Ageing of Some Lacquers Due to Microbiological Stress

Abstract

This paper shows the ageing study of some coatings and / or impregnation lacquers due to microbiological stress through fungal attack. Dielectric spectroscopy has shown that the dielectric losses of the investigated materials increase as result of microbiological ageing. The mean recorded increases are about 4 times for the alkyl-epoxy-melamine copolymer, 2 times for epoxy polymer and 1.5 times for urethane polymer in agreement with the mould coverage degree of about 20 %, 10 %, and 3 %, respectively. The fungal attack of the investigated polymers led to a decrease in volume resistivity of about 65 % for the alkyl-epoxy-melamine copolymer, 45 % for the epoxy polymer, and 14 % for polyurethane, in agreement with the increase of dielectric losses and degree of mold coverage of the samples. FTIR determinations have shown that fungal attack significantly increased the number of aliphatic -OH and C-H bonds and decreased the number of C-O bonds, respectively of C-O-C oxiran groups and C-C aromatic bonds. DSC thermograms recorded at different temperature ranges and the activation energies calculation for first major oxidation process indicate that after the fungal attack the thermooxidative reactivity of the investigated polymers increases.

The Hydrophily of Some Lacquers for Electrical Use

“…Analysing the data in Figures 2 -4 and comparing them, it is found that systematically, for both reference and immersed samples in water, the lowest values of tgδ were recorded for the polyurethane (LS) based lacquer followed by the values for the epoxy lacquer (LG), while the alkyd-epoxy-melamine lacquer has the highest values (L-528). This hierarchy coincides with the values reported in [9,20] for these lacquers.…”

“…Humidity, including water absorbed due to the hydrophilic process, favours the formation and growth of microbial colonies, which leads to biodeterioration of polymers [3,4,[10][11][12][13] and metal components corrosion [4][5][6][7][8]. On the other hand, by exposure in the extremely low frequency electric field especially at the industrial frequency of 50Hz, the growth and multiplication of microorganisms (especially moulds [15][16][17][18]) is stimulated heaving as consequence an accelerated biodeterioration of polymers [19,20] and metal components corrosion [21][22][23][24]. The electrical stress acting on the polymeric insulations is intensified by the harmonic components of the 50 Hz industrial frequency primarily generated by the reactive consumers [25][26][27][28], a situation when, in the presence of humidity, the initiation and growth of the water tree in the polymeric insulation is greatly accelerated [29].…”

Obtaining and Preliminary Characterization of Some Polyethylene Composites with Nickel-Silver Ferrite Filler

“…On the other hand, increasing the lifetime of the polymeric materials exposed to various environmental factors such as chemical and microbiological aggression [24,25], temperature [26][27][28], gamma radiation [28][29][30][31], UV [32] etc.) can be achieved by using natural antioxidants [33,34,38] or synthetic antioxidants [28,30].…”

Mineral Oil versus Vegetable Oil as Electroinsulating Fluids in Contact with Coating LacquersA thermochemical stability study

“…In different electrical applications, including the contact with electroinsulating fluids, coatings and / or impregnation lacquers are often used [36,37]. In view of these considerations, the paper purpose is to determine the flammable gases formed in a mineral electroinsulating fluid as compared to a vegetal oil that is in contact with three different types of electroinsulating lacquers used.…”