The effect of y-irradiation on thermal stability urea-formaldenyde resin with TiO2 and furfuryl alcohole

The thermal stability of organic-inorganic nano-composites prepared by a twostage polymerization of urea-formaldehyde resin (UF) with furfuryl alcohol (FA) and TiO2 before and after irradiation has been investigated. The two resins of ureaformaldehyde–TiO2 composites, namely: Resin 1 (UF+TiO2) and Resin 2 (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 percentage in all prepared samples was determined. DTG peaks of both UF resin are shifted to a higher temperature after irradiation. The minimum percentage values of free formaldehyde (4% and 3%) for Resin 1 and Resin 2, respectively, after irradiation dose of 50 kGy are detected.Physical chemistry 2012 : 11th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 201

Properties of Vulcanized Polyisoprene Rubber Composites Filled with Opalized White Tuff and Precipitated Silica

Opalized white tuff (OWT) with 40 mu m average particle size and 39.3m(2)/g specific surface area has been introduced into polyisoprene rubber (NR). Their reinforcing effects were evaluated by comparisons with those from precipitated silica (PSi). The cure characteristic, apparent activation energy of cross-link (E-ac) and reversion (E-ar), and mechanical properties of a variety of composites based on these rubbers were studied. This was done using vulcanization techniques, mechanical testing, and scanning electron microscopy (SEM). The results showed that OWT can greatly improve the vulcanizing process by shortening the time of optimum cure (t(c90)) and the scorch time (t(s2)) of cross-linked rubber composites, which improves production efficiency and operational security. The rubber composites filled with 50 phr of OWT were found to have good mechanical and elastomeric properties. The tensile strengths of the NR/OWT composites are close to those of NR/PSi composites, but the tear strength and modulus are not as good as the corresponding properties of those containing precipitated silica. Morphology results revealed that theOWT is poorly dispersed in the rubber matrix. According to that, the lower interactions betweenOWT and polyisoprene rubber macromolecules are obtained, but similar mechanical properties of NR/OWT (100/50) rubber composites compared with NR/PSi (100/50) rubber composites are resulted

The High-Energy Irradiation Ageing of Reinforced Elastomers Based on Rubber Blends

Elastomers are very often used in severe environments, for instance, in nuclear power plants, where they may be degraded by high-energy radiation and heat. The ageing behaviour of materials used in different equipments is very important. Elastomers based on chlorosulfonated polyethylene (CSM) are used for cable jacketing materials and have excellent radiation resistance needed in nuclear power stations. In the current work, the influence of gamma-irradiation dose (100, 200 and 400 kGy) on the ageing of reinforced blends based on CSM, styrene butadiene rubber (SBR) and natural rubber (NR) has been evaluated. The content of silica in CSM/SBR and CSM/NR rubber blends was varied. The curing behavior of compounds was estimated using the oscillating disk reometer. The irradiation of nano composites has been performed in air in the Co 60 radiation sterilization unit with the dose rate of 10 kGy h(-1). The thermal properties were studied by thermogravimetric test. The mechanical properties (hardness, modulus at 100% elongation, tensile strength and elongation at break) were determined before and after irradiation. A decrease in the elastic modulus and in the strain at break has been observed with increasing irradiation. At higher doses, the network chain scissions become the main degradation process, the cross-linked topology becomes irregular, and material contains more and more weak zones, which deteriorate the ultimate properties.4th International Conference on Radiation and Applications in Various Fields of Research (RAD), Proceedings, May 23-27, 2016, Nis, Serbi

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 effect of gamma radiation on the ageing of sulfur cured nr/csm and nbr/csm rubber blends reinforced by carbon black

In this work the effect of the γ-radiation dose on ageing of carbon black reinforced elastomeric materials was studied. The compounds based on natural rubber/chlorosulfonated rubber blend (NR/CSM) and butadiene acrylonitrile rubber/chlorosulfonated rubber blend (NBR/CSM) (50:50, w/w) with different loadings (0, 20, 40, 50, 60, 80 and 100 phr) of the filler with the average particle size of 40 nm were cured by sulfur. The obtained elastomeric composites were subjected to radiation doses (100, 200, 300 and 400 kGy) in the presence of oxygen. The changes of material mechanical properties were estimated after radiation accelerated ageing. By using Fourier transform infrared measurements (ATR-FTIR) it was assessed that after exposure to doses of 100 kGy alcohols, ethers, lactones, anhydrides, esters and carboxylic acids are formed in materials. The formation of shorter polyene sequences and aromatic rings in aged samples are assumed on the basis of the obtained spectra

Gamma-radiation aging of silica filled chlorosulphonated polyethylene/ butadiene acrylonitrile rubber blends

In this applicative work curing behavior, mechanical properties and gammaradiation aging of silica filled elastomeric nanocomposites based on rubber blend: butadiene acrylonitrile rubber (NBR) and chlorosulphonated polyethylene rubber (CSM) were used as network precursors. The vulcanization characteristics were assessed for NBR/CSM rubber blends (50:50, w/w) using oscillating disc rheometer. The gamma radiation resistance of composites was determined from the tensile properties (hardness, tensile strength and elongation at break) after prolonged exposure to γ-irradiation (dose rate of 10 kGyh-1 and total absorbed dose of 100, 200 and 400 kGy

The effect of UV-irradiation on the thermal stability of modified urea-formaldehyde resins with thermally activated montmorillonite

The montmorillonite as a 2:1 smectite type clay has two tetrahedral sheets of silica sandwiching the alumina octahedral sheet. The particles of this mineral are plate-shaped with the thickness of 0.96 nm and an average diameter about 1 μm. This type of clay (K10) is using to improve the characteristics of different materials in the fields of catalysis, food additives, polymers, sorbents, etc. In this study thermally activated montmorillonite (DK10) was used because the thermal treatment alters its properties. The degree of activation was determined using specific surface measurement (Sear’s method). The specific surface area (SSA) of K10 was 119 m2/g but after the thermal treatmant it was 317.4 m2/g. The effect of UV-irradiation on the thermal stability of a urea-formaldehide resin (UF) nanocomposites based on DTK10 was assessed. For this purpose UF nanocomposites were synthesized and irradiated using UV light at two wavelengths l (254 and 366 nm). Characterization of nanocomposites with modified and not modified clay was performed using XRD, FTIR, and TG/DTA analysis. The peaks at 2q values of 26.74, 26.6, 26.54, 26.6 originate from quartz in sample DTK10, non-irradiated UF/DTK10 and UV-irradiated sample at l=254 nm and l= 366nm, respectively. From the IR spectra it was assessed that intensity of the carboxyl group at 1630 cm−1 decreased with UVirradiation in modified nanocomposite. The aliphatic stretch band about 2956 cm−1 and –C–O band at 1130 cm−1 also decreases due to the formation of hydrogen bonds with the hydroxyl groups on the DTK10 surface. Based on thermogravimetric measurements it was estimated that before and after UV-irradiation modified UF/DTK10 nanocomposites have almost identical temperature intervals in which degradation processes are occurred. The total mass loss for non-irradiated and irradiated UF/DTK10 was 60.18, 55.26 and 58.6%, respectivelyIX International Conference on Radiation in Various Fields of Research : RAD 2021 : book of abstracts; June 14-18, 2021; Herceg Novi, Montenegr

Zeolite and Bentonite as Formaldehyde Scavengers in Urea-Formaldehyde Resins

Urea-formaldehyde (UF) resins are the leading adhesive in the wood industry. Their disadvantages are low water resistance and formaldehyde (FA) emissions from wood panels due to the low stability of the amino-methylene bond. Since FA has a detrimental effect on the environment and human health, the main goal of the modern adhesives industry is to produce efficient UF adhesives with low amounts of emitted, if not without, FA. One way to achieve this is to add a formaldehyde scavenger. In this work, UF resins modified with zeolite type ZSM-5 and bentonite as free FA scavengers are analyzed and compared. A total of three UF resins were synthesized: pure UF resin (UF), UF composite containing zeolite (ZUF), and bentonite (BUF) under the same conditions. Specific surface area (SSA) and cation exchange capacity (CEC) for bentonite and zeolite were determined. SSA (Sears' method) for bentonite is 19.9 m2/g and for zeolite 39.1 m2/g. The CEC of bentonite is 0.68 mol/kg, and that of zeolite is 0.1 mol/kg. The disulfide method was used to determine free FA in modified UF resins. The amount of free FA in the ZUF composite is 0.06%, while in the BUF composite is 0.18%. The hydrolytic stability of modified UF resins was determined by measuring the amount of liberated FA in the modified UF resins after acid hydrolysis. The results show that the amount of released FA in the ZUF composite is 4.08%, while in the BUF resin, it is 4.8%. Based on the obtained results, it can be concluded that zeolite is a better scavenger of free FA than bentonite and that its ZUF composite is hydrolytically more stable than the BUF composite.15th International symposium „Novel technologies and sustainable development", October 20-21 2023, Leskovac

The effect of gamma irradiation on ethylene propylene diene terpolymer/chlorosulphonated polyethylene rubber blend cured with different systems

This work aimed to study the effects of gamma irradiation on the properties of ethylene propylene diene terpolymer/chlorosulphonated polyethylene rubber blend (EPDM/CSM) 50/50 reinforced with 50 phr (parts per hundred rubber) of carbon black and crosslinked either with sulphur/tetramethyl thiuram disulphide or dicumyl peroxide. Irradiation dose rate were 100, 200 and 400 kGy h-1. It was observed that doses higher than 200 kGy practically destroy the assessed properties for all obtained elastomeric materials, irrespective of used curing system. However samples cured with sulphur showed a pronounced decrease in mechanical properties.Physical chemistry 2012 : 11th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 201

Influence of modified montmorillonites on formaldehyde content in urea-formaldehyde/montmorillonite composites

The effect of different montmorillonites (KSF and K10) and their modifications (Na-KSF, Na-K10) on content of formaldehyde-FA (free and liberated) modified urea-formaldehyde (UF) composites was investigated. KSF and K10 were modified by sodium chloride (NaCl). A total of four samples were synthesized, with the designations UF/KSF, UF/Na-KSF, UF/K10, and UF/Na-K10, under the same conditions. The content of free FA was determined by the bisulfite method. The hydrolytic stability of modified UF resin was determined by measuring the concentration of liberated FA of modified UF composites after acid hydrolysis. The specific surface area of the tested montmorillonites was determined by the Sear's method. Higher values of specific surface area were obtained for pure KSF (149.4 m2/g) compared to modified Na-KSF (48.6 m2/g). Specific surface area for pure K10 was 111 m 2/g, compared to value of 71 m2/g for modified Na-K10. The amount of free and liberated FA was 0.4%, 0.12% and 1.2% and 2.3%, respectively for UF/KSF and UF/Na-KSF composite. The values for free FA for UF/K10 and UF/Na-K10 composite are the same and amount to 0.6%. It was concluded that the UF/Na-KSF composite has a smaller content of free FA (0.12%) compared to other UF composites. The UF/KSF composite has a higher resistance to acidic hydrolysis and lower liberated FA percent (1.2%)