Some bioplastics are made from cellulose, a plant-based polysaccharide material, but the researchers developed one from chitosan, a form of chitin, the second most abundant organic material on Earth.
There are pilot plants for the production of chitosan from squid pens, fungi, and krill, said the Harvard Wyss Institute researchers.
Javier Fernandez, postdoctoral fellow, told FoodProductionDaily.com that they have started collaborations with two companies to scale up the process.
“We don’t suggest chitosan bio-plastics to be a full replacement to plastic, but an example of production of plastic based on the local availability of raw materials.”
Selection based on application
Fernandez said there are a number of materials for manufacture, the selection of which to use should be made regarding the application.
“In some cases a synthetic polymer derived from oil can be the best option, while a plastic degradable in a composting plant or a material fully compostable in a natural environment can be better options,” he said.
The Wyss Institute team, led by Fernandez and Don Ingeber, founding director, developed a process so that it can be used to fabricate large, 3D objects with complex shapes using traditional casting or injection molding manufacturing techniques.
Their chitosan bioplastic breaks down when returned to the environment within about two weeks and they have demonstrated it can be recycled, or composted in regular soil.
A potential limitation is the cost of chitosan at three to four times more expensive than nonspecialized commodity plastics. However, use of composites of chitosan and wood filler drop the cost of the material to the range of commodity plastics.
Chitosan is also the subject of an EU project (n-CHITOPACK) which will create active packaging based on the substance.
The approach of nature
Fernandez said they figured out how to use chitin in a similar way to nature uses it to produce structural components.
“We have studied the molecular arrangement of chitosan chains in nature and the resulting mechanical characteristic of the different arrangements,” he said.
“Then we have developed a manufacturing approach reproducing those natural characteristics at molecular scale to produce different objects.
“In this case one of the greatest achievements is that we don’t need to transform a natural component in a polymer similar to those used in manufacture in order to manufacture it.
“We have demonstrated that we can use a natural material as it, without modifications, and reproducing the natural hierarchical design of the natural material we can also reproduce its natural mechanical properties.”
Preserve integrity
Researchers learned that the molecular geometry of chitosan is very sensitive to the method used to formulate it. The goal was to fabricate it to preserve the integrity of its natural molecular structure and maintain its strong mechanical properties.
After characterizing how temperature and concentration affect the mechanical properties on a molecular level, Fernandez and Ingber looked at a method that produced a pliable liquid crystal material for use in large-scale manufacturing methods, such as casting and injection molding.
They also found a way to combat the shrinkage where the chitosan polymer fails to maintain its original shape after the injection molding process by adding wood flour, a waste product from wood processing.
Source: Macromolecular Materials & Engineering
Online ahead of print, DOI: 10.1002/mame.201300426
“Manufacturing of Large-Scale Functional Objects Using Biodegradable Chitosan Bioplastic”
Authors: Javier Fernandez and Don Ingber