Cellulose objects

Experiment 14. Purification of proteins on DEAE-cellulose Object... 

With the aid of equations (33) and (34) the orientation factor and the average angle of orientation of uniaxially oriented cellulose objects can be computed, if their birefringence is measured. This may be of some use in botanical work and in fibre research. It is necessary, however, to use the correct values of % and n jj. For practical purposes it will be sufficient to discriminate between native cellulose and regenerated cellulose. Further, the moisture content must be taken into account. The figures of % and n y for the usual density of 1.555 in native and 1.520 in regenerated fibres, adjusted to the usual regain at 65 % rel. humidity which the fibres attain if first swollen in water and then conditioned in air of this humidity, arc listed in Table 9. 

Cellulose nitrate also has widespread use as an adhesive and coating material. Whereas stabilizers are added to products, eg, sodium carbonate as a neutralizer, many conservators are hesitant to use cellulose nitrate materials because of the inherent instabiUty and the dangers to the object from nitric acid, formed when the nitric oxide combines with moisture. 

Compression and injection molding are used with amino resins to produce articles such as radio cabinets, buttons, and cover plates. Because melamine resins have lower water absorption and better chemical and heat resistance than urea resins, they are used to produce dinnerware and laminates used to cover furniture. Almost ah molded objects use fillers such as cellulose, asbestos, glass, wood flour, glass fiber and paper. The 1997 U.S. production of amino resins was 2.6 billion pounds. 

The objective of this research was to examine the effect of crystallinity, additives and data analysis technique on isothermally pyrolyzed cellulose. The Ea, activation enthalpy (AH+) and activation entropy (AS+) were determined from the mass loss rates. This data was used to develop an understanding of how cellulose pyrolysis is affected by crystallinity and additives and how the results obtained are dependent on the data analysis technique. 

It is probable that varying degrees of ordering of chains exist in a cellulosic material and that a sharp differentiation of crystalline and non-crystalline celluloses may not be feasible or even possible. Theoretically, the lateral surfaces of crystallites are amorphous but may have far less importance in determining such properties as strength, flexibility and extensibility than the non-crystalline cellulose which supplies continuity of structure in the direction of crystallite orientation. Yet properties like moisture absorption and swelling may be more dependent upon the amount of cellulose which exceeds a certain degree of disorder (permeability) than upon location. The definition of crystallinity may, therefore, be made ultimately in terms of practical objectives. 

Random copolymerization of one or more additional monomers into the backbone of PET is a traditional approach to reducing crystallinity slightly (to increase dye uptake in textile fibers) or even to render the copolymer completely amorphous under normal processing and use conditions (to compete with polycarbonate, cellulose propionate and acrylics in clear, injection molded or extruded objects). 

The objective of this work is to determine the surface concentration of the hydroxyl groups of cellulose and PVA films utilizing their chemical modification. We chose these polymers mainly because the hydroxyl group is their sole functional group. Recently we have reported that a cellulose film is more excellent in wettability towards water than PVA, though cellulose is insoluble in water, in contrast to PVA(4). Since only the chemical composition of the surface must be responsible for water... 

The prime object of the present study was to determine the compositional polydlspersity of commercial cellulose triacetate and to examine the effect of molecular weight and molecular weight distribution on the mechanical properties of the fibres. 

Measurement of pH is a potentiometric technique frequently used for measuring the degree of the deterioration of materials that are subjected to natural aging. The determination of pH levels is commonly carried out on ethnographic objects manufactured with parchment or leather, and it is especially relevant in altered paper due to the formation of acidic compounds from the decomposition of the woodpulps and other raw materials, which can induce the hydrolysis of the cellulose and then decrease the resistance and mechanical properties of the document [29]. 

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