Measurement Melamine

In response to these events, a spectrophotometric method was developed to distinguish protein from melamine. Also, mass spectrometric and chromatographic methods were developed to measure melamine and cyanuric acid in foods. 

In the final product, the formaldehyde has completely reacted to form a very inert thermoset resin. Spontaneous emission of formaldehyde from high pressure laminates is measured at approximately the accepted background level of 0.035 ppm (15). Melamine surfaced laminates are tested and approved for food service equipment by the National Sanitation Foundation (16). 

Hydrolysis of polyamide-based formulations with 6 N HC1 followed by TLC allows differentiation between a-aminocaproic acid (ACA) and hexamethylenedi-amine (HMD) (hydrolysis products of PA6 and PA6.6, respectively), even at low levels. The monomer composition (PA6/PA6.6 ratio) can be derived after chromatographic determination of the adipic acid (AA) content. Extraction of the hydrolysate with ether and derivatisa-tion allow the quantitative determination of fatty acids (from lubricants) by means of GC (Figure 3.27). Further HC1/HF treatment of the hydrolysis residue, which is composed of mineral fillers, CB and nonhydrolysable polymers (e.g. impact modifiers) permits determination of total IM and CB contents CB is measured quantitatively by means of TGA [157]. Acid hydrolysis of flame retarded polyamides allows to determine the adipic acid content (indicative of PA6.6) by means of HPLC, HCN content (indicative of melamine cyanurate) and fatty acid (indicative of a stearate) by means of GC [640]. Determination of ethylene oxide-based antistatic agents... 

Gierlinger, N., Hansmann, C., Roder, T., Sixta, H., Gindl, W. and Wimmer, R. (2005). Comparison of UV and confocal Raman spectroscopy to measure the melamine - formaldehyde resin content within ceU walls of impregnated spruce wood. Holzforschung, 59(2), 210-213. 

The calculation requires measurements of the extent of reaction and of the distribution of functionality on the polymer and crosslinker. The functionality of the isocyanate crosslinker is formally three although it must be recognized that all of these materials have a distribution of functionality. Fully alkylated melamines have a functionality of 6. Coatings are formulated with an excess of alkoxy to hydroxy in order to achieve rapid cure (2). Thus, not all of the melamine alkoxy groups will react (ignoring side reactions) and the effective functionality will be less than six. 

Polymer-melamine crosslinks are also broken during exposure to UV light. Although some crosslink scission occurs in the dark by direct hydrolysis, the rate of scission (as measured by the rate of disappearance of residual methoxy functionality) Increases dramatically with Increasing UV light Intensity (11). Scission occurs with UV light in the absence of humidity but at a much reduced rate. 

The effect of the interaction between two types of SPs (naphthalene formaldehyde sulfonates-NFS and melamine formaldehyde sulfonate-MFS) and the VEA on the fluidity of mortar is seen in Fig. 7.46. In the case of NFS, the mortar flow decreases with increasing addition of the VEA. This result indicates an appreciable interaction between NFS and the VEA. On the other hand, the fluidity of the mortar containing the MFS does not change. Measured amounts of the SPs showed that there was good correlation between the amount of SP adsorbed and observed fluidity. 

Figure 10.51 Melamine-cyanuric acid derivatives arranged according to their relative stability as measured by the HBI(N — 1) parameter. (Reprinted with permission from Section Key Reference 1995 American Chemical Society).

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