Researchers create clear film from birch fibril pulp
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VTT Technical Research Centre and Aalto University have developed a method that, for the first time, enables the manufacture of a wood-based and plastic-like material on a large scale.
The method reportedly enables the industrial-scale roll-to-roll production of nanofibrillated cellulose film, which is suitable for applications including food packaging to protect products from spoilage.
According to VTT, nanofibrillated cellulose typically binds high amounts of water and forms gels with only a few per cent dry matter content.
This characteristic is said to have been a bottleneck for industrial-scale manufacture. In most cases, fibril cellulose films are manufactured through pressurised filtering, but the gel-like nature of the material makes this route difficult.
In addition, the wires and membranes used for filtering may leave a so-called ‘mark’ on the film that has a negative impact on the evenness of the surface.
According to the method developed by VTT and Aalto University, nanofibrillated cellulose films are manufactured by evenly coating fibril cellulose onto plastic films, so that the spreading and adhesion on the surface of the plastic can be controlled.
The films are dried in a controlled manner by using a range of existing techniques. Thanks to the management of spreading, adhesion and drying, the films do not shrink and are completely even. The more fibrillated cellulose material is used, the more transparent films can be manufactured.
Several metres of fibril cellulose film have been manufactured with VTT’s pilot-scale device in Espoo, Finland. All the phases in the method can be transferred to industrial production processes and the films can be manufactured using devices that already exist, without the need for any major additional investment.
VTT and Aalto University are applying for a patent for the production technology of nanofibrillated cellulose film.
