PTFE Injection Molding

PTFE injection molding manufacturing and design guide

What is PTFE?

PTFE (Polytetrafluoroethylene) is a high-performance fluoropolymer made of carbon and fluorine atoms. It is a synthetic polymer made by sticking together tetrafluoroethylene monomers. PTFE is famous for its amazing thermal and cold resistance, so it can be used for a long time in temperatures from -180 to 260°C. This synthetic polymer is famous for its special properties like strong chemical resistance, heat resistance, and wear resistance, so it is used in many industrial and consumer applications. It is resistant to acids, alkalis, and many organic solvents and is almost impossible to dissolve in any solvents.

The discovery of PTFE was a game-changer for the world of fluoropolymers, opening up a whole new world of possibilities. Because it doesn’t react with anything, it’s perfect for making pipes and containers for chemicals that would eat through anything else. It’s also slippery as hell, so it’s used as a lubricant. And because it’s so easy to clean, it’s used as a non-stick coating on pots and pans and as the lining inside pipes.

PTFE materials can be further divided into different categories based on manufacturing techniques, product characteristics, and processing methods. Each type is tailored to specific application requirements. PTFE is widely used in the production of sealing and filler materials because of its excellent chemical corrosion resistance.

What are the characteristics of PTFE injection molding material?

PTFE (Polytetrafluoroethylene) is a synthetic fluoropolymer with a unique combination of properties, making it a versatile and widely applied material. Some key characteristics of PTFE include:

1. Non-stick Surface: PTFE is super slippery, like one of the slipperiest things ever. That’s why it’s perfect for things that need to slide around, like pots and pans, medical tools, and big machines.

2. Chemical Resistance: PTFE is super resistant to chemicals, like acids, alkalis, and solvents. It can take a beating from harsh chemicals without breaking down or reacting, except for molten alkali metals and fluorine at high temps.

3. Heat Resistance: PTFE has a high melting point (327°C/621°F) and can withstand high temperatures without degrading or losing its properties. You can use it continuously at temperatures up to 260°C (500°F) and as low as -270°C (-454°F).

4. Low Friction: PTFE has a low coefficient of friction, which makes it great for things that need to move smoothly, like bearings, seals, and gaskets.

5. Non-Reactivity: PTFE doesn’t react with anything, making it ideal for applications where contamination is a concern.

6. High Dielectric Strength: PTFE is great for electrical stuff because it has a high dielectric strength. That means it’s good for things like insulation and wire coatings. It has a low dielectric constant of 2.1 and a dielectric strength of up to 60 MV/m.

7. Lightweight: PTFE is a lightweight material, which makes it great for applications that need to reduce weight, like aerospace and automotive industries.

8. Corrosion Resistance: PTFE is resistant to corrosion, which makes it perfect for use in harsh environments, like marine or industrial applications.

9. Flexibility: PTFE holds its strength, toughness, and flexibility from super cold to super hot, with a tensile strength of 4,600 psi and a stretch of 318.7%. PTFE can take different amounts of a bend, so it works for all sorts of different things like really hard tubes or sheets that bend easy.

10. Biocompatibility: Teflon is an excellent choice for medical stuff cause it doesn’t make people sick or nothing. It’s also bio-compatible.

11. UV Resistance: PTFE does not mind the sunshine, so it is good for things like solar panels and other things that sit outside in the sunshine for a long time.

12. Low Moisture Absorption: PTFE has lower moisture absorption making it useful in applications where moisture is an issue, like food processing and pharmaceuticals.

13. Thermal Stability: PTFE can handle heat up to 400 degrees Celsius (that’s 752 degrees Fahrenheit) before it starts to break down. It has a narrow temperature range, too. It also expands less as it gets hotter with a coefficient of 112 to 112-125×10^-6 K^-1.

What are the properties of PTFE?

PTFE, or polytetrafluoroethylene, is a synthetic fluoropolymer that has a unique combination of properties that make it extremely useful in a wide range of applications. Some of the key properties of PTFE include:

Properties	Characteristic
Stability	1. Stable under normal temperature and pressure; avoid moisture, heat, and high temperatures. It has no true melting point; it decomposes slowly above 450°C, turning directly into gas. At 327°C, mechanical strength suddenly disappears. It is insoluble in any solvent. Except for reactions with molten alkali metals, it is not affected by any substances. It remains unchanged even when boiled in hydrofluoric acid, aqua regia, fuming sulfuric acid, or sodium hydroxide.
Stability	2. A white, odorless, tasteless, and non-toxic powder, commonly known as "the king of plastics." It possesses excellent chemical stability, corrosion resistance, sealing properties, high lubrication non-stickiness, electrical insulation, and good aging resistance. It is heat-resistant with a working temperature up to 250°C. It is also cold-resistant, maintaining good mechanical toughness even at temperatures as low as -196°C, with a 5% elongation at that temperature. It is corrosion-resistant, showing inertness to most chemicals and solvents, able to withstand strong acids, strong bases, water, and various organic solvents. It has excellent weather resistance, providing the best aging life among plastics. It is highly lubricating, with the lowest friction coefficient among solid materials. It is non-adhesive, with the smallest surface tension among solid materials, not adhering to any substances. It is non-toxic, with physiological inertness, making it suitable for long-term implantation in the body as artificial blood vessels and organs without adverse reactions.
Solubility	Insoluble in any solvent.
Additional Properties	1. Appearance: Available in granular, powdery, and dispersion liquid forms; transparent in neutral state, turning grayish-white as thickness increases.
	2. Thermal Decomposition Temperature: > 415°C
	3. Vicat Softening Point: 110°C
	4. Heat Deflection Temperature: 55°C
	5. Refractive Index: 1.37
	6. Volume Resistivity: 10^18 Ω·cm
	7. Poisson's Ratio: 0.40 (at 25°C)
	8. Flexural Strength: 20.7 MPa
	9. Flexural Modulus: 700 MPa
	10. Thermal Diffusivity: 0.124 mm²/s
	11. Friction Coefficient: 0.05–0.10
	12. Young's Modulus: 0.5 GPa
	13. Tensile Strength: 27.6 MPa
	14. Tensile Modulus: 550 MPa
	15. Yield Strength: 23 MPa

Can PTFE materials be injection molded?

Teflon, also known as PTFE, can’t be injection molded because it’s different. Unlike regular plastics, Teflon is thick and doesn’t flow when it gets hot. Instead, it turns into a goo, which makes it hard to mold using normal methods like injection molding. This means it’s impossible to inject it into the mold like other plastics.

If you want to use PFA instead of injection molding products, PFA can be injection molded. It has better fluidity and is suitable for injection molding. For example, PFA and FEP, which have similar performance characteristics and are suitable for injection molding processes.

But, even though PTFE is hard to injection mold, some companies have made special injection molding machines and technologies to process PTFE. These machines usually use:

①. High-temperature barrels and screws: to handle the high processing temperatures of PTFE.

②. Specialized mold design: to accommodate the unique properties of PTFE and ensure proper filling and cooling.

③. High-pressure injection system: Injects PTFE at the desired pressure.

④. Advanced cooling system: Rapidly cools PTFE parts to prevent degradation.

Why is PTFE material injection molding difficult?

PTFE injection molding is a challenging process due to the following factors:

1. High Melting Point and Low Melt Viscosity:

PTFE has a high melting point of about 327°C (621°F) and a very low melt viscosity, even at high temperatures. This makes it hard to melt and shoot into molds. Traditional injection molding machines may not get hot enough or have enough pressure to process PTFE well, so you need special equipment and conditions.

2. Non-stick Properties:

3. Gas Emissions:

PTFE releases gases, like hydrogen fluoride, at high temperatures. This off-gassing can cause voids and defects in the molded parts. Properly ventilated equipment is also required to safely handle these emissions.

4. Thermal Expansion and Shrinkage:

PTFE expands and shrinks a lot when you heat it up and cool it down during injection molding. PTFE doesn’t conduct heat very well, so it’s hard to get rid of the heat that builds up when you’re injection molding. If you don’t control it right, the high shrinkage rate (usually 2-5%) can make the dimensions change and make the part warp.

5. High Pressure Requirements:

You need to use a lot of pressure (usually more than 10,000 pounds per square inch) to get PTFE into the mold and make it into a part.

6. Difficult Demolding:

PTFE has a high surface energy, which makes it hard to get parts out of the mold cleanly. This can cause parts to stick to the mold, making it hard to get them out without damaging them.

7. Post-processing:

PTFE parts usually need more steps to make them work right, like annealing, machining, or grinding, to get them to do what you want and fit right.

8. Limited Mold Life:

PTFE is highly reactive with mold materials, which increases the risk of mold damage. As a result, PTFE molds have a limited lifespan.

9. Specialized Equipment:

To overcome these challenges, PTFE injection molding requires specialized equipment with precise temperature control, high-pressure capabilities, and custom non-stick coatings. Molds must also be specially designed to accommodate PTFE’s unique properties.

What are the advantages of PTFE Injection Molding?

PTFE injection molding offers several advantages, including:

1. Non-stick Properties: PTFE’s non-stick surface is perfect for applications that need to come out easily, like cookware, medical devices, and food processing equipment.

2. Chemical Resistance: PTFE is super resistant to acids, alkalis, and solvents, which makes it perfect for harsh environments like chemical processing, pharmaceuticals, and aerospace.

3. High-Temperature Resistance: PTFE’s high melting point allows it to withstand extreme temperatures, which makes it suitable for high-temperature applications in aerospace, automotive, and industrial equipment.

4. Low Friction: PTFE is great for things that need to move easily and not wear out, like bearings, seals, and gaskets.

5. Biocompatibility: PTFE is biocompatible and non-toxic, so it’s good for medical stuff like implants, surgical tools, and medical devices.

6. Electrical Insulation: PTFE is great at insulating electricity, so it’s good for electrical and electronic stuff like connectors, switches, and sensors.

7. UV Resistance: PTFE resists UV light, making it perfect for outdoor applications like outdoor equipment, lighting, and signage.

8. Low Moisture Absorption: PTFE has low moisture absorption, so it’s good for moisture-sensitive applications in humid environments, food processing, and pharmaceuticals.

9. Ease of Cleaning: PTFE is super easy to clean and take care of, which makes it perfect for places where you gotta be clean, like food processing, pharmaceuticals, and medical devices.

10. Cost-effectiveness: PTFE injection molding is a cost-effective process, especially for large-volume production, making it suitable for applications requiring high production volumes.

11. Variety of Materials: There are different types of PTFE materials you can choose from, like pure PTFE, filled PTFE, and modified PTFE copolymers such as PFA and TFM. These materials can give you better performance, like more strength, better wear resistance, and improved conductivity.

What are the disadvantages of PTFE Injection Molding?

Despite its many advantages, PTFE injection molding also has some disadvantages, including:

1. High Mold Costs: PTFE injection molding needs special tools and molds, which can make the design and manufacturing costs high.

2. Limited Material Properties: PTFE has limited mechanical properties like tensile strength and impact resistance, which can affect its performance in certain applications. It also has a high coefficient of thermal expansion and is sensitive to temperature changes, making temperature control critical during molding.

3. Difficult to Bond: PTFE is hard to stick to other stuff, so it’s tough to put it together and make connections.

4. Permeability: PTFE lets gases and liquids through, so it might not work so good if you need to keep stuff sealed up.

5. Limited Color Options: PTFE usually only comes in a few colors, so if you need a special color, you might be out of luck.

6. High Processing Temperature: PTFE needs a high temperature to work with, so it might not work so good with some machines and it might not come out so good.

7. Low Moisture Absorption: PTFE doesn’t absorb much moisture, but it’s not completely waterproof. That means it might not work so well in humid places.

8. Limited Recyclability: PTFE is hard to recycle, which isn’t great for the environment.

9. Specialized Equipment: To make PTFE parts, you need special equipment like high-temperature molds and machines. That stuff can be expensive to buy and take care of.

10. Limited Molding Options: PTFE doesn’t work for parts with thick walls or complicated shapes. That means it might not be right for some things you want to make.

11. Post-Molding Processing: Sometimes, you have to do more stuff to PTFE parts after you make them. You might have to heat them up or cut them to make them work right.

12. Material Variability: PTFE is a semi-crystalline material, which means its properties can vary depending on how it’s processed and the grade of the material.

13. Limited Chemical Resistance: PTFE is resistant to many chemicals, but not all of them, which can affect how well it performs in certain applications.

14. High Material Cost: PTFE is relatively expensive, which drives up the overall cost of the final product.

15. Limited Sustainability: PTFE is a non-renewable resource, so it’s not as sustainable as other materials.

What are the application of PTFE injection molding?

PTFE (polytetrafluoroethylene), also known as Teflon, is used in many industries because it has great properties, like being able to resist chemicals, stay stable at high temperatures and not cause a lot of friction. You can use the injection molding process to make PTFE into complicated shapes and parts that are important in a lot of different things.

Application areas	Specific application situations
Chemical Processing	PTFE is used a lot in chemical industries for things like seals, gaskets, and linings, because it can resist corrosive chemicals without breaking down. It’s also good for applications where you don’t want stuff to stick to it, because you don’t want to contaminate the material you’re handling or processing.
Aerospace and Automotive	PTFE is used in aerospace and automotive applications like seals, gaskets, and bearings because it can handle high temperatures, has low friction, and is resistant to chemicals. PTFE parts are used in fuel system parts, electrical connectors, and seals because they can handle extreme temperatures and don’t wear out, which makes them great for high-performance applications.
Medical Devices	PTFE is a great material for medical devices like catheters and surgical instruments because it’s biocompatible and can be sterilized. It’s also resistant to chemicals, so it won’t get messed up when you sterilize it.
Electrical and Electronics	PTFE is used a lot in the electronics industry because it insulates electricity, resists chemicals, and can handle high temperatures. It’s used for insulating wires, making circuit boards, connecting things, turning things on and off, sensing things, and making parts that have to work in hot and nasty places.
Food Processing	PTFE is used a lot in the food industry for conveyor belts, seals, and gaskets because it doesn’t stick to stuff, it’s resistant to chemicals, and it’s easy to clean. It doesn’t stick to stuff, so it reduces friction and keeps food from sticking to it, which makes it easier to process food and keeps things clean.
Industrial Applications	PTFE is also used to make bearings, bushings, and valve seats, where low friction and wear resistance are important. Its durability and stability in different conditions make it good for many industrial uses. PTFE's chemical resistance, high-temperature tolerance, and non-stick properties also help in industrial equipment like pumps, valves, and piping.
Sporting Goods	PTFE is used in sports equipment like golf balls, tennis equipment, and fishing gear because it doesn’t stick, it can handle chemicals, and it can handle high temperatures.

PTFE Injection Molding