TABLE OF CONTENTS Dennis Price
Casein is the main protein in cow s milk, and depending on the treatment route, can be used to make either glues and plastics, or cheese.
The calcium caseinates form an insoluble white curd when acidified. This acid casein is used widely in wood-working adhesives, water paints, for coating paper, and in printing textiles and wallpaper. In neutral solutions the enzyme rennin (EC 3.4.23.4) can convert caseins to an insoluble curd; this being the dominant protein in cheese. When treated with formaldehyde the curd can be formed into casein plastic. These casein plastics were amongst the first commercially developed plastics, with a German patent being issued in 1899 to Kirsch and Spitteler for a plastic composition . The plastics were used to make washable white boards for use in schools to replace slates which kept getting broken and because paper was just too expensive for children to practice their writing on. Applications in the field of composites manufacture are limited as the compound is usually made up into stock shapes for machining, as it is not well suited to moulding processes.
This section will therefore concentrate on the application of casein adhesives as a composite matrix material. Like much naturally occurring glue, casein has been used for thousands of years, for example, as the pigment binder in ancient Egyptian wall paintings, and more recently in Europe in tempera paintings. In these early times it was often used in the crude form of precipitated curd. The commercial marketing of...
