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Epiform F-6975 | Grey Coil Insulation Epoxy Coating Powder

Harmonization Code : 3907.30.00.90 |   Polyacetals, other polyethers and epoxide resins, in primary forms; polycarbonates, alkyd resins, polyallyl esters and other polyesters, in primary forms : Epoxide resins : Other
Main features
  • For 400V - 800V hairpin coating
  • Excellent resistance to ATF
  • Adheres to Cu and PEEK

Product Description

Epiform F-6975 Grey Coil Insulation Epoxy Coating Powder was designed specifically to be used to coat the copper hairpin on 400V and 800V Interior Permanent Magnet of Electric Vehicle motors. It is a gray fusion-bonded functional epoxy coating powder formulated to have adhesion to both copper and PEEK and designed to be used in a continuous automatic transmission fluid (ATF) environment.

Epiform F-6975 has a proven track record and is being used by most automotive manufacturers across the globe in Japan, China, India, Europe and the USA at car manufacturers from all of these regions. It achieves a heat resistance classification of 180°C and therefore can be used in applications that require a Class H rating. F6975 is perfect for fludized bed application methods. 

Product Family
15 kg 1 kg

Catalog Product

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Technical Specifications

General Properties
Bulk Density
Bulk Density
The amount of a certain product that comes in a bulk.
0.78 g/cm3
The color
Process Method Fluidized bed
Mechanical Properties
Shear strength
Shear Strength 20 N/mm2
Electrical Properties
Cut Through Temperature
Cut Through Temperature
the thermal resistance temperature/ durability
400 °C
In electromagnetism, the absolute permittivity, often simply called permittivity and denoted by the Greek letter ε, is a measure of the electric polarizability of a dielectric.
3.5 F/m
UL Rating Class F
Volume Resistivity
Volume Resistivity
Volume resistivity, also called volume resistance, bulk resistance or bulk resistivity is a thickness dependent measurement of the resistivity of a material perpendicular to the plane of the surface.
2.5x1016 Ohms⋅cm
Thermal Properties
Coefficient of Thermal Expansion (CTE)
Coefficient of Thermal Expansion (CTE)
CTE (Coefficient of thermal expansion) is a material property that is indicative of the extent to which a material expands with a change in temperature. This can be a change in length, area or volume, depending on the material.

Knowing the CTE of the layers is helpful in analyzing stresses that might occur when a
system consists of an adhesive plus some other solid component.
Coefficient of Thermal Expansion (CTE), α1
Coefficient of Thermal Expansion (CTE), α1
CTE α1 (alpha 1) is the slope of the Coefficient of thermal expansion in a temperature range below the Glass transition temperature (Tg).

It explains how much a material will expand until it reaches Tg.
36 ppm/°C
Coefficient of Thermal Expansion (CTE), α2
Coefficient of Thermal Expansion (CTE), α2
CTE α2 (alpha 2) is the slope of the Coefficient of thermal expansion in a temperature range above the Glass transition temperature (Tg).

It explains the extent to which a material will expand after it passes Tg.
110 ppm/°C
Glass Transition Temperature (Tg)
Glass Transition Temperature (Tg)
The glass transition temperature for organic adhesives is a temperature region where the polymers change from glassy and brittle to soft and rubbery. Increasing the temperature further continues the softening process as the viscosity drops too. Temperatures between the glass transition temperature and below the decomposition point of the adhesive are the best region for bonding.

The glass-transition temperature Tg of a material characterizes the range of temperatures over which this glass transition occurs.
128 °C
Specific Heat Capacity
Specific Heat Capacity
Specific heat capacity is the amount of heat energy required to raise the temperature of a substance per unit of mass. The specific heat capacity of a material is a physical property. It is also an example of an extensive property since its value is proportional to the size of the system being examined.
1.5 J/g °C
Thermal Conductivity
Thermal Conductivity
Thermal conductivity describes the ability of a material to conduct heat. It is required by power packages in order to dissipate heat and maintain stable electrical performance.

Thermal conductivity units are [W/(m K)] in the SI system and [Btu/(hr ft °F)] in the Imperial system.
0.5 W/m.K

Additional Information

What happens if we cure in a lower temperature?

There is always a contour plot of Tg that depends on time and temperature.  Please see this article that discusses this and the following image:

The recommended cure schedule at 190°C is 20mins and the general rule of thumb is that for every 10°C (up or down) generally halves or doubles the rate of reaction.  Dropping the temperature by 15°C or 25°C would then mean a cure time of approximately 60-80 minutes.  However, as you see in the image, the rings get further apart as the cure temperature and the Tg get higher.  Given that the Tg of the powder is only 130C and the cure temperature is still 165C or 175C, we would feel comfortable saying that a cure time of 30-40 mins would be sufficient still. There are cure kinetic curves that can be generated but this should last least give you a starting point to work with. 


Troubleshooting delamination issues with PEEK (Polyether Ether Ketone)

PEEK, also known as magnet wire, can add a smaller heat capacity compared with non-PEEK bare copper wires, which can result in thin epoxy coating results and cause adhesion problems. This is not the norm but it can happen.

It is probable that due to this, oxidation proceeds easily, and peeling can occur. The epoxy is being oxidized and oxidation manages to occur at the interface between the epoxy and PEEK. Oxidation occurs in all epoxy layers.The action at the interface means that the thin part of the epoxy oxidizes easily, dampening the plasma effects that normally aid in the adhesion between the PEEK and the epoxy.

This phenomenon can be resolved by coating the wire in a way that reduces the coating area. Reducing the coating area means painting only near the non-PEEK bare copper wire. Non-PEEK bare copper wire has higher heat conduction compared to PEEK. During coating the non-PEEK bare copper wire can adhere a large amount of powder to increase the film thickness. This is thought as an effective countermeasure because dripping occurs after coating and the epoxy layer on PEEK becomes thin. 

If delamination has not occurred in all samples, or you never faced this issue before, it is also probable that the pretreatment plasma irradiation was non-uniform and has to be tried again.

Another cause of delamination of the coating to PEEK has been by having too large of a temperature differential between subsequent dips of epoxy coating powder.  Because the recommended pre-heat temperature causes an expansion rate difference between the PEEK and the copper, it is important to limit the pre-heat temperature to 160°C (and not higher) to avoid large temperature differentials between the pre-heat and dipping process.  Paying attention to this temperature differential will ensure a coating without delamination.

Please see the following image for a standard coating process: