Viscosity measurements, degradation

Fig. 5.—The partial degradation of decamethylene adipate polyester with small percentages of decamethylene glycol (experiments 8, 13, and 17), or with lauryl alcohol (experiment 19), at 109°C, catalyzed with 0.1 equivalent percent of p-toluenesulfonic acid. The fraction of added glycol, or alcohol, unassimilated has been calculated indirectly from melt viscosity measurements and is plotted on the logarithmic ordinate scale.2 ...

Figure 13.20 The rate of thermal degradation of PET as a function of the intrinsic viscosity measured at different temperatures 1, 280 °C 2, 290°C 3, 300°C 4, 310°C [29b, 29c, 39], From Thermal degradation of PET. A kinetic analysis of gravimetric data, Covney, J. D., Day, M. and Wiles, D. M., J. Appl. Polym. Sci., 28, 2887 (1983), copyright (1983 John Wiley Sons, Inc.). Reprinted by permission of John Wiley Sons, Inc.

Osborn [13] reported work on 25 im (1 mil) thick oriented PET film exposed either to a carbon arc or to fluorescent light sources using inherent viscosity measurements to track the degradation and related them to the number-average... 

The oxidative degradation of polyfvinyl alcohol) is followed at 25 °C by viscosity measurements in an Ostwald viscometer (capillary diameter 0.4 mm). One proceeds as follows ... 

A third evaluation which can be applied to good effect to describe the processability of the polymer is a variable-load melt viscosity measurement. A precaution here is to conduct this test last, on the scraps left over from other physical testing, since the temperature in the rheometer may degrade the precious material irreversibly. A variable-load capillary rheometer simulates extrusion and may thereby provide the strand for evaluation of qualitative... 

Strips of JPN proplnt, containing 51.4 weight percent NC, 42.9 NG, 3.23 diethyl phthalate, 1.25 K sulfate, 1.00 ethyl centralite, 0.2 carbon black, and 0.02 candelilla wax, were exposed to total doses of 1 to 5 x 106 R at a dose rate of 1.93 x 10s R/hr at Co60 sources at Brookhaven National Laboratory. Significant changes were observed in the viscosity of NC, the available centralite stabilizer, and the stability of the proplnt. Viscosity measurements indicated the degradation of the NC polymer chains. The highest dose sample was approx comparable in stability to a similar proplnt produced by an... 

Bradley, T. D., and Mitchell, J. R. (1988). The determination of the kinetics of polysaccharide thermal degradation using high temperature viscosity measurements. Carbohydr. Chem. 9 257-267. 

Curing the quinone-sensitized photooxidative degradation of polystyrene film and its solution in benzene,an initial rapid decrease of average molecular weight has been observed by viscosity measurement (Fig.8) and GFC (Fig.9) (10 ). 

Fig. 61. Changes in the number average molecular weights of polyoxymethylene during degradation at 170°C. (The molecular weights were obtained via viscosity measurements.) [227],...

Samples of pectins with varying degrees of esterification (0-60%) were obtained from this preparation by deesterification with alkali and with enzyme. The main characteristics of these samples are indicated in Table I. It is likely that the action of alkali leads to pectic molecules in which free and methyl esterified carboxylic acids are randomly distributed (1 ). The temperature was chosen in order to minimize chain-cleavage by B-elimination ( ) and intrinsic viscosity measurements of the samples (sodium form in 0.1 M NaCl) showed that the degradation was minimal (15). 

Allcock studied the thermal degradation of poly [bis (trifluoroethoxy )-phosphazene] via gel permeation chromatography and solution viscosity measurements on samples aged at 150°-300°C (II) in sealed, evacuated tubes. The mechanism of degradation was presented as a two-step process (1) chain scission at weak links and (2) depolymerization to cyclic oligomers. Allcock also reported similar studies on the thermal breakdown of poly [bis (phenoxy) phosphazene] and arrived at the same degradation mechanism (12). 

Thermal Degradation Techniques. PFAP(II) samples (5.0g) were contained in small glass Petri dishes and placed in forced-air ovens maintained at 135°, 149°, 177°, or 200°C =b 2°C for the specified time intervals. The weight loss of these samples was monitored as a function of aging time. Small portions of these samples were dissolved in acetone for viscosity measurements and in dimethylformamide for GPC studies. 

FIGURE 10.32 Degradation effects on steady shear viscosity measurements for polyacrylamide 1000-wppm solution as a function of circulation time. 

Torikai et al. [1994] compared the effects of gamma irradiation of films of PS/PMMA blends and PS-PMMA copolymer (co-PS-PMMA) (Table 11.9). Polymer films were cast from methylene chloride solutions and were dried under vacuum. Based on the UV and FTIR spectroscopy, and viscosity measurements, Torikai et al. [1994] concluded that whereas the presence of PS in the copolymer provided protection against radiation-induced degradation to the PMMA units, similar... 

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