Search

Cellulose and some of its derivatives form liquid crystalline solutions in a variety of solvents. The present work investigates cellulose acetate phthalate/hydroxypropyl cellulose blends in N,N-dimethylacetamide, in function of concentration and composition, by rheology, considering dynamic viscometry and oscillatory shear tests. The effects of composition, concentration, shear rate, and oscillatory deformation on the rheological functions determines the orientation or mobility of the chain segments in the shear field. Atomic force microscopy and polarized light microscopy studies on corresponding films show that specific interactions, such as the hydrogen bonds between cellulose acetate phthalate and the liquid crystalline component—hydroxypropyl cellulose, stabilizes the morphology, leading to the emergence of different formations typical for lyotropic liquid crystal phases. These studies contribute to a better knowledge of the specific interactions that generate and modify the liquid crystalline properties of cellulose derivatives, required by the applications in electronic domains.

A comparative study of the influence of acetone, isopropyl alcohol and mixtures of ethanol-acetone and ethanol-isopropyl alcohol on the cellulose structure during alkalization is presented. The kinetic behavior and distribution of substituents in the carboxymethylation stage are explained tentatively. It is shown that the decrystallization is more pronounced and the proportion of cellulose I is higher for samples alkalized in ethanol-isopropanol and ethanol-acetone mixtures containing up to about 50% ethanol, as compared with those produced in isopropyl alcohol or acetone. The distribution of substituents in the C 6 position, as evaluated by 1 H NMR spectroscopy, is correlatedwith the change of the cellulose structure revealed by X-ray analysis data.

This paper reports a novel method for the synthesis of wholly aromatic polyazomethines by oxidative polymerization of monomers having a preformed azomethine linkage. Two monomers having a Schiff base type structure: N -pyrrolylmethylen-1-aminonaphthalene ( I ) and N -pyrrolylmethylen-2-aminonaphthalene ( II ) were synthesized by coupling of pyrrole 2-carboxaldehyde with 1- and 2-aminonaphthalene, respectively. Their cation-radical polymerization was performed by chemical oxidation with ammonium persulfate and iron trichloride. Aromatic polyazomethines were obtained with good thermal properties. The structures of the polymers were studied by IR spectroscopy and were correlated with Huckel molecular orbital calculations for evaluating the monomers reactivity and the most probable linkage sites of the monomer units in the polymer chain.

In a 7206 C high-speed, mist-lubricated ball-bearing, both the film thickness and lubricant parameter λ in ball—race tribo-systems have been analytically investigated in terms of starvation and thermal effects, and good correlations with experimental results were obtained for 5,000 to 35,000 rpm rotational speeds. Including a lubricant parameter in ball—race tribosystems as a safety criterion for ball-bearings, friction losses, temperature, and limit speeds have been correlated with this criterion for a 7206 C ball-bearing. Friction losses in ball-outer race tribosystems have been computed for both EHD and mixed lubrication regimes. The influence of the bricant parameter on friction losses has been shown both theoretically and experimentally. A new speed limit concept including the lubricant parameter λ, has been developed by the authors.