Cellulose acetate history

Tliere is another type of application where the damping effect of plastic structures can be used to advantage. It has a long although not obvious history. The early airplanes used doped fabric as the covering for wings and other aerodynamic surfaces. The dope was cellulose nitrate and later cellulose acetate that is a damping type of plastic. Conse-... 

M. Raheel, History of cellulose acetate fibers , pp. 142-168, in Manmade Fibers Their Origin and Development. Proceedings of an international symposium, ed. R. B. Seymour and R. S. Porter, Elsevier, London, 1993. 

The development of asymmetric membrane technology in the 1960 s was a critical point in the history of gas separations. These asymmetric structures consist of a thin (0.1 utol n) dense skin supported on a coarse open-cell foam stmcture. A mmetric membranes composed of the polyimides discussed above can provide extremely high fluxes throuj the thin dense skin, and still possess the inherently hij separation factors of the basic glassy polymers from which they are made. In the early 1960 s, Loeb and Sourirajan described techniques for producing asymmetric cellulose acetate membranes suitable for separation operations. The processes involved in membrane formation are complex. It is believed that the thin dense skin forms at the... 

Figures 8a-c show typical DSC melting endotherms for water in membranes 1-3. The shapes of the peaks, compared to that for pure water in Figure 8d, are quite complex, and give the appearance of two endothermic events near 0°C. This may be due to interaction of water with the polymer film as suggested by earlier workers who have made similar observations in hydrogels (8, ) and in cellulose acetate membranes (10). or perhaps to a change in thermal conductivity of the sample during melting (11). In any case, the shape of the endotherm does depend on the thermal history of the sample, as shown in Figure 9, while its total size remains unchanged within the precision of the experiment.

Large body of information is available on the plasticization of cellulose acetate beearrse of the long history of the polymers and the wide spread applications for plasticized eellrrlose acetate. " The following plasticizers and plasticizing compounds are frequently rrsed ... 

The last section Applied Aspects of Membrane Gas Separation contains three chapters. Brunetti et al. start their contribution with a brief review of membrane materials and membranes used in gas separation and survey the main directions of industrial applications of gas separation (hydrogen recovery, air separation, etc.). In the second part of their chapter they present a new concept for comparison of membrane and other, more traditional, methods for gas separation. Their approach includes a consideration of engineering, economical, environmental and social indicators. Something similar had been written 15 years ago [2] but this analysis is now rather outdated. White (Chapter 15) focuses on a specific but very important problem in industrial gas separation membrane separation of natural gas. The main emphasis is on cellulose acetate based membranes that have the longest history of practical applications. This chapter also contains the results of field tests of these membranes and considers approaches how to reduce the size and cost of industrial membrane systems. The final chapter is an example of detailed engineering... 

It seems that mixing has been a natural tendency for the human beings from the dawn of civilization. No sooner do two materials become available than someone starts experimenting with them. Blending is a natural way to widen the range of properties. This has been well illustrated by the history of polymer blends. When in 1846 only natural rubber, NR, and gutta percha, GP, were available, these were blended. Once nitrocellulose, NC, was invented, its blend with NR was patented in 1865 — three years before commercialization of NC. Then cellulose acetate, CA, was invented — blends of CA with NC were... 

HISTORY OF CELLULOSE ACETATE MEMBRANE 2.2.1 Development of Loeb-Sourirajan Membrane... 

Plastics are made up of polymers and other materials that are added to them to give the desired characteristics. Natural polymeric materials such as mbber, shellac and gutta percha have a long history as raw materials for man. The first thermoplastic, celluloid, was also manufactured from a natural product, from cellulose. Even today, there are still some cellulose based plastics, i.e., the cellulose acetates (CA). Cellulose is already composed of the large molecules that are characteristic of plastics (macromolecules). However, to manufacture CA plastics, they still have to be prepared with acetic acid. The first injection moulding machine was built and patented in 1872 in order to mould cellulose materials. 

Cochineal extract (Colour Index 75470, E 120)is the final alcohol-free material obtained after aqueous ethanolic extraction of the dried bodies of the female scale insect Dactylopius coccus Costa which lives on cacti such as Opuntia or Nopalea coccinellifera a species indigenous to Peru and Mexico, although also found in the Canary Islands. In practice a simpler procedure consists of aqueous alkaline extraction. The colourant principle is carminic acid which is more well-known in the form of carmine, an aluminium chelate of carminic acid, a material insoluble in water and stable on the acidic side. A uv spectrophotometric study has been made (ref. 21). Thin layer chromatography of cochineal has been examined on acetylated cellulose with the solvent system, ethyl acetate-tetrahydrofuran-water (6 35 47) in which the Rf was 0.94 (refs.22,23). The history of the chemistry of cochineal has been discussed (ref.24). 

An important factor in the esterification reactivity of cellulose is the history of its method of manufacture and pretreatment or activation prior to the reaction. Since cellulose is insoluble in the acGtylation solvent and is in a fibrous form, it is necessary to make the hydroxyl groups as accessible to the acetylating agent as is possible. The pretreatment or activation is designed to accomplish this. Soaking the cellulose in acetic add or aqueous acetic add prior to esterification greatly improves its reactivity. 

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