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Fluororesin Insulated Thermocouples

Fluororesin Insulated thermocouples are duplex thermocouples that are useful with excellent flexibility and with simple anatomy. Insulated thermocouples are covered insulation with Fluororesin on thermocouple bare wire guaranteed with accuracy of measurement.
We will immediately deliver orders for Fluororesin Insulated thermocouples as we always keep them in stock.
Please appoint the processing method for Fluororesin Insulated thermocouples for the whole length or for terminal parts, at the time of ordering welding the contact points of temperature measurement.
Fluororesin Insulated thermocouples have excellent heat resistance, chemical resistance, electric features, mechanical features, climate resistance, and are non-flammable.

The classifications and conductor standards of Fluororesin Insulated thermocouples

The classifications Insulated type Insulator type Core wire materials Linear diameter
Heat electromotive force (mV)
Standard point of contacting 0˚C
+ side core - side core + side core - side core 100˚C 218˚C
K Blue Red White Chronic *1 Alnich *1 1/0.32

E Purple Red White Chronic *1 Copper-Nickel Alloy 6.319±0.100
J Yellow Red White Iron Copper-Nickel Alloy 5.269±0.080
T Brown Red White Copper Copper-Nickel Alloy 4.279±0.023

*1 Chronic and Alnich are our registration trademarks of Chromel and Almel.

We will introduce the classifications of insulated thermocouples and their features. Please choose with your order.

Table-5 The classifications and features of Fluororesin Insulated thermocouples
K insulated thermocouples The used temperature ranges used are most diverse from -200˚C ~ 1200˚C, and also, most similar to a straight line as in the relationships of temperatures in-between them and heat electromotive force. These thermocouples are inexpensive on comparison with noble metal thermocouples, and so they are the most diversely used as industrial thermocouples.
E insulated thermocouples These have the highest heat electromotive force among thermocouple used today, and are the most sensible thermocouples. E insulated thermocouples are 50 % higher on a comparison with K insulated thermocouple, and are 20 % higher on comparison with J insulated thermocouples in heat electromotive force. Therefore, they are used within a temperature range below 700˚C to 800˚C.
J insulated thermocouples These are usually used for temperature measurement under 600˚C. They have the second best sensibility next to E insulated thermocouples, and on comparison with E insulated thermocouples, they are more inexpensive in value. Furthermore, J insulated thermocouples have strength sufficient for use at reduced atmosphere.
T insulated thermocouples These are usually used for temperature measurement under 300˚C. Since they have high accuracy and the excellent process ability for drawing, they are widely used as highly accurate insulated thermocouples for low temperature, and are processed on glass fiber or Fluororesin insulation. These thermocouples are also widely used as insulated thermocouples for extremely low temperature.

* Our standard Fluororesin Insulated thermocouple products are different from the ones for usual temperatures listed above due to thin wire diameters of 0.32 and 0.65 (refer to graph-4).

Insulated thermocouple electromotive force graph

The classifications and lengths of insulated thermocouples

No. Standard products Formal symbols Bare wire diameter
Standard matching length
Insulation, Protection insulation
Materials Highest temperature used for insulation (˚C)
1 K-0.4=FEPFEPF 1/0.32
Fluororesin 200
2 K-0.4=FEPFEP 1/0.32
Fluororesin 200
3 E-0.4=FEPFEPF 1/0.32
Fluororesin 200
4 J-0.4=FEPFEPF 1/0.32
Fluororesin 200
5 T-0.4=FEPFEPF 1/0.32
Fluororesin 200

The features of Fluororesin (FEP) insulation

Table-7 All features

1) In organic insulation materials, FEP insulation has the highest heat-resistant.

FEP is capable of being sequentially used up to 200˚C.
(refer to Graph-10)

2) FEP insulation has excellent cold resistance.

FEP is resistant to extremely low temperatures
under -200˚C.

3) This insulation has excellent chemical resistance.

FEP is not affected by most chemical products.
(refer to Graph-11)

4) FEP insulation has excellent electric features.

It has high resistant capability and high resistance to insulation. (refer to graph-10)

5) In regards to mechanical features, FEP insulation has excellent flexibility.

In a comparison with PVC, it has strength of flexibility, and can easily be handled.

6) It has excellent resistance to climate.

As FEP does not absorb light, it does not corrode by light. And furthermore, it is resistant to ozone, high-temperature, and extreme low temperature, and also it does not absorb humidity. Therefore, it does not change due to exposure to the outside for long periods of time.

7) FEP insulation is nonflammable. It does not flame as it gets closer to wax.

It is nonflammable, and has the least percentage of smoke occurrence. The limited index of oxygen, which is the density for continuation of flame, is 95 vol%. (refer to Graph-9)

Features of Fluororesin

1. The classifications of Fluororesin Insulators

Table-8 Classifications of Fluororesin insulators
PFA Demonstrates excellent features that are capable of wide temperature ranges from extremely low temperature to high temperature.
FEP Has excellent features such as being cold-resistant, chemical-resistant, climate-resistant, adhesive-resistant, and dielectric, however, the heat-resistant temperature is a little low (200˚C for continuous usage). FEP is most widely used as Fluororesin Insulated material.
ETFE As the heat-resistant temperature at continuous usage is 150˚C, ETFE belongs to the middle rank of Fluororesin for heat resistance, however it has a good balance of mechanical strength, chemical resistance, and electrical features.

2. Chemical resistance and mechanical features

Table-9 Feature comparison list of Fluororesin and hard polyvinyl chloride
Heat-resistant(˚C) electrical features flammable-resistant(%) mechanical features low-friction chemical-resistant non-adhesive climate-resistant transparency formality
oxygen alkali solvent
PFA 260 95
FEP 200 95
ETFE 150 30
Polyvinyl chloride 60 45

◎:Highly-excellent    ○:excellent    △:available on usage    ×:unavailable on usage

Table-10 Featured details of Fluororesin
Feature item unit ASTM test method TFE PFA FEP ETFE
Physical feature melting point ˚C --- 327 310 270 270
specific gravity --- D792 2.14-2.20 2.12-2.17 2.12-2.17 1.7
Mechanical feature Strength to pull kgf/cm2 D638 140-350 280-300 190-220 410-470
rate of growth % D638 200-400 280-300 250-330 420-440
compressibility kgf/cm2 D695 50-60 --- 50-60 109
impact kgfcm/cm D256A 16.3 --- non-destructive
hardness Shore hardness D2240 D50-65 D60 D55 D75
bending modulus of elasticity 103kgf/cm2 D790 5.0-6.0 6.6-7.0 5.5-6.5 9.0-14.0
Heat-resistant feature wire swell index 10-5/˚C D696 10 12
(+20 ~ +100˚C)
(+20 ~ +100˚C)
Temperature of heat transformation
˚C D648 55 47 50 74
Temperature of heat transformation
˚C D648 121 74 72 104
maximum temperature for usage
˚C (no load) 260 260 200 150
Electric features volume resistant Ω-cm D257
>1018 >1018 >1018 >1018
insulator destructive strength kV/0.1mm
D149 6-10 >10 >10
dielectric (106Hz) D150 <2.1 <2.1 2.1 2.6
dielectric tangent (106Hz) D150 <0.0002 <0.0003 <0.0005 <0.0005
resistant-arc sec D495 >300 >300 >300 75
Miscellaneous chemical-resistant D543 Excellent Excellent Excellent Excellent
absorbent % D570 <0.00 <0.01 <0.01 <0.1

Table-11 Chemical resistance of Fluororesin
Liquid TFE FEP
Four Carbon
Carbon disulfide
Ethyl alcohol
Petroleum ether
Nitric acid(10%)
Sulfuric acid(10%)
Hydrochloric acid(10%)
B Heavy oil
Transformer oil


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