Formaldehyde emission function

Figure 4. Formaldehyde emission of MDF as a function of age and molar ratio F U. (27).

Figure 2 shows the evolution of formaldehyde content of particleboards in Sweden (5,10). Table IV shows relative production rates of particleboard as a function of formaldehyde emission, using the sales data for France from CDF-Chimie. 

Table IV. French Particleboard Production as a Function of Formaldehyde Emission (% of total Sales by CDF-Chemie).

Ismail Aydin and Gursel Colakoglu, Formaldehyde Emission, Surface Roughness, and Some Properties of Plywood as Function of Veneer Drying Temperature, Drying Technology, 2005,23 1107-1117. 

The condensation pH played a significant role in increasing the Internal Bond (IB) strength tmd reducing the Formaldehyde Emission (FE). The sequential addition of urea also has a noticeable influence on resin performance. Optimum conditions for production of UF resins have been proposed and tested by the response surface methodology using the desirabUity function. 

Figure 7 Response surface for formaldehyde emission as a function of (a) tune span between urea additions and number of urea additions (for different pH values of condensation step), (b) pH of condensation step and time span between urea additions (for different numbers of urea additions), and (c) pH of condensation step and number of urea additions (for different time spans between urea additions).

Carpets emit a variety of VOCs depending upon their chemical compositions. SBR-backed carpets primarily emit 4-phenylcyclohexene (4-PCH), the chemical identified with new carpet odor, and styrene. PVC-backed carpets primarily emit formaldehyde, vinyl acetate, 1,2-propanediol, and 2-ethyl-l-hexanol. Carpets with a PU backing primarily emit butylated hydroxytoluene (BHT). Carpet emissions of VOCs are most pronounced immediately after a new carpet is laid, with emission rates falling off rapidly as a function of time, as depicted in Fig. 12.1. Even though emission rates fall off rapidly, sensitized individuals often continue to exhibit symptoms for long periods of time. 

The monitoring and toxicological studies of formaldehyde exposure, as well as studies on the emission of this chemical from wood products generate large numbers of samples to be analyzed. Furthermore, it is necessary to monitor the emissions on a routine basis during production to ensure that the material continues to release low level of formaldehyde. In homes, particularly in mobile homes, the amount of formaldehyde release depends on the construction technoloy, ventilation, indoor temperature and relative humidity, and age, structure and porosity of building materials. It is, therefore, necessary to study the emislon of formaldehyde from wood products as a function of these parameters. 

VOC emissions from tobacco plants exposed to ozone were investigated with PTR-MS in conjunction with GC-MS, and the formation of volatile Ce emissions was found to be inversely proportional to the O3 flux density into the plants [57]. Jasmonic acid, a signaling compound with a key role in both stress and development in plants who elicits the emission of VOCs, was sprayed on the leaves of the Mediterranean tree species Q. ilex, and the emissions and uptake of VOCs were detected with PTR-MS and GC-MS after a dark-light transition [58]. Monoterpene and methyl salicylate emissions were enhanced and formaldehyde foliar uptake decreased significantly 24 h after the jasmonic add treatment. The release of VOCs from eucalypt as a function of temperatures from ambient to combustion were analyzed by PTR-MS, GC-MS, and direct analysis in real time (DART) MS [59]. The biogenic VOCs seem to provide a protection against high temperatures [60] and oxidation stress [61]. 

The primary function of methyl tert-butyl ether (MTBE) as an additive in gasoline is to enhance the octane level of unleaded gasoline. By virtue of the oxygen atom it contains, it increases the oxygen-to-fuel ratio in gasoline. It has also been shown that adding MTBE results in lower emissions of carbon monoxide and hydrocarbon as well as polycychc aromatic hydrocarbons (PAHs). MTBE oxidation, initiated by hydroxyl radicals, can yield a number of products such as tert-butyl formate, formaldehyde, methyl acetate, and acetone, depending on the pathway. 

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