Revolutionizing sustainable packaging: The role of thermoforming in pulp-based materials

In a significant development for sustainable packaging, researchers from RISE PFI AS in Norway and TU-Berlin have uncovered the influence of thermoforming conditions on the properties of softwood pulp, specifically northern bleached softwood Kraft pulp (NBSK) and chemi-thermomechanical softwood pulp (CTMP). Published in the Journal of Bioresources and Bioproducts, the study aimed to develop advanced wood-fiber-based materials as a replacement for fossil plastics, a step towards reducing environmental pollution and embracing a circular economy.

The researchers varied thermoforming conditions between 2–100 MPa and 150–200 °C, pressing sheets of 500 g/m² for 10 minutes to closely represent thin-walled packaging. Their findings revealed that temperature had a more pronounced effect on CTMP substrates than on Kraft pulp, attributed to the greater abundance of lignin and hemicelluloses in CTMP. The study also found that CTMP exhibited an optimum in terms of tensile strength at intermediate thermoforming pressure, due to improved fiber adhesion and densification, yet also embrittlement caused by the loss of extensibility.

High temperatures were found to soften the lignin, enabling fiber collapse and tighter packing, which could be crucial for the development of high-density materials with strength comparable to established plastics. Both pulps showed reduced wetting at elevated thermoforming temperatures and pressures, attributed to hornification and densification effects. The research concluded that the thermoforming temperature and pressure significantly affected the properties of the final material, with the chemical composition of the pulps distinctly affecting their response to thermoforming.

This study's innovative approach to understanding the thermoforming process of wood pulp offers valuable insights for tailoring cellulose-based replacements for packaging products. The findings suggest that by manipulating thermoforming conditions, it is possible to create high-density materials with enhanced mechanical properties, potentially revolutionizing the sustainable packaging industry.

See the article:

DOI

https://doi.org/10.1016/j.jobab.2023.10.001

Original Source URL

https://www.sciencedirect.com/science/article/pii/S2369969823000609

Journal

Journal of Bioresources and Bioproducts