XLPE Curing

hi gents,
Why is it imperative to check the EAB of an insulated core when a hot set test can itself demonstrate whether curing has taken place? How is Elongation at break related to curing? Can re-curing or increasing the curing period decrease the chances for EAB failures?

Hello anishj2002,

I think we will have to wait for a chemist, chemical engineer, polymer engineer or polymer scientists to answer your questions. EAB is however a standard test which of course clearly shows the elongation at the time the insulation was extruded and crosslinked. It therefore gives an important point of reference if indeed the insulation on the cable later has a problem.

To explain EAB for all the rest of us:

ELONGATION-AT-BREAK (EAB)

"Elongation-at-break (EAB) is a measure of a material’s resistance to fracture under an applied tensile stress. It is often termed the “ductility” of a material and is defined as the percent increase in elongation at the time of fracture. It is well known that cable insulation and jacket materials, like most polymers, lose ductility as they age."

Sincerely
Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com

Hi all,

There is no relationship between hot set and EAB. If you increase the curing time you will not see any changes in EAB. Generally EAB is between %500-800 in XLPE but you can see the problems about shrinkage. It is related to what type of tools you use. If you use the tube tools you can see the problems about shrinkage and also is related to compound. Generally we can see the problems while using one component that includes catalyst and polymers together.

anishj2002 and serdar1970,

Could one of you please give a simple overview of how the Hot Set Test is performed and how long it takes? Thank you.

Sincerely
Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com

www.ssinstruments.com

(Web Site not universally coded - Internet Explorer Only)

first the drum is cured using steam curing.
then a standard length of sample is selected, and a gauge length is marked. The thickness of the sample is measured and corresponding weight is calculated with the values given in the specification (0.2N/mm²). The weight is attached to one end of the sample and kept in an oven maintained at 200°C for 15mins. The elongation is then measured. if the sample breaks, the sample is a failure.

Anish K