The biopolymer lignin is a by-product of papermaking and a promising raw material for manufacturing sustainable plastic materials.
The biopolymer lignin is a by-product of papermaking and a promising raw material for manufacturing sustainable plastic materials. However, the quality of this naturally occurring product is not as uniform as that of petroleum-based plastics. An X-ray analysis carried out at DESY reveals for the first time how the internal molecular structure of different lignin products is related to the macroscopic properties of the respective materials. The study, which has been published in the journal Applied Polymer Materials, provides an approach for a systematic understanding of lignin as a raw material to allow for production of lignin-based bioplastics with different properties, depending on the specific application.
Lignin is a class of complex organic polymers and responsible for the stability of plants, stiffening them and making them “woody” (i.e. lignification). During paper production, lignin is separated from cellulose. Lignin forms so-called aromatic compounds, which also play a key role in manufacturing synthetic polymers or plastics. “Lignin is the biggest source of naturally occurring aromatic compounds, but until now it has been viewed by the paper industry primarily as a by-product or a fuel,” explains Mats Johansson from the Royal Institute of Technology (KTH) in Stockholm, who led the research team. “Millions of tonnes of it are produced every year, providing a steady stream of raw material for new potential products.”
Some first applications of hard lignin-based plastics (thermosets) already exist. However, their properties often vary and until now it has been difficult to control them specifically. The Swedish team has now shed light on the nanostructure of different fractions of commercially available lignin at DESY’s X-ray source PETRA III. “It turns out that there are lignin fractions with larger and smaller domains,” reports the principle author Marcus Jawerth, of Stockholm’s KTH. “This can offer certain advantages, depending on the particular application: it makes the lignin harder or softer by altering the so-called glass transition temperature at which the biopolymer adopts a viscous state.”
Read more at Deutsches Elektronen-Synchrotron DESY
Image: Lignin is a promising raw material (left) for thermoplast (right) production. (Credit: KTH Stockholm, Marcus Jawerth)
