Equilibrium concentration formaldehyde release from

This is sufficient for partial conversion to cellulose-hemiacetal, with a residual formaldehyde concentration of less than 0.1 wt% In the cell water. This formaldehyde concentration is enough to produce an equilibrium vapor pressure of 20 Torr of formaldehyde (34) in the wood cell. The kinetics of the formaldehyde release from water are also pH dependent (35). 

In cooperation with DSM, MCN developed a method of measurement for the determination of the formaldehyde release from particle board, based on a theorie for mass transfer, implying that under steady state conditions the emission of formaldehyde of a given particle board can and should be defined by two parameters of the particular board. These two parameters are (1) Ce defined as the equilibrium formaldehyde concentration (with ventilation rate 0") and (2) kgg defined as the overall mass transfer coefficient of the board. In (ideal mixed) climate rooms the stationary formaldehyde... 

In dynamic (ventilated) chambers, release rate coefficients were increased by a factor of 4.4 for particle board and 2.2 for plywood at loadings of 1.4-1.6 m /m over values at loadings of 9-11 m2/m3 (Table IV). Increased pressure of formaldehyde in the chamber was associated with reduced release of formaldehyde from wood products, as indicated by comparing equilibrium concentrations of formaldehyde (H). 

Urea-formaldehyde (U/F) products are readily synthesised from water solutions of urea and formaldehyde at pH 7.5-9. The resulting iV,iV-dimethylol urea (DMU) is often modified by further reaction at pH 8-9 with methanol to the more stable and liquid dimethylether of DMU (dimethoxymethyl urea) as shown in Fig. 5.1. These reactions are equilibrium reactions with significant concentrations of the starting compounds. These equilibria are the reasons for the high content of free and easily released formaldehyde found with U/F products. Because of their high reactivity, unmodified U/F finish baths must be used within a few hours. The high stiffness and firmness of the U/F finish can be important for rayon fabrics which often are considered too limp when compared with cotton. The U/F finish gives the best elastic resilience. ... 

As the system is initially far from equilibrium, it was proposed" that the decomposition of the carboxonium intermediate is favored, allowing a rapid buildup of formaldehyde until a steady-state concentration of 4 x 10" mol 1 is reached, a value that is comparable with that reported (6 X 10" mol 1") in the early study of Jaacks and Kem in the case of polymerization ofTOX at 30 °C in CH2CI2 solution (a much longer induction period). The subsequently formed TEOX is then protonated and releases formaldehyde and longer oxymethylene sequences, which favor the formation of the polymer and shorten the indurtion period." " ... 

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