Plasticiser camphor

Although originally a trade name the term celluloid has come into general use to describe camphor-plasticised cellulose nitrate compositions. 

Figure 2 Poster made from cellulose nitrate in 1960s showing shrinkage due to loss of camphor plasticiser and cracking...

Comparison of Table 5.4 and 5.7 allows the prediction that aromatic oils will be plasticisers for natural rubber, that dibutyl phthalate will plasticise poly(methyl methacrylate), that tritolyl phosphate will plasticise nitrile rubbers, that dibenzyl ether will plasticise poly(vinylidene chloride) and that dimethyl phthalate will plasticise cellulose diacetate. These predictions are found to be correct. What is not predictable is that camphor should be an effective plasticiser for cellulose nitrate. It would seem that this crystalline material, which has to be dispersed into the polymer with the aid of liquids such as ethyl alcohol, is only compatible with the polymer because of some specific interaction between the carbonyl group present in the camphor with some group in the cellulose nitrate. 

The rather unexpected plasticising effect of camphor was first appreciated by Hyatt over a hundred years ago and, in spite of all that has been learned about polymers since then, no superior plasticiser has yet been discovered. 

Nitration of cellulose followed by plasticisation of the product with camphor has the effect of reducing the orderly close packing of the cellulose molecules. Hence whereas cellulose is insoluble in solvents, except in certain cases where there is chemical reaction, celluloid is soluble in solvents such as acetone and amyl acetate. In addition the camphor present may be dissolved out by chloroform and similar solvents which do not dissolve the cellulose nitrate. 

Cellulose nitrate is a semi-synthetic plastic based on cellulose from wood or cotton. It is mixed with nitric and sulphuric acids, and uses camphor as a plasticiser. It is another compound that was being developed by various people in different places at the same time, but was launched in England in 1862 as Parkesine . It was later called Xylonite . Cellulose nitrate was finally patented in America in 1870 under the name celluloid , but has been known by over 60 different trade names during the years it has been in production. 

A useful synthesis (ref.ll)of patchouli alcohol, an important fragrant constituent of patchouli oil, from (+)-camphor, that onetime important natural product which was employed as a plasticiser for nitrocellulose (itself a semi-synthetic polymer), was complicated by structural revision of the sesquiterpene alcohol. Dihydrocarvone (14) obtained by saturation of the ring double bond in carvone, a major constituent of oil of spearmint has been employed for two very different sesquiterpenes, the ketone campherenone (15) and the alcohol, occidentalol (16). In the first case an enol acetate was converted to a bicyclic intermediate by earlier established methodology and the route emulated a plausible biogenetic sequence giving racemic campherenone (ref.12) as shown. Any chirality in (14) is apparently lost. 

Details Crystals, with a special odour a plasticiser specifically for cellulosics, lacquers and varnishes. Camphor, 464-49-3 ((IR)-Camphor), 464-48-2 ((IS)-Camphor)... 

Between 1862 and 1866 in England and the USA, nitrocellulose was produced by treating cellulose with nitric acid, which in 1872 was plasticised with camphor to become the first plastic material known as celluloid [1]. 

The first plastic material to be made from non-plastic precursors was cellulose nitrate. This was obtained by Alexander Parkes (1813-1890) by treating cellulose fibres with nitric acid, and was first displayed at the Great International Exhibition in Ijondon in 1862 under the name Parkesine. Parkes moulded his new material into small decorative articles, as well as utilitarian objects such as knife handles. Parkesine was the first semi-synthetic plastic, so called because one of the starting materials was polymeric. The applications of cellulose nitrate were much extended by J. W. Hyatt (1837-1920) in the United States, who found that camphor was effective as a plasticiser, and the resulting mixture was known as celluloid. Another semi-synthetic plastic, cellulose acetate, was introduced around the end of the nineteenth century, and had the advantage over cellulose nitrate of being less flammable. 

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