7/28/2019 Efecto de radiaciones ionizantes en los polmeros.pdf

1/10

Radiation Effects on PolymericSystemsPolyethylene Crosslinking

Wire and Cable InsulationHeat-Shrink Products

7/28/2019 Efecto de radiaciones ionizantes en los polmeros.pdf

2/10

Plastics Used inWire and Cable Insulation

PVCPE and copolymers

EPDMChlorosulfonated PEPE/EVA CopolymerFluoropolymers

7/28/2019 Efecto de radiaciones ionizantes en los polmeros.pdf

3/10

Crosslinking ofPolyethylene is ofGreat Industrial Interest

Heat-shrinkfilmHot WaterPipes

Wire and CableInsulation

tCrosslinking. . . . of .....Polyethylene ' - -_ .......+MiscellaneousHeat-shrinkItems

7/28/2019 Efecto de radiaciones ionizantes en los polmeros.pdf

4/10

Heat-Shrink Products Based on crosslinking of polyethylene and other polymers(PVC, PVDF, rubbers, acrylates, etc.) Include films, sheets, tapes, tubes and shaped products Basis of the technology, the "memory effect" (cross-linkingin the amorphous regions and "none" in the crystallineregions) Heat-shrink products a uniqueness of radiation treatment;not possible with thermal/peroxide process

Electric connectors and poultry packaging two prominentexamples

7/28/2019 Efecto de radiaciones ionizantes en los polmeros.pdf

5/10

Crosslinking ofPolyethyleneAdvantages

Increased tensile strength Higher service temperature Improved weathering characteristics Increased resistance to stress cracking Decreased solubility

7/28/2019 Efecto de radiaciones ionizantes en los polmeros.pdf

6/10

Radiation and Chemical Crosslinking ofPE as Wire and Cable Insulator

ParameterTemperatureAtmosphereCrystallinityCrosslinkingDimensions ofinsulationPost-treatmentannealingDielectric propertiesCostProduction speedQualityEnvironmentaleffectsSilverman (1992)

Irradiationambient 70C)air (electron or nitrogen)hardly affectedamorphous regionsunchangeddesirable (70-85C, -1 h)betterlowerhigherbetterbetter

Chemical (Peroxide)high (-125C)airlostuniformsome non-uniformitynot neededinitiators harmfulhigherlowerpoorerpoorer

7/28/2019 Efecto de radiaciones ionizantes en los polmeros.pdf

7/10

Factors that Affect RadiationCrosslinking ofPE

Presence of oxygen Presence of additives(anti-oxidantsfire retardantscrosslinking agents)

7/28/2019 Efecto de radiaciones ionizantes en los polmeros.pdf

8/10

Crosslinking in Crystalline Regions ofPEA Controvercial Topic Patel and Keller (1975) prepared crystallinemonolayers of PE

Concluded that there is no crosslinking in thecrystalline regions on irradiation Tabata and coworkers (1984, 1991) haveconcluded that there is some crosslinking (""1/3rd)in the crystalline regions

7/28/2019 Efecto de radiaciones ionizantes en los polmeros.pdf

9/10

Aim of 10 MeV Electron IrradiationofPolyethyleneDetermine whether commercial samples of PEcan be crosslinked with 10 MeV electrons, onirradation in air, to a gel fraction greater than 70%

ResultCommercial polyethylenes can be crosslinked inair by 10 MeV electron irradiation to yield the gelfraction required (70 0/o) for wire and cableinsulation

7/28/2019 Efecto de radiaciones ionizantes en los polmeros.pdf

10/10

Conclusions

Radiation crosslinking for the production of heatshrink products would continue to grow Since radiation crosslinked PE has better insulatorproperties, this would also remain a growth area Radiation processing has enabled the plasticsindustry to expand the scope of their markets Continuing R&D should further expand the use ofradiation processing in the plastics industry