How to mold synthetic plastics

The first fully synthetic plastics were made many years before they were manufactured industrially. In 1838 the French chemist Henri Regnault observed resini fication of vinyl chloride under the influence of sunlight but he did not appreciate the possibilities of the new material he had produced, now called polyvinyl chloride (PVC). The following year, the German chemist Simon reported the polymerization of the UNSATURATED HYDROCARBON Styrene to give polystyrene, but it was not for another nine decades that this material was made industrially. In 1909 Leo H. Baekeland patented a resinous product he had obtained by reacting phenol with formaldehyde, although the first phenol-formaldehyde resin had been discovered more than 30 years before by Adolf von Bayer in 1872.

Baekeland’s product, called Bakelite, was one of the first commercially successful synthetic plastics. Methyl methacrylate was first polymerized in 1877 by the German chemists Fittig and Paul, and the product they obtained, polymethylmethacrylate, was to form the basis of the plastic Plexiglas, which was introduced half a century later. The first experiments in polymerizing ethylene were conducted in 1879, but a lubricating oil and not a plastic was produced. Today, ethylene is polymerized industrially on an enormous scale to give the well-known, extensively used plastic polyethylene.

Although celluloid was being manufactured commercially at the end of the nineteenth century, it was not until early this century that the first significant advances were made in manufacturing techniques. Baekeland succeeded in developing a molding technique for his phenol-formaldehyde resin Bakelite, and in 1919 a patent was granted for the injection molding of cellulose acetate. Injection molding is an extremely important technique for shaping plastics, and without it many utensils and implements could not be made.

Polystyrene – In the 1920s, much research was done into the chemical structure of plastics, particularly by the German chemist Hermann Staudinger, who was awarded the Nobel Prize for chemistry in 1953 in recognition of his work. Staudinger’s research led to the development of new plastics on a more rational basis, and in 1930 commercial production of polystyrene, one of the most important of today’s plastics, was launched by the German company I.G. Farbenindustrie. The raw materials for polystyrene production are ethylene and benzene, which are first reacted together to give styrene (C6H5CH=CH2). The styrene is then polymerized to give polystyrene, the molecules of which consist of chains of styrene units. Its chemical formula can be represented as follows:

-CH(C6H5)-CH2-CH(C6H5)-CH2-CH(C6H5)-CH2