Applications of Fluoropolymer Films: Properties, Processing, and Products

By Jiri George Drobny

Applications of Fluoropolymer Films: Properties, Processing, and Products presents an overview of fluoropolymer films, manufacturing methods, typical properties, and commercial grades for each type of fluoropolymer film. The second part of the book is uniquely focused on the applications of fluoropolymer films, with detailed information on their use in cutting-edge items across major industries, including aerospace and automotive, architectural, chemical processing, construction, consumer products, electronics, food packaging, pharmaceuticals and solar energy.

• Presents a focused approach on the practical applications of fluoropolymer films, supporting their use in state-of-the-art products across a range of industries
• Contains detailed coverage of manufacturing methods, properties and commercial grades for fluoropolymer films
• Unlocks the potential of the advanced properties offered by fluoropolymer films

• Language: English
• Publisher: Elsevier Science
• Release date: Jan 15, 2020
• ISBN: 9780128163023

Jiri George Drobny

Jiri G. Drobny is President of Drobny Polymer Associates, and former Adjunct Faculty of Plastics Engineering at the University of Massachusetts, Lowell. Drobny is an active educator, lecturer, writer, and internationally known consultant. His career spans more than 40 years in the rubber and plastic processing industry, mainly in research and development with senior and executive responsibilities.

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Preface

Fluoropolymer films are high-performance films based on fluoroplastic polymers, such as polytetrafluoroethylene, and others. These films as a class exhibit low coefficient of friction, chemical inertness, exceptional dielectric properties, weather and UV resistance, excellent optical properties, negligible moisture absorption, and outstanding performance at very high temperatures.

Fluoropolymer films are used in many markets, although none of them is used in large quantities. Current market demand for specialty fluoropolymer films is approximately $150 million and expected to rise 5.4% per year to $177 million in 2023. The growth is expected to be among the fastest of any major specialty resin, driven largely by expanding use of fluoropolymers mainly in photovoltaic modules and also in other markets, including fuel cells, health care, and specialty packaging materials.

Recently published books on the general subject of films are Film Properties of Plastics and Elastomers, Fourth Edition, by L.W. McKeen (Elsevier 2017); Manufacture and Novel Applications of Multilayer Polymer Films, by D. Langhe and M. Ponting (Elsevier 2016); and Science and Technology of Flexible Packaging: Multilayer Films from Resins and Process to End Use by B.A. Morris (Elsevier, 2017). There is only one book on the subject of fluoropolymer films, namely the very comprehensive and well-written monograph Polyvinyl Fluoride: Technology and Applications of PVF, by S. Ebnesajjad, (Elsevier, 2015). Clearly, considering the importance and the large number of types of fluoropolymer films currently being used, the decision was made by the Elsevier publishers to publish a book that would be dedicated to that subject.

This book is written with the intention to be useful for industrial and business practitioners and have its main focus on the practical use. We hope that it will provide relevant information about the essential technology of materials, processing and properties and applications of every type of fluoropolymer films. The main focus is on applications. In order to accomplish that, the publication is divided into the following three parts:

Part I: Materials, Technology, and Properties

Part II: Typical Properties of and Applications for Fluoropolymer Films

Part III: Commercial Grades of Fluoropolymer Films and Their Applications

The Part I is written so that it does not require any deep understanding of polymer chemistry, since we limited the discussion to industrial processes for the production of individual polymers and then to their processing into films. We provided ample references, and in addition to that we listed all known published books covering the subjects of fluoropolymers, polymeric films, and film processing technology, and testing and applications as the bibliography. A comprehensive glossary of terms is also included. An entire chapter is dedicated to testing and current standard for the testing of thermoplastic films in general and fluoroplastic films in particular.

The Part II covers typical properties and examples of applications for every single type of fluoropolymer films. Each type of film is presented as a separate chapter in order to focus on all important details.

The Part III is a comprehensive description of essentially all commercial grades of fluoropolymer films. We did a thorough research of available manufacturers, suppliers, and grades. Eventually, we decided to list the major manufacturers and suppliers and essential grades. The sources are data published by individual companies. It should be noted that not all companies producing and supplying fluoropolymer films use data in a uniform fashion; for example, often different units are shown. Where possible, units have been changed for the sake of uniformity. In addition, sometimes the number of different grades are very large so a few typical ones have been selected. For additional information the reader is advised to study the entire range of products listed on the website of a given company. Our intention is to provide as much useful information as possible for the reader, but it is in no way to guarantee accuracy and to claim that the data are specific. The reader is advised to contact the manufacturer, supplier, and/or distributor for that.

Many thanks are due to my friend and colleague Dr. Sina Ebnesajjad, President of FluoroConsultants Group for encouragement, help, and valuable advice and to Edward Payne and Dr. Peter Adamson from Elsevier for outstanding support and help during the preparation and writing of the manuscript and to Corinne Gangloff from Freedonia Group for supplying market data and forecasts. Additional credit is due to the Elsevier production team managed by Kamesh Ramajogi for bringing this work to fruition.

Jiri George Drobny

Merrimack, NH, Boulder, CO, and Prague, Czech Republic

Part I

Materials, Technology, and Properties

Outline

1 Introduction

2 Materials for Fluoropolymer Films and Sheets

3 Polytetrafluoroethylene Films

4 Films from Melt-Processible Fluoropolymers

5 Films from Polyvinyl Fluoride

6 Secondary Processing of Fluoropolymer Films

7 Testing of Thermoplastic Films

8 Safety, Hygiene, Disposal, Recycling of Fluoropolymer Films

1

Introduction

Abstract

This chapter is an introduction covering a number of important subjects, including definitions, manufacturing methods for manufacture of films from melt-processible films, and their secondary processing, introduction to fluoropolymer films and their general applications, and current demands and forecasts.

Keywords

Polymeric films and sheets; thermoplastics; melt processing; fluoropolymer films; typical properties; applications; current demand and forecasts; secondary processing of films; corona treatment; plasma treatment; chemical etching; flame treatment; film extrusion; film coextrusion; surface preparation methods; lamination; metallization; orientation (stretching) of films; machine direction orientation (MDO); transverse direction orientation (TDO); biaxial orientation (BO); tenter frame; oriented films

Fluoropolymer films are high-performance films based on fluoroplastic polymers, such as polytetrafluoroethylene (PTFE), known under its trade name TEFLON and others. These films as a class exhibit low coefficient of friction, chemical inertness, exceptional dielectric properties, weather/UV resistance, excellent optical properties, negligible moisture absorption, and outstanding performance at temperature extremes. Some of them can be thermoformed, laminated, heat-sealed, die-stamped, and oriented for use in a wide variety of applications. The key application industries for these films include packaging, construction, automotive, electronics, electrical, health care, and aerospace and typical applications include anticorrosive linings, composite part mold release, industrial roll covers, circuitry, pharmaceutical cap liners, sterile packaging, cable insulation, hot-melt adhesive, microphone electret membranes, photovoltaic cell glazing (backsheet), antigraffiti coverings, erasable surface coverings, automotive interiors, fuel hose permeation barrier, hot-melt adhesive, and more.

Fluoropolymer films are used in a wide array of markets, although none of them is used in large quantities. Demand for specialty fluoropolymer films is expected to rise 5.4% per year to $177 million in 2023 [1]. The growth will be among the fastest of any major specialty resin, driven largely by expanding the use of fluoropolymers in photovoltaic modules. The demand will be also driven by other markets, including fuel cells, health care, and packaging materials. However, the gains will be limited by less expensive alternative materials than the relatively high-priced fluoropolymer materials. Thus fluoropolymer films will be used only where their high barrier properties, chemical resistance, or toughness are essential [1]. As it stands now, the share of fluoropolymer films amounts to 1.8%–2% of the total specialty film demand.

Polyvinyl fluoride (PVF) is currently the leading fluoropolymer used in film applications. PVF and PVDF are widely used in backsheets of photovoltaic modules. In fact majority of backsheets produced in 2018 contained at least one layer of fluoropolymer-based film [1]. There is a possibility that the share of PVF-based backsheets may decline despite increasing demand for solar energy products, as newer technologies gain market share [1].

US demand for all specialty films is forecast to rise 4.0% per year to $9.0 billion in 2023. The gains will be fueled by many factors, including demand for high-performance films with barrier properties, growth construction activity, acceleration in packaging production, and food manufacturing. Key markets for barrier films will be food packaging, pharmaceutical blister packaging applications, particularly fluoropolymer, and nylon films in multilayer constructions [1]. Details summarizing the relevant data are in Tables 1.1 and 1.2.

Table 1.1

Table 1.2

1.1 Definitions

1.1.1 Polymeric Films and Sheets

Polymeric films are defined as thin continuous materials typically up to 200 μm (0.008 in.) thick. Plastic materials thicker than that are referred to as sheets. Polymeric films can be manufactured from various resins, each with its own unique physical properties that are differently suited to different applications. Besides all the different materials it can be made from, a polymeric film can be clear, colored, smooth, rough, functionally embossed, opaque, or semitransparent.

Polymeric films are essentially made from thermoplastic resins using the following manufacturing methods:

• Film extrusion using a flat die and subsequent cooling and wounding up on a roll.

• Cast film extrusion is an extrusion method in which the polymer melt is cooled or quenched and then wound up on a roll.

• Blown film extrusion using a special extrusion die to extrude a tube. The melted tube is then inflated to the required circumference and subsequently cooled down and collapsed between two steel rolls as two sheets.

• Coextrusion produces films composed from two or more different polymeric layers.

• Calandering, in which a polymeric melt is shaped between two steel rolls.

• Skiving is peeling of the film or sheet from a solid roll (billet) in a similar fashion as a wood veneer.

• Film casting is a deposition of a polymer solution or aqueous dispersion on a carrier or another substrate.

• Extrusion coating is similar to film casting, but in this method the melt is deposited on the carrier or another substrate.

Finished films can be either laminated by several methods, or stretched (oriented) in machine direction, or cross-machine direction or biaxially. Stretched films are often annealed when desired. Other common treatments of finished polymeric films are surface treatment and metallization.

Typical uses of polymeric films include packaging, bags, labels, in automotive, aerospace, electrical and electronic, in chemical industry, optical industry, in the military, and in building construction and landscaping.

1.1.2 Fluoropolymers

Fluoropolymers are polymeric materials containing fluorine atoms in their chemical structures. Their chemistry is derived from the compounds used in the refrigeration industry, which has been in existence for more than 70 years [1]. The serendipitous discovery of PTFE in 1938 by Plunkett [2] in the laboratories of E.I. du Pont de Nemours and Company during the ongoing refrigerant research opened the field of fluoropolymers and their commercialization. PTFE was commercialized by that company as Teflon in 1950, but the technology had been used exclusively in the Manhattan Project already during the World War II [3].

Fluoropolymers in their simplest form are homopolymers or copolymers of saturated hydrocarbons in which all or some hydrogen atoms have been replaced by fluorine atoms or combination of fluorine and chlorine. Theoretically, there are many possible combinations but most commercially significant are derivatives of ethylene and propylene, sometimes referred to as fluorocarbon polymers. Other, more complex fluoropolymers are fluorinated acrylates, silicones, polyurethanes, polyimides, and other.

From general organic polymer concepts, there are two types of fluoropolymer materials: perfluoropolymers and partially fluorinated polymers. In the former case, all the hydrogen atoms in the analogous hydrocarbon polymer structures were replaced by fluorine atoms. Perfluoropolymers represent the largest volume of industrially processed fluorocarbon polymers, and the partially fluorinated polymers are mainly used in special applications. From the point of view of processing, the thermoplastic fluoropolymers, also referred to as fluoroplastics, there are melt-processible and nonmelt-processible fluoropolymers. Currently, the nonmelt-processible fluoropolymers include PTFE and PVF, while the remaining commercial fluoroplastics can be processed by melt-processing techniques.

The most common monomers used for the preparation of the known fluoropolymers are shown in Table 1.3. These can be combined to yield typically homopolymers, copolymers, and terpolymers. The resulting products possess excellent properties, such as outstanding chemical resistance, weather stability, low surface energy, low coefficient of friction, and low dielectric constant. These properties come from the special electronic structure of the fluorine atom, the stable carbon–fluorine covalent bonding, and the unique intramolecular and intermolecular interactions between the fluorinated polymer segments and the main chains. Commercial fluorocarbon polymers are available in the two following distinct groups [4].

Table 1.3

Fluoroplastics, which include a relatively large number of thermoplastic materials.

Fluoroelastomers, which are used as raw materials for applications where elastomers with enhanced heat resistance, chemical resistance, resistance to aging and oxidation are required. These are processed by techniques usual in the rubber industry and their typical applications include hose, belts, gaskets, seals, bladders, membranes, rubber-covered rolls, valve and pump linings, coatings, and sealants. It should be noted here that for the purpose of this publication, only fluoroplastics and to a degree fluorinated thermoplastic elastomers will be discussed since they are suitable for the use in commercial fluoropolymer films.

Due to their special chemical and physical properties, fluoropolymers are widely applied in the chemical, electrical/electronic, space, construction, architectural, food processing, medical and automotive industries, in engineering, and in military. Details are shown in Table 1.4. Table 1.5 lists major producers of thermoplastics.

Table 1.4