The main benefit of PTFE coatings (such as Teflon) is the non-stick properties of the material, which means applications such as commercial bakeware have excellent non-stick / release properties and are very easy to clean.
We have developed a range of PTFE coating systems with many benefits to suit most applications. The function that the coating is to be used for and the operating conditions will define the selection of the right coating for the job.
In this blog, we explore some of the benefits in more detail.
A PTFE coating applied to a component will give excellent non-stick/release properties and is very easy to clean. This type of coating is also excellent at preventing both hot and cold products from permanently sticking to the substrate and therefore is widely used in the cookware, confectionery, food processing and bakery industries. PTFE coatings are also used for non-stick in the packaging, heat sealing, moulding, automotive, aerospace, chemical and pharmaceutical industries.
NON-WETTING
PTFE surfaces are hydrophobic and oleophobic, and will not readily wet. This allows the material to self-clean. For the semiconductor industry, this property is vital as it allows all chemical media to run off and be collected.
TEMPERATURE RESISTANCE
PTFE coatings can service arduous application conditions involving extremes of temperature. They can remain stable at advanced temperatures of +260°C and for short periods at +290°C. PTFE can be used on extrusion dies and sealing of plastic/elastomers where other treatments may degrade or cause clogging of molten material. These coatings can also perform at cryogenic temperatures and can remain stable at -270°C.
LOW FRICTION AND ABRASION RESISTANCE
PTFE coated surfaces reduce friction and can achieve very low coefficients of friction, typically from about 0.04 to 0.15. Where oils and grease evaporate at elevated temperatures PTFE remains and is therefore ideal for shafts, bearing surfaces, moving mechanisms, stud bolts and fasteners. For added abrasion resistance and increased wear life, this type of coating can be reinforced with the addition of fillers and also by combining with a metal sprayed base layer.
CORROSION AND CHEMICAL RESISTANCE
PTFE is inherently resistant to attack from most chemicals and when combined with other fluoropolymers such as FEP and PFA greatly enhances the life of the component. PTFE applied as a surface coating will increase the corrosion resistance of the component and can also be enhanced with the use of primers, other pre-treatments such as plating and phosphating. Stud bolts and fasteners, valves, pumps, pipe clamps and connectors all benefit from these types of coatings.
PTFE has a high dielectric strength, a low dissipation factor, insulating and high surface resistivity, giving protection and uses in many electrical applications. Our coatings can also be made to become conductive and used as an antistatic coating. Light fittings, connectors, cable guides and portable electrical equipment all benefit from PTFE.
PTFE coatings prevent galling and give excellent bearing properties. Mating surfaces and rotating parts benefit from this coating and help provide minimal maintenance downtime.
Here are just some of the examples of how we have helped our clients with our PTFE coatings:
Anyone considering the use of ePTFE/graphite packing in a plant environment needs to know its basic characteristics, including its manufacturing process and potential benefits and pitfalls. This article will serve as a primer to educate readers and help in the compression packing decision-making process.
Many of the properties of PTFE-including excellent chemical resistance and a low coefficient of friction-make it a superior material for both pump and valve packing, in both braided and solid forms. The distinction between the various braided forms, along with their advantages and disadvantages, was reviewed in a previous Sealing Sense. Expanded PTFE (expanded polytetrafluoroethylene), or ePTFE, a unique form of yarn widely used as a pump packing, was part of that review.
Expanded PTFE is processed from an extruded paste of PTFE powder and lubricant. After evaporation of the lubricant, the paste is stretched while heating to form the ePTFE yarn. One of the limitations of packing made from all PTFE yarns, including ePTFE, is its low thermal conductivity. Since ePTFE is an insulator, it imposes limits on maximum pump shaft speed because of poor dissipation of frictional heat. The process of expanding the PTFE greatly improves the strength of the fiber at less mass than the original structure. The expansion process also creates pockets of air in the microstructure that allows the impregnation of additional raw materials.
A combination of ePTFE with graphite was first introduced through a propriety process more than 25 years ago as ePTFE/Graphite fiber. Until that time, all materials used in packings were engineered for purposes other than compression packing, but most demonstrated some desirable packing attributes including natural lubricity and the ability to seal against the shaft and pump housing to prevent fluid leakage.
Link to Huakai Anti-Corrosion Equipment
The aim of this combination was a packing material with improved thermal conductivity and shaft speed capability as compared with ePTFE. Since this original development, a number of other approaches to manufacturing ePTFE/Graphite fiber have been developed. The extent of property enhancement of these and all ePTFE packing is dependent upon the raw materials and manufacturing processes, as well as the construction of the braid.
ePTFE/Graphite for braided packings is made with three components. The first is PTFE, which provides the backbone of the structure and natural lubricity to minimize friction.
The inclusion of graphite as the second material helps to solve some of the problems associated with PTFE and ePTFE. Packings made with PTFE and ePTFE are natural insulators. When the frictional forces associated with packing begin to generate heat, this heat is trapped near the shaft. This causes the packing to harden and become abrasive to the shaft. During replacement of the packing, the shaft or shaft collar often needs to be replaced. This problem is solved by graphite and its excellent thermal properties and helps promote heat transfer away from the shaft, which extends the life of the packing and pump.
The final material is a lubricant such as silicon oil. The lubricant helps to minimize friction during start-up and break-in. The inherent ePTFE structure helps the fiber capture and retain lubricants.
One important factor to consider is how these materials are integrated into the structure. Packings with graphite and lubricant dispersed throughout, instead of coated on the surface, will enable the packing to perform more effectively for a longer time.
Since ePTFE/graphite was originally developed specifically for packing, its properties have been optimized for reliable sealing, as well as ease of braiding and installation. The benefits of ePTFE/Graphite packing include:
ePFTE/graphite packing, like any packing, has potential pitfalls to consider:
ePTFE /Graphite packing tolerates a wide range of service conditions and has the capabilities inherent in PTFE while overcoming limitations of low thermal conductivity. These characteristics of ePTFE enable standardization of packing to simplify operations and improve productivity in many cases. To ensure proper choice and application of any ePTFE packing, it is always advisable to consult your packing manufacturer.
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