PTFE: The Wonder Thermoplastic
Posted by CDI Products on Oct 04, 2021
American painter, art instructor, and beloved television host Bob Ross once said, “We don’t make mistakes. We just have happy accidents.” Ross understood that even when things do not go as planned, something unexpectedly wonderful can result.
Scientific discovery is rampant with examples of happy accidents that changed the world. As it turns out, many of society’s most famous inventions were merely errors made by scientists pursuing unrelated goals:
- Sir Alexander Fleming discovered penicillin by accident after noting that bacterial colonies would not grow near the mold on his staphylococcus bacteria cultures.
- Wilson Greatbatch invented the pacemaker while trying to build a device to record the rhythm of the heart.
- Percy Spencer would go on to create the microwave oven after working on a radar machine when he realized a chocolate bar in his pocket was melting abnormally quickly.
Like those great discoveries, polytetrafluoroethylene, or PTFE, was created by a happy accident.
PTFE Was a Happy Accident
PTFE was discovered by chemist Dr. Roy Plunkett while attempting to develop a coolant gas. He was experimenting with tetrafluoroethylene (TFE) for synthesis of useful refrigerants. On the morning of April 6, 1938, the TFE gas inside had polymerized into a waxy white powder, polytetrafluoroethylene (PTFE) resin.
Plunkett had analyzed the white powder, which was conclusively proven to be PTFE. The slippery PTFE could not be dissolved in any solvent, acid, or base, and upon melting formed a stiff, clear gel without flow. The accidental discovery of PTFE revolutionized the plastics industry during World War II and led to various applications not otherwise possible.
What Makes PTFE So Special
In the over 80 years since its discovery, PTFE (often referred to as Teflon®1) has revolutionized the production of a multitude of essential goods and enriched the capabilities of many vital industries. With a robust characteristic profile, a wide breadth of applications, and its unique mechanical properties, it’s no surprise that PTFE is regarded as a wonder material.
The unique properties of PTFE have led to a wide variety of applications, including food preparation, electronics, aviation, medical implants, and so much more. Before we look at the various industries, let’s look at some of the characteristics of this wonder material:
- Excellent chemical resistance and insolubility
- Wide service temperature range
- High thermal stability – useful mechanical and physical properties at extremely low and high temperatures
- Flexibility and fatigue resistance
- Low water absorption and permeation
- Flame resistance
- Good electrical insulating power in hot and wet environments
- Good resistance to light, UV, and weathering
- Low coefficient of friction
- Low dissipation factor
- Strong anti-adhesion properties over a wide temperature range
- Availability of food, medical, and high-purity grades
Characteristics like chemical inertness, heat resistance, excellent electrical insulation, and a low coefficient of friction enable PTFE to be used in a wide variety of applications, including seals, gaskets, compressor valves and pump parts, wire insulation, insulated transformers, printed circuit boards, textiles, and surface coatings.
This robust profile makes PTFE a versatile material for an incredible number of products, shapes, and design applications. Some of PTFE’s basic near net shapes include discs, rods, tubes, blocks, sheets, balls, plates, and molded blanks (also known as billets).
PTFE can also be custom designed into very intricate parts and components subject to some of the highest quality standards and specifications. PTFE’s diversity of application makes it perfect for so many industries that drive our world.
You may have heard people ask the question: If nothing sticks to Teflon, how does Teflon stick to pots and pans? The answer is Teflon’s slick surface is due to the fluorine that surrounds its molecules.
Almost all other materials are repellent to these fluorine atoms, preventing them from sticking to Teflon. However, by chemically modifying one side of the Teflon, chemists can break away many of the fluorine atoms on the surface and mitigate Teflon’s natural anti-adhesion characteristics.
The changes to one side of the Teflon are done with a reducing agent that breaks the strong bonds between the fluorine and the carbon, allowing the fluorine to bond together. This leaves the carbon free. The free carbon, which forms into unsaturated hydrocarbons, is sticky enough to get the Teflon sheet to stick to a pan.
What Industries Trust PTFE
PTFE is most commonly known for its nonstick characteristics and its prevalence as a coating in food preparation products like pots, pans, and more. Outside of the kitchen, PTFE plays a significant role in a host of industries. Let’s take a look at some of those industries and the key benefits at work:
- Chemical Processing – PTFE delivers the mechanical strength and abrasion resistance vital to the chemical processing and refinery industries. Modern chemical processing is a complex process that often involves a range of substances in varying degrees of corrosiveness, temperature, and pressure. PTFE is a reliable material for pump, compressor and valve components, piping, fuel cells, storage and containment coating, and lab equipment.
- Fluid Handling and Filtration – With its anticorrosive capabilities, low water absorption, and permeability, PTFE is excellent for fluid handling and filtration applications. Whether handling steam, chemicals, water, or gas, PTFE can handle the extreme environmental conditions and maintain its dimensional stability and integrity.
- Semiconductor Fabrication – PTFE’s high purity level and corrosion resistance make it an effective material solution for semiconductor applications. Whether it’s for smaller scale tubing, filters, and sensors or for larger scale applications like pipes and fitting, storage and transport containers, and process vessels, PTFE helps support a corrosion- and impurity-free process.
- Aerospace – In our recent blog on thermoplastics for aviation, we dive deep into the benefits for the industry. Due to its excellent strength-to-weight ratio, thermoplastics like PTFE solve many challenges in the aviation industry, including radar materials, freshwater systems, landing gear systems, cable insulation, fuel hoses, surface coatings, seating protectants, and much more.
- Medical – Although you might immediately think of hazardous material containers and IV bags, PTFE is commonly used as a coating on catheters to restrict the growth of bacteria and infections and as a graft material in surgery. PTFE has many applications in healthcare owing to its high purity, chemical resistance, and flexibility.
- Automotive – Car drivers and manufacturers alike look for vehicles that can deliver improved efficiency, lower emissions, and greater quality. PTFE provides the low friction, improved strength-to-weight ratio, and fatigue resistance manufacturers can rely on for brake and fuel systems, powertrains, diagnostic systems, radar sensors, shock absorbers, window vents, seat protectant, and coated weather stripping.
How Do Additives Impact PTFE?
At this point, it might be easy to think of PTFE as the picture-perfect thermoplastic material. Like all materials, PTFE has its own share of limitations, including sensitivity to creep and abrasion, low radiation resistance, and difficulties of joining.
Depending on the application and environment, some of PTFE’s limitations can be improved with the addition of fillers or additives. Let’s take a look at some of the more common fillers and additives as well as some of their benefits:
- Increases compressive strength, hardness, wear, and load properties
- Good chemical resistance
- Various types and amounts of carbon can be added to alter conductivity
- Increases compressive strength, rigidity, and wear
- Reduces creep and cold flow
- Minimal effect on chemical and electrical properties
- Reduces coefficient of friction
- Reduces initial wear
- Increases strength
Bronze and Copper Powders
- Increases hardness and wear resistance
- Increases dimensional stability and compressive strength
- Protects against fretting corrosion
- Decreases friction with increasing loads
- Improves load-carrying capacity
- Supports identification, visibility, or branding
Happy Accidents Change the World
If not for an accident on the morning of April 6, 1938, the world as we know it would likely be a very different place. We have only scratched the surface on the many applications for PTFE. Scientists and chemists are constantly experimenting with PTFE and discovering new and safe applications for this amazingly versatile material.
Tough, flexible, waterproof – the list goes on. So do the potential opportunities for PTFE to positively impact the world. Every day, scientists uncover a new way PTFE can improve a product or resource – often by happy accident – and we anticipate many more discoveries in the future.
PTFE is a thermoplastic that cannot be handled using typical polymer processing procedures due to its high viscosity. PTFE is processed by cold shaping followed by heat treatment (also known as sintering), which causes the polymer particles to fuse together to produce a solid molding.
Some of the production techniques/manufacturing processes for granular and fine powder polymers are:
- Compression molding – manual and automatic
- Isostatic molding
- Ram extrusion
- Paste extrusion
Some of the production techniques/manufacturing processes for melt processable fluoropolymers are:
- Paste extrusion
- Melt extrusion
- Injection molding
- Blow molding
- Transfer molding
To learn more about the production capabilities for your next project, for custom-engineered components or near net shapes, contact us today.
1The Teflon® trademark was coined by DuPont and registered in 1945; the first products were sold commercially under the trademark beginning in 1946.