This work investigates the surface and bulk properties of nanofibrillated cellulose (NFC) and bacterial cellulose (BC), as well as their reinforcing ability in polymer nanocomposites. BC possesses higher critical surface tension of 57 mN m-1 compared to NFC (41 mN m-1). The thermal degradation temperature in both nitrogen and air atmosphere of BC was also found to be higher than that of NFC. These results are in good agreement with the higher crystallinity of BC as determined by XRD, measured to be 71% for BC as compared to NFC of 41%. Nanocellulose papers were prepared from BC and NFC. Both papers possessed similar tensile moduli and strengths of 12 GPa and 100 MPa, respectively. Nanocomposites were manufactured by infusing the nanocellulose paper with an epoxy resin using vacuum assisted resin infusion. The cellulose reinforced epoxy nanocomposites had a stiffness and strength of approximately ~8 GPa and ~100 MPa at an equivalent fibre volume fraction of 60 vol.-%. In terms of the reinforcing ability of NFC and BC in a polymer matrix, no significant difference between NFC and BC was observed.

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Aqueous foam can be used as a transfer medium to form lightweight materials from natural and man-made fibers together with other types of raw materials. This review discusses mechanisms that underlie the forming process and thus influence physical properties of formed fiber networks such as microporous structure, strength behavior, and transport properties. Homogeneous fiber materials can be formed from versatile raw materials, which makes the technology suitable for a vast range of product applications. An intriguing feature of the method is that the wet foam characteristics provide an additional tool to tailor the performance of the dried material. Understanding foam rheology and how that is affected by added fibers is important in developing the forming process. We introduce both fundamental foam properties and practical forming methods, and show how the material properties are affected by the foam-fiber interaction. The basic features of an industrial production process are also described. The potential material properties are compared against key requirements in typical product applications.

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Foam forming has recently attracted increasing interest due to the paper industry’s continual efforts to find new possibilities to minimize raw material consumption, and to improve energy and water efficiency. Foam forming is also thought to be a possible solution to the industry’s need to widen its product portfolio with novel and more valuable products. In foam forming, foam properties (air content, bubble size and half-life) are obviously key process variables, but there are only a few studies in which their effect on the sheet properties have been studied in pilot conditions. Moreover, all previous studies have used foam generated in stirring tanks, and there are hitherto no studies in which in-line foam generation has been considered. In this paper both these gaps are filled with experiments performed in VTT’s pilot foam forming environment. The combination of tank and in-line generation was found to work well in foam forming, providing extra flexibility for foam generation and decreasing surfactant needs. The results show that foam forming generally improves formation, but the foam quality can have a significant effect on sheet properties.