Cross-Linking

By a Contract Processing Service

by:

Chad Rhodes

Sales and Technical Support

STERIS Corp. Isomedix Services

2500 Commerce Drive

Libertyville, IL 60046 USA

www.isomedix.com

The high capital cost of electron beam

equipment has been cited as a deterrent

to its widespread use as a cross-linking

method. The use of contract electron beam

service centers is a cost-effective solution

to this situation.

STERIS expertise using irradiation techniques to preventinfection and contamination of health care products has beenapplied to the wire and cable industry. Electron beam (E-beam)irradiation has been a successful method of cross-linking (cur-ing) wire insulation andcable jacketing for over50 years.

Cross-linking formsa bond between poly-mer chains, modifiesphysical and chemicalcharacteristics, andthus improves productperformance (e.g. it in-creases the tensilestrength, decreaseselongation and in-creases resistance toflame and solderingiron heat).

The products beingcross-linked are ap-plied in a wide range ofindustries includingconstruction, commu-nication, aircraft, ma-rine and automotive.

At the Libertyville,IL, USA Isomedix facil-ity the E-beam accel-erator has been specially adapted for the handling of wire andcable in a continuous reel-to-reel process.

The EquipmentA look inside this facility can provide a better understand-

ing of how the process works.

Processing equipment. The electron beam is produced bya technically advanced 5 MeV high-power unit, Figure 1.This combination of high energy and power makes it ideal forcross-linking a wide range of products and polymer formula-tions. The accelerator’s sophisticated control system main-

tains the line speed of the equipment and the accelerator’soutput to precisely control the amount of irradiation dosedelivered. A calibrated dosimetry system is used to measuredelivered doses within close tolerances.

Handling equip-ment. The handlingequipment includes apayoff that can handlereels up to 12,000 lb(5443 kg) with diam-eters to 96" (2438 mm),Figure 2. A similartake-up at the end of theprocess re-spools theproduct after it hasbeen cross-linked in theirradiation chamber.

Inside the irradiationchamber, interchange-able precision guideson an under-beam cap-stan are used to directthe product throughthe correct number ofradiation exposures foroptimal cross-linking,Figure 3.

Processing speedsto 1000 fpm (305 mpm)

are attainable, depending on the desired level of cross-linkingand the dimensions and composition of the product beingprocessed.

Product diameters from primary wire to 1.50" (38 mm) heavywall cables can be accommodated. The diameter of the cableis an important variable when determining which process pa-rameters to apply.

The Process Manufacturers who contract with us for their cross-link-

ing needs typically send reels by common carrier or their ownin-house transportation.

Fig. 1—E-beam accelerator is the heart of the process.

Emphasis: Cross-Linking

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When scheduled for processing, the product is threadedthrough a series of guides and sheaves using “leader’ mate-rial. At this point pro-cess parameters are setaccording to specifica-tions, the electron beamis energized and theproduct rapidly movesfrom the payoff onto thetake-up reel as it passesthrough the irradiationchamber.

For products that aretemperature sensitive,the in-line water coolingsystem can be used toreduce temperatures in-process.

After irradiation, theproduct is certified, pre-pared for shipment andsent back to the manu-facturer within days af-ter receipt.

ConclusionsA contract E-beam service center can be valuable to manu-

facturers considering the use of electron beam as a means ofcross-linking, and to those who are currently experiencing

Fig. 2—Payoff for product entering the irradiation system.

Company Profile...

Isomedix Services is a division of STERIS Corp., a world

leader in sterilization products and services. Through its NorthAmerican network of 16 facilities, Isomedix Services providesits Material Modification services as part of a complete man-aged program that emphasizes exceptional process quality, effi-cient turnaround and optimum cost containment.

WCTI

Fig. 3—Under-beam capstan controls the degree of cross-

linking. Above shows full width of capstan. Left shows cable

threaded through guides at irradiator’s scan horn.

capacity constraints on their existing in-house units.There are several advantages to e-beam cross-linking that

make it valuable to wireand cable manufacturers:

• There are no chemicalsadded to the polymer mix.

• No post-processing isrequired after the productis exposed to the electronbeam.

• The high output rates ofa contract facility such asthis make it easy for manu-facturers to optimize theirproduction process.

With today’s demandfor production efficiencyand for new products,companies may also findthe use of a service cen-ter beneficial as it relatesto the timing and costs as-sociated with researchand development. An

electron beam cross-linking service center can help bridge thegap between R&D and full-scale production for many wireand cable applications.

For more information contact the author.

REPRINTED FROM WIRE & CABLE TECHNOLOGY INTERNATIONAL NOVEMBER, 2002

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