Efecto de radiaciones ionizantes en los polímeros.pdf
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Transcript of Efecto de radiaciones ionizantes en los polímeros.pdf
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7/28/2019 Efecto de radiaciones ionizantes en los polmeros.pdf
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Radiation Effects on PolymericSystemsPolyethylene Crosslinking
Wire and Cable InsulationHeat-Shrink Products
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Plastics Used inWire and Cable Insulation
PVCPE and copolymers
EPDMChlorosulfonated PEPE/EVA CopolymerFluoropolymers
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Crosslinking ofPolyethylene is ofGreat Industrial Interest
Heat-shrinkfilmHot WaterPipes
Wire and CableInsulation
tCrosslinking. . . . of .....Polyethylene ' - -_ .......+MiscellaneousHeat-shrinkItems
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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
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Crosslinking ofPolyethyleneAdvantages
Increased tensile strength Higher service temperature Improved weathering characteristics Increased resistance to stress cracking Decreased solubility
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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
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Factors that Affect RadiationCrosslinking ofPE
Presence of oxygen Presence of additives(anti-oxidantsfire retardantscrosslinking agents)
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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
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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
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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