Radiation stability of hybrid composites based urea-formaldehyde resin modified with micro- and nano-tio2

The thermal stability of organic-inorganic composites prepared by a twostage polymerization of urea-formaldehyde resin (UF) with micro- and nano-TiO2 before and after irradiation has been investigated. Composites of urea-formaldehyde and particles of TiO2 of different size were synthesized, namely: Composite 1 (UF+ micro-TiO2) and Composite 2 (UF + nano- TiO2). The thermal stability of obtained materials was studied by nonisothermal thermo-gravimetric analysis (TG), differential thermal gravimetry (DTG) and differential thermal analysis (DTA). Hybrid composites based on UF resin have been irradiated (50 kGy) and after that their radiation stability was evaluated on the basis of thermal behavior. DTG peaks of both composites are shifted to a higher temperature after irradiation, but Composite 1 after irradiation shows less change in thermal behavior than Composite 2

The influence of different doses of γ-radiation on the hydrolytic stability of modified urea-formaldehyde (UF) resins

Zbog emisije formaldehida (CH2 O) iz drvenih proizvoda, gde se urea- formaldehidne (UF) smole, između ostalog, koriste za impregnaciju drvenih panela koje se koriste u unutrašnjosti stambenih i drugih objekata poželjno je da procenat slobodnog formaldehida (CH2 O) u samoj smoli bude što manji, jer je poznato da formaldehid ima štetno dejstvo na čoveka, odnosno ceo živi svet. Pare formaldehida jako nadražuju disajne puteve. Koncentracije od 10-20 ppm otežavaju disanje, a koncentracije od 650 ppm mogu uzrokovati i smrt za samo nekoliko minuta. Često udisanje para niskih koncentracija mogu uzrokovati hronična oboljenja disajnih puteva. Simptomi i granice su individualni i javljaju se u širokim granicama izloženosti. Pojedine osobe mogu da osete simptome, kao što su iritacija očiju, grla, umor, glavobolja i mučnina, usled izloženosti i niskoj koncentaciji formaldehida (0.1 do 1 ppm). Osim slobodnog formaldehida, u samoj smoli, koji se spontano emituje, zbog niske otpornosti na vlagu, može doći do hidrolize UF smole što podrazumeva raskidanje samih veza u smoli (metilenetarskih) i dodatne emisije formaldehida u okolinu [1,2]. U ovom radu je ispitivana hidrolitička stabilnost modifikovanih UF smola sa “hvatačima” formaldehida, TiO2 sa različitim sadržajem (3,75 g i 7,25 g) u UF smoli i kombinacijom TiO2 i drvnog brašna (TiO2 /DB) u ekvimolarnim količinama. Tri modifikovane UF smole s odnosom formaldehida i uree (F/U) 0.8 s modifikovanim punilima su sintetizovani istim postupkom [3]. Hidrolitička stabilnost ispitivanih modifikovanih UF smola je određivana merenjem koncentracije oslobođenog formaldehida [4] iz modifikovane UF smole nakon kisele hidrolize. Zračenje sintetisanih modifikovanih smola je vršeno u vazdušnoj atmosferi u Co-60 radijacionoj jedinici na Institutu za nuklearne nauke, Vinča, Srbija. Uzorci smola su zračeni γ–zračenjem na sobnoj temperaturi i ukupnom apsorbovanom dozom od 50 kGy i 100 kGy [5]. Pre zračenja najmanji procenat slobodnog formaldehida (0.06%) imaju uzorci koji su modifikovani TiO2 . Usled γ-zračenja dolazi do degradacije makromolekula što uzrokuje povećanje slobodnog formaldehida u zračenim uzorcima u odnosu na nezračene. Povećanje doze zračenja sa 50 kGy na 100 kGy dovodi do smanjenja količine slobodnog formaldehida u umreženoj UF smoli. Najmanji procenat slobodnog formaldehida nakon zračenja sa ukupnom apsorbovanom dozom od 100 kGy nalazi se u UF smoli koja sadrži 100% TiO2 u količini od 0.12%. S druge strane i drvno brašno koje sadrži celulozu i hemicelulozu ima veliki broj hidroksilnih grupa, takođe reaguje sa slobodnim formaldehidom iz UF smole. γ-zračenjem je smanjen procenat oslobođenog formaldehida u svim ispitivanim modifikovanim UF smolama, posebno kod uzoraka smole sa TiO2 u količini od 100% u izosu od 0.25%. To se objašnjava činjenicom da kisela hidroliza nakon zračenja dovodi do dodatnog umrežavanja u svim uzorcima, što rezultuje „hvatanjem“ formaldehida u toku samog procesa hidrolize. Uzorci ispitivane kompozitne smole sa TiO2 /DB pokazuju lošiju hidrolitičku stabilnot zbog povećane interakcije između hidroksilnih i karbonilnih grupa u drvnom brašnu i hidroksilnih grupa sa površine TiO2 , zbog čega dolazi do smanjene interakcije hibridnog punila sa polimernom matricom odnosno smanjuje se procenat slobodnih grupa koje bi inače reagovale sa formaldehidom i smanjile njegovu emisiju iz smole.8th Symposium Chemistry and Environmental Protection : May 30 - June 1, Kruševac, 2018

The effect of y(gamma)-irradiation on mechanical properties of NR/BR/SBR ternaryrubber blend reinforced with carbon black

In this study the effect of radiation dose on the mechanical properties of ternary NR/BR/SBR (25/25/50) rubber blend reinforced with carbon black (CB) (0–100 phr) has been investigated. The cure characteristics of compounds were assessed using the rheometer with an oscillating disk. The mechanical properties hardness, modulus at 100% elongation, tensile strength and elongation at break were assessed before and after γ--600 kGy). The vulcanizates were prepared in a hydraulic press. It was estimated that the values for tensile strength increased when the CB content increased up to 80 phr. Tensile strength and elongation at break are decreasinge, but hardness and cross linking density are increasing with the increase of the irradiation dosePhysical chemistry 2016 : 13th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-30 September 201

The latest geological study of the underlying productive layer of the "Garajevac Istok" deposit in Novi Bečej

In this paper, the latest geological study of the "Garajevac Istok" brick clay deposit near Novi Bečej is presented. The clay of the overlying productive layer of this deposit has been exploited by Polet from Novi Bečej since 2008 as raw material for the production of roof tiles. This study is focused on the underlying productive layer of soil, which has not yet been exploited due to the abundance of water in the working environment. Detailed studies by depth of the second silt-clay complex planned for exploitation were carried out. The obtained results confirm that the quality of the raw mineral materials meets the standards for tile production. This paper summarizes the results of the studies

Nano-silica-based urea–formaldehyde composite with some derivates of coumarin as formaldehyde scavenger: hydrolytical and thermal stability

The hydrolytic stability of two nano-SiO2-based UF composites with derivates of coumarin (names as K-1 and K-2) was investigated. K-1 is 3-nitro-4-(p-tolylamino)-2H-chromen-2-one and K-2: 4-((3-nitro-2-oxo-2H-chromen-4-yl)amino)benzenesulfonamide. Two types of nano-silica-based urea–formaldehyde (UF), composite materials with a formaldehyde-to-urea (F/U) ratio of 0.8, were synthesized (UF/K-1/SiO2, and UF/K-2/SiO2). The hydrolytic stability of modified UF composite was determined by measuring the mass loss and liberated formaldehyde concentration of modified UF composite after acid hydrolysis. Obtained results showed that the hydrolytic stability of modified resins with derivates of coumarin was enhanced. The formaldehyde emission of modified UF/K-1/SiO2 composite is lower compared with UF/K-2/SiO2 composite. The thermal behavior of materials was studied by non-isothermal thermo-gravimetric analysis and differential thermal gravimetry supported by data from ATR-IR spectroscopy. The shift of temperature values for selected mass losses (T5%) to a high temperature indicates the increase in thermal stability of samples based on UF resin modified with K-2. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature

Radiation stability and thermal behaviour of modified UF resin using biorenewable raw material-furfuryl alcohol

The thermal stability of organic-inorganic nano-composites prepared by a two-stage polymerization of urea-formaldehyde resin (UF) with furfuryl alcohol (FA) and TiO2 before and after irradiation has been researched. The two resins of urea-formaldehyde–TiO2 composites, named: UF/TiO2 and UF/TiO2/FA, were synthesized. The thermal stability of obtained materials was studied by non-isothermal thermo-gravimetric analysis (TG), differential thermal gravimetry (DTG) and differential thermal analysis (DTA). UF hybrid composites have been irradiated (50 kGy) and after that their radiation stability was evaluated on the basis of thermal behavior. The free formaldehyde (HCOH) percentage in all prepared samples was determined. The minimum percentage values of free formaldehyde (0.04% and 0.03%) for UF/TiO2 and UF/TiO2/FA, respectively, after irradiation dose of 50 kGy are detected. The shift of temperature values for selected mass losses (T10%) to a high temperature indicates the increase in thermal stability of samples based on UF resin modified with FA

Effect of gamma-irradiation on the hydrolytic and thermal stability of micro- and nano-TiO2 based urea-formaldehyde composites

The hydrolytic stability and thermal behavior of organic-inorganic composites prepared by two-stage polymerization of urea-formaldehyde resin (UF) with micro-and nano-TiO2 before and after irradiation has been investigated. Composites of urea-formaldehyde and particles of TiO2 of different sizes were synthesized, namely: UF/micro-TiO2 and UF/nano-TiO2. The hydrolytic stability of the modified UF composites was determined by measuring the mass loss and liberated formaldehyde concentration of modified UF composites after acid hydrolysis. The studied modified UF composites have been irradiated (50 kGy) and the effect of gamma-irradiation was evaluated on the basis of the percentage of liberated formaldehyde before and after irradiation. The minimum percentage (0.16%) of liberated formaldehyde was obtained in nano-TiO2 modified UF resin after gamma-irradiation which indicated a significant improvement in the hydrolytic stability compared with micro-TiO2 modified UF resin (0.52%). The effect of gamma-irradiation was evaluated also on the basis of the thermal behavior of the same modified UF composites before and after irradiation. The thermal behavior was studied by non-isothermal thermogravimetric analysis (TG), differential thermo-gravimetry (DTG) and differential thermal analysis (DTA) supported by data from attenuated total reflection infrared (ATR-IR) spectroscopy. DTG peaks of both composites are shifted to a higher temperature after irradiation, but UF/micro-TiO2 after gamma-irradiation shows less change in the thermal behavior than nano-TiO2. In other words, UF/micro-TiO2 shows better radiation stability. Gamma irradiation causes a minor effect on the ATR-IR spectra, specifically the decrease of the intensities of some bands

Effect of gamma-irradiation on the hydrolytic stability and thermo-oxidative behavior of bio/inorganic modified urea-formaldehyde resins

In order to minimize emission of formaldehyde from urea formaldehyde resins (UF) and to improve their thermo-oxidative behavior, the effect of low gamma-irradiation on hydrolytic and thermo-oxidative stability of nano-silica modified UF resin, modified UF resin with wood flour (Pinus silvestris L.) as natural filler and modified UF resin with mixture of SiO2/WF fillers were investigated. The hydrolytic stability of modified UF resins was determined by measuring the mass loss and liberated formaldehyde concentration of modified UF resins after acid hydrolysis. The studied modified UF resins have been irradiated (50 kGy) and effect of gamma-irradiation was evaluated on the basis of percentage of liberated formaldehyde before and after irradiation. The minimum percentage (1.23%) of liberated formaldehyde and mass loss of a 25.35% were obtained in wood flour modified UF resin after 7-irradiation which indicate significant improvement in the hydrolytic stability compared to other modified UF resins. The effect of gamma-irradiation was evaluated also on the basis of thermo-oxidative behavior of the same modified UF resins before and after irradiation. The thermo-oxidative behavior was studied by non-isothermal thermo-gravimetric analysis (TG), differential thermo-gravimetly (DTG) and differential thermal analysis (DTA) supported by data from IR spectroscopy. After gamma-irradiation, the shift of DTA peaks a higher temperature indicates that thermo-oxidative stability of modified UF/SiO2/WF is increase. (C) 2014 Elsevier Ltd. All rights reserved

Recultivaction of opencast mine of clay "Garajevac Istok", near Novi Bečej

The surface exploitation of mineral raw materials is realized in the natural environment, causing the degradation of the narrower and wider space: the change of the physical appearance of the terrain and the degradation of the soil and autochthonous vegetation cover. The recultivation of the surface mine area, after the exploitation of mineral raw materials, is an important and mandatory measure in the function of environmental protection. In a biologically empty space, with damaged or destroyed natural content, in parallel with the slow and long-lasting process of spontaneous self-revitalization, technical and biological reclamation measures and procedures are applied to control and accelerate the revitalization process.The subject of this work is the design of reclamation on the surfaces affected by the exploitation of clay, on the example of the Garajevac Istok surface mine near Novi Bečej, with the aim of creating habitats for plant and animal life. The planned goals of the reclamation of the post-exploitation area of the Garajevac Istok surface mine will be realized by applying a combination of afforestation measures and spontaneous self-reclamation

Nanosilica and wood flour-modified urea-formaldehyde composites

In this study, the thermal behavior of modified urea-formaldehyde (UF) resin with nanosilica (nano-SiO2), wood flour (WF), and their mixture of SiO2/WF was investigated. Five modified UF hybrid composite materials with 0.8 F/U ratio with different filler were synthesized using the same procedure. The thermal behavior of materials was studied using nonisothermal thermogravimetric analysis, differential thermal gravimetry (DTG), and differential thermal analysis and supported by data from infrared spectroscopy. The shift of DTG peaks to a high temperature indicates the increase in thermal stability of modified UF resin with hybrid SiO2/WF fillers, which is confirmed by the data obtained from the Fourier transform infrared spectroscopic study. It was estimated that the UF/WF samples based on nano-SiO2 have better thermal stability