Tanning material analysis

Analysis of tanning materials may comprise qualitative analysis for detecting and distinguishing them and quantitative analysis for the estimation of the proportions of the different components, especially of the tannin. 

The principal methods for the quantitative analysis of tanning materials are given below. 

Total acid number (TAN) is a measure of the amount of acid or acid-like material in the oil sample. Because new oils contain additives that affect the TAN number, it is important to compare used oil samples with new, unused, oil of the same type. Regular analysis at specific intervals is important to this evaluation. 

Quantitative analysis of tanning products (raw materials and extracts) requires firstly rational sampling and then suitable preparation of the sample and solution, and includes mainly determinations of the total soluble matters, the tannins and non-tannins, water and insoluble substances.1 Other determinations sometimes made are those of the ash, sugar and sulphurous anhydride, and in industrial practice the specific gravity and colour of the solutions are often measured. 

The dynamic mechanical response of a material can be characterised through the loss modulus, the loss tangent, tan S, or the loss compliance, However, as already mentioned for Ar-Al-PA (Sect. 6), the loss compliance can be considered the most relevant parameter for quantitatively comparing different materials, at least for additive purposes. For this reason, the semi-quantitative analysis and the comparison of viscoelastic data determined for different systems have been performed [63] in terms of /", whereas the determination of activation energies and entropies are based on loss modulus data. 

The above equations allow us to solve for Tc, 7), Tan, Tca, Nh2, Nh2o- No2 (bars have been dropped) as a function of time. As in the model of the prior section, an additional assumption is needed namely, that the Tumped internal conditions for the anode and cathode gases will be the average of the inlet and outlet values. The given parameters for this analysis are all the cell design parameters (geometry, materials, properties, etc.), the input temperatures, pressures, mass flow, and compositions of the anode and cathode gases, and the load current on the cell. Such a simple set of coupled ordinary differential equations is readily solved via Matlab-Simulink, and a sample case is presented in Section 9.5. 

Dynamic mechanical analysis (DMA). This technique is mainly used for determining the viscoelastic properties of a sample. The sample is subjected to an oscillating deformation and the amount of energy stored or lost is measured. In a purely elastic material, Hooke s law will be obeyed and the stress and strain will be in-phase. In a viscoelastic material, the ratio of the viscous (or dissipating) energy to elastic (or storage) energy is obtained as tan 8. 

Another possibility of determining the gel point with the help of rheological methods is dynamical mechanical spectroscopy. Analysis of change of dynamic mechanical properties of reactive systems shows that the gel point time may be reached when tan S or loss modulus G" pass a miximum [3,4,13], Some authors proposed to correlate the gel point with the intersection point of the curves of storage and loss moduli, i.e., with the moment at which tan 5 = 1 [14-16], However, theoretical calculations have shown that the intersection point of storage modulus and loss modulus meets the gelation conditions only for a certain law of relaxation behavior of the material and the coincidence erf the moment of equality G = G" with the gel point is a particular case [17]. The variation of the viscosity... 

Strain rate of 5x10" s , while the strain rates within the epoxy surface layer are in the order of 10 s under fretting conditions. Accordingly, the values of the octahedral shear stress at the onset of yield are probably underestimated. In addition to the limited viscoelastic response of the epoxy material at the considered frequency and temperature (tan 8 = 0.005 at 25°C and 1 Hz, table I), this analysis supports the validity of a global elastic description of the contact stress environment. 

For the yield stress in compression, deviations from Tabor s relation giving values of 2Yc are found. This is presumably due to the elastic strain of the indented material. A detailed analysis of the H/Yc ratio on the basis of mechanical models of elastoplastic indentation reveals that H/Yc linearly increases with ln[(tan/3Ec)/Yc]. Compression-moulded (chain-folded) PE samples, which present the lowest crystallinity of all the samples investigated, also show the lowest H/Yc ratio as a consequence of the comparatively large elastic strains. 

Describes the estimation of RDX HMX by nonaqueous titrimetry analysis of HMX, Poly (2,2-dinitropropyl-actylate, silica, and ethyl methyl 4,4-din itropen tan oate in expls determination of PETN silica in LX-02-1 spectrophoto-metric detn of acetyl tributyl citrate in ex-tnidable expl LX-02-1 analysis of a mixt of HMX, Viton oxamide analytical procedure for RDX in RX-05 analysis of tungsten HMX in RX 12 analysis of a mock e q l 90010 analysis of a mock material for LX-0-4-1 and determination of cyanuric acid, melamine, and Viton in mixt LM-04-0... 

---