Nitrocellulose, low-grade

Membrane filtration has been used in the laboratory for over a century. The earliest membranes were homogeneous stmctures of purified coUagen or 2ein. The first synthetic membranes were nitrocellulose (collodion) cast from ether in the 1850s. By the early 1900s, standard graded nitrocellulose membranes were commercially available (1). Their utihty was limited to laboratory research because of low transport rates and susceptibiUty to internal plugging. They did, however, serve a useflil role in the separation and purification of coUoids, proteins, blood sera, enzymes, toxins, bacteria, and vimses (2). 

In 1855, the moldable features of collodion were exploited by the British inventor and chemist Alexander Parkes, who marketed the material as Parkesine. Combs, earrings, buttons, bracelets, billiard balls, and even false teeth were manufactured in his factories. Parkes chose to focus more on quantity than on quality, however. Because he used low-grade cotton and cheap but unsuitable solvents, many of his products lacked durability, which led to commercial failure. In 1870, John Hyatt, a young inventor from Albany, New York, discovered that collodions moldable properties were vastly improved by using camphor as a solvent. Hyatts brother Isaiah named this camphor-based nitrocellulose material celluloid. Because of its greater workability, celluloid became the plastic of choice for the manufacture of many household items. In addition, thin transparent films of celluloid made excellent supports for photosensitive emulsions, a boon to the photography industry and a first step in the development of motion pictures. 

Fortunately, the less specialized formulations do not employ such a difficult malerial in fact, only rarely does one find a water-soluble colloid. A frequently found binder material is lacquer-grade nitrocellulose (MIL-N-244A, Grade D, sometimes also Grade A), dissolved in acetone (O-A-51) or other low-boiling solvents such as ethyl acetate. Celluloid (MIL-B-10854) solutions in acetone are sometimes preferred. Usual amounts are 1.8-4.0% on a dry basis. 

Nitrocellulose of 11.8-12.3% N intended for celluloid manufacture is obtained in a way resembling the production of lacquer-grade material with the exception that the viscosity of the product is not of such decisive importance. Low viscosity of the nitrocellulose can cause the celluloid gel to be brittle, however. For this reason care should be taken to keep the viscosity above a certain limit. The essential stabilization can be carried out in boilers without recourse to autoclaves, but in order to shorten the stabilization process it is possible to carry out the kiering in autoclaves, the process then requiring only a few minutes. 

Recently interest was evinced in nitrocelluloses of very low nitration grade, e.g. 0.5-2.0% [4], They were obtained by nitrating cellulose with mixtures containing 32% HN03, 31-38% H2S04 and 32-37% H20 at 8-30°C. 

T. Urbanski (I27j suggested recrystallization to add a protective colloid such as an acetone solution of nitrocellulose (low viscosity grade collodium cotton). 

Nitrocellulose (high nitrogen grades) Car re-finishing Clear coating for wooden furniture Ketones Esters Glycol ethers Aromatic and aliphatic hydrocarbons Mainly low and medium boiling solvents. Alcohols act as latent solvents. 

A second important criterion for classification of nitrocellulose is its average MW, which is more conveniently expressed as the viscosity of its solutions. Based on this, it is classified as low viscosity, medium viscosity, and high viscosity grades. 

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