Development of Environment-Harmonized Electric Wires
by Hitoshi Yamada * and Masaki Nishiguchi *In recent years, adequate consideration on the problem of environment preservation has become a social task, requiring wire materials to be halogen-free to minimize the environmental effects at landfill and incineration. While conventional halogen-free materials have such problems as insufficient mechanical properties, sensitivity to mechanical damages, and poor heat resistance, the new halogen-free material developed this time is provided
with not only excellent flame retardant properties but also superior mechanical properties.
Moreover, since the material does not contain toxic heavy metals and phosphorus without mentioning halogens, it can cope with recycling processes, thus making it very useful for covering
electric wires. Besides electric appliance wires, the material has a wide area of applications suchas automotive wires and the like. The authors have also developed a molding material suitablefor plugs of insulated flexible cords.

ABSTRACT1.

INTRODUCTION

Waste disposal and recycling have become an essentialsocial task, requiring the volume reduction and resource
recycling of waste. Thus, the development of engineering
products that are harmonized with the environment is anurgent need to be pursued.
Figure 1 compares the disposal system of conventionalwires and cables with that of environment-harmonized
ones. At present, although the recycling process for theconductor inside the wires and cables has been established thus enabling the reuse of the material, the process
for the covering material remains undone allowing only asmall fraction of the covering material to be recycled.
While most of the covering materials are disposed of bylandfill and incineration, these materials may cause aproblem, when buried in the earth, such that toxic heavy
metals are eluted into the earth. That is, we cannot deny
the possibility of environment contamination by lead compounds used as a stabilizer for polyvinyl chloride (PVC) -a general-purpose covering material for electric wires-after the covering material is disposed of by landfill.
Recent years have seen a countermeasure for this inwhich lead stabilizers have been replaced by new stabilizers containing zinc and the like.
Furthermore, the covering material system has to becompletely halogen-free in order to suppress the emissionof toxic gases at incineration. However, the present situation is such that the polymer that constitutes PVC contains
in itself chlorine --one of halogens-- and polyethylene contains halogen compounds to make it flame retardant.
To cope with such a situation, we have developed an*

Electronic Materials Group, Research Dept., OptoTechnology Lab., R&D Div.

environment-harmonized material together with electric
wires using it. The material, while provided with intrinsic
properties equivalent to those of conventional materials,
contains neither halogens nor toxic heavy metals and thus
imposes little impact on the environment at the time oflandfill and incineration. This report describes the development.

Conventional material
Electric wires and connectors
RecyclePlastics waste
Toxic gas
Incineration
Generation?
Landfill
Elution of environmentcontaminating substance?
Soil and water

Human being

Environment-harmonized material
Electric wires and connectors
RecyclePlastics waste

UsableIncineration
Landfill

Figure 1

Heat

Disposal systems for the conventional and environment-harmonized wires and cables

81

2.

PROBLEMS WITH FLAME-RETARDANT
MATERIALS USED IN CONVENTIONALWIRESVarious developments of flame-retardant materials using
no halogens are known so far. However, since they areless effective in flame retardance than halogen flameretardant materials, non-halogen flame retarders have tobe added in large quantities to ensure the desired level offlame retardance. This incurs the following problems whencompared with the conventional halogen flame retarders:(1) Degradation in mechanical properties, (2) Degradation
in formability, (3) Degradation in termination workability;each of which will be briefly discussed below.
2.1 Degradation in Mechanical Properties
Non-halogen flame retarders dispersed in polymers
degrades the mechanical properties of the material substantially, when the quantity added exceeds a certain
level. Specifically, such properties as tensile strength,
elongation, and abrasion resistance degrade in addition toflexibility.
2.2 Degradation in Formability
Inorganic flame retarders such as hydrous metals reduce,
when added to a large quantity, the fluidity of materials at
the time of material melting, thus reducing the formability
in the extrusion or injection molding. The degradation informability adversely affects the productivity and appearance of products. Especially in injection molding, it often
results in poor molding.
2.3 Degradation in Termination Workability
Electric wires are usually removed of their covering on
their ends and terminated with connectors. Insufficient termination workability leads to covering residuals formationon the exposed conductors due to unsuccessful cutting,thus causing poor electrical contacts.

3.

materials such as halogens but also solves the entire
problems that vex the conventional flame-retardant wires.
The specific goal is thus to develop both a wire covering
material and a connector molding material that are provided with such mechanical properties, formability, and termination workability as are equivalent to those of PVC.
Making efforts to this end, we have been successful indeveloping the materials that fulfill the above-mentioned
goal thereby complying with the JIS standards as well.

4.

DEVELOPED MATERIAL AND ITS
PROPERTIES

Preliminary production and evaluation of the developed
environment-harmonized materials were carried out togive the results described below.
4.1

General Properties of the EnvironmentHarmonized Material1) Tensile strength and elongation [JIS K 6723]
2) Hardness [JIS K 7215]
3) Oxygen index [JIS K 7201]
4) Low temperature resistance [JIS K 6723]
5) Heat deformation [JIS K 6723]
Table 1 compares these evaluation results with those of
PVC material for flexible cords. As can be seen, the developed material harmonized with the environment has theproperties equivalent to those of conventional PVC material as well as an excellent brittleness temperature. The
developed material is white in natural color since it does
not include phosphorus and the like, enabling easy coloring by using a color master batch for general purpose.
4.2 Application to Flexible Cords
Prototypes of single flexible cord (VSF-0.75SQ) and flat
flexible cord (VFF-0.75SQ), both specified in JIS C 3306
"PVC Insulated Flexible Cord", were manufactured using
the developed environment-harmonized material. Thecords were evaluated in accordance with the JIS, giving
the results shown in Table 2 in comparison with those ofDEVELOPMENT

In this development, a goal has been set such that thenew material not only excludes environment-affecting

Table 2Item
DielectricTable 1

Properties of the environment-harmonized material

Item
Tensile strength

Evaluation
conditions
JIS K 6723

Elongation

withstand voltage

Properties of insulated flexible cords
Evaluation
conditions

UnitGoodGood

Developed

Conventional

Tensile strength

JIS C 3306

Mpa

15.2

19.6

material

PVC material

Elongation

JIS C 3306%

180240

Mpa

18.0

20.0

Tensile strength

JIS C 3306 Residual%

180250after aging

120°C 96 hr

103102

102

95

Unit

ratio %JIS K 7215

–8685

Elongation

JIS C 3306 Residual

JIS K 7201

–3228

after aging

120°C 96 hrJIS K 6723

°C-52-35

JIS K 6723

%

8.0

7.0

Heat deformation

82

PVC cord-

Oxygen index

temperature

cord

JIS C 3306

Hardness

Brittleness

Developed Conventionalratio %

Flame retardance JIS C 3306

-GoodGood

Cold bend

JIS C 3306

-GoodGood

Heat-shock

JIS C 3306

-GoodGood

Furukawa Review, No. 19. 2000

Table 3

Table 4

Properties of insulated wires for electrical apparatus
Item

Dielectric

Evaluation
conditions

Unit

Developed Conventionalwire

PVC wire

Item
Dielectric

Properties of automotive wires
Evaluation
conditions

Item

JASO D 611-DevelopedConventional

wire

AVSS wireGoodGood

18.5

21.8

JIS C 3316

-GoodGood

Tensile strength

JIS C 3316

Mpa

18.0

20.0

Tensile strength

JASO D 611 Mpa

Elongation

JIS C 3316%

173250Elongation

JASO D 611%

200190Tensile strength

JIS C 3316 Residual

Oil resistanceJASO D 611

-Good

Good

after aging

120°C 96 hr

Flame retardance

JASO D 611-

GoodGoodElongation

JIS C 3316 Residual

Cold bend

JASO D 611-

GoodGood

after aging

120°C 96 hr

Heat resistanceJASO D 611-GoodGood

Tensile strength

JIS C 3316 Residualwithstand voltage

ratio %

ratio %

ratio %9999961069097

10498

withstand voltage

Abrasion resistance JASO D 611 times Approx. 1500 Approx. 1500

after JIS #2 oil test

85°C 4 hr

Elongation

JIS C 3316 Residual

after JIS #2 oil test

85°C 4 hr

ratio %

Flame retardance

JIS C 3316

-GoodGood

Cold bend

JIS C 3316

-

Good

Good

Heat-shock

JIS C 3316-

GoodGood

Heat deformation

JIS C 3316%

215Insulation resistanceHeat shrinkage

JIS C 3316%

00

Dielectric

Table 5

Properties of injection molding material for insulated
flexible cords
Item

Application to Insulated Wires for Electrical
Apparatus
Prototypes of insulated wire for electrical apparatus (KIV0.75SQ) specified in JIS C 3316 "PVC Insulated Wires forElectrical Apparatus" were manufactured using the developed halogen-free material; and the wires were evaluatedin accordance with the JIS, giving the results shown inTable 3 in comparison with those of conventional PVC
wires (H-KIV). It has been confirmed again, as is clear
from the table, that the developed wires have the properties equivalent to those of conventional PVC wires, conforming to the type 1 (KIV) and type 2 (H-KIF) wires specified in JIS C 3316.
4.4 Application to Automotive Wires
Automotive wires are required to be provided with anexcellent abrasion resistance which is higher than that forelectrical appliance wires, to protect them from insulation
breakdowns due to harsh contact with other members.
Prototype wires equivalent to AVSS-0.5SQ specified in
JASO D 611 --standards for Japanese automotive wires-were manufactured using the developed halogen-freematerial; and the wires were evaluated in accordance with

Developed Conventional
material

PVC materialMΩ>1000>1000

JIS C 8303

-GoodGoodJIS C 8303

-GoodGood

Sharp-bend resistance JIS C 8303

-GoodGood

Shell compression

JIS C 8303

-GoodGood

Ammonia resistance

JIS C 8303

-GoodGood

Water-tightness

JIS C 8303

-GoodGood

Flame retardance

JIS C 8303-

GoodGood

Approx.

Approx.

50×10340×103Heat resistance

4.3

Unit

JIS C 8303

withstand voltage

conventional PVC cords. It has been confirmed, as isclear from the table, that the developed cords have theproperties equivalent to those of conventional PVC cords,
conforming to the type 1 (VSF) and type 2 (H-VSF) cords
specified in JIS C 3306. The developed cords are highly
resistant to surface scratches, making themselves quite
suitable for practical use. Moreover, the cords are superior
in termination workability, so that the same termination
procedures as those for conventional PVC cords areapplicable to the new cords.

Evaluation

Entire breakage
bending

conditions

JIS C 8303 times

the standards. Table 4 shows the results in comparison
with those of conventional AVSS wires. As can be seenfrom the table, it has been confirmed that not only are thedeveloped wires in compliance with the JASO standards,
but also they are as abrasion resistant as the conventional
AVSS wires covered by PVC.
4.5

Application to Molding Material for Flexible
Cords
The molded portion of flexible cords is required to beexcellent in both flexibility and appearance. While thedeveloped environment-harmonized material was intended to be used for extrusion molding, we have been successful in developing another environment-harmonizedmaterial for injection molding. Prototypes of flexible cords
for home appliances having injection molded portions
were manufactured using the developed environment-harmonized material for injection molding use. The molded
prototypes were subjected to tests in accordance with JIS
C 3316 to give the results shown in Table 5. It is thus
shown that the developed environment-harmonized material for injection molding conforms to JIS C 3316, and thatit compares favorably with conventional molded plugs interms of bendability as well. Furthermore, the plugs for83

insulated flexible cords thus obtained are excellent inexternal appearance and are sufficiently resistant to suchmechanical damages as scratches.

5.

CONCLUSION

The environment-harmonized materials developed thistime are provided with excellent low temperature resistance and flame retardance in addition to superior flexibility and mechanical characteristics equivalent to those ofPVC. Since the materials do not contain such environment-affecting substances as toxic heavy metals andphosphorus without mentioning halogens, they are excellent in terms of safety and recyclability at waste disposal.
The materials, including those for injection molding, arebelieved to be useful for a variety of electric components
as well as electric wires.
Manuscript received on July 8, 1999.

84

Furukawa Review, No. 19. 2000