The Thermooxidation and Resistance to Moulds Action of Some Polyethylene Sorts Used at Anticorrosive Insulation of the Underground Pipelines

Abstract

Polyethylene (PE) insulations have a wide applicability in the insulation of both underground pipelines and underground power cables. In this context, by coupled techniques of thermal analysis (TG/DTG+DTA) and microbiological determinations, have been studied thermooxidability and resistance to moulds action of some polyethylene sorts. Following the processing of the experimental data obtained by thermal analysis it was found that during the applied heat treatment (100 grd C), in the first approx. 380 h, there is a growth of LDPE (low density polyethylene) polymerization degree by elongation of the aliphatic chains, after which the predominant process consists in the structure crosslinking. For MDPE (mean density polyethylene) samples, during the thermal treatment applied, it was found that the crosslinking degree of polyethylene (PE) increased without significant molecular weight change (with all the related consequences of increasing the weight of the tertiary and quaternary carbon atoms in the molecule). Microbiological determinations have highlighted that the resistance to filamentous fungal action of LPDE is higher than that of the investigated MDPE. It was found that after heat treatment applied (1000 h and 100 oC), both at LDPE and at MDPE, decreases the resistance to moulds action is decreased. It has also been found that moulds action resistance is substantially decreased when inoculated culture media and PE samples are exposed to an alternative electric field of 50 Hz - 6 Vrms/cm.

Ageing of Some Lacquers Due to Microbiological Stress

“…The enzymatic apparatus of the microorganisms and their metabolic products produce the polymeric materials biodegradation [20][21][22] with implications on the durability of various construction systems such as: corrosion protection with polymeric protective layers [2][3][4][23][24][25], underground plastic pipelines [26,27], underground power cables [28][29][30], etc.…”

Effects of Electromagnetic Field Use on Jaw Bone Densification

“…After the results of Caramitu et al [9], the field of 5V/cm & 50Hz stimulates the growth of Aspergillus niger, inhibits completely those of Trichoderma viride and Aspergillus flavus. Bors et al [10], founded that the presence of the disturbing electric field of 50 Hz -6 Vrms/cm, intensifies the microbiological activity, especially of Aspergillus niger, which inhibits the development of other species -including Trichoderma viride. The researches of Bunoiu et al [11], underlined that dispersing magnetic nano-microparticles in liquid polymers followed by polymerization in a mixture with a suitable catalyst, with or without a magnetic field, one obtains magnetorheological elastomers with various applications.…”

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

“…In these conditions, the prevention of biofouling growth can be achieved either by the selection and application of high resistance coating materials to natural thermooxidative processes (thermal stress and UV action [6,13,14,16] and the molds action [8,10,15]), or through the use of appropriate antifungal biocides [35][36][37][38][39][40][41] (obviously with the necessary precautions -taking into account that the investigated bridge is in the Natura 2000 protected area [24]).…”

“…In these conditions, the durability and the safety of bridges is largely disturbed by the quality and resistance to the action of environmental factors (atmospheric weather, aggressive pollutants from the atmosphere, micro-and macro-biological factors, solar radiation -especially in the UV spectrum [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] and / or some fatty substances [19][20][21][22][23]), of the polymeric finishing materials applied to the strength structure for anticorrosion protection (usually paint film -polymer composites with the addition of various ingredients and colour pigments).…”