The safety effects of crosslinked polymers in wire & cable ... · PDF fileThe safety effects of crosslinked polymers in wire & cable applications AMI hCables 2012 Ron Goethals Inhol

The safety effects of crosslinked polymers

in wire & cable applications

h Cables 2012

AMI

Ron Goethals

Inhol bv, The Netherlands

www.inhol.com

Miami, USA, April 18 & 19, 2012

http://www.inhol.com/

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AMI

Main topics

- What is crosslinking?

- A comparison of the 3 main XL-systems in the W & C industry.

- Why can crosslinking make the world safer?

- Global geographical trends in W & C crosslinking.

- Conclusion

The safety effects of crosslinked

polymers in wire & cable applications

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Main topics


\

Definition (Wikipedia):

“When polymer chains are linked together by cross-links, they

lose some of their ability to move as individual polymer chains”



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Main topics


\

Creating a 3-dimensional

polymer network

A simple answer is:



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How is crosslinking achieved in the wire & cable industry?

A comparison of the 3 main crosslink systems

* E-beam (or radiation) crosslinking

* CV (or chemical) crosslinking

* Silane (or moisture) crosslinking

Comparison of 3 crosslink systems

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How is crosslinking achieved in the wire & cable industry?

A comparison of the 3 main crosslink systems

* Description / Explanation

* Chemistry

* Advantages & Disadvantages


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* E-beam (or irradiation) crosslinking

• Resulting in:

Formation of carbon-to- carbon bonds (-C-C-) between adjacent polymer molecules.

• High energy electrons collide with polymer molecules

Picture: By courtesy of Beta-Gamma-Service (D)


Description / Explanation

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(Target)

(Electron source)

E-beam accelerators work on the same principle as an (old) television!



(accelerator)

40

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(Electron source) (Electron source)

(accelerator)

(Target

= cable)

E-beam accelerators work on the same principle as an (old) television!



(accelerator)

(Target) Scan horn

25 kV

500 – 5000 kV

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Photo: Reidar Hahn, Fermilab

Scan horn



Picture: By courtesy of IBA (B)

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The wire is ‘passing’ the

e-beam many times

Depending on f.i.:

- wire size & wall thickness

- speed

- required homogenity

- power of the e-beam (mA)

- ‘crosslink-degree’ needed

the number of passes

can be adapted.



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Under Beam Handling System (=

rotating drums / conveyor system)

The so-called ‘Figure-8’

handling system.

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The wire is ‘passing’ the

e-beam many times

Depending on f.i.:

- wire size & wall thickness

- speed

- required homogenity

- power of the e-beam (mA)

- ‘crosslink-degree’ needed

the number of passes

can be adapted.



Absorbed dose

after 1 pass

Absorbed dose

after 8 passes

Scan horn

Homogenous crosslinked

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• Machine Energy (= Voltage):

Defines penetration or max. wall thickness



3 Characteristics are of main-importance in this crosslink process:

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• E-beam (or irradiation)

crosslinking: Penetration



WT

This is defining the actual required beam-voltage.

E-beam WT = “actual” Wall Thicknes

Chordal length = “effective” Wall Thickness

d

OD Chordal Length = CL

Note: The chordal length can be calculated with mathematics (‘Pythagoras’ ).

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2 examples of the required energy (= Voltage) for a defined cable size

Jacket

Density g/cc 1,6

Wall thickness mm 2,5

OD mm 60

Chordal length mm 12,0

Required Energy MeV 4,1

Quiet

some

difference!

Density g/cc 1,6

Wall thickness mm 2,5

OD mm 12

Chordal length mm 4,9

Required Energy MeV 1,9

OD = 12 mm OD = 12 mm

Same wall-thickness , but totally different Voltaqes required!

Note: by increasing the number of passes and sufficient twisting of the cable, the energy in praxis may be lower

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• Machine Energy (= Voltage):

Defines penetration or max. wall thickness

• Dosage

Higher dosage more crosslinks per cm3

Typical in wire & cable : 50 – 250 kGy ( 5 – 25 Mrad)

• Machine Current (= Amperage)

Defines throughput or speed



3 Characteristics are of main-importance in this crosslink process:

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Advantages

• In use since the 1950’s

• Highly reliable

• X-linking time : milliseconds

• Applicable on wide range

of polymers

• Dry process (no water)



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More advantages

• Easier compound formulation

• Environmental friendly (= TV)

• Easy to modify crosslink-degree

• Clean process

• No scorching during extrusion

•Wall-thicknesses up to 250-350 mil



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Special building (concrete bunker) is required.

Note: Self-shielded e-beams (< 0,8 MeV) are available.

‘Capital intensive’ underbeam handling equipment is needed

Rather highly skilled engineers shall be available



Disadvantages

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High initial investment (indication : 1,0 – 3,0 Million $)

At a 20 year lifetime and 75% capacity : Depreciation of

approx. $ 16 / used hr



Disadvantages

Is this really high ?

This is approximately: 0,0002 $ (= 0,02 $-cent) p/ft!

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At a 20 year lifetime and 75% capacity : Depreciation of

approx. $ 16 / used hr



Disadvantages

Is this really high ?

This is approximately: 0,0002 $ (= 0,02 $-cent) p/ft!

Even if you include a building of 2 million Euro, reduce

the depreciation period (20 years) down to 10 years and

the actual capacity (75%) down to 50%, the depreciation

will be around $ 96/ used hr:

which means 0,0012 $ (= 0,12 $ cent) p/ft

(at an average speed of 1100 ft/minute)

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Let’s have a look at the crosslink-costs per kg or lbs



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225 kW (3 MeV x 75 mA)

1134 kg / hr (= 2498 lbs / hr)

9934 ton / year (= 21.9 million lbs / year)

70%

Another calculation crosslink costs per kg (lbs)

Depriciation costs (10 years) of building + beam : $ 96,-- / hr

Electricity cost of the e-beam : Euro 0,10/kw : $ 22,50/hr

Process engineer : $ 30,--/hr

Other costs (maintenance, others) : $ 10,--/hr

$ 131,50/hr

Efficiency factor Power of beam

Required dose

Typical Example

(seconds)

(3 shifts/365 days)

100 kGy

Capacity:

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225 kW (3 MeV x 75 mA)

1134 kg / hr (= 2498 lbs / hr)


70%






$ 131,50/hr

Efficiency factor Power of beam

Required dose

Typical Example

(seconds)

(3 shifts/365 days)

100 kGy

Capacity:

But just look at the 2 numbers below:

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225 kW (3 MeV x 75 mA)

70%





$ 131,50/hr

$ 0,05 / lbs

Typical Example

(seconds)

100 kGy

Power of beam Efficiency factor

Required dose


1134 kg / hr (= 2498 lbs / hr)


(3 shifts/365 days)

= $ 0,05/lbs


The question was: Is this really high ?

$ 0,05/lbs

$ 0,0002/feet What do you think?

For those factories who do not want to invest (yet), please note:

specialized radiation centers sell their e-beam radiation services to the market.

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* E-beam (or irradiation) crosslinking : The chemistry


The chemistry

G. Gielenz, SPE - 2003

‘ ‘

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* E-beam radiation misunderstandings

* Due to high levels of X-rays produced during the

E-Beam processing.........

X-rays?

Please…

explain!

Braking Heat!

80

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X-rays?

Please…

explain!

Braking Heat!

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X-rays?

Please…

explain!

Braking

X-rays

E-beam Radiation

Also known as: “Bremsstrahlung”

Production of

‘Bremsstrahlung’

when an electron

decelerates through

interaction with an

atom

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Picture: By courtesy of IBA (B)



Heavy wall

‘bunker’

thick

concrete walls



E-Beam processing, the equipment is shielded by

thick layers of concrete and steel or lead.

Heavy wall

‘bunker’

thick

concrete walls

X-rays?

Please…

explain!

Thick

walls

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• When the beam is switched off … NO X-rays are

produced any more, and NO RESIDUAL X-rays are

left.

(This is like :

- switching off your television-set, as mentioned before.

- having a picture made of your teeth at your dentist.)

* Products are NOT made radioactive



More misunderstandings to clear

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*Silane (or moisture) crosslinking

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Extrude and WAIT… that is all!

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Polyethylene

Mechanism:

+ Silane

Si (OMe)

Peroxide 1.Step: Grafting

Humidity

Catalyst Si

O

Si

Crosslinked PE

(XLPE)

2.Step:

Crosslinking

Si(OMe)3

Grafted PE-Compound

3

--------------------------------------------------------------------------------------------------------------

(Also available Silane-Co-Polymers : Silane incorporated in the backbone)



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Polyethylene

Mechanism:

+ Silane

Si (OMe)

Peroxide 1.Step: Grafting

Humidity

Catalyst Si

O

Si

Crosslinked PE

(XLPE)

2.Step:

Crosslinking

Si(OMe)3

Grafted PE-Compound

3

--------------------------------------------------------------------------------------------------------------

(Also available Silane-Co-Polymers : Silane incorporated in the backbone)

Chemistry :

• Cross-linking through a C-Si-O-Si-C ‘bond’ (= link)

• This bond is more flexible compared to the C-C

bond of E-beam and CV-crosslinking.



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Advantages:

• Low initial investment required

• Easy understandable technology

• Small batches can be made rather efficiently (Sioplas, Silane co-polymers)

• Steam, hot water or the open air will do the XL job

• ‘In house’ crosslinking (both Monosil, Sioplas and Silane co-polymers)

• No scientific- or highly-skilled people required



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Advantages:

• Low crosslinking costs



In ambient environment : $ 0,00 / lbs

In ‘sauna’ environment :

Typically in the range $ 0,02 – 0,06 / lbs, for heating

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Disadvantages:

• Higher compound costs (lower output during compounding)

• Complexity in compound design

• Only limited to a small number of polymers (mainly PE – kind )

• Limited storage life of the compounds

• More tight tolerances in extrusion parameters

• Risk of premature crosslinking (due to moisture and design of head and tooling)



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Disadvantages:

• Risk of premature crosslinking ( f.i. due to pre-crosslinking during compound production or due to moisture pick-up during extrusion or design of head and tooling)



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Disadvantages:

• Hardly any influence on crosslink degree (if Sioplas or silane-copolymers outside sources are converted)

• Rather long crosslink times (typically 24 hrs (hot sauna) to several weeks (ambient) Hot-set elongation tests needed)

• If tested before FULL crosslinking has occured, some

unexpected results may show up (think about heat-ageing)

• Decrease of MFI during storage. This may effect

output of extrusion line and surface of extruded product

• Mainly applicable in rather thin wall (< 80 - 120 mil) cables

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* CV (or chemical) crosslinking How does it work?

• Step 1:

The compound is plasticized and extruded as insulation or jacket.

Step 2:

The cable is then fed into a long metal tube, which is pressurized

in an environment of steam (= wet) or nitrogen (=dry) to achieve

high temperatures, for increased crosslinking speed.



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Extruder-area

Pressurized vulcanization tube (Temperatures of well above 200 C / 400 F)

Cooling Insulated

conductor

Conductor



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Long (pressurized) tubes (These can be as long as 100 m or more)

How does it work?

These tubes can be

as long as 350 ft

(or even longer!)



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Long (pressurized) tubes (These can be as long as 100 m or more)

How does it work?

These tubes can

be as long as 100

m (or more!). Extruder area

Picture:

by courtesy of Maillefer (CH)



Take-up

Cable

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Heat

1) R-O-O-R ----> 2 R-O *

2) --- CH2 - CH2 – CH2 ---- + R-O * --- CH2 - CH – CH2 ---- + R-O-H

*

3) --- CH2 - CH – CH2 ---- --- CH2 - CH – CH2 ----

* |

* --- CH2 - CH – CH2 ----

--- CH2 - CH – CH2 ----

2 polymeric radicals recombine

to form a C-C bond (= crosslink)

(the peroxide is split in radicals (*) at elevated T)

(polymer + peroxide radical react) (polymer radical is created)

* CV (or chemical) crosslinking : The chemistry



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• Well proven since the 1960’s

• (Rather) Easy understandable technology

• A limited, but reasonable, range of polymers available

• Reliable

•‘In-house’ crosslinking, which is ready after take-up

•Thick wall cables can be crosslinked

Advantages




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Disadvantages

• High initial investment needed (a complete line can cost as much as $ 1,5 – 2,0 million. This can be compared

with e-beam costs and thus depreciation levels.)

* Large area (m²) required

• Some complexity in compound design

• High pressure and high processing temperatures may

melt, flow, crush or fuse internal components of the cable




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Disadvantages

• Less favourable for small size wires/cables (mainly due to the reduced strength of the processed wire/cable)

• Risk of premature-crosslinking in the extruder

• Rather complex production lines (incl. Nitrogen handling system)

• Power consumption is typically in the 500 – 1000 kVA range,

which is a factor 2 – 6 times higher compared to an e-beam.

The crosslink-costs (incl. depreciation) will be in the same range

as an e-beam.




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\

Heat

Heat

Thermoplastic

Crosslinked

The individual polymer chains

start to ‘move’’ (= melting!).

The individual polymer chains

can hardly ‘move’(= no melting!)

Some major safety effects of crosslinked wire & cable are :

No melting



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No melting

NO short-circuits due to melting of the insulation of the wire,

therefore keeping electrical circuits and functioning of electrical

systems in place.

F.i. in area’s like: elevators, large public buildings, such as

theatres, schools, universities, stadiums and airports, mines,

ferries, etc.

A ‘simple PE’ , with a melting point of

around 90 -110 °C, can easily withstand

temperatures up to 250 °C for several

hours without melting, after it has been

properly crosslinked!

Result:

Allowing people to escape and thus makes our world safer!



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Improved heat resistance

Reduced risk of short-circuits due to mechanical pressure /cut

through at elevated temperatures on the insulation of the wire .

This results in keeping electrical circuits and functioning of

electrical systems in place and reduce the start of a fire due to

‘electrical sparking’ of a short-circuit.. and

thus makes our world safer!



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Improved fluid and oil resistance

- Crosslinking keeps the mechanical properties after fluid immersion at

higher levels, due to its 3-dimensional structure,

Elongation at break

T

e

n

s

i

l

e

10

10

5

15

Non-crosslinked jacket, IRM 902 oil immersion

96 hrs @ 100 C

Crosslinked jacket, IRM 902 oil immersion

96 hrs @ 100 C



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Improved fluid and oil resistance

- Crosslinking gives a reduced swell of the insulation and jacket

a and keeps the mechanical properties at higher levels

Swelling due to oil

Swollen cables may lose :

- Mechanical properties, and

- Electrical properties

and thus …. lose safe conditions !

This results in keeping electrical circuits and functioning of electrical systems in

place and




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Improved stress crack resistance

Cracks after

heat shock @ 136°C

Non-crosslinked insulation Crosslinked insulation

NO cracks after

heat shock @ 250°C

This results in keeping electrical circuits and functioning of electrical systems in

place and


Pictures by courtesy of Habia



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Reduced wallthicknesses possible


…. Due to improved abrasion resistance

(Non-halogen automotive

wire, acc. LV 112 Class C)

Non-crosslinked Crosslinked

(120 kGy)

Abrasion resistance

(Cycles) 315 971

This results in reduced wallthicknesses for wire & cables on ships, vessels,

cars, trains, aeroplanes and other transportation systems.

This reduces the weight and therefore the fuel consumption and CO2

production and




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Slide 1/

Non flame-retarded PE

Horizontal LSFOH polyolefin

(standing direction)

Vertical LSFOH polyolefin

Horizontal LSFOH polyolefin

(flat direction)

Video of burning of

non-crosslinked and

crosslinked samples



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crosslinked wire & cables


Reduced or no dripping during burning

This results in reduced flame-spread


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Increaing

Radiation dose

Gelc

on

ten

t

High

Low

High

Low

Low High

Correlation between hot-set-elongation and gel content

For every unique compound on a specific wire or cable,

the hot-set-elongation is an excellent tool to rapidly correlate

to a gel-content, provided a ‘calibration graph’ has been made.

Ho

t-set-

elo

ng

ati

on

* Measuring the hot-set-elongation



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Increaing

Radiation dose

Gelc

on

ten

t

High

Low

High

Low

Low High

Correlation between hot-set-elongation and gel content

For every unique compound on a specific wire or cable,

the hot-set-elongation is an excellent tool to rapidly correlate

to a gel-content, provided a ‘calibration graph’ has been made.

Ho

t-set-

elo

ng

ati

on

* Measuring the hot-set-elongation

Laser

Can be

connected

to PC



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USA + Canada

+ Mexico

Around

100 - 150

Around 275 -350 Around

400 - 500

Europe

Rest Around

100

Number of CV-lines for wire & cable and related industries (incl.

heat-shrinkable tubing)

Asia, incl. China

Global geographical trends

in W & C crosslinking

There is some growth in the # of

CV-lines in USA, as USA is

importing less MV- & HV-Cables.

Info: Maillefer, February 2012

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USA + Canada

+ Mexico

Around

100

Around

175 Around

225

Europe

Rest Around

100

Number of “Silane-lines” for wire & cable and related industries

(incl. heat-shrinkable tubing).

Asia, incl. China



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USA + Canada

+ Mexico

Around

40

Number of e-beams for the wire & cable related industries (incl.

heat-shrinkable tubing) and incl. beams at e-beam radiation centers

Around

40

Europe Asia, incl. China

Around

300!



Of which

around 250

in China

Rest Around

25

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USA + Canada

+ Mexico

Around 240-290

Around

500- 550

Asia, incl. China

Around 875 - 975

Europe

Rest Around 200 - 250

TOTAL Number of XL-lines for wire & cable and related industries



General total :

around 1800 – 2100 XL-lines

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XL-lines for wire & cable and related industries



Global geographical trends in W & C crosslinking

The number of CV-lines in USA is gradually increasing

The number of E-beams in China is dramatically increasing

What is the reason?

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Around 200

Around

300- 350

Asia, incl. China

Around 450 - 500

Growth of number of e-beams in China



There is a much stronger growth in E-beams in China than elsewhere.

Reasons:

- There is a chinese manufacturer of e-beams, building approx. 1 e-beam

every 2 – 3 weeks (!) at low cost for use in the chinese market.

- Chinese factories tend to choose the most versatile system. The

philosophy behind this is: “Start with the best system from day one”.

- In Europe and USA, most (conservative) cable factories tend to keep using

their ‘existing technologies’. This is different in China.

- In Europe and USA, there is still the idea that an e-beam is ‘magic’ and

expensive. This is different in China.

- In Europe and USA, many authorities ( incl.city governments,

are ‘afraid’ of e-beams (due to lack of knowledge) and often come with

lots of barriers for companies, who want to install an e-beam.

This is different in China.

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XL-lines for wire & cable and related industries



Global geographical trends in W & C crosslinking

The number of CV-lines in USA is gradually increasing

The number of E-beams in China is dramatically increasing

The total number of ‘crosslink lines (e-beam, CV, Silane)’ is

increasing

Approximately 50% of all XL-lines can be found in the Far East

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AMI Crosslinking and the safety effects of

crosslinked wire & cables

Conclusions:

Crosslinked cables contribute to our safety.

There is a steady growth in cable crosslinking systems

Therefore:

Think : Crosslink

Documents

The safety effects of crosslinked polymers in wire & cable ... · PDF fileThe safety effects of crosslinked polymers in wire & cable applications AMI hCables 2012 Ron Goethals Inhol