Nitrocellulose molecular weight determination

Fig. 1-11 Plot for molecular weight determination by osomotic pressure for nitrocellulose in (a) acetone, (b) methanol, and (c) nitrobenzene [18, 19].

The problem of solvent selection is most difficult for high molecular-weight polymers such as thermoplastic acryHcs and nitrocellulose in lacquers. As molecular weight decreases, the range of solvents in which resins are soluble broadens. Even though solubihty parameters are inadequate for predicting ah. solubhities, they can be useful in performing computer calculations to determine possible solvent mixtures as replacements for a solvent mixture that is known to be satisfactory for a formulation. 

Figure 3.5b shows data for a sample of nitrocellulose in three different solvents. All show the same intercept corresponding to a single molecular weight as required. Note, however, that the slopes are different, including even a negative slope, indicating that wide variations in B are possible. We examine the factors that determine B in Section 3.4. 

More recently Staudinger and Dreher [96] have confirmed these observations, by determining the effect of the time of pulping nitrocellulose in a colloid mill on its molecular weight as determined by viscosity measurement. They further established that owing to intensive milling a partial denitration of nitrocellulose took also place, as seen in Table 56. 

Using the ultracentrifuge sedimenting method, Gralen and Svedberg [40] have determined the molecular weight of nitrocellulose prepared from various types of cellulose. The nitration was carried out at 0°C by means of a mixture composed of 40% of nitric acid, 40% of phosphoric acid, and 20% of phosphorus pentoxide. The results are collected in Table 79. 

Structure of cellulose polymer and determination of molecular weight Pyrolysis of nitrocellulose Thcrmochemical properties of nitrocellulose Mixed esters nitrates and sulphates Stabilization of nitrocellulose Knccht compound Manufacture of nitrocellulose Semi-continuous methodof Bofors-Nobel-Chematur Drying of nitrocellulose Safety in the manufacture of nitrocellulose Starch nitrates (nitrosiarch)... 

Moltzer. Benoit and Doty (45) undertook the task of fractioning samples of nitrocellulose with 13.8-14.1% N. -llexane was added dropwise while stirring to 0.2% solution of nitrocellulose in acetone and several fractions were obtained. Their molecular weight was determined by light scattering, viscosity and osmotic pressure measurement. 

Low molecular weight plasticizers migrate from flexible PVC towards other surfaces in contact. There are different tests to evaluate such a process. According to ASTM D 2134 ° two sheets, one of PVC and another of nitrocellulose, are kept in contact followed by determination of nitrocellulose hardness. 

Schulz made his investigations with nitrocellulose containing 12.5— 12.7% nitrogen. (About 2.5 NO2 per Q) and with various preparations of molecular weight 50.000 — 443,000, determined with the osmotic method by extrapolation to infinite dilution. Macromolecular substances generally do not follow Van t Hoff s law, which... 

For the determination of the amino acid composition of a protein, a highly purified sample is hydrolyzed under acidic conditions to its constituent amino acids. The amino acid composition of the protein is determined from the concentrations of the individual amino acids and from the molecular weight of the protein. Because the protein sample is normally very pure, the composition of the hydrolysate is limited to amino acids commonly found in proteins. One does not have to be concerned about other endogenous amines that may interfere with the analysis. Most commercial amino acid analyzers quantify only the 20 amino acids commonly found in proteins. Therefore, the biggest challenge for this application is to produce a method with adequate sensitivity to accurately determine the amino acid composition of very small amounts (< 1 pg) of protein isolated from gels or nitrocellulose membranes. 

Cellulose and Cellulose Derivatives. The solubilization of cellulose to determine its molecular weight is delicate one of the most powerful solvents is cupriethylenediamine for which the Mark-Houwink parameters relating the intrinsic viscosity to the molecular weight ([ j] = KM" ) have been determined (see Table 4). Some authors previously prepared cellulose derivatives (nitrocellulose or cellulose tricarbanilate) to determine the molecular weight and molecular weight distribution, assuming no polsrmer degradation (72-83,91,92). 

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