The Saviour and The Devastator : Fire Retardants of the Future

Mankind, since time immemorial has been using polymers. Before you read any further, lift up your head and look around. Almost everything that catches your eye is either a polymer or made up of polymers. Such is the influence of these macro molecules on one of nature’s macro creations, the Humans. Most polymers that we use on a daily basis are petroleum based i.e. they are made up of long chain of carbon, making them highly inflammable. A tiny spark can cause a massive burn down of everything around us. But this seldom occurs because of materials that are added to polymers called Flame Retardants.

Flame Retardants are compounds added added to polymers to check their ability to catch fire and there by prevent the scale of damage caused in a fire accident. Flame Retardants have been used in the production of dyes, varnishes, adhesives, resins, plastics, textiles, mattresses, couches, carpet padding, curtains, flooring, composite materials, packaging, insulating materials, glues, surface coatings, electronic components and many more. In order to understand the working of Flame Retardants we must first understand how a polymer catches fire and burns out rapidly. When a polymer comes in contact with thermal stress like fire, it first degrades. As a result, small molecules are liberated, which mix with air. If these particles are at a temperature above their ignition temperature, they react with the atmospheric oxygen and combustion occurs. This further increases the temperature of the system. A closed loop system with heat-feedback is generated. The heat feedback increases the intensity of fire in multitude. In such a case, Flame Retardants come as a saviour to avoid any massive destruction.

Different Flame Retardants act in different ways based on their structure. Some form a char layer on the polymer surface. This layer insulates the polymer and cuts off the heat feedback. Another type of Flame Retardants are materials which degrade at decomposition temperature of the polymer to form particles which scavenge the combustion propagation radicals.

 

Flame Retardants can be broadly classified into three categories based on their chemical composition: organohalogen compound, organo phosphates and minerals. They work by either cooling, diluting or insulating and thereby slowing down or preventing the spread of fire. Flame Retardants don’t make

the polymer resistant to fire but give people the time to escape and put off the fire in case of an accident. Typically, 1-30% of Flame Retardants are present in a polymer depending upon the nature of the material. The biggest challenge about choosing the right Flame Retardant is that it should not alter the properties of the host polymer. Hence, they are usually made up of volatile compounds and added such that there is no bond formed with the polymer.

Like every invention till date, Flame Retardants have also been a two-edged knife. Mineral Flame Retardants like Alumina trihydrate requires open cast mining. This affects the natural habitat of several species, causes erosion and disrupts hydrology. Though an excellent flame retardant, because of these reasons, it cannot be used in a large scale. The organo halogen flame retardants like organochlorides and brominated compounds are very good flame retardants in gas phase. But they are soluble in organic solvents. They enter the food chain and traces of them being accumulated in human tissues have raised severe concerns. The toxicology studies further led to ban on these compounds. The organophosphates, though expensive than organohalogen compounds are very effective flame retardants and active in solid state. In the presence of excess of oxygen, there is char formation and thus insulation. But when the availability of oxygen is very less, they form volatile radicals and become as hazardous as the organohalogen compounds. These volatile compounds are called Persistent Organic Pollutants. They break down very slowly and persist in the environment as well as in human tissues. In the presence of UV light, they break down to give toxic substances like dioxin and furan.

These concerns gave rise to the need for development of a non-toxic, Eco friendly and biodegradable Flame Retardant. One such material can be synthesised using plant precursors like Gallic acid and 3,5-dihydroxy benzoic acid which are abundantly present in grass and buckwheat. Conversion of these hydroxyls to esters using phosphites gives the eco-friendly flame retardants.  Phosphorous can be recovered from the the waste water treatment plants.  It is a very important element in all organisms, present in food and hence not toxic. About 5-20% of  this flame retardant was incorporated into the polymer and tested for its properties. It is not petroleum based, but plant based. This reduced the huge pressure on non-renewable sources. Also, the compound can be easily synthesised on a large scale due to abundance of starting materials in nature. Upon decomposition, the degradation fragments can be consumed by microbes thus making it a more sustainable and safe material to guard us against fire accidents.

Beneath the Layers: Tattooing

For over a thousand years, tattooing has been a part of the human history, be it for an expression of religious belief and rites or personal interests. Today, people have converted their bodies into canvases, transforming themselves into a piece of art. Kat Von D, a popular American tattoo artist and reality TV star, holds the Guinness World Record for most tattoos given to a single person in 24 hours with 400 tattoos! With the rise in popularity, there is also a need to know the chemistry of tattoos, what exactly is in those inks and how safe they are.


Tattoo ink is composed of two components namely the carrier and the pigment. The carrier is a suspension which keeps the pigment evenly mixed and free from pathogens. Carriers usually consists of glycerine, water, isopropyl alcohol and witch hazel. They are used either individually or as a mixture of similar carriers.



A tattoo needle punctures the skin and causes a tiny wound. The body responds to all wounds by sending macrophages to the site, which swallow up any foreign invader. The pigment particles being too large for the macrophages to destroy, they remain in the dermis. This is layer of skin which lies below the epidermis, the outer most layer of the skin.  There is always generation of new cells and degeneration of old cells in the epidermis. If tattoo ink is placed here, it would last only for about a month before disappearing. But cells of the dermis do not replace themselves that often, making it an ideal spot for installing a permanent image. The dermis also is home to nerve endings and the part of the skin that receives blood supply. Hence one can feel each needle prick and things can even get messy.   A tattoo would fade if the macrophages succeed in breaking up the pigment into particles. In order to get a permanent tattoo removed, laser treatment is usually adopted where a a single colour in the tattoo is broken down into pigment particles which is further broken down by macrophages.


Tattoo colourants are intensely coloured compounds that can reflect light in the visible region of the electromagnetic spectrum. They are not dyes. Dyes require a physical or chemical interaction to react with the surface of the skin, develop their colour and to stay in place. Pigments provide colour without a chemical reaction and are held in its place by intermolecular or physical forces. The inks used for tattoos can be thus either inorganic or organic pigments. Inorganic inks are made
of minerals, salts or oxides found in nature. Organic inks come in a much wider array of colours than the inorganic ones.


Historically, pigments used in tattoo inks were from geological sources to produce certain colours. Carbon black and iron oxide were used to produce a black ink. Cinnabar, a mercury sulfide compound, was used to produce red hues. Cadmium red (CdSe), Cadmium yellow (CdS or CdZnS) were used to produce shades of red, orange, and yellow. Nowadays, ink manufacturers have moved from mineral based pigments to organic inks. Most of the colourants used today are carbon-based. A very small percentage of the pigments are approved for cosmetic use. Other pigments were originally developed for industrial applications, like paints or textiles and not for people. The Food and Drug Administration, which makes rules about what kinds of colours can be added to food, cosmetics and drugs, has made no such regulation for tattoo inks. Officially, no ink currently is approved to be used on human skin.


Tattoo inks also include many additives such as surfactants, binding agents, fillers, and preservatives. Many of these additives are employed to keep the pigments in a uniform suspension to avoid microorganism growth.

There are many risks involved with inks and the tattoo process. The most common of these risks is - infection. Other known adverse reactions include allergichypersensitivity and auto-immune reactions, granulomas, and interferences with medical diagnoses and treatment.


There are more than 200 colourants and additives currently used to produce tattoo inks, but their long-term outcome on the body is not studied well. Azo pigments are known to release carcinogenic aromatic amines as they break down specifically when exposed to solar or ultraviolet radiation. Some azo pigments found in tattoos, such as Solvent Red 1, can degrade into compounds such as o-anisidine, a potential carcinogen. The top chemicals of concern, found in tattoo inks are polycyclic aromatic hydrocarbons which is listed as a human carcinogen by the International Agency for Research on Cancer (IARC). These compounds can migrate from the skin to lymph nodes causing further problems. These carcinogenic chemicals are found mostly in the black inks and are mostly impurities from industries. Most of tattoo formulations are only between 70–90% pure. Tattoo inks may also contain potentially harmful metal impurities such as chromium, nickel, copper, and cobalt, which give bright colours. 


Despite the risks, tattoos are an inseparable part of world culture, having its own history, from a tribal art to a modern way of self-expression. There is always a story behind every tattoo. Humans, by nature, always have a liking to add a bit of colour and self-expression to their surroundings and even themselves. If the chemical industry would do a little bit of investigative research, tattooing will become a more safe, healthy and vibrant art in the future.

MARK OF A CHEMIST

Science is an art of keen observation and understanding of what we see around us. There is a widespread, firm belief in our society that “Science” is a dry and rigorous study reserved only for the elite. Changing the psychology of the society over issues that have been believed over a long period of time is a herculean task. Today, science has reached all corners of the world enlightening people. But all this started in the twentieth century. With the industrial revolution, there was a scientific fervur created in the public. Primo Levi, Peter Atkins, Robert Woodward, Fyodor Dostoyevsky, Emily Dickinson and Geoffrey Chaucer are some of the very few people, who, for the first time, brought “Science” out of the labs and gave it a human touch!

In the words of Feynman, “these folk are typically of a Platonic mindset, revealing in what they regard as the crystalline beauty of physical theory, with its deep principles of symmetry and universality, to them, it seems as if the ability of chemists to make sense of the messy complexities of molecules is akin to magic.”

Primo Levi

Primo Michele Levi was an Italian Jewish chemist who authored several books, novels, collection of short stories, essays and poems. He was a Holocaust survivor. Levi was a student of University of Turin. The racial laws and the prevalent fascism in the then Italy forced him to work in remote places of Milan with a false name and false papers. He later joined the partisans and fought against the Germans; captured and sent to the death camps in Auschwitz. He survived only because he was a chemist, an incident which in turn made him a writer!

The Germans, during the second world war, were running out of rubber for their military vehicles. So, they set up a synthetic rubber factory, very close to the death camp. They needed chemists to work in this new factory and Levi, starving in the German winter, successfully cleared an exam, to prove to the Nazis that he was indeed a real chemist. As he worked inside the warm labs, others froze to death outside. He is more famed for the way he wrote about chemistry, writing about the choice of turning one chemical into the other, the mysteries, not sounding like the precise science of the textbooks. He spoke of what chemists feel like. He was not a great chemist; he did not do any special discoveries. But he represents thousands of chemists, who worked very hard, during the 1940s but whose voices were never heard, making him a great chemist!

The Periodic Table, by Levi in 1975 is a masterpiece, where he uses his experience and knowledge as a chemist to narrate the intriguing relationships of

his childhood. Levi knows everything about chemistry and we know very little, which is crucial to enjoy The Periodic Table. Many of the situations are presented as puzzles that Levi solves or fails to solve. He presents fiction and reality wrapped in a metaphor of Chemistry. Levi had been concerned that his books might be admired more as a wartime witness than as a literary achievement. The reader begins to understand that chemistry is not just a "subject" instead, as he says “bewildering intellectual scaffolding laboriously erected to frame reality: it is reality”. Chemistry is what happens when we breathe,  when we see, when we touch .Our behaviour with others is also chemistry at some greater level. 

Levi describes the laboratory preparation of zinc sulphate as “the so tender and delicate zinc, so yielding to acid which gulps it down in a single mouthful, behaves, however, in a very different fashion when it is very pure …”.When he could not find the sodium necessary to purify and dehumidify the Benzene he wanted to distill, he used it twin in the periodic table, Potassium, and nearly blew up the laboratory. From it he concludes that one dare not trust the almost the-same, the practically identical. "The differences can be small, but they lead to radically different consequences, like a railroad's switch points; the chemist's trade consists in good part in being aware of those differences, knowing them close up, and foreseeing their effects. And not only the chemist's trade." He offers parallels between the reactions in a test tube and the things that happen in the world at large. The Periodic Table was named the Best Science Book Ever written in Chemistry, by the Royal Institution of Great Britain.

The Mark of a Chemist is another very famous work by Levi. He writes about what it is like to be a student of Chemistry. In the theatrical dialogue based on a selection of his texts, he answers to the questions of the interviewer. In an intense and unique exchange, he talks about his scientific vocation, his life, witness to the concentration camp, and his experiences as narrator and a laboratory technician. The conversation touches upon the discoveries and emotions of a young chemist who was attracted by the secrets of matter. It covers the painful perversions on scientific knowledge in the laboratories of Auschwitz, the challenges and the joys of the work done well. Primo Levi carried the mark of he being a chemist on his skin. He was a chemist by trade and a chemist out of a deep passion.  The mark is in his writings.

INDIGO

In this culturally diverse world, it is difficult to find anything that is equally embraced all across the globe. One such thing that has made to this list and found place in wardrobes all around the world, transgressing the local culture is the Jeans!

The Indigo dye used for blue Jeans, today, is a billion dollar industry, with its history dating back to 55 BC. The Britons used this wonder dye, which was made of woad. Blue was a symbol of valour and courage. A document written after the invasion of Britain by Julius Caesar records the love they had for blue. They believed that the occasional bluish colour gave a more terrible appearance during the fight!

In ancient India, the Indigo industry was thriving and was the led producer in the world. The etymology of the word INDIGO can be traced back to the Greek work INDIKON meaning Indian.

Indigo is a tetracyclic organic compound. It has alternate double bonds which give rise to the typical blue colour in the range of 450-420nm. This dye is found naturally in the leaves of woad or Isatis tinctorial found in Asia and Africa. The leaves are fermented in vat, in the presence of strong alkali such as potash. This when hydrolysed yields a colourless water soluble form of the dye, known as the leuco dye. The fabric to be dyed is immersed in it and on exposure to air, the leuco dye undergoes oxidation to form Indigo, which is water insoluble blue pigment, firmly attached to the fibres.

Isatin

Thanks to the presence of few colouring compounds present along with the natural Indian dye and its uneven colouring and the huge market worldwide, there began a search for effective ways to artificially synthesise Indigo.

Adolf von Baeyer, for the very first time, in 1870, synthesised Indigo using isatin as the starting material and published the same in1883. In 1890, BASF & Hoechst found an economic way for large scale production of Indigo using naphthalene as the starting material. Four years later, Hoechst also reported a method for synthesising Indigo from aniline. This was a huge blow to the Indian Indigo Industry. By the start of 20^th century, the global demand shooted up while that for natural Indigo crashed. During I world war, the trade between Germany and Britain virtually came to a standstill, creating a market for Indian Indigo in Britain. Though this was a significant revival, it failed to compete in the global market. Aniline, which is toxic, is locked into the fabric and can’t be washed off. Arachroma, a Swiss firm found an aniline free process of synthesis of Indigo for denims.

There is a rich chemical, cultural and political history weaved between each and every strand of denim. So, the next time you flaunt a pair of Jeans, do remember the pigmented past of the the brave blue!

INDIGO