Purdue University researchers have developed tough, flexible, biodegradable films from cellulose, the main component of plant cell walls.
The films could be used for products such as food packaging, agricultural groundcovers, bandages and capsules for medicine or bioactive compounds.
Food scientists Srinivas Janaswamy and Qin Xu engineered the cellophane-like material by solubilising cellulose using zinc chloride, a common inorganic salt, and adding calcium ions to cause the cellulose chains to become tiny fibers known as nanofibrils, greatly increasing the material’s tensile strength. The zinc chloride and calcium ions work together to form a gel network, allowing the researchers to cast the material into a transparent, food-grade film.
“We’re looking for innovative ways to adapt and use cellulose – an inexpensive and widely available material – for a range of food, biomedical and pharmaceutical applications,” said Janaswamy, research assistant professor of food science and principal author of the study.
“Though plastics have a wide variety of applications, their detrimental impact on the environment raises a critical need for alternative materials. Cellulose stands out as a viable option, and our process lays a strong foundation for developing new biodegradable plastics.”
Cellulose’s abundance, renewability and ability to biodegrade make it a promising substitute for petroleum-based products. While a variety of products such as paper, cellophane and rayon are made from cellulose, its tightly interlinked structure and insolubility – qualities that give plants strength and protection – make it a challenging material to work with.
Janaswamy and Xu loosened the cellulose network by adding zinc chloride, which helps push cellulose’s closely packed sheets apart, allowing water to penetrate and solubilise it. Adding calcium ions spurs the formation of nanofibrils through strong bonds between the solubilised cellulose sheets. The calcium ions boost the tensile strength of the films by about 250 per cent.
The production process preserves the strength and biodegradability of cellulose while rendering it transparent and flexible. (phys.org)
