Special Issue

Polymer Materials Technology

Development of a Halogen-free Insulation Material
for Overseas Railway Rolling Stock Lightweight Electric Wire
Hiroki Chiba*, Masaki Nishiguchi*Electric wire for overseas railway rolling stocks is requiring a high abrasion resistance, in addition to a vertical flame resistance, a high heat resistance and a hightemperature oil resistance, to withstand vibration and other conditions experienced during railway
operation. On the other hand, a thinning of the wire insulation materials is desired for further
reduction in weight of railway rolling stocks. Generally, engineering plastic is used as an insulationmaterial, but it has issues with its flexibility and its wire stripability.
Using general-purpose polyolefin as a base material for the insulation material and adopting ourown technique of polymer materials this time, we have successfully developed a halogen-free
insulation material which is also superior in flexibility and in wire stripability, in addition to characteristics equivalent to those of the engineering plastic, and which is reduced its thickness compared to conventional electric wire, and therefore can achieve a reduction of approximately 15-35% in weight.

ABSTRACTINTRODUCTION
1.1. INTRODUCTION
In recent years, while a concern about environmental
issues grows in the world, rail transportation has a lessenergy consumption and less carbon dioxide emissions
than other means of transportation. Therefore, it draws
the attention as an eco-friendly mean of transportation,and the current worldwide market size related to railway
is as large as 14 trillion and continues to grow at an annual rate of about 2-3%.1) Especially, improvements of railway systems are currently pursued in overseas markets
mainly in Europe and in Asia, and subsequently, it isexpected that the railway construction will accelerate inSouth America and in the continent of Africa. Insuch situation, demands for various components which are usedin the railway rolling stocks will increase, and it is estimated that business related to the railway rolling stocks willgrow larger in the future.
For the future development of the railway rolling stocks,
the weight reduction of the railway rolling stock body isalso discussed. 2) When the railway rolling stock is
reduced in weight, not only further energy saving andspeeding up of railway are expected, but also preventing
noise and less loading to the rails and others will be provided, and an attenuating effect for the truck maintenancework are also expected. Therefore, as the purpose ofweight reduction on the electric wire for the railway, fur* Research & Development Div.
Polymer Materials R&D Laboratories

ther thinning of wire insulation material thickness is considered.
In the above the context, in the area of the wires for railway rolling stock, this time, we have focused on the lightweight electric wire which is used mainly for railway signals and have developed its new insulation material.

ELECTRICWIREWIREDEVELOPEDDEVELOPED FOR
2.2. ELECTRICFOROVERSEASRAILWAY
RAILWAY ROLLINGROLLING STOCKOVERSEASSTOCK
The electric wires for overseas railway rolling stock mainlyin Europe and in Asia are required, in addition to the thinning of the wire insulation material thickness, the high levels of abrasion resistance, the vertical flame resistanceand the high temperature oil resistance which comply
with an EN Standard (European Norm, European
Standard) to withstand the vibration experienced during
the railway construction or the railway operation.
Therefore, the engineering plastic which is superior in its
strength properties and in its heat resistance have beenused as a base material. However, such material is generally rigid and poor in flexibility, and it has been considered that its wiring to the thin part of the railway rollingstocks and its included components have been difficult.
This time, we have developed a new polymer material
made entirely of a general-purpose polyolefin resin, without using an engineering plastic. By using it as the insulation material for the electric wire, it complies with themechanical properties, such as abrasion resistance, heat
resistance, high temperature oil resistance and others,
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Development of a Halogen-free Insulation Material for Overseas Railway Rolling Stock Lightweight Electric Wire

which meet requirements of EN 50264-3-1and EN 503062 which are the standards for electric wires with thinwalled insulation and right weight, vertical flame resistance of IEC 60332-3-24, Category C (EN 50264-1) andlow smoke generation property and others of IEC 61034(EN 50264-1). Additionally, we have developed an insulation material for the railway rolling stock light weight electric wire, which has an advantage in the flexibility and thestripability of terminals which are concerning issues forthe conventionally used engineering plastic.

ducted such that the tubular test sample is kept in a hightemperature environment of 200℃ for 15 minutes, withthe suspension of a load weight of 20 N/cm2. To pass thetest, the sample is required that the limit of elongation
between gage points must be ≦100% after 15 minutes
and also that the limit of permanent elongation between
the gage points after the load is removed, must be≦25%.
Initial condition

Under loading

After removal ofload weight

200℃×15 min.

CONSTRUCTION OF
OF THETHE OVERSEAS
3.3. CONSTRUCTIONOVERSEAS
RAILWAYROLLINGROLLING STOCK
STOCK LIGHTRAILWAY
LIGHTWEIGHTELECTRICWEIGHT
ELECTRICWIRE WIRE
The construction of the overseas railway rolling stock
lightweight electric wire is shown in Table 1. The insulation thickness of this electric wire is 0.4 mm, which isapproximately 1/2 of thickness compared with that of theconventional railway rolling stock electric wire. Therefore,
the electric wire is reduced in weight and has a construction accommodated to the energy saving. At the sametime, since the insulation thickness becomes thinner, theinsulation material requires various tough properties suchas a further higher strength, a higher level of abrasion
resistance and other properties.

Table 1

Structure of the lightweight electric wire developed forthe overseas railway rolling stock.
Conductor

Insulation
thickness（mm）

Overall
diameter
（mm）

0.7

0.4

1.5 ± 0.2

0.9

0.4

1.7 ± 0.2

0.75

1.1

0.4

1.9 ± 0.2

1.00

1.3

0.4

2.1 ± 0.2

1.25

1.5

0.4

2.3 ± 0.2

1.50

1.6

0.4

2.4 ± 0.2

2.00

1.8

0.4

2.6 ± 0.2

2.50

2.2

0.4

3.0 ± 0.2

Nominal crosssection area
（mm2）

Conductor
diameter
（mm）

0.30
0.50

THEREQUIREDREQUIRED PROPERTIESANDAND THE
4.4. THEPROPERTIESTHETESTMETHODSFORTHE
INSULATIONTEST METHODS FOR THE INSULATION
MATERIALS FOROVERSEAS
RAILWAY
MATERIALSFORTHETHEOVERSEAS
RAILROLLING
STOCK
ELECTRIC
WIRE
WAY
ROLLINGSTOCK
ELECTRIC
WIRE
4.1 Hot-set Test
As per EN Standard (EN 50264-3-1 and EN 50306-2), it isrequired to meet the hot-set property as the evaluation
method to confirm that the insulation material of the electric wire maintains its strength without melting at hightemperature. The method of the hot-set test is shown in
Figure 1. In accordance with EN 50305, the test was con-Gauge
lengthTubularsample20 N/cm 2weightChange inpermanent
elongation

Change in
elongation

Elongation must be≤ 100%

Permanent elongationmust be ≤ 25%

Figure 1 Hot-set test.

4.2 Abrasion Resistance Test
The present insulation material is required to meet theabrasion resistance test conducted in accordance with
EN 50305. This test method is shown in Figure 2. This
test was conducted in such a manner that the load weightof 9 N was applied on the horizontally set electric wire
sample and the insulation material was abraded by using
a steel blade of 0.45 mm diameter. The blade continuously ran back and forth until it reached the conductor of thetest sample. Abraded parts were 4 sections in total as circumferential direction of 90, 180, 270, and 360 degree foreach sample. EN 50306-2 requires ≧100 cycles per eachsection and ≧150 cycles in average of the 4 sections.

Load weight
Insulation

Steel blade

Conductor

Figure 2 Abrasion resistance test.

4.3 Vertical Flame Resistance Test
The present insulation material is required to meet thevertical flame resistance test conducted in accordancewith the flame resistance of IEC60332-3-24, Category C(EN 50264-1). This test method is shown in Figure 3. As
shown in Figure 3, the electric wire samples trimmed at alength of 3500 mm were vertically installed with no spacein-between. The bottoms of the samples were exposed toignite for 20 minutes by a burner, and then the flame wasremoved and the samples were left until the fire self-extinguished. The sample passes the test if the length of thecharred section from the burner ignition point is 2500 mm
or less after the fire has completely extinguished itself.
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Development of a Halogen-free Insulation Material for Overseas Railway Rolling Stock Lightweight Electric Wire

Bunchedsample4.7 Flexibility Test
An evaluation method of wire flexibility is shown in Figure
4. The electric wire was cut out in 280 mm length and bothof the wire ends were connected to each other to make aloop. The looped sample was hanged on a mandrel of
4.0 mm diameter and suspended a load weight of 3.4 N.
The flexibility of the electric wire was measured by measuring the minor axis diameter of the looped sample suspended with the load weight. As short as the minor axis
diameter of the looped electric wire is, as flexible the wire.

Mandrel (4.0 mm diameter)
BurnerMeasured

Figure 3 Vertical flame resistance test in accordance with
IEC60332-3-24, Category C.

4.4 Smoke Generation Property Test
The present insulation material is required to meet the
3 m cube smoke test conducted in accordance with
IEC61034 (EN 50264-1) for its smoke generation property.
The samples trimmed at a length of 1000 mm wereburned for 40 minutes by a burner in the 3 m cube test
chamber. Light transmissibility in the test chamber which
is filled with smoke generated from the insulation material, was measured. The sample passes the test if this lighttransmissibility is 70% or more.
4.5 High Temperature Oil Resistance Test
The present insulation material is required to meet thehigh temperature oil resistance test defined by EN 50305.
The test was conducted in such a manner that the tubular
insulation material was immersed for 24 hours and 72
hours in the oil of ASTM IRM 902 which was already100℃ hot, and then the tensile test was carried out. The
sample passes the test if the each residual of the tensile
strength and residual of the elongation at break is within
the range of 70-130% and 60-140% respectively, after a
24 hours immersion for the standard oil resistance of EN
50264-3-1 and after a 72 hours immersion for the special
oil resistance of EN 50264-3-1.
4.6 Long-term Heat Resistance Test
The present insulation material is required a long-term
heat resistance at 105℃ or higher temperature. The heat
aging test is conducted usually at more than three different temperatures and a long-term heat resistant temperature is determined by the Arrhenius plot from the ending
points of each temperature. The heat aging test for thistime was conducted at the three points of 180, 158 and
133℃ and the time (ending point) on which the elongation, at break achieves 50% for each temperature, wasinvestigated. The long-term heat resistant temperature
was calculated for 20,000 hours by the Arrhenius plot
from the ending points of each temperature.

Loopedsample3.4 N weight

Figure 4 Evaluation of wire flexibility.

DEVELOPMENTOF
OF THETHE POLYMERPOLYMER
5.5. DEVELOPMENT
MATERIALWHICH
WHICH MEETSMEETS THE
MATERIAL
THE REQUIREDPROPERTIESREQUIREDPROPERTIESIN ACCORIN ACCORDANCEWITH EN STANDARDDANCEWITH EN STANDARD
For the required properties in accordance with EN
Standard of section 4 of the above, we have developed
the insulation material for overseas railway rolling stock,from a general-purpose polyolefin resin. The present
material development is described in the followings.
First, in the case that a general-purpose polyolefin resin
is provided to the hot-set test at 200℃, and since themelting point of the polypropylene resin is around 160℃
even though it is the highest melting point in polyolefin,
the resin melts in a short period and can not comply with
the EN Standard. Therefore, we have provided electron
beam cross-linking to the general-purpose polyolefin
resin for this time.
Secondly, abrasion resistance property is described. To
improve the abrasion resistance, the usage of a high-density polyolefin resin and a cross-linking treatment such as
electron beam cross-linking are effective, however thehigh-density polyolefin is generally rigid and its flexibility
is of concern. Although the present insulation material
also requires a flame resistance, such high-density resin
has a low acceptability of fillers such as flame retardant,
and it is difficult to provide a sufficient flame resistance.
Therefore, to ensure the flexibility and the acceptability of
fillers, it is necessary to select the resin, ethylene-based
polymer (for example, ethylene-vinyl acetate copolymer,
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Development of a Halogen-free Insulation Material for Overseas Railway Rolling Stock Lightweight Electric Wire

EVA) or others with a certain level of low-density.
However, these materials are inferior in mechanicalstrength. Also, even if an electron beam cross-linking isprovided to these materials, it is difficult to provide theabrasion resistance property of EN Standard. Therefore,
we adopted the new cross-linking technique of our own
that ionically-bonds polymer and metal hydroxide as aflame retardant (Figure 5). With this technique, it is possible to provide the hardness of an inorganic filler to polymer, and to improve substantially the abrasion resistanceproperty. Also, this technique can improve the abrasion
resistance property if the introduction amount of the metalhydroxide is large at some level, therefore a high-level offlame resistance property can be additionally reached.
Although the technique has been used mainly for highstrength wires of electronic devices and automobile, we
provided cross-linking which is more stable for the current development than of those products.

Cross-linking
by E-beam

For high temperature oil resistance at 100℃, as shownin Figure 6, it is considered that no collapse in the crystallinity of the polymer structure is necessary. Therefore, we
focused on the polymer structure at high temperature andselected the base material which does not collapse in
crystallinity of the polymer structure and has no oil penetration at 100℃.

Crystal state

Non-crystal state
due to melting and swelling

Oil cannot go into the polymer

Oil can go into the polymer easily

Polymer

Oil

Oil

The polymer can keep its
mechanical properties.

New lightweight electric wirewith general-purpose polyolefin
Base material tech.

Anti-oxidant tech.

Oil resistance（100℃）

 Heat resistance（More than 105℃ ）6.1 Hot-set Test
The hot-set test results are shown in Table 2, with noncross-linking polyolefin material.

Metalhydroxide

Figure 5 New cross-linking technique.

Oil Hot-set property（200 ℃）

New cross-linking tech.
Abrasion resistanceFlame retardanceLow smoke

RESULTSAND
ANDCONSIDERATIONCONSIDERATION
6.6. RESULTS
Polymer

Oil

Electron beamcross-linking tech.

Figure 7 A wide variety of material techniques on the insulationmaterial for railway rolling stock electric wire.

New
cross-linking
tech

Oil

the electric wires for electronic devices and industrial
cables.
The above polymer techniques compiled are shown in
Figure 7. The present insulation material substantiallyincorporates our polymer technique in addition to thecomplex cross-linking technique of electron beam crosslinking and our own new cross-linking.

Oil

Oil

Oil
Oil

Oil

The polymer loses its mechanicalproperties remarkably.

Figure 6 Schematic illustration of the structure of polyolefin athigh temperature.

For long-term heat resistance, we adopted the heat
resistance technique which we had developed so far with

Table 2

Results of hot-set tests.

Requirement

Comparedmaterial(non-crosslinking)Developed
material(electron beamcross-linking)

Under loading (%)≦ 100

NG withmelting

22.6

After load isremoved (%)≦ 25

NG withmelting

8.6

While the non-cross-linking material melted in a shortperiod under the environment of 200℃, on the other
hand, our developed material succeeded to meet the hotset property with providing our own electron beam crosslinking to the polyolefin.
6.2 Abrasion Resistance Test
Result of the abrasion resistance test which was conducted in accordance with the method specified in EN 50305
is shown in Figure 8. The test results, of the conventional
electric wire used engineering plastic as the insulationmaterials for overseas railway rolling stock, and of theelectric wire used polyolefin material which is not using
the new cross-linking technique, are shown together forcomparison purposes.

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Development of a Halogen-free Insulation Material for Overseas Railway Rolling Stock Lightweight Electric Wire

Cycle number of abrasion

10000

100
Requirement（150 cycles)

1

Wire A

Wire B

Wire C

Developed
wire

Figure 8 Results of the abrasion resistance tests in accordancewith EN 50305 with 0.45 mm diameter steel blade and aload of 9 N.

The conventional electric wires, using engineering plastic as the insulation material for overseas railway rollingstock, are Wire A and Wire B. The electric wire using thepolyolefin material which is not using the new cross-linking technique is Wire C. The average cycle number ofWire C which did not adopt the new cross-linking technique is about 50 cycles and it is significantly inferior in its
abrasion resistance. This can be considered that the inorganic filler itself contributes to the abrasion of the polymer
because the polymer and the inorganic filler are notbonded. On the other hand, using the material adopting
the new cross-linking technique, the average cycle number of the wire is improved up to approximately 1000
cycles and it can be seen that the target value of 150
cycles is well satisfied. As just described, it can be seenthat the developed material which is adopting the new
cross-linking technique has the abrasion resistance specified in EN50306-2 and is comparable to the electric wires
using engineering plastic for overseas railway rollingstock (Wire A and Wire B).
6.3 Vertical Flame Resistance Property
The results of the vertical multiple wire flame resistancetest in accordance with IEC60332-3-24, Category C areshown in Figure 9.

test was 1030 mm. For such vertical multiple wire flame
resistance test a high level of flame resistance is required,
therefore it is typical to use red phosphorus together as aflame retardant. Alternatively, a flame retardant, such as
metal hydroxide, is needed to be added in large amounts;
however such prescription significantly impairs mechanical properties such as the abrasion resistance in general.
Using the new cross-linking which tightly bonds the polymer and the metal hydroxide, it is confirmed that the highlevel of flame resistance as well as the superior abrasion
resistance can be achieved simultaneously.
6.4 Smoke Generation Property Test
The result of the smoke generation property test in accordance with IEC 61034 is shown in Table 3. Test result of awire insulated with the material which is adopting 5 pts.
mass of red phosphorus against 100 pts. mass of a baseresin is also shown in the Table 3 for comparison purposes. From the result of the smoke generation property test,
it is found that the wire with the material which used thered phosphorus has 35.4% of light transmissibility anddoes not meet the standard. To meet the vertical multiple
wire flame resistance, the red phosphorus is generally
used, however it is found that the wire cannot meet the
EN Standard if the present wire is using it. On the other
hand, the wire which uses the present developed material
has 86.4% of light transmissibility after the flame test andit sufficiently exceeds 70% of light transmissibility as
required by the standard. That is, it is confirmed that even
if the insulation material burns, the smoke generation islow. With the low smoke generation property, under an
enclosed space, for example subway, there is no smoke
generation even though the fire breaks of railway rollingstocks occur. Therefore it facilitates the evacuation andthe fire fighting without reducing the visibility in the surroundings.
Table 3Results of the smoke generation tests.
ComparedDeveloped
materialmaterial
Requirement( 5 pts. mass of(no redred phosphorus) phosphorus)Lighttransmissibility(%)
1 min.

5 min.

10 min. 15 min. 20 min.

≧ 70

35.4

86.4

After test

1100 mm1030 mm(<2500 mm)

Figure 9 Result of the vertical flame resistance test inaccordance with IEC 60332-3-24, Category C.

The height of the flame became 1100 mm in 5 minutes
after being ignited, however the fire didn’t spread morethan that. Also, the time for sustaining flame after theburner is removed was only 90 seconds and the fire selfextinguished. The length of the charred section after the

6.5 High Temperature Oil Resistance Property
The result of the high temperature oil resistance test is
shown in Table 4. The halogen-free electric wires (Wire D,
Wire E) which are constructed with insulation material
based on the polyolefin resin and which have the typicalvertical flame resistance were simultaneously measured.
When the typical polyolefin based insulation material isimmersed in oil at 100℃, it loses its crystallinity andswells. Therefore, its mechanical properties become significantly low. On the other hand, for the insulation material of the present electric wire, the crystallinity of its polymer is stable without collapse at high temperature, thereFurukawa Review, No. 45

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Development of a Halogen-free Insulation Material for Overseas Railway Rolling Stock Lightweight Electric Wire

fore it is confirmed that oil does not penetrate into thepolymer and it is superior in its oil resistance. It is also
found that the present developed material meets a tougher special oil resistance as well as a standard oil resistance of EN 50264-3-1.
Table 4

Results of the high temperature oil resistance.
Requirement Wire D Wire E

Developed
wireStandard oil resistanceof EN50264-3-1
ASTM IRM902,
at 100℃ for 24 hours
Residual of tensile
strength (%)

70 − 130

40

57

82

Residual of elongation
at break (%)

60 − 140

111

167

86

Special standard oil
resistanceof EN50264-3-1
ASTM IRM902,
at 100℃ for 72 hours
Residual of tensile
strength (%)

70 − 130−−

90

Residual of elongation
at break (%)

60 − 140

−

−

111

6.6 Long-term Heat Resistance Property
The result of the long-term heat resistance, in 20,000
hours, which is calculated by using the Arrhenius plot, isshown in Figure 10. Continuous operating temperature of
the wire with insulation material which is adopting ourheat resistance technique is 113℃ and it is confirmed thatit sufficiently meets the 105℃ of the standard.

6.7 Flexibility Test
The result of the flexibility evaluation is shown in Table 5.
The results of the wires (Wire A, Wire B) for the conventional overseas railway rolling stock, which uses engineering plastic as an insulation material, are shown forthe purpose of comparison.
As just described, it is confirmed that the developed
wire is significantly superior in its flexibility, compared withthe wire which is using engineering plastic as an insulation material. That is, it suggests that the wiring to the thinparts of the railway rolling stocks’ inside and its included
components contained on becomes easier than everbefore.
Table 5

Wire A

Wire B

Developed
Wire

Photographs of
the flexibility
evaluation
with 3.4 N load
weight

4.0 mmdiametermandrelSample3.4 N
weight

Before test (mm)

84

84

84

With 3.4 N
weight (mm)

62

57

37

6.8

Evaluation of the Wire Stripability by General
Insulation Striper
The evaluation results of the stripability by general insulation striper for each wire are shown in Table 6.
Table 620,000 Hr

Evaluation of the wire flexibility.

Evaluation of the wire stripability by general insulation
striper.
Wire A

Wire B

Developed Wire

10,000Time / Hr

1,000

100

10

113ﾟC
1

200

180

160

140

120

100

Temperature / ﾟC
Figure 10 Evaluation of the heat resistance temperature by using
Arrhenius plot.

The results of the wires (Wire A, Wire B) for conventional overseas railway rolling stock, which uses engineering
plastic as an insulation material, are shown for the purpose of comparison.
The wire which uses the developed material has noleaving, such as burrs at the stripped cutting site and issignificantly superior in its stripability.
6.9 Other Properties
It is found that the results of evaluating other properties forthe wire which uses the material developed in accordancewith the relevant EN Standards are shown in Table 7.
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Development of a Halogen-free Insulation Material for Overseas Railway Rolling Stock Lightweight Electric Wire

Table 7

Properties of the lightweight electric wire developed
for overseas railway rolling stock.
Relevant
standard

Requirement

Developed
Wire

EN 50264-3-1

≧ 10

25

≧ 150

167

Residual tensile strength(%)

70 − 130

112

Residual elongation atbreak (%)

70 − 130

93

Test item
Tensile strength (MPa)Elongation at break (%)
Heat aging test

EN 50264-3-1

at135℃ for 168 hours

Flame resistance

EN 50264-3-1

ASTM IRM903,
at 70℃ for 168 hours
70 − 13092

60 − 140

99

≧ 70

91

≧ 100

183

Residual tensile strength
(%)

≧ 70

91

Elongation at break (%)

≧ 100

183

Tensile strength (%)
Elongation at break (%)
Acid resistance

EN 50264-3-1

0.5 mol of oxalic acidaqueous solution,
at 23℃ for 168 hours
Residual tensile strength(%)
Elongation at break (%)
Alkali resistance

EN 50264-3-1

1.0 mol of sodiumhydroxide solution,
at 23℃ for 168 hours

Bending test at low temperature
at -40℃

EN 50264-3-1

No cracks

Pass

Impact test at low temperature
at -25℃

EN 50264-3-1

No cracks

Pass

Dynamic cut-through (N)EN 50264-3-1

≧ 100

123

Ozone resistance

EN 50264-3-1

No cracks

Pass

Notch propagation

EN 50306-2
No
breakdown

Pass

at 20℃ for 3 hours→ 1.0 kV for 1 minuteNo
breakdown

Passat 85℃ for 3 hours→ 1.0 kV for 1 minuteNo
breakdown

Pass

＜ 45

34.7

＜ 1.5

0.33

No
insulation
breaking

PassNo
damage on
external
layer

Pass

EN 50306-2

at 160℃ for 168 hours,
Cone type mandrel→ 1.5 kV for 1 minute
Blocking of coreat 150℃ for 168 hours,
Adhesion with PTFE

1) “UNIFE World Railway Market Study 2012”, Roland Berger
2) Yasufumi Suzuki : “Weight Reduction of Railway Vehicles by
Applying Aluminum Alloy and Its Future Problems”, Light Metals
Volume 60, Item 11, (2010), 565-570

EN 50306-2

300 mm,at 150℃ for 1 minute→ 20℃
Stress cracking

We have developed a halogen-free insulation material foroverseas railway rolling stock lightweight electric wire byusing a variety of our own polymer material techniquebased on general-purpose polyolefin resin. Using thismaterial as an insulation material, not only it meets theproperties complying with EN Standards, but also theinsulation thickness can be thinner than that of the conventional electric wire. Therefore it is possible to obtain
the wire that meets the energy saving which suits theneeds of weight reduction in the railway rolling stock
development in the future. Since this developed material
consists of a general-purpose polyolefin resin, it is superior in its flexibility to the conventional electric wire for overseas railway rolling stock which uses engineering plastic
and also superior in its stripability. Therefore, it can bestated that it is superior in mass productivity and in wiring
workability for the practical assembling of rolling stocks
and various components that it include.
The electric wire adopting this developed material canbe expected to be in high demand as a lightweight electric wire for overseas railway rolling stock in the future.

EN 50306-2

at 20℃ for 72 hours, 15 N
Shrinkage (mm)CONCLUSION
7.7. CONCLUSIONREFERENCES

at -15℃ for 3 hours→ 1.0 kV for 1 minuteFlexibility ( °)It is found that the developed wire was superior in properties such as mechanical property, heat resistance, abrasion resistance, oil resistance, chemical resistance, lowtemperature capability, flame resistance, smoke generation property and flexibility, and met the EN Standard
required for the electric wire of railway rolling stock. The
thickness of its insulation was reduced to 1/2 comparing
with that of the conventional wire, and it was successful inthe reduction of approximately 15-35% of its weight.

EN 50306-2

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