Increasing Shielding Capabilities of Cement Mortars by Fly Ash Addition

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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.

mentioning

confidence: 99%

Ageing of Some Lacquers Due to Microbiological Stress

Bors¹,

Lungulescu²,

Nicula³

et al. 2019

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“…The range relatively low of temperatures at which takes place melting, as well as the process energy (134.25 J / g) indicates a relatively high degree of ordering (crystallinity) of the polymer. These data and the start temperature of the first thermooxidation process (230.15 o C), indicate that high crystallinity is due to a relatively high degree of polymer crosslinking (large weight of tertiary and quaternary carbon atoms) [46][47][48].…”

Section: Resultsmentioning

confidence: 99%

Dielectric Behavior and Morphostructural Characteristics of Some HDPE Composites / Metal Nanopowders

Caramitu¹,

Mitrea²,

Marinescu³

et al. 2019

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HDPE composite samples with aluminum and iron nanopowders were made by extrusion and injection. Samples of material obtained were characterized by comparative determinations of dielectric spectroscopy and SEM microscopy. SEM images have indicated that the agglomerations of the powders used are persistent, do not decompose during extrusion and injection processing. Determinations by dielectric spectroscopy indicated that HDPE composite materials with metal nanopowder filler have higher dielectric losses than pure HDPE (reference). The highest increases in tgd up to 2.6 times, were recorded for 50 nm nanopowders with specific high surface area (over 20 m2 / g). The electrical conductivity of the investigated samples increases with increasing frequency, both for pure HDPE and for HDPE with metal powder filler. As a result of the film effect in the HDPE case with metal filler, the increases in the high frequencies range are lower than in the extremely low frequencies range.

“…It is noted that relatively low resistance to filamentous molds action was also found in some sorts of polymer used in underground power cables [31,53] and / or plastic pipelines [54].…”

Section: Resultsmentioning

confidence: 99%

Assessment of Paint Layers Quality 2. Identification of biological species grown on a railway bridge

Nicula¹,

Varga²,

Bors³

et al. 2018

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The species from the increased biofouling on the paint layers applied to the metallic strength structure of a railway bridge located in a Natura 2000 protected area have been identified by specific biologic and microbiological methods. As a result of the analysis of the biological samples taken on the field, it has been found that relatively large variety of filamentous molds are present (Aspergillus fumigatus, Asprgillus flavus, Aspergillus niger, Paecilomyces variotii, Chaetomium globosum, Trichoderma viride, Stachybotris atra, Trichoderma sp., Alternaria sp and Penicillium sp.). Samples also show, lichens (Xanthoria parietina and Hypogymnia physodes) and lower plants capable of photosynthesis such as algae (Chlorophyta Xanthophyceae, Chrysophyceae) and moss (Lunularia cruciata, Marchantiophyta).