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Search Results: 1 - 10 of 1400 matches for " UF resin "
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Short Communication—A Novel Sample Preparation Method That Enables Ultrathin Sectioning of Urea-Formaldehyde Resin for Imaging by Transmission Electron Microscopy  [PDF]
Adya P. Singh, Arif Nuryawan, Byung- Dae Park
Microscopy Research (MR) , 2013, DOI: 10.4236/mr.2013.11001
Abstract: Urea-formaldehyde (UF) resin is widely used as an adhesive for the manufacture of a range of wood and fiber based products. Although the microstructure of this resin has been examined at high resolution by field-emission scanning electron microscopy and atomic force microscopy, transmission electron microscopy (TEM) has thus far not been used, perhaps because of difficulties in ultrathin sectioning this resin in cured (polymerized) state. In the technical note presented here, a novel sample preparation method is described which enabled us to examine the microstructural morphology of UF resin by transmission electron microscopy in ultrathin sections, revealing the presence of spherical particles within the resin. Our initial attempt to ultrathin section the resin directly was not successful as it was too brittle to trim blocks for sectioning. Then, we developed a sample preparation technique that involved impregnation ofPinus radiatawood tissues with the UF resin, and then embedding of resin impregnated wood tissues with Spurr’s low viscosity embedding medium, which has been widely employed in plant and wood ultrastructure work. The TEM images illustrated and the information on the microstructural morphology of the UF resin presented are based on this novel sample preparation approach.
UF-pMDI Hybrid Resin for Waterproof Particleboards Manufactured at a Shortened Pressing Time
Dorota Dziurka,Rados?aw Mirski
Drvna Industrija , 2010,
Abstract: The aim of the study was to determine properties and potential shortening of pressing time of particleboards resinated with urea-formaldehyde (UF) resin thanks to its modification with pMDI (polymeric 4,4’ - methylene diphenyl isocyanate), introduced to the resin at 2.5 – 10 %. Tests showed that strength properties and water resistance of manufactured boards were improved with the increase of the pMDI amount introduced to UF resin. Furthermore, particleboards manufactured at a shortened pressing time were characterized by better mechanical and physical properties than those of reference boards manufactured under identical conditions, resinated with pure UF resin. It should be emphasized that boards, manufactured with a 10 % share of pMDI in the glue mixture, irrespective of their pressing time, were characterized by water resistance measured by the V100 test at the level required by the standard for exterior boards not bearing loads (type P3).
Influence of uron resins on the performance of UF resins as adhesives for plywood
Gao,Wei; Li,Jianzhang;
Maderas. Ciencia y tecnología , 2012, DOI: 10.4067/S0718-221X2012000100001
Abstract: uron resin, a kind of urea-formaldehyde (uf) resin containing much more uron structure, were prepared. several modified uf resins were obtained from mixing uron resins with normal uf resins as well as synthesizing uf resin with uron resin as raw material. this work demonstrated that the introducing of the uron structure reduced free formaldehyde content of uf resin and formaldehyde emission levels in bonded plywood panels significantly, the former were reduced by 76% and 84% in the latter. the synthesis time of uron resin can be shortened to 8 hours. the test result of free formaldehyde content, formaldehyde emission levels and bond strength indicated that specimen of 20 parts uron resin synthesized in 8 hours mixed with 100 parts uf resins (f/u molar ratio of 1.3) had a potential advantage to industrial application. the beneficial effect of uron resin on the performance of uf resin can be attributed to the opening of uron cycle structure and the following reaction with free formaldehyde and its oligomeric glycol forms.
Influence of uron resins on the performance of UF resins as adhesives for plywood
Wei Gao,Jianzhang Li
MADERAS : Ciencia y Tecnología , 2012,
Abstract: Uron resin, a kind of urea-formaldehyde (UF) resin containing much more uron structure, were prepared. Several modified UF resins were obtained from mixing uron resins with normal UF resins as well as synthesizing UF resin with uron resin as raw material. This work demonstrated that the introducing of the uron structure reduced free formaldehyde content of UF resin and formaldehyde emission levels in bonded plywood panels significantly, the former were reduced by 76% and 84% in the latter. The synthesis time of uron resin can be shortened to 8 hours. The test result of free formaldehyde content, formaldehyde emission levels and bond strength indicated that specimen of 20 parts uron resin synthesized in 8 hours mixed with 100 parts UF resins (F/U molar ratio of 1.3) had a potential advantage to industrial application. The beneficial effect of uron resin on the performance of UF resin can be attributed to the opening of uron cycle structure and the following reaction with free formaldehyde and its oligomeric glycol forms.
Desenvolvimento de queijo minas frescal adicionado de Lactobacillus acidophilus produzido a partir de retentados de ultrafiltra??o
Ribeiro, Eliana Paula;Sim?es, Luciana Guedes;Jurkiewicz, Cynthia Hyppolito;
Ciência e Tecnologia de Alimentos , 2009, DOI: 10.1590/S0101-20612009000100004
Abstract: probiotic brazilian minas soft cheese was produced by ultrafiltration. cheese was produced from retentates obtained from ultrafiltration of milk with a volumetric concentration factor of 5:1. the pasteurized retentates were inoculated with 106, 107, and 108 cfu.ml-1 of lactobacillus acidophilus. the viability of l. acidophilus, protein breakdown, and ph changes were monitored during cheese storage at 5 oc for 1, 7, 14, 21, and 28 days. the chemical composition and the sensory acceptability of the cheese were also determined. the experimental design consisted of complete blocks with one variable, three levels, and three replications. the results show that different populations of l. acidophilus did not significantly change cheese composition, ph, and proteolysis (p > 0.05). the population of l. acidophilus during the 28 days of storage period was not significantly affected (p > 0.05). the sensorial analysis showed a non-significant preference among the three types of cheese. it can be said that the probiotic brazilian minas soft cheese produced from retentates has a great potential as a probiotic food.
Evaluación de tres adhesivos en la fabricación de tableros enlistonados de Aspidosperma quebracho blanco estabilizado con polietilenglicol
Sanabria, Ernesto Osvaldo;Cayré, María Elisa;Frank, Walter Adrián;
Revista Chapingo. Serie ciencias forestales y del ambiente , 2011, DOI: 10.5154./r.rchscfa.2010.05.030
Abstract: this study analyzed what type of adhesive is most suitable for use in the manufacture of aspidosperma quebracho-blanco wood blockboards impregnated with polyethylene glycol (peg). three types of adhesives that could potentially be used to form the boards were analyzed: polyvinyl acetate (pvac), urea-formaldehyde (uf) and phenol-formaldehyde (pf). bond quality was determined by the glue-line strength in boards made with impregnated and non-impregnated wood. the use of peg as a stabilizer of aspidosperma quebracho-blanco wood did not interfere in the adhesion process when uf and pf adhesives were tested. the pvac adhesive decreased (<15%) the resistance of the glue line in comparison with the non-impregnated wood. the adhesive that performed the best according to the spanish standard une 56-777-92, pertaining to the determination of glue-line strength, was the uf one. the pvac and pf adhesives failed to reach the minimum specifications of 10 nmm-2 even in those boards manufactured with non-impregnated wood.
Comparison between the irrigation qualities of conventional tertiary and UF + RO advancedtreated wastewaters  [PDF]
Abdallah Abusam, Bader Al-Anzi
Agricultural Sciences (AS) , 2011, DOI: 10.4236/as.2011.24068
Abstract: The Ultrafiltration and Reverse Osmosis (UF + RO) membrane system is nowadays frequently used in wastewater reclamation. The almost complete removal of the dissolved elements, however, raises concerns about the suitability of the water treated by this system for agricultural irrigation. This study compared the irrigation qualities of UF + RO permeate and conventional tertiary effluent, using the WHO guidelines. Obtained results indicated slight to moderate degrees of restrictions are required for the reuse of the tertiary effluent as agricultural irrigation water, while no restrictions are needed for the UF + RO permeate. But it had also been found that the UF + RO system unnecessarily deprive the reclaimed water from nutrients and organic matters, which would have been recycled beneficially through agricultural irrigation.
Application of Salt Whey from Egyptian Ras Cheese in Processed Cheese Making  [PDF]
Sameh Awad, Nour Elhoda Ahmed, Morsi El Soda
Food and Nutrition Sciences (FNS) , 2013, DOI: 10.4236/fns.2013.49A2011
Abstract:

The objective of this study was to evaluate characteristics of processed cheese made from salt Ras cheese whey and young Cheddar containing exopolysaccharide producing cultures (EPS) as compared with those in cheese made from EPS-negative cheeses. Processed cheeses were manufactured using young (1 day) or 1-month-old EPS-positive or EPSnegative Cheddar cheese and replacing the added water by Ras cheese whey or ultrafiltrated (UF) whey. Moisture and fat of processed cheese were standardized to 54% and 23%, respectively. Exopolysaccharide-positive processed cheese was softer, less chewy and gummy than the EPS-negative cheeses. The hardness and chewiness were lower in processed cheeses made from 1-month-old Cheddar than in the corresponding cheeses made from 1-day-old Cheddar cheese. Sensory scores for texture of EPS positive processed cheeses were higher than those of the EPS-negative cheeses. Generally, processed cheese made from replacing all added water with whey received higher scores in flavor and overall than did the corresponding cheeses made without whey. The obtained results are showing promise for application of salt whey in processed cheese making.



Modelling Best Oil Palm Site Planting in Njimom, West-Cameroon: A GIS-Analysis Combining Weighted Linear Combination, Fuzzy Analytical Hierarchy Process and Utility Function  [PDF]
Alfred Homère Ngandam Mfondoum, Roland Bruno Ngouyamsa Mfondoum, Pauline Ngùet Wokwenmendam, Paul Gérard Gbetkom, Marthe Ntengo
Journal of Geographic Information System (JGIS) , 2019, DOI: 10.4236/jgis.2019.112011
Abstract: Oil Palm (Elaeis guineensis Jacq.) has recorded a boom production the last decades and its main productive zone is inside the tropics that meet the best biophysical conditions. Investors as well as geospatial practitioners are increasingly interested on the best growing and harvesting conditions. So said, the aim of this paper is to select the best oil palm planting site through the best methods combination. The study area is the district of Njimom located in the west-Cameroon, transitional between the equatorial and the climatic zones. In the same GIS environment, the Weighted Linear Combination (WLC) and Fuzzy Analytic Hierarchy Process (FAHP) respectively highlight the subtle differences between capability and suitability, while the Utility Function (UF) helps to assess the consideration of sustainability aspects. The first results consist in eight layers representing natural conditions, that is rainfall, temperatures, sunshine, slope, elevation, soil richness, soil moisture and forest cover, recoded in six classes ranked from 5 to 0 according to the FAO standardised scale. They are crossed using the straightforward method of WLC to give the “Capability layer”. The second results consist in three layers related to the social-economical constraints for production, as built-up area, distance to road and distance to rivers. These layers are recoded in binary with 1 and 0, they are weighted by the FAHP priority vector and membership approach to give the “suitability layer”. Then, the number of occurrences of each aspect of the sustainability is counted in each of the two preceding processes to perform the UF. The resulting value, that is 0.542 for the capability process and 0.315 for the suitability process, serves to weight their respective layers, and their sum gives the final map with the best oil palm site planting in the northern part of the study area, on about 34,950 ha, representing 44.8% of Njimom district.
Microleakage of Nanofilled Composite Resin Restorative Material  [PDF]
Ibrahim Hamouda, Hagag abd Elkader, Manal F. Badawi
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2011, DOI: 10.4236/jbnb.2011.23040
Abstract: The role of nanofillers in reducing the microleakage of dental composite resins has not been previously investigated. So this study was designed to evaluate microleakage of nanofilled composite resin in comparison to the conventional hybrid composite. Twenty extracted sound molars were selected. Class II cavities were prepared. All cavities were etched (enamel and dentin) with 37% phosphoric acid. Dentin bonding agents were applied to etched tooth surfaces and restored with nanofilled and hybrid composite restorative materials. The restored teeth were thermocycled. Specimens were immersed in 2% methylene blue dye, sectioned along the mesio-distal direction; dye penetration of occlusal and gingival margins of each section was evaluated using a stereo-microscope. No significant difference was found between the microleakage of nanofilled and hybrid composite restorations at occlusal / enamel and at gingival / dentin margins. Also, there were no significant differences for nanofilled composite restorations at occlusal / enamel margins and gingival / dentin margins. On the other hand, there were a significant differences for hybrid composite restorations at occlusal / enamel margins and gingival / dentin margins.
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