Focus on bioplastics research: chicken plastic rather than rubber chickens

William Thomas Astbury (1898-1961) and Henry John Woods (1903-1984) carried out in-depth research into keratin as long ago as the 1930s. They found out “that keratin normally contains polypeptide chains with a statistical sequence of the individual amino acids, adjacent chains being connected to form net-like structures via ‘side chain bonds’”. The British chemists also “induced stretching and contraction [...] by various forms of treatment”, as the Austrian physical chemist Otto Kratky (1902-1995), Departmental Manager at the Kaiser Wilhelm Institute in Berlin, wrote in his essay “The radiographic investigation of fibrous materials” that appeared in 1939. So although there were already indications at an early stage that keratin is a natural polymer and although the first bioplastics were invented as early as the end of the 19th century (see “Bioplastic: historical predecessors”), there has been an almost complete lack of interest in keratin within the plastic industry. Polymer research scientists from the University of Nebraska / USA are now putting the spotlight on it again: they have succeeded in isolating keratin from chicken feathers. In a second stage, the research scientists have treated it in such a way that it remains water-resistant and mechanically stable. In other words: they have managed to make plastic from chicken feathers.

Chicken feathers normally react to moisture in a similar way to horsehair – they expand. This is why classic hygrometers have been made out of horsehair: advantage is taken of the stretching effect to measure the change in air humidity. “Although attempts were already made in the past to use feathers for composite plastics, problems were encountered in contact with water”, explains Yiqi Yang, Professor at the Institute for Material Sciences and Nanotechnology at the University of Nebraska. Problems that appear to have been overcome, because Professor Yang’s team has come up with a special cocktail, has added methyl acrylate to the chicken feathers. Long molecular chains form as a result that interact in different ways and thus form a solid mass. The chicken plastic created as a result now has properties that have been found lacking in it up to now, particularly water resistance, durability and a longer useful life. It also weighs less than comparable compounds made from polyethylene or polypropylene. And last but not least: it is biologically degradable.

Although the research scientists are keen to avoid excessive optimism, since a modest start is all that has been made so far, a patent application has already been filed for the process in the USA. Tests to produce a bioplastic from keratin have already been carried out in Germany too. Horn to which caustic soda solution or acetic acid has been added has been used for this purpose rather than feathers: “The final product itself was a solid, film-like substance. It is possible that short peptide fragments have been created as a result of the separation of the peptide bond by the solution / acetic acid. They could perhaps be repolymerised by adding a catalyst. The model for this could be the polymerisation of caprolactam, a feedstock used in the chemical industry for polyamides such as Perlon.”