5 things you didn’t know about...bio-based polymers

Credit: tinglee1631 / Shutterstock 

1. Bio-based polymers are generally referred to as bioplastics, which are defined as a plastic that is either bio-based, biodegradable, or both. So bioplastics are not only derived from biomass but can include fossil-based polymers, too, if they are biodegradable.

2. Most biodegradable plastics will only decompose in an industrial composting facility.

3. Coca-Cola introduced the first version of its PlantBottle, made from 30% bio-based polyethylene terephthalate (PET), in 2009. Standard PET, used widely in drinks bottles, pots, tubs and oven-ready trays is a combination of 32.2% monoethylene glycol (MEG) and 67.8% purified terephthalic acid (PTA).

4. Companies and research institutions are developing bio-based polymers with a variety of natural feedstocks. Lactips, a French start-up, is expecting its milk protein-based polymers to enter the laundry, water treatment and agrochemicals market in the third quarter of 2017.

5. Banana peel provides the base for polymers developed at the University of Sonora, Mexico. Strips of banana endocarp are immersed in two antioxidants and then dried, lyophilised and mixed with either citric acid or propolis, a resinous mixture produced by honey bees to create a mouldable paste. When mixed with propolis, the biopolymer is food-safe and prevents the proliferation of bacteria and fungi. The University of Strathclyde, UK, has even developed a polymer using a waste product of the seafood industry.

To find out more see page 61 of the upcoming April issue of Materials World.

An extra dimension

A group of researchers at ETH Zurich, Switzerland, have added an additional dimension to 3D printing. They have created moveable and shape variable 4D objects that can be folded into 3D shapes or can change shape as a reaction to external influences such as temperature. The team also developed a construction principle that allows them to control the objects deformation. Each structure is designed to change configuration in a certain way, and are able to support weight, making them the first load-bearing 4D objects.

Credit: ETH Zurich / Tian Chen

The objects are made on the structural principle that depends on two states, retracted or extended. Combining these states allows for the creation of more complex structures, and gives them the ability to form several stable forms. A multi-material 3D printer, using a rigid polymer and an elastic polymer, printed the structures.

The space saving potential of these structures makes them a candidate for aerospace applications. The researchers are also considering their use in ventilation systems and medicine.


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Flexible and biodegradable semiconductor for electronics

Credit: Bao lab

A new semiconductor developed by researchers at Stanford University, USA, is as flexible as skin and easily degradable and is hoped to tackle electronic waste.

The team developed a semiconductor polymer that can decompose by adding a weak acid-based vinegar, a degradable electronic circuit and a biodegradable substrate material for mounting the electrical components. This substrate supports the electrical components, flexing and molding to rough and smooth surfaces. When the electronic device is no longer needed it can biodegrade into non-toxic components.

The substrate carries the electronic circuit and the polymer from cellulose fibres to make the material transparent and flexible, while still breaking down easily. The thin film substrate allows the electronics to be worn on the skin or implanted inside the body.

The electronic device could be used in wearable electronics and large-scale environmental surveys with sensor dusts. ‘We envision these soft patches that are very thin and conformable to the skin can measure blood pressure, glucose value, sweat content. A person could wear a specifically designed patch for a day or week, then download the data. According to Bao, this short-term use of disposable electronics seems a perfect fit for a degradable, flexible design,’ said Stanford engineer Zhenan Bao. 

Although the polymer was found to be biocompatible, Bao said that more studies would need to be done before these implants are used.