Spectra cellulose acetate

All polymers utilized in this investigation have been listed in Table 2, along with their supplier and the concentration range over which they were tested. Polymers were either used as received or purified by filtration through a 0.22 or 0.45-pm MiUipore cellulose acetate membrane. For aseptic applications autoclaving was carried out for 20 min at a temperature of 121 °C. Qualitative properties of each polymer are listed in Table 3. For polymers supplied as solutions, dialysis was carried out in membranes (Spectrum Medical Industries, Houston, TX) with a MWCO of 10,000 daltons. 

Figure 10. IR spectrum of normal cellulose acetate membrane...

Figure 10 shows the IR spectrum of a normal cellulose acetate membrane. Figure 11 shows the spectrum of the hydrolyzed membrane. The decrease of absorption around 1,720 cm, and the increase of absorption around 3,200 to 3,500 cm are shown. The first peak correspond to the C = 0 double bond, and the second to the 0 - H single bond. These spectra show the decrease of the acetyl content in the membrane. 

Membranes manufactured by Spectrum Separations, Inc., a subsidiary of SEPAREX CORPORATION, are of the cellulose acetate type. They are similar to those made for reverse osmosis except they must be dried for gas separation use. A proprietary process is used to accomplish this so that the membrane does not collapse and lose its asymmetric character upon removal of the water. 

Figure 7. Brillouin spectrum of a commercial cellulose-acetate film...

Figures 2B-E show Che IR-ER spectra for a 170 10 nm cellulose acetate film at GC as a function of hydrolysis time. Figure 2B is the spectrum of the film prior to hydrolysis. Figures 2C-E are IR-ER spectra for the film at hydrolysis times of 40, 50, and 80 min, respectively. Optical dispersion effects, which are enhanced due to the low IR reflectivity of materials such as GC, cause the observed band-shape distortions in the reflection spectra (38)- I or short Immersion times ( 40 min), the changes in the absorbances for Che acetate marker bands (1731 and 1234 cm ) suggest a reaction mechanism that is consistent with the hydrolysis of an ester. For example, at an immersion time of 40 min the integrated absorbances of the acetate markers decrease by about 3SZ whereas chat for Che marker for the polymeric backbone (1052 cm ) decreases only by 14Z. Althou not shown in the figure, the decrease in the acetate composition of the film is accompanied by an increase in the number of hydroxyl groups of the film. These data indicate that at short immersion times the composition of the film evolves from Chat of cellulose acetate to one which is more "celluloslc" in nature.

Figure 2. Infrared spectra for cellulose acetate films at silicon and glassy carbon. (A) Transmission spectrum for a 1.85 0.01 im film at silicon (B E) IR-ERS spectra for a 170 10 nm film at glassy carbon as a function of base hydrolysis (B) 0 min. (C) 40 min. (0) 50 min. and (E) 80 min. hydrolysis. Reflection spectra were acquired at an angle of Incidence of 60 with p-polarlzed llgiht.

Numerous multipulse and two dimensional experiments are used to identify unknown (co)polymers and these experiments are most useful in analyzing differences between copolymers or impurities in production problems. The Distortionless Enhancement via Polarization Transfer (DEPT) pulse sequence is frequently used to determine the carbon multiplicity (CH vs. CHj vs. CH3) of a carbon spectrum. Newmark showed excellent DEPT spectra could be obtained on sidechain groups in vinyl polymers or in typical polyesters and polyurethanes, but that it was difficult to observe good DEPT spectra (at 200 MHz) on backbone carbons, such as the ring carbons in cellulose acetate butyrate (CAB) with very short carbon spin-spin relaxation times (Tj) (8). 

Figwre 7. 2D gCOSY spectrum of cellulose acetate butyrate (CAB), 1 transient 256 increments (9 minutes). Contour spacing in all figures is a factor of 1.7. 

Figure 15.6. Most peaks disappeared for carbon membranes when the temperature was higher than 550, and the new characteristic absorption peaks were found at 2350 cm and 670 cm which contribute to the CO2 adsorbed in carbon matrix or C=0 bond formed in the membrane surface and the aromatic =C-H out of plane deformation. In vacuum condition, the characteristic absorption peak of CO2 also appears in the FTIR spectrum which indicates the CO2 comes out during the decomposition of deacetylated cellulose acetate and adsorbs strongly in the carbon matrix.

Figure 4 shows the off-resonance proton decoupled C NMR spectrum of the cellulose acetate-polyacrylonitrile graft polymer. The spectrum of the graft polymer showed a) the carbonyl carbon of the acetate at 172 ppm, b) the nitrile carbon at 120, c) the carbon of the sugar at 101 ppm, d) the C2 -carbons of the sugar between 60-80 ppm, and e) the aliphatic carbons in the 10-20 ppm region. 

The IR and Raman spectra of cellulose acetate are presented in Reference Spectrum 60. A decrease (or even disappearance) in band intensity of the... 

Infrared spectra of the fiber samples were obtained from solvent-cast films of the fibers. The acrylic sample, the polyamide samples and the polyester samples were cast from hexafluoroisopropanol, while the acetate samples were cast from acetone. The infrared spectrum of the acetic acid-insoluble residue from the degraded cellulose acetate fibers was obtained from a potassium bromide disk. All infrared spectra were obtained with a Beckman 4220 Infrared Spectrophotometer. 

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