the nth circle, d_n,  d_n = ¹/_n(n+1). But if you did not realize that, you could still solve the problem. After all_, we’re interested in the leftover distance between the top of the billionth circle and point A.

After we squeezed in one circle , we had a diameter of  ¹/₂ . After squeezing in a pair, the sum of the two circles’ diameters ¹/₂ + ¹/₆ = ²/₃. Squeeze in three circles and the sum is  ¹/₂ + ¹/₆ + ¹/₁₂ = ³/₄ .  A fourth insertion yields ¹/₂ + ¹/₆ + ¹/₁₂ + ¹/₂₀ = ⁴⁸/₆₀ = ⁴/₅.

So for squeezing in an n-number of  circles, the sum of the diameters is ⁿ/_n+1 and since the side of the square is 1 meter in length, the remaining distance will be 1 – ⁿ/_n+1. Using a common denominator, that expression is equal to ^{n+1 -n}/_n+1 = ¹/_n+1.  For a billion circles then, the leftover distance would be

¹/_{1 000 000 000 +1} = ¹/_{1 000 000 001} meters,

which is extremely close to being to a nanometer.

α-D-Glucopyranose, the hexagonal form of glucose. ^{Image from Wikimedia commons.}

¹/_{1 000 000 000} meters or 1 nanometer, is a little more than three times the size of a single water molecule, and just slightly wider than the ring of one glucose molecule, the fuel for all brains, including those that devised and solved this puzzle. And use up just an extra iota of  glucose to realize that the leftover space would be long enough but not wide enough to accommodate the entire molecule. Finally, imagine a circle for every person alive on Earth in 2050, about 9.4 billion, and the distance remaining between the smallest circle and point A will only as big as the diameter of the smallest and most common atom in the universe.