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Adhesives in the Wood Industry
Published in A. Pizzi, K. L. Mittal, Handbook of Adhesive Technology, 2017
The most important parameters for the aminoplastic resins (UF, melamine-fortified UF [mUF], melamine–urea–formaldehyde [MUF]) are: The type of monomers used.The molar ratio of the various monomers in the resin, such as F:U, F:M, or F:(NH2)2, whereby urea contributes two NH2 groups, and melamine three NH2 groups; the molar ratio is sometimes also expressed as F:(U + M); F, U, M, and NH2 represent moles.The purity of the different raw materials, such as the level of residual methanol or formic acid in formaldehyde, biuret in urea, or ammeline and ammelide in melamine.The parameters of the reaction procedure used, such as the pH and temperature sequence, the type and amount of alkaline and acidic catalysts, the sequence of addition of the different raw materials, and the duration of the different reaction steps in the production procedure.The achieved DOC and the MWD in the final resin.
Application of a FIGAERO ToF CIMS for on-line characterization of real-world fresh and aged particle emissions from buses
Published in Aerosol Science and Technology, 2019
M. Le Breton, M. Psichoudaki, M. Hallquist, Å. K. Watne, A. Lutz, Å. M. Hallquist
Gas phase measurements of HNCO indicated inefficient hydrolysis of HNCO, enabling HNCO to further react via several pathways, a known major problem of SCR technology (Bernhard et al. 2012; Wentzell et al. 2013). Upon initial analysis of the HNCO byproducts, the RMEHEV fuel appeared to emit more mass than the diesel buses, with biuret and triuret dominating, whereas the diesel emissions were composed mainly of cyanuric acid, HNCO and triuret. HNCO was a significant particle phase mass contributor for all SCR related peaks, which is unexpected due to its partitioning significantly to the gas phase. HNCO began to come off the filter at 84 °C and exhibited two maximum in desorption temperature (Tmax) at 182 °C and 200 °C. The desorption profile did not return to background levels after the final Tmax value and continued reporting a constant amount of counts after a small dip, suggesting a number of sources of HNCO from the filter. HNCO has a boiling point of 23.5 °C, therefore should begin to come off from the filter if present in the particle phase much earlier than observed. Urea has a melting point of 133 °C and vaporization starts around 140 °C. Upon vaporization it can decompose to form HNCO which can either further react with the remaining urea to form biuret or trimerise and form cyanuric acid. HNCO can further react with biuret to form ammelide and ammeline at temperatures up to 190 °C, with further reactions of biuret contributing to their production and cyanuric acid. At temperatures up to 250 °C, melamine can be formed via reaction of ammeline with ammonia. The ramping of temperature in the FIGAERO to 250 °C may add an unsolvable level of complexity due to the formation rates of a number of these compounds. A standard thermogram for these compounds is displayed in the supplementary (SI Figure S5) confirming the detection of these products, although production of HNCO complicates their direct quantification. We conclude that it is not possible to diagnose the exact composition of the emissions via analyzing relative desorption profiles observed by the CIMS. The high concentration of HNCO could simply be via consumption of byproducts to produce HNCO. Nevertheless, the ability for CIMS to identify these compounds enables the technique to positively confirm the production of these byproducts formed from incomplete hydrolysis of HNCO. Their detection by CIMS also confirms the emission of SCR system particle phase products into the urban atmosphere in forms other than urea and HNCO.