Naslov
Thermally Stimulated Current in Glass-Laminated Unsaturated Polyester Resins

Autori
Jelčić, Želimir ; Ranogajec, Franjo ; Babić, Lenija ; Ivanović, Zoja

Izvornik
Polymer Composites (0272-8397) 12 (1991), 6; 384-390

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
Polyester resins; Composite materials; Glass fiber reinforced plastics; Electrical properties; Laminates; Activation energy; Phase transformations; Depolarization; Dipoles

Sažetak
Experimental results are reported on the electrical properties of glass-laminated unsaturated polyester (UP) resins. Measurements of the poling current as a function of temperature reveal two different activated processes. Above 50 deg C, the activation energy is 160 kJ/mol and has been associated with ionic condition, possibly byprotons, while at lower temperatures ( < --70 deg C) the activation energy is very low < 40 kJ/mol) and is associated with dipole relaxation. It is concluded that the laminated UP resin undergoes a phase transformation between low and high temperatures, which gives rise to a completely different electrical response. This phase transformation can be associated with the glass transition of UP resin phase. In view of the low activation energy, giving rise to a polarization peak, it is concluded that the low temperature range (glassy state) favors strictly localized motions of charges--most likely electrons. At higher temperatures, the behavior corresponds to dc conductivity and is associated with extended motions of charge carriers with limitations at contacts and at internal barriers. According to the air gap measurements, the pronounced dip found in the temperature dependence of the poling current (in the range from 20 to --30 deg C) may be due to separation of conduction and dipole relaxation current. Thermally stimulated depolarization (TSD) current measurements reveal the presence of high internal fields due to space charges accumulated at the phase boundaries of glass fibers.

Izvorni jezik
Engleski

Znanstvena područja
Kemijsko inženjerstvo

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