Urea Formaldehyde
Mostrando 25-36 de 41 artigos, teses e dissertações.
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25. AMÉLIORATION DE LA STABILITÉ DIMENSIONNELLE DES PANNEAUX DE FIBRE DE BOIS MDF PAR TRAITEMENTS PHYSICOCHIMIQUES
The objectives of this study were 1) to improve the dimensional stability of medium density fiberboards (MDF) by three physical or chemical treatments: a) esterification, b) maleated polypropylene wax and c) heat treatment; 2) to determine the effect of these treatments on the mechanical properties, vertical density profiles and wetting properties of the pan
Publicado em: 2005
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26. Alternative castor oil-based polyurethane adhesive used in the production of plywood
Plywood is normally produced with urea-formaldehyde and/or phenol-formaldehyde adhesives. However, the former is considerably toxic and environmentally damaging, while the latter is expensive, thus motivating the search for alternative raw materials in plywood production. The castor oil-based polyurethane adhesive developed at the São Carlos Institute of Ch
Materials Research. Publicado em: 2004-09
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27. Mechanical and physical properties of MDF panels of different densities and resin content. / Propriedades físicas e mecânicas de painéis MDF de diferentes densidades e teores de resina.
MDF Panelboards of Pinus spp fibers were prepared in laboratorial scale, with a range of densities (550 - 750 kg/m3) and urea-formaldehyde resin content (6; 8; 10; 12 and 14 wt. %), with the purpose of evaluating their mechanical and physical properties. The effect of density and resin content and their interactions were analyzed based on panel mechanical an
Publicado em: 2000
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28. Sintese de macro esferas porosas de amino polimero : aplicação em imobilização de biocompostos
The work presented here concems the synthesis of N Methylolacrylamide (NMA) and Urea-formaldehyde (DF) resins through the polycondensation reactions of the acrylamide and urea with formaldehyde. Theses resins and the acrylamide monomers were used in the synthesis of macrospheres. Their solutions were dropped in hot silicon oil; after that macrospheres of pol
Publicado em: 1996
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29. Occupational asthma due to formaldehyde.
Bronchial provocation studies on 15 workers occupationally exposed to formaldehyde are described. The results show that formaldehyde exposure can cause asthmatic reactions, and suggest that these are sometimes due to hypersensitivity and sometimes to a direct irritant effect. Three workers had classical occupational asthma caused by formaldehyde fumes, which
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30. Persistence of the ten-nucleotide repeat in chromatin unfolded in urea, as revealed by digestion with deoxyribonuclease i.
It is shown by enzymatic digestion of chromatin from rat liver or Guerin ascites tumour (GAT) that treatments, which abolish the 180 base pair repeat, as revealed by digestion with micrococcal nuclease (shearing in salt solutions of medium ionic strength, sonication, fixation with formaldehyde in the presence of 5 M urea), have little effect on the 10 nucleo
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31. Six year follow up of lung function in men occupationally exposed to formaldehyde.
The long term effects of formaldehyde on the respiratory tract have been investigated in a group of 164 workers exposed daily to the chemical during the production of urea formaldehyde resin, together with 129 workers not exposed to free formaldehyde. Exposure was classified as high (corresponding to an eight hour time weighted exposure of more than 2.0 ppm)
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32. Effect of Phloretin on Water and Solute Movement in the Toad Bladder
It is generally believed that urea crosses the cell membrane through aqueous channels, and that its movement across the membrane is accelerated in the direction of net water flow (solvent drag effect). The present report presents evidence for a vasopressin-sensitive pathway for the movement of urea, other amides, and certain non-amides, which is independent
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33. Separation and infectivity of circular and linear forms of potato spindle tuber viroid.
Potato spindle tuber viroid can be separated into two fractions by polyacrylamide gelelectrophoresis in the presence of formamide and urea. One fraction contains predominantly circular molecules; the second fraction contains almost exclusively linear molecules. The purity of the fractions was estimated by electron microscopy of formaldehyde-denatured molecul
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34. Characterization of virus-specific RNA synthesized in bovine cells infected with bovine viral diarrhea virus.
Infection of bovine kidney cells with bovine viral diarrhea virus resulted in the synthesis of a single species of virus-specific RNA. Electrophoresis of this RNA on agarose-urea and agarose-formaldehyde gels indicated that it had a molecular weight of 2.9 X 10(6), corresponding to 8,200 bases (8.2 kilobases). This 8.2-kilobase RNA was resistant to RNase A t
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35. Antimicrobial activity of silicone rubber used in hydrocephalus shunts, after impregnation with antimicrobial substances.
Colonisation of cerebrospinal fluid shunts by coagulate-negative staphylococci (Staphylococcus albus) is a serious problem. Because of its possible role in prevention of the condition, the antimicrobial activity of silicone rubber after impregnation with antimicrobial drugs was studied. The method of impregnation used and test methods were found to be import
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36. Respiratory disease in foundry workers.
A survey was carried out in a steel foundry in Brisbane to evaluate the nature and frequency of respiratory symptoms and to assess ventilatory function. The foundry used many moulding processes including the Furane, Isocure, Shell, carbon dioxide, and oil sand systems. Nasal symptoms and wheeze were often reported, particularly by workers in the general foun