Manufacture and biodegradation of wheat gluten/basalt composite material

Wheat gluten is a naturally occurring protein polymer. It is biodegradable and very inexpensive (less than $1.00/kg). Nonfood applications of wheat gluten have been explored to develop biodegradable polymers from renewable resources. In this work, gluten was reinforced with unidirectional basalt fibers in a compression molding operation. Biodegradation behavior of wheat gluten/basalt composites was examined by putting specimens into soil of prescribed moisture content. Specimens were removed at various time intervals and tested for mass loss and change in mechanical properties. Both mass and mechanical properties show a steady decline over a soil exposure time of 40 days. However, the basalt composite retained mechanical properties longer. At the same time, the bacterial count on the specimen surfaces increased exponentially. Field emission scanning electron microscope images show smooth fracture surfaces, indicating brittle failure of the wheat gluten. However, there are many small holes in the protein matrix with diameter of order 100 nm. These small inclusions may contribute to the brittleness through stress concentration.