Sažetak
Kvarenje materijala je problem koji zaokuplja pozornost stručnjaka oduvijek, jer, prije svega, dovodi do velikih ekonomskih gubitaka. Zato su uzroci kvarenja različitih materijala predmet istraživanja već dugi niz godina. Organizirane grupe istraživača većinom u kemijskoj industriji podržane vladinim organizacijama bave se analizama i istraživanjima u tome području.
Najveću ulogu u kvarenju ima biološko kvarenje koje je po definiciji svaka neželjena promjena svojstava materijala uzrokovana aktivnostima živih organizama. Biorazgradnja pod nazivom kvarenje, nepoželjan je proces kada je u pitanju proizvodnja i čuvanje materijala, ali je vrlo poželjan proces kada taj materijal postaje otpad, a u pitanju su obično često iste vrste mikroorganizama.
Emulzije za hlađenje i podmazivanje pri obradbi metala s velikim udjelom vode do 98% upravo su zato vrlo podložne rastu mikroorganizama. Uljna faza je dobra hranjiva podloga za mikroorganizme kao izvor ugljika. Zbog raspršenih kapljica u vodi dodirna međufazna površina ulje/voda vrlo je velika pa je i površina za rast mikroorganizama dovoljna budući da je voda neophodni medij za razvoj. Pod utjecajem metabolizma mikroorganizama proizvod se mijenja kemijski i funkcionalno zbog čega nastaju sluzave mikrobne nakupine koje uzrokuju stalno čepljenje filtara i uređaja.
Iako su koncentrati emulgirajućih tekućina od kojih se spravljaju radne emulzije obično sterilni, što je ispitano i u našem radu, mikroorganizmi se vrlo brzo nakon namješavanja s vodom razvijaju, jer niti okolina niti voda nisu sterilni. Budući da u spremnicima već postoje mikrorganizmi, nove emulzije se brzo inficiraju pa broj mikroorganizama vrlo brzo raste, ako nema antimikrobnog agensa i ako se uređaji i spremnici pravilno ne održavaju. Kako kvarenje napreduje, pjena i sluz postaju vidljivi. Suspendirane nakupine na površini upućuju na infekciju gljivama, a često se pojavljuje miris na amonijak, ali češće na sulfide. Emulzija promijeni boju, pH vrijednost progresivno pada, a isto tako i svojstvo zaštite od korozije.
Naša ispitivanja su pokazala da su spremnici za emulzije u dva pogona bili znatno inficirani s više vrsta mikroorganizama, što je dokazano uzgojem na selektivnim hranjivim podlogama, kao i mikrobiološkom kontrolom u ovlaštenim laboratorijima. Ispitivanja su, nadalje, pokazala da se pravilnim postupanjem i održavanjem postrojenja i spremnika uvelike smanjuje kvarenje emulzija a time i zastoj u pogonu, čega je posljedica znatna financijska ušteda.Abstract
Material degradation is a problem which has always been occupying the attention of experts, because, first of all, it leads to major economic losses. That is why the causes of deterioration of various materials have been the object of research for a number of years now. Organized groups of researchers, mostly in chemical industry, supported by governmental organizations, are engaged in analyses and research of this particular area.
The biggest role in degradation is that of biodeterioration, defined as any unwanted change of the material properties caused by the activities of living organisms. Biodegradation in the form of deterioration constitutes an unwanted process when it comes to the production and storage of materials, but is in turn a most desirable process when the material in question becomes waste, both of these processes usually involving often the same kinds of microorganisms.
Emulsions for cooling and lubrication at metalworking with a high water content of up to 98%, and are precisely for this reason most prone to microorganisms growth. The oil phase makes a good nutritional basis for microorganisms as a source of carbon. Because of the tiny drops dispersed in water, the contact interphase oil/water surface is very large, which is why the surface for microorganisms growth is sufficient as well, water being the essential medium for their development. Under the impact of the metabolism of microorganisms, the product changes both chemically and functionally, which is why the slimy microbial growths cause constant clogging of filters and devices.
Although the concentrates of emulsifying fluids from which working emulsions are made are usually sterile according also to the results of this paper, microorganisms, after blending with water, develop very soon. That is because neither the environment nor the water are sterile. Since there already are microorganisms in the containers, new emulsions are soon infected and the number of microorganisms grows very fast unless there is an antimicrobial agent present, respectively unless the devices and containers are properly maintained. As deterioration progresses, the foam and the mucilage become visible. Suspended growths on the surface point to infection by fungi, while the smell of ammonia and even more frequently that of sulphides also frequently appears. Emulsion changes colour, while pH progressively decreases, along with the corrosion protection property.
Our tests have shown that reservoirs for emulsions in two plants were quite infected with several kinds of microorganisms, which has been proven by cultivation on selective nutritive media, as well as through determination of species in authorized laboratories. The tests have furtherly shown that proper handling and maintenance of the plants and reservoirs considerably reduces emulsion deterioration, and hence also plant standstills, resulting in considerable financial savings
