Perfluorinated Chemicals (PFCs)

Contaminants of Concern

Nicholas P. Cheremisinoff

• Publisher: Wiley-Scrivener
• Year: 2016
• Print ISBN: 9781119363538
• eBook ISBN: 9781119363842
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Industrial & Technical Chemistry

This new volume provides a timely study on the environmental challenges from a specific class of perfluorinated chemical compounds (PFCs) that are now being recognized as a worldwide health threat. Recent studies report that levels of classes of PFCs known as polyfluoroalkyl and perfluoroalkyl (PFASs) exceed federally recommended safety levels in public drinking-water supplies for 6 million people in the United States and that as many as 100 million people could be at risk from exposure to these chemicals.

These chemicals occur globally in wildlife and humans. Both PFCAs and PFSAs have been produced for more than 50 years, but have only become of interest to regulators and environmentalists since the late 1990s. Recent advances in analytical methodology has enabled widespread detection in the environment and humans at trace levels. These toxic chemicals have been found in outdoor and indoor air, surface and drinking water, house dust, animal tissue, human blood serum, and human breast milk. Of great concern to communities is the presence of these compounds in a number of drinking water supplies in the U.S. and other countries.

This new volume provides a timely explanation of the chemicals, provides a detailed review of the regulations both in the US and European Community, explains the health risk literature, and then explores in great detail available treatment technologies. The volume is a must for public water supply facilities, industrial operations that have historically used these chemicals and face legacy pollution issues, policy makers and the general public.

Chapter 1
What Fluoropolymers Are

1.1 Introduction

Fluorine-based polymers are referred to as fluoropolymers. These are man-made products that impart certain attributes and properties to coatings used in industrial, household, and construction products, as well as in firefighting foam applications. The qualities of fluoropolymer resins and oligomeric additives in coatings make them useful in applications requiring a high resistance to solvents, acids and bases, and most importantly, an ability to greatly reduce friction.

The use of surfactant additives reduces surface energy while increasing chemical, UV, moisture, grease and dirt resistance, and surface lubricity. In addition to more common fluorinated olefin-based polymers, specialty fluoroacrylates, fluorosilicone acrylates, fluorourethanes, and perfluoropolyethers/perfluoropolyoxetanes exhibit properties beneficial to various coatings applications. Coatings containing fluorochemicals find broad applications in electronics such as photomask covers, anti-reflection coatings; in construction as protective coatings for exterior substrates; as cool-roof coatings and optics such as antifouling coatings for eyeglass lenses and liquid crystal displays. Other coatings that often contain fluoropolymers include floor polishes, wood stains, and automotive clear coats, as well as ink jet inks, pigment dispersions, and adhesives.

At the heart of these products is the chemical fluorine. Unique characteristics of the fluorine atom impart certain properties to polymers that contain it. Fluorine is a fairly small atom that has very low polarizability and high electronegativity. Because there is a high degree of overlap between the outer orbitals of fluorine and the corresponding orbitals of second period elements, bonds formed between carbon and fluorine are very strong. The higher bond energy of the C-F bond compared to the C-H bond leads to greater thermal stability.

A perfluorinated chemical (PFC) is an organofluorine compound containing only carbon-fluorine bonds (no C-H bonds) and C-C bonds but also other heteroatoms. PFCs have properties that represent a blend of fluorocarbons (containing only C-F and C-C bonds) and the parent functionalized organic species. For example, perfluorooctanoic acid functions as a carboxylic acid but with strongly altered surfactant and hydrophobic characteristics. Perfluoropolymers, which contain only C-F bonds, have excellent chemical and weather resistance. The small dipole moment of these compounds contributes to their oil and water-repellency, as well as low surface tension, low refractive index, low friction coefficient, and reduced adhesion to surfaces. Even partially fluorinated polymers exhibit a strong electron-attracting ability, resulting in a high dielectric constant and optical activity. In small molecules, this attribute leads to enhanced acidity, lipophilicity, and the ability to block metabolic pathways, making fluorine-substituted compounds well-suited for pharmaceutical applications.

Other characteristics of fluoropolymers, which are determined by the strength of the C-F bond and the low polarizability and high electronegativity of fluorine, include soil resistance, insulating properties, and the ability to act as a gas barrier.

Commercial fluoropolymers are generally classified according to morphology (crystalline, semi-crystalline, and amorphous categories) and perfluorinated and partially fluorinated. See Figure 1.1.

Figure 1.1 The major types of today’s commercial fluoropolymers.

1.2 Evolution of Fluoropolymers and the Markets

The following is a timeline of the evolution of fluoropolymers and the market applications.

1886	Henri Moisson isolated elemental fluorine, for which he received the Nobel Prize in Chemistry.
1890s	SbF3 is applied in a Cl/F exchange reaction to prepare fluorinated aromatics and the first chlorofluorocarbon gas (CF2Cl2).
1931	General Motors, in partnership with E. I du Pont de Nemours & Co., formed a new corporation, Kinetic Chemicals Inc., to produce commercial quantities of the trademarked product Freon-12.
1930s	Several other Freons were developed, including Freon-114 (CClF2CClF2) a precursor of tetrafluoroethylene (TFE).
1934	The first patent for a fluoropolymer was filed by IG-Farbenindustrie in Hoechst/Frankfurt, in Germany.
1938	Roy Plunkett, a DuPont chemist working on new types of Freons, independently discovered PTFE (Teflon) while attempting to chlorinate gaseous TFE.
1949	DuPont introduces Teflon. Plunkett began working for DuPont Jackson Laboratory in Deepwater, N.J., as a research chemist in 1936. Plunkett’s discovery was found to be both heat-resistant and stick-resistant. After 10 years of research, DuPont introduced Teflon in 1949.
Late 1940s	3M purchases the Simon Electrofluorination Patent. Electrochemical fluorination (ECF), or electrofluorination, is a foundational organofluorine chemistry method for the preparation of fluorocarbon-based organofluorine compounds. The general approach represents an application of electrosynthesis. The fluorinated chemical compounds produced by ECF are useful because of their distinctive solvation properties and the relative inertness of carbon–fluorine bonds. Two ECF synthesis routes are commercialized and commonly applied, the Simons Process and the Phillips Petroleum Process. Additionally, it is also possible to electrofluorinate in various organic media. Prior to the development of the Simon method, fluorination with fluorine, a dangerous oxidant, was a dangerous and wasteful process. Also, ECF can be cost effective, but it may also result in low yields.
1953	Kellog Co. introduced polychlorotrifluoroethylene (PCTFE) under the trade name Kel-F 81. PCTFE, a homopolymer of CTFE, contained chlorine in the fluoropolymer backbone making it a more processable alternative to PTFE.
1956	3M begins selling Scotchgard Protector. Scotchgard Protector contained a fluorochemical that helped it repel stains.
1960	FEP (fluorinated ethylene propylene), the first copolymer of TFE was introduced.
1961	Dupont released polyvinylfluoride (PVF) which contained only one fluorine in the ethylene monomer unit, ...

Table of contents

• Cover
• Title page
• Copyright page
• Preface
• About the Author
• Abbreviations and Acronyms
• Useful Conversion Factors
• Chapter 1: What Fluoropolymers Are
• Chapter 2: Definitions, Uses, and Evolution of PFCs
• Chapter 3: Fire Fighting Foams
• Chapter 4: Health Risk Studies
• Chapter 5: Overview of the Environmental Concerns
• Chapter 6: The Supply Chain and Pathways to Contamination
• Chapter 7: Standards, Advisories, and Restrictions
• Chapter 8: Overview of Water Treatment Technology Options
• Chapter 9: Adsorption Technology
• Chapter 10: Case Studies
• Index
• End User License Agreement