Introduction to Fluoropolymers

Materials, Technology and Applications

Sina Ebnesajjad

• Publisher: William Andrew
• Year: 2013
• eBook ISBN: 9781455775514
• Topic: Technology & Engineering
• Subtopic: Materials Science
• Index: Technology & Engineering

Introduction to Fluoropolymers demystifies fluoropolymers for a wide audience of designers, engineers, sales staff and managers. This important group of high-performance polymers has applications across a wide range of market sectors, including automotive, aerospace, medical devices, high performance apparel, oil & gas, renewable energy / solar photovoltaics, electronics / semiconductor, pharmaceuticals, and chemical processing. Dr. Ebnesajjad covers the history and applications of a wide variety of materials, including expanded polytetrafluoroethylene, polyvinyl fluoride, vinylidene fluoride polymers and fluoroelastomers, just to name a few. Properties and applications are illustrated by real-world examples as diverse as waterproof clothing, vascular grafts and coatings for aircraft interiors. The different applications of fluoropolymers show the benefits of a group of materials that are highly water-repellant and flame-retardant, with unrivalled lubrication properties and a high level of biocompatibility. Health and safety and environmental aspects are also covered throughout the book. - Demystifies fluoropolymers for a broad audience of engineers in areas such as product design and manufacturing, as well as for non-engineers such as technical sales and management professionals - Explains the potential of fluoropolymers for a wide range of applications across sectors such as aerospace, energy and medical devices - Ideal for both recently qualified engineers and engineers with limited experience of fluoropolymers

1

Fluorine, Fluorocarbons, and Fluoropolymers in Human Life

A Day with the Smiths

A review of a day in the life of Mr. and Mrs. Smith who live in Tucson, Arizona, will illustrate the essential role of fluorine, fluorocarbons, and fluoropolymers in society.

Mr. Smith begins the day shaving using a fancy razor, which has a strip of polytetrafluoroethylene (PTFE) fluoropolymer as a part of the safe design of this razor. Taking eggs out of a refrigerator kept cool with a fluorocarbon refrigerant hidden inside its compressor, Mr. Smith makes an omelet for breakfast. He uses a nonstick pan to cook; the pan is nonstick because of the fluoropolymer coating on its surface.

After breakfast, everyone in the family flosses using floss made from PTFE fluoropolymer that does not scar gums. Then everyone brushes using toothpaste that contains fluoride to protect the teeth. Fluorine compounds are added to the toothpaste to help prevent tooth decay. Pain, loss of teeth, gum disease, and disfigurement associated with tooth decay have been reduced since the introduction of fluoridation more than 60 years ago.

Numerous studies since 1945 have illustrated the impact of community water fluoridation in the prevention of tooth decay [1]. For example, in 1993, the results of 113 studies in 23 countries were compiled and analyzed [2]. (Fifty-nine out of the 113 studies analyzed were conducted in the United States.) This review provided effectiveness data for 66 studies in primary teeth and for 86 studies in permanent teeth. Taken together, the most frequently reported decay reductions observed were:

• 40%–49% for primary teeth (or baby teeth)

• 50%–59% for permanent teeth (or adult teeth)

Mrs. Smith is dressing the children. Rain is in the forecast, so to stay dry, the children dress in waterproof coats that have an expanded PTFE fluoropolymer fabric inside them best known as Gore-Tex® (by W.L. Gore and Associates). These coats keep the water out but “breathe,” keeping the children cool. A similar material is used in modern hospitals.

The couple is pressed for time, so they leave the food spilled on the carpet for cleanup after work because a very thin layer of fluorocarbon protects the carpet. They pick up their cell phones and laptop computers on their way out of the house. Every one of these devices contains coaxial cables that contain insulation made from fluoropolymers and components, which depend on the unique dielectric properties of PTFE. The modern electronics age has depended on fluoropolymers. The silicon chips are made using fluorine-containing gases for etching and chamber cleaning.

Mrs. Smith takes her son’s asthma drug along to school. A fluorinated chemical enables safe delivery-metered doses of the asthma medicine out of the metal container. A thin layer of fluoropolymer coats the inside of the metal container to prevent the drug from sticking to the surface. The metered-dose inhaler, as it is called, allows the drug to be administered in a targeted and precise form. This keeps the child’s exposure limited to the required amount of the asthma drug.

Because of its unique chemical properties, fluorine has been instrumental in the development of novel medicines. Approximately 25% of all marketed drugs contain fluorine, including three of the 10 best-selling drugs in 2011 [3]. Fluorine-enhanced compounds have better pharmaceutical properties, some of which are listed here:

Potency: Improved efficacy and therapeutic window

Selectivity: Fewer side effects

Tissue penetration: Enhanced drug delivery to target

Drug half-life: Less frequent dosing

Metabolism: Reduced drug interactions

Mr. Smith, who is the last to leave the house, turns off the fluorine-containing displays on his desktop computer and television. Last, he sets the thermostat to reduce the air conditioning operation while the house is empty. The central air unit in the house contains a fluorocarbon refrigerant called hydrofluorocarbon (HFC). This material complies with Montreal Protocol by having unique stability and reduced global warming potential. It also helps the air conditioning work efficiently. Tragic events occurred in France in the summer of 2003, when nearly 15,000 people died because of the heat and absence of air conditioning in many homes and buildings. It is well accepted by the medical profession that air conditioning saves lives. Modern hospitals, even in temperate zones, air-condition their facilities.

There are negative environmental impacts resulting from air conditioning, however. Some of these have been corrected, and others will be corrected by additional inventions. The fluorocarbon and fluoropolymer industries have been working for a long time to lower the negative effects of these products on the environment and on global warming.

The Smiths’ house is partially powered by photovoltaic cells that the family installed several years ago. Using these cells is a good deal because after the family paid for the installation of the cells, they have been enjoying free power for some of the family’s electric needs. A special fluoropolymer called polyvinyl fluoride (PVF) plays an important role in photovoltaic units by protecting them from damage and increasing their useful life.

The power plants that supply the rest of the house’s electricity have many fluorocarbon-based components, which help reduce carbon dioxide and other emissions. For example, fluoropolymer-coated bag filters remove harmful particles (fly ash) from the smoke discharged by coal-burning plants. There would be a huge decrease in particulate emissions if every coal-burning plant in the world installed fluoropolymer-coated bag filters.

Before leaving, Mr. Smith looks at the house, admiring the landscaping and the crisp-looking aluminum siding and steel roof that still look as bright and clean as they did 10 years ago. What is great is that he has not had to do a thing to keep the exterior looking good! Both the siding and roof are coated with a paint made with a fluoropolymer called polyvinylidene fluoride (PVDF). This paint endures all the elements of climate, is maintenance free, and is expected to last 30 years.

Later, Mr. Smith will travel on an aircraft that is equipped with fluorocarbon fire extinguishers in its cargo compartment to prevent passive fires started by phantom sparks. The many miles of wires and cables in the aircraft are insulated by fluoropolymers or composite materials that contain fluoropolymers. They allow safe performance of the electrical and signal systems of the aircraft over its lifetime. Mr. Smith may not realize that the interior of the aircraft is surfaced by a composite of fluoropolymer PVF, which is fire safe, durable, and stands up to the harsh cleaning chemicals and disinfectants.

Mrs. Smith’s 76-year-old mother is recovering from an operation in which parts of her arteries were replaced by vascular grafts made from expanded polytetrafluoroethylene (ePTFE) material. 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 ePTFE veins. She will never know that the anesthesia from which she recovered was a fluorocarbon gas, but she will go on with her active life and enjoy her grandchildren for a long time.

In 1951, Dr. Charles Suckling began attempting to prepare the ideal anesthetic gas, which resulted in the clinical introduction of fluorocarbons with names such as halothane, enflurane, isoflurane, desflurane, sevoflurane, and methoxyflurane. Every year, more than 25 million surgical procedures are performed in the United States, most of which require general inhalation anesthetic. Fluorocarbon compounds such as Sevoflurane® and Isoflurane® have drastically reduced the long-standing anesthesia risk of using anesthesia.

Since the 1990s, decade estimates for the number of deaths attributed to anesthesia have dropped greater than 25-fold from 1 in 10,000 anesthetics to 1 in 200,000 to 1 in 300,000 today [4]. Today, surgeons save lives thanks to safe fluorocarbon anesthetics pioneered by Charles Suckling.

There are many more similar everyday life examples of the use of fluorocarbons that save lives and enhance the quality of human life. More exotic examples include parts in spacecrafts from the early days to the Space Shuttle to the International Space Station. Fluorocarbons, whether chemicals or plastics, are invisible and often go unnoticed. The reason is that they are inside the systems that have enabled today’s societal human standards.

Out of sight, out of mind! This metaphor taken to extreme may narrow the focus to the challenges of fluorocarbons without placing due weight on their critical roles in human life. The fluorocarbon and fluoropolymer industries and governments have been working voluntarily for decades on reducing the negative impact of these products on the environment, on global warming, and on human health. They will continue as they should, but because of the importance of these compounds.

References

1. American Dental Association, Fluoridation Facts. 2005; In: www.ADA.org; 2005.

2. Murray JJ. Efficacy of preventive agents for dental caries. Caries Res. 1993;27(Suppl. Q):2–8.

3. www.Scifluor.com, 2003.

4. American Society of Anesthesiologists, History of Anesthesiology—An Overview. 2003; In: http://asatest.asahq.org/Newsletters/2000/09_00/asaLeadership0900.html; 2003.

2

Fluorine and Fluorocarbons

Chapter Outline

2.1 Uniqueness of Fluorine

2.2 Fluorine Characteristics

2.2.1 Fluorination

2.2.2 Reactivity: An Extreme Element

2.2.3 Preparation of Fluorine

2.2.4 Inorganic Chemistry

2.2.5 Organic Chemistry

2.2.6 Fluorine and Nature

References

What sets fluorine apart from other halogens? Technically speaking, the term “halogen” provides little descriptive value in scientific and technological discussions. The common characteristic of halogens is that they all have seven electrons in the outer shell of their atomic structure. They all have a valence of –1 in their reactions with hydrogen and metals. The reactivity of halogens decreases from the top (fluorine) to the bottom (astatine) of Group 17 in the Periodic Table of Elements. When fluorine is substituted for any element such as hydrogen in a chemical structure, it will have a profound impact on the compound’s properties, because fluorine is the most reactive of all elements [1]. It has a perfect electronegativity of 4, which is the maximum value of the Pauling scale (0.7–3.98, dimensionless). Even platinum is not immune to fluorine and reacts with F₂ gas and forms platinum hexafluoride.

2.1 Uniqueness of Fluorine

Fluorine forms an extremely strong bond with other elements such as carbon because it is the most electronegative of all elements. The carbon–fluorine bond (C–F) is the fundamental reason that polytetrafluoroethylene (PTFE) is one of the most stable and inert plastics known to man. Yet tetrafluoroethylene (TFE) is highly explosive, adding to the diversity of the fluorine effect. A key point is made in the McGraw-Hill Encyclopedia of Chemistry about the stability of halogenated compounds: “Organic halogen compounds generally show progressively increased stability in the order iodine, bromine, chlorine and fluorine” [2].

It is clear that fluorine is a special element beyond all others. It is relatively easy to substitute fluorine for hydrogen (and other elements) in organic compounds because of its extreme affinity for grabbing electrons. Substituting fluorine for hydrogen in a chemical compound gives rise to a variety of unique and useful effects. Examples include increased polarity, decreased polarity, chemic...

Table of contents

• Cover image
• Title page
• Table of Contents
• Series Page
• Copyright
• Introduction
• 1. Fluorine, Fluorocarbons, and Fluoropolymers in Human Life: A Day with the Smiths
• 2. Fluorine and Fluorocarbons
• 3. Discovery and History of Fluoropolymers
• 4. History of Expanded PTFE and W.L. Gore and Associates
• 5. Polyvinyl Fluoride: The First Durable Replacement for Paint
• 6. Introduction to Fluoropolymers
• 7. Manufacturing Polytetrafluoroethylene
• 8. Fluorinated Additives
• 9. Introduction to Vinylidene Fluoride Polymers
• Chapter 10. Fluoroelastomers
• 11. Fluorinated Coatings: Technology, History, and Applications
• 12. Fluorinated Ionomers: History, Properties, and Applications
• 13. Safety, Disposal, and Recycling of Fluoropolymers
• Index