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Fluorine (F) is the tiger of elements – tamed it is a friend!
Posted on February 29th, 2016 by Dr. Sina Ebnesajjad in Chemical R&D
Fluorine is the most reactive of all elements, capable of reacting with everything, even gold, often violently. The exceptions are helium, neon and argon. Yet it has entered human life in quiet and vital ways resulting in today’s standards of living. From medicines to vascular grafts, cars, aircrafts, solar cells, International Space Station materials containing fluorine have silently redefined human life. They have also replaced dangerous alternatives such as anesthesia, PVC and mercury, all enhancing mankind’s chances of survival and living a healthy life.
A day with the Smith’s
A look at the daily lives of Smith family in Tucson, Arizona, reveals the profound essential role of fluorine chemistry through its salts, fluorocarbons and fluoropolymers in human lives.
Mr. Smith begins the day with shaving using a comfortable razor; it has a thin strip of polytetrafluoroethylene (PTFE) fluoropolymer. Besides lessening the cuts, the slippery PTFE makes the razor glide on his face. He gets dressed and puts on a favorite tie. It has never been dry-cleaned thanks to the dirt repellent fluorocarbon treatment of the tie.
He takes eggs out of the refrigerator that is chilled with a fluorocarbon refrigerant gas. The same fluorocarbon gas refrigerates the supermarket and food warehouse refrigerators. Mr. Smith makes an omelet for breakfast in a non-stick pan using just a few drops of avocado oil. The pan is coated with a thin layer of fluoropolymer paint. Recently, a friend asked him whether non-stick pans are safe. Mr. Smith told the friend he had been eating food cooked in fluoropolymer-coated pans for 40 years without any health issues.
Rain is in the forecast so to stay dry the children dress in water-repellent coats that include a microporous expanded PTFE (ePTFE) membrane in the fabric laminate (see my previous post). It keeps water out but perspiration vapors leaves through the fabric thud keeping the children comfortable. A similar material is used in hospitals to keep away bacteria from the surgery sites and wounds.
Everyone in the family flosses using a dental loss made of a PTFE fiber that does not scar gums. Inorganic fluoride salts are added to the toothpaste to help prevent tooth decay. Pain, loss of teeth, gum disease and disfigurement associated with tooth decay has been reduced since the introduction of fluoridation practice over 70 years ago. The Centers for Disease Control and Prevention proclaimed community water fluoridation as one of 10 great public health achievements of the 20th century (Source: Fluoridation Facts, American Dental Association, www.ada.org, 2005).
They pick up their cell phones, tablets and laptop computers on their way out of the house. Every device contains coaxial cables insulated with fluoropolymers and other components that rely on the unique dielectric properties of fluoropolymers. Modern electronics age has heavily utilized fluoropolymers. The required purity in the range of a few hundred parts per trillion can only be achieved using fluoropolymer process surfaces. Semiconductors silicon chips are manufactured with the aid of fluorine-containing gases for etching and chamber cleaning.
Mrs. Smith takes her son’s asthma inhalant along to his school. A fluorocarbon propellant allows him to receive accurate metered doses of the powder asthma medicine. A thin layer of a fluoropolymer coats the interior of the metal can to prevent the expensive drug from sticking to the surface. Metered Dose Inhalers (picture) allow the drug to be administered in a targeted and precise form. This keeps the exposure of the child limited to the required amount of the asthma drug. Today, 30-50% of the newly developed medicines contain fluorine in their chemical structure.
Mr. Smith leaves the house last, turns off the fluorine containing LCD displays on his desktop computer and the plasma TV screen. He resets the thermostat to reduce the running of the air conditioning. The central air unit contains a fluorocarbon called HFC. This gas has unique stability and reduced global warming potential. It keeps the air conditioning work efficiently.
Smith’s house is partially powered by photovoltaic cells installed several years ago. It is a good deal because after paying for the installation of the cells, they have been enjoying free power. A special fluoropolymer called PVF plays an important role in photovoltaic units by increasing their efficiency, protecting them from damage and increasing their useful life.
The rest of the power is supplied by power plants that have many components containing fluoropolymer. Those devices contribute to reducing carbon dioxide and other emissions. Fluoropolymer coated bag filters remove harmful particles of fly ash from the smoke discharged by coal burning plants (there are still many running). There would be a huge decrease in particulate emissions if every coal burning plant in the world installed fluoropolymer coated bag filters.
Mr. Smith looks at the house admiring the landscaping, the crisp looking aluminum siding. The siding looks as bright and clean as it did ten years ago (Fig. 2). What is great is that he has not had to do a thing to keep the exterior of the house looking good! Both the siding and roof are coated with a paint made with a fluoropolymer called PVDF. This paint endures all the elements of climate, is maintenance free and expected to last thirty years.
Later in the day, Mr. Smith will travel on an aircraft equipped with fluorocarbon fire extinguishers in its cargo compartment to prevent passive fires started by phantom sparks. There are many miles of wires and cables in the aircraft all insulated by fluoropolymers. They allow safe performance of the electrical and signal systems of the aircraft over its lifetime. There are many structural composite parts in the aircraft that contain fluoropolymers. Mr. Smith puts his on the sidewall to takes a nap. He does not realize the aircraft interior is surfaced by a composite of fluoropolymer PVF, a durable fire safe plastic. PVF stands up to the chemicals and disinfectants that airlines use for cleaning cabin interiors.
Mrs. Smith’s 76-year old mother had an operation. The surgeon repaired an isolated lesion of her thoracic aorta using a thoracic endoprosthesis graft made from ePTFE. It is the white section with metal scaffolding reinforcement in the picture (Fig.3). She suffered no pain during the operation and had a normal anesthetic experience thanks to the use of a fluorocarbon gas. Mrs. Smith’s mother has been given an excellent prognosis for recovering from the surgery and is adapting well to her new PTFE graft without knowing the anesthesia from which she recovered was a fluorocarbon gas.
Every year tens of millions of procedures are performed in the US, nearly all require general inhalation anesthetic. Fluorocarbon compounds such as Sevoflurane® and Isoflurane® have drastically reduced the anesthesia risk (Fig. 4). Between 1995 and 2005, the number of deaths attributed to anesthesia is estimated to have dropped > 25-fold from 1 in 10,000 anesthetics to 1 in 300,000 today. Dr. Charles Suckling in 1951 began attempting to prepare the ideal anesthetic gas. It resulted in clinical introduction of fluorocarbons with names like halothane, enfluorane, isoflurane, desflurane and sevoflurane allowing surgeons to save lives.
There are many more examples of fluorinated materials saving lives and enhancing the quality of human life. More exotic examples include parts in spacecrafts from the early days to the International Space Station. Fluorocarbons whether chemicals or plastics are invisible and often go unnoticed. The reason is they play a functional role inside the systems that have achieved today’s living standards.
Chlorine gas (Cl2) is a common industrial material produced in large quantities by electrolysis of table salt (NaCl) in water. Electrolysis cells require a separator between the anode and cathode sections. For decades mercury (Hg) or asbestos, two very toxic materials, were used as separators. Emission of mercury in the environments has had horrific consequences. Enter perfluorinated ionomers such as Nafion® by DuPont and FlemionTM by Asahi Glass! As membranes replacing mercury and asbestos have had an incredible impact on reducing mercury emissions. In Europe mercury emission has been reduced from >26 g/ton chlorine in 1970’s to <1 g/ton today; still too much but a far cry from 1970’s levels!
Out of sight, out of mind! This metaphor taken to extreme puts a myopic focus on the environmental challenges of fluorocarbons without considering the critical roles they play in human life. The industries have been striving for decades to reduce the detrimental impact of fluorocarbons on the environment and global warming. But it takes time, effort, investment and most of all patience to solve problems.
In the meantime let’s be sure we do not throw the baby out with the bath water!
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Dr. Sina Ebnesajjad
President at FluoroConsultants Group, LLC
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