Abstract
Tests were performed to evaluate the effects of thermal and solvent aging on the mechanical and dielectric breakdown properties of four types of polyester resins, namely, the insulation layer of poly(butylene terephthalat) (PBT)- based thermoplastic elastomer (TPE, TPE1), poly(butylene 2,6-naphthalate)-based TPE (TPE2), PBT/poly(ethylene terephthalate) alloy (Alloy), and PBT extruded onto a copper conductor of low voltage electric wire. The tensile specimens used in this series were prepared from the same extruded resins. The prepared electric wires and tensile specimens were thermally aged in air and in toluene, xylene, TCB, and NMP. When Alloy and PBT were thermally aged in toluene, xylene and TCB at 120°C for 6 h, the tensile properties were significantly decreased compared to TPE1 and TPE2 at the same condition. The reduction of elongation at break of Alloy was more discernible than that of PBT. This result indicated that Alloy is more affected by thermal and solvent ageing. Among them, TPE2 showed the highest breakdown voltage (BDV), and it has also the highest BDV after thermal and solvent aging.
Highlights
The service life of electric wire is determined by the condition of the insulating material
The extruding weight of samples increased in the order of Alloy < TPE2 < poly(butylene terephthalate) (PBT) < TPE1 at the same conditions due to the mobility of the polymer molecules being more restricted as the melt is contained with poly(ethylene terephthalate) (PET) and PBN unit
TPE1, TPE2, PBT, and Alloy were extruded as the insulation layer of low voltage electric wire, and its dielectric breakdown voltage (BDV) changes after thermal and solvent aging were investigated
Summary
The service life of electric wire is determined by the condition of the insulating material. The insulating varnish is applied to coils of polyester insulated wire, in the process of which it fills the gaps and micropores, and after curing it forms into a continuous resin film. It is important for mechanical stability and protection of coiled wire against dust, moisture, and chemicals which might cause insulation deterioration. The insulating varnishes, which are provided for this purpose, are highly reactive materials They are usually included in one or more solvents, such as toluene, xylene, isophorone, naphtha, 1,2,4-trichlorobenzene (TCB), and 1methyl-2-pyrrolidinone (NMP). Thereby, the varnish treatment process influences the deterioration of the insulation made from polyester materials and reduces the ability of the wire to withstand short circuits. The changes in tensile properties of dumb-bell type specimen after the aging have been evaluated
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