Natural polymers, commercial

The commercial samples of pectins mainly used as food additives represent modified forms of the natural polymers due to the conditions of extraction. Nevertheless, it is usually recognized two categories of pectins the high methoxyl pectins (HM) with a degree of methylation DM>50% forming gels at low pH in presence of saccharose to reduce the water activity and the low methoxyl pectins (LM with DM<50%) forming gel in presence of calcium [4]. 

Commercial grades of HR (butyl rubber) are prepared by copolymerising small amounts of isoprene with polyisobutylene. The isoprene content of the copolymer is normally quoted as the mole percent unsaturation , and it influences the rate of cure with sulphur, and the resistance of the copolymer to attack by oxygen, ozone and UV light. The polyisobutylene, being saturated, however, naturally confers on the polymer an increased level of resistance to these agencies when compared to natural rubber. Commercial butyl rubbers typically contain 0.5-3.0% mole unsaturation. 

The first true synthetic polymer was probably a material produced in 1865 by the English inventor Alexander Parkes (1813-90). Parkes synthesized this material by reacting cellulose (a natural polymer) with nitric acid and dissolving the product (called pyroxylin) in a mixture of alcohol, camphor, and castor oil. Parkes called his product parkesine, or Xylonite. Although the material had many desirable qualities (for example, it could be shaped and molded easily while still warm), it was too expensive to be a commercial success, and, perhaps more important, no one quite knew how to use the product. 

In the following paragraphs, we will present the technologies needed to overcome these and other disadvantages. In this way, the natural polymer structure becomes profitable for industrial applications as biomaterials. We have selected only the main biopolymers currently used in commercial products. 

In Chapter 4, we will discover that the field of polymer science essentially began when scientists chemically modified natural polymers to prepare new materials with improved properties. Some of these reactions are still commercially important today. However, the specificity in the structures of most biopolymers themselves makes their laboratory synthesis extremely difficult. 

Performic acid is an unstable, hazardous percarboxylic acid, and must always be generated in situ. Epoxidation with in situ performic and peracetic acid are well established commercial processes. They find application in the epoxidation of alkenes, particularly those of high molecular weight. Many such epoxides are produced on a large scale, and can be classified as vegetable oils, unsaturated esters, unsaturated acids, a-alkenes, natural polymers and synthetic polymers. The most important vegetable oil which is epoxidized commercially is soyabean oil. World production of epoxidized soyabean oil (ESBO) exceeds 150000 metric tons per annum. Epoxidized linseed oil is also important, but produced at a lower rate than ESBO. Both products are formed by usual in situ performic and peracetic acid techniques.23,24 Typical procedures are outlined in Table 3.1.25... 

Plastic materials are widely used in numerous industries. The physiochemical nature of these materials provides a multitude of diverse products with their necessary, desirable performance characteristics. Commercial plastics are very complex materials. In addition to the various base polymers, commercially viable plastics contain a number of compounding ingredients (additives) whose purpose is to give the material its desired physical and/or chemical properties. Table 1 provides a brief summary of the types of additives typically encountered in commercial polymer systems. 

Many important fibers, including cotton and wool, are naturally occurring polymers. The first commercially successful synthetic polymers were made not by polymerization reactions but through the chemical regeneration of the natural polymer cellulose, a condensation polymer of the sugar glucose that is made by plants ... 

We learned much from nature with these early attempts to produce useful polymer products based on modified, or reconstituted ( semisynthetic ) natural polymers, and many of these processes are still in use today. The first of the purely synthetic commercial polymers came with the small-scale introduction of Bakelite in 1907. This phenol-formaldehyde resin product was developed by Leon Baekeland. It rapidly became a commercial reality with the formation of The General Bakelite Company by Baekeland, and construction of a larger plant at Perth Amboy, New Jersey, in 1910. At about this time styrene was being combined with dienes in the early commercialization of processes to produce synthetic rubber. Polystyrene itself was not a commercial product in Germany until 1930 and in the U.S.A. in 1937. The only other purely synthetic polymers that made a commercial appearance during this early development period were polyvinyl chloride and polyvinyl acetate, both in the early 1920s. 

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