Development of Insulated Wire and Cable Using Recycled PVC
by Kouichi Murata *, Kiyoshi Aiba *, Shingo Ooya *2, Yasuhiro Tominaga *2,
Tetsuo Matsumoto *3, Kouichi Mizuno *3 and Hideyuki Motomiya *3

Most of polyvinyl chloride (PVC) used for sheathing distribution wires and cables
have seldom been reused for wire sheathing when they are retrieved, so thatthey are usually applied in other uses or disposed of as industrial waste. By investigating the sorting retrieval and the recycling methods of the sheath material as well as its applications, theauthors have been successful in developing insulated wire and cable that use recycled sheathmaterial out of retrieved wire and cable, together with a recycling system that permits obtaining
recycled material comparable to unused material in terms of cost. All the sheath material investigated in this study are retrieved from used wires for power distribution owned by Tokyo ElectricPower Co. (TEPCO), and will be used again in the recycled wire and cable to be delivered to thesame company.

ABSTRACT1.

INTRODUCTION

Sheath material not recycled
Disassembly

Currently various sheath materials are used depending on
the objectives in power distribution wires and cables for
TEPCO, including mainly polyvinyl chloride (hereafter
called PVC), polyethylene (PE), and cross-linked polyethylene (XLPE). Whereas valuable conductors of electric
wire and cable have been recycled conventionally, sheathmaterials have been directed, without being reused inelectric wire and cable, to other uses with less performance requirements in addition to thermal recycling anddisposal as industrial waste. Thus, due to the increased
awareness of environmental issues together with thestandpoints of global resource preservation and industrial
waste reduction over the last several years, it has beenrequired to establish a closed recycling system for reusing
the sheath materials of electric wire and cable, so that we
proceeded to develop such a system as shown in Figure
1.
In this study, PVC of electric wire sheath was investigated for recycling. With respect to sorting and retrieval
which is an important issue for recycling in the first
instance, a retrieval method with a sorting level equivalent
to that of the current level was studied first. Then a recycling system based on this retrieval method was investigated in an effort to make this system using recycledmaterial capable of achieving a cost level comparable tothat of using unused material.

Sheath material:
Disposal, Other uses

Manufacture
Conductor: Recycled material
Insulation: Unused material

Sheath material recycled
Disassembly

Closed recycling system

Conductor:
Reprocessing

Use

Sheath material:
Reprocessing

Manufacture
Conductor: Recycled material
Insulation: Recycled material

Figure 12.
* Tokyo Electric Power Co.
*2 Engineering Dept., Power Cables Div.
*3 Ecology and Energy Lab.

Conductor:
Reprocessing

Use

Conceptual image for recycling of insulated wire andcable.

DEVELOPMENT OF INSULATED WIRE
AND CABLE USING RECYCLED PVC

PVC is most extensively used as a general sheath material for low-voltage electrical wires, so that its retrieved

1quantity is the greatest. This makes it possible to somedegree to select the application areas that match the properties of recycled material. In this study we used samples
as shown in Photos 1 and 2, which were obtained througha process where the wire and cable were finely shredded
followed by separating the conductor and sheath by vibration, etc. Although the retrieved wire undergoes sorting
before shredding by classifying such PVC-based wires
and cables as OW, DV, IV, SV, etc. to obtain sorted PVC
material, it is difficult to carry out perfect sorting, so thatthe retrieved material contains some amount of othertypes of wires including tapes such as F-CO tape. Since atarget was set at implementing a cost-viable recycling system in this study, the retrieved material out of the practicalsorting level mentioned above was evaluated to see if
recycling was feasible or not. Retrieval experiments in different periods were also carried out several times to evaluate the property fluctuation of retrieved material.
Specific procedures for the study are as follows.
1) Understanding of the properties of retrieved PVC
sheath material.
2) Evaluation of the properties of recycled PVC material.
3) Investigation of application areas for the recycledmaterial with improved properties.
4) Manufacture and evaluation of electrical wire andcable using recycled PVC.
Understanding the Properties of Retrieved PVC
Sheath Material
Sheet samples were prepared by roll processing theretrieved PVC sheath material shown in Figure 1, and thesamples were evaluated for their properties. Photo 2 andTable 1 show the macrophotograph of retrieved PVC
sheath material and the properties of sheet samples,
respectively.
Photo 2 confirms that the retrieved PVC sheath material
include some deteriorated samples which have cracks ontheir surface.
Table 1 shows the results of property evaluation ofrolled sheet samples, from which the following propertiesof retrieved PVC sheath material can be confirmed.
• The surface of the rolled sheet is somewhat granular,i.e., the surface is roughened.
• Volume resistivity does not meet the standard.
• Embrittlement property tends to be deteriorated, insufficiently satisfying the standard in some cases when

Photo 1

Photo 2Retrieved PVC jacket material.

Retrieved PVC jacket material. (Enlarged photograph)

2.1

Table 1

2

deviation is considered.
• Except for volume resistivity and embrittlement, no
problems of practical importance were found.
• No property fluctuations were appreciable among theresults of four evaluation tests.
2.2 Properties of Recycled PVC Material
We have prepared compounds of recycled PVC material
taking into consideration the problems described in
Clause 2.1, and the properties of the recycled PVC material are shown in Table 2. In the compound preparation,
plasticisers and such were added to improve embrittlement property, and the compounds were filtered through amesh strainer with an objective of removing dust and foreign particles. Evaluation was carried out based on
extruded samples so as to check the appearance of recycled material.

Properties of retrieved PVC sample sheet.

Volume resistivity(Ω . cm)

Embrittlement(°C)

Room temp.
tensile strength(MPa)

Room temp.
elongation(%)

Heated tensile
strength

JIS K 6723

≥ 5.0E+13

≤ -15

≥ 10

Unused material

1.1E+14-24

17

Retrieved material A1

1.2E+13-14

Retrieved material A2

1.2E+13Retrieved material A3

1.2E+13Retrieved material A4

1.4E+13

Heated elongation

Oil resistance &(Residual in %)(Residual in %)others

≥ 200

≥ 90

≥ 80

——

300

99

105

Passed

20.3

260

101

94

Passed

-19

20.4

278

101

88

Passed

-18

19.9

262

103

97

Passed

-20

20.3

284

102

90

PassedFurukawa Review, No. 22

2002

Table 2

Properties of recycled PVC sample jacket after extrusion.

Appearance of Volume resistivity Embrittlement(Ω . cm)(°C)

Room temp.
tensile strength(MPa)

Room temp.
elongation(%)

extruded surface

Heated tensile Heated elongation Oil resistance &strengthothers(Residual in %) (Residual in %)JIS K 6723——

≥ 5.0E+13

≤ -15

≥ 10

≥ 200

≥ 90

≥ 80

——

Unused materialGood

1.1E+14

-24

17

300

99

105

PassedSample No. 1

9.6E+12

-23

18.6

306

103

96

PassedSample No. 2

Somewhat

9.8E+12

-21

19.0

328

105

90

PassedSample No. 3

granular

1.2E+13

-23

18.9

324

101

86

Passed1.1E+13

-21

19.6

318

98

91

PassedSample No. 4

Table 3

Volume resistivity of retrieved PVC jacket material
blended with unused material.
Blending ratio

Sample No.
Retrieved material Unused material

Photo 3

Surface of recycled PVC jacket after extrusion.

No.1

100 %

——

7.0✕1012

No.2

2/3

1/3

7.7✕1012

No.3

1/3

2/3

3.3✕1013

No.4

——

100 %

1.1✕1014
5.0✕1013

Standard (JIS K 6723)

1) Appearance of recycled material
Photo 3 shows an appearance of recycled PVC
material after extrusion. The material shows a partly
degraded surface with somewhat granular appearance due to unavoidable entry of small amounts offoreign particles. However, as can be seen from Table
2, the degree of deterioration was not so serious as togive significant influences on mechanical properties
such as tensile strength and elongation.
2) Results of improving embrittlement property
The embrittlement property has been improved by
the addition of plasticisers. It was shown that an
improved level could be secured that was slightly inferior to that of unused material but not below the standard.
3) Results of improving volume resistivity
It was confirmed from the results in Table 2 that thevolume resistivity of recycled PVC material was little
improved by foreign particle elimination at the time ofcompound preparation based on filtering using amesh strainer. We then examined whether or not the
retrieved PVC sheath material improves in volume
resistivity by blending unused material. Table 3 shows
the results of evaluation when an unused material isblended with ratios of 1/3 and 2/3 over the retrieved
PVC sheath material.
It is seen from Table 3 that blending unused material
improves the properties only to a level not exceeding thestandard, thus demonstrating that the volume resistivity isdifficult to be improved.
4) Long-term weather resistance
As shown in Sub-clause "2) Results of improving
embrittlement property" above, the initial value ofembrittlement property of the recycled PVC material
proved to be improvable. Accordingly accelerated
aging tests were conducted using a sunshine weath-

Volume resistivity(MΩ . cm)

Table 4

Weather resistance properties represented by embrittlement temperature.
Unused material

Unused material(Black)(Blue)

0h

-26°C

-25°C

-17°C

1000 h

-15°C

-13°C

-14°C

2000 h

-13°C

-5°C

-9°C

Recycled material

erometer to determine the long-term weather resistance property. Because long-term weather resistance strongly depends on the color of samples, comparisons were made with black and blue unusedmaterials in use for TEPCO's DV wire.
It has thus been confirmed, as shown in Table 4, that
whereas the recycled material is slightly inferior to blackand blue unused materials in terms of the initial value, it issuperior to the blue unused material with respect to thelong-term performance because its color is nearly black.
2.3

Study on the Application Methods of Recycled
Material
From the results in Clause 2.2, features of the recycledmaterial may be summarized as follows.
• It is equivalent to unused material in terms of
mechanical properties such as tensile strength andelongation.
• In terms of embrittlement property, although the material has inferior initial properties compared with
unused material, its long-term properties are superior
to those of some unused material --e.g., blue-colored-- because of its natural color which is nearly
black.
• Volume resistivity is deteriorated when compared with3

unused material.
• The extruded surface is somewhat granular, but thispresents no practical problems.
Given the features mentioned above, potential applications of recycled material have been proposed as follows.
Proposal 1: Although its electrical properties are ratherpoor, the material has excellent weather resistance, sothat application to cable jacket is proposed. However, thecolor should be black in principle.
Proposal 2: A double-skin structure is proposed wherean unused material is used for outer layer for identification, while a recycled material is used for inner layer. In
this case, the issues of color and appearance will solve
themselves but a decline in insulation resistance is
expected.

al. Table 5 shows the results of tests equivalent to
TEPCO's type tests.
The results of manufacture and evaluation of prototype
cable demonstrated that the cable passed every type test
items satisfactorily, thereby confirming that there is no
problem in using the recycled material for the inner insulation layer and the jacket. With respect to the insulation
resistance at room and elevated temperatures a considerable decline was seen compared with the average valueof unused material, as could be expected from thedeclined volume resistivity manifested by the sheet sample evaluation. But it was also confirmed that the use ofunused material for the identification layer ensured theinsulation resistance of the product.
2.5

2.4

Manufacture and Evaluation of Electrical Wire
and Cable Using Recycled PVC Material
A prototype of SV cable (3 ✕ 8 mm2) has been manufactured as a typical electrical wire based on recycled materiRecycled material

Unused material coloredfor cable identification

Proposal 1: Cable jacket

Figure 2

Specifications for Applications of Recycled PVC
Material
Both Proposals 1 and 2 were confirmed to be feasible forapplication through the results of prototype wire manufacture followed by evaluation, making Proposal 2 applicablewithout modification to insulation wires such as DV, IV,
and OW. In cases where Proposal 1 is applicable, on theother hand, consideration must be given to the fact thatthe jacket is going to be black in color. In the case of SV
cable for TEPCO, the jacket color is specified to be gray.
In consideration of efficiency improvement due to color
identification at the time of cable retrieval and sorting
work, it was decided to adopt Proposal 2 for SV cable, i.e.,
an unused material in gray is used for the outer jacket anda recycled material for the insulated inner core.

Proposal 2: Inner layer ofcable insulation

Applications of recycled PVC material.

Table 5Characteristics of prototype cable using recycled PVC.
Standard

Black phase White phase

Red phase

Sheath*4

Appearance, Structure, Flame-retardance test

——

Good

Good

Good

Good

Withstand voltage (in air, in water)

——

Good

Good

Good

——

Conductor resistance (Ω/km)

2.36

2.23

2.24

2.24

——

Tensile strength (MPa)

10

20.3

20.4

19.9

20.3

Elongation (%)

120

260

278

262

284

Tensile strength (MPa)Room temp.

90

101

101

103

102

temp. (100°C x 48 h) Elongation (%)

70

94

88

97

90

Residual after oil test Tensile strength (MPa)

85

94

97

99

98

(70°C x 4 h)

75

84

84

93

84

Residual in elevatedElongation (%)

Room temp. insulation resistance (MΩ . km)*1

50

170

110

160

——

High temp. insulation resistance (MΩ . km)*2

0.15

0.40

0.40

0.39

——

Windability (Low temp. and high temp.)

——

Good

Good

Good

Good

Low temp. resistance (°C)*3

-15

-24

-23

-24

-22

Heated deformation test (%)

50

9.5

8.6

7.2

6.8

Notes: *1) Room temp. insulation resistance: 900~1300 MΩ is typical with Furukawa's unused material conventionally used.
*2) 4 MΩ is typical with Furukawa's unused material conventionally used.
*3) Identical to unused material due to the skin layer of unused material for identification.
*4) In this study the sheath was also made of recycled material.

4

Furukawa Review, No. 22

2002

3.

IN CONCLUSION

Recycling of PVC sheath of wires and cables retrieved
from the installed fields of TEPCO was studied, and theauthors have been successful in demonstrating that aclosed recycling system is applicable to recycle this material to be reused in the sheath of electrical wire and cable.
In terms of cost which often raises problems, a cost levelthat compares favorably with unused material has beenrealized through the examination of sorting retrieval
method as well as the operation of recycling system.
The recycled PVC electrical wire developed in this study
has passed the type tests of TEPCO for their inventory
items and is scheduled for delivery in due time. A study
program for recycling PE and XLPE is planned to follow
this study on PVC.

5