The Effect of Cellulose Nanofibres on Dewatering during Wet-Forming and the Mechanical Properties of Thermoformed Specimens Made of Thermomechanical and Kraft Pulps

Abstract

Due to environmental concerns regarding single-use plastic materials, major efforts are being made to develop new material concepts based on biodegradable and renewable resources, e.g., wood pulp. In this study, we assessed two types of wood pulp fibres, i.e., thermomechanical pulp (TMP) and Kraft pulp fibres, and tested the performance of the fibres in wet-moulding and thermopressing trials. Kraft pulp fibres appeared to retain more water than TMP, increasing the dewatering time during wet-moulding and apparently increasing the compression resistance of the pulp during thermoforming. Additionally, cellulose nanofibres (CNF) were added to the pulps, which improved the mechanical properties of the final thermopressed specimens. However, the addition of CNF to the pulps (from 2 to 6%) had a further decrease in the dewatering efficiency in the wet-moulding process, and this effect was more pronounced in the Kraft pulp specimens. The mechanical performance of the thermoformed specimens was in the same range as the plastic materials that are conventionally used in food packaging, i.e., modulus 0.6–1.2 GPa, strength 49 MPa and elongation 6–9%. Finally, this study demonstrates the potential of wood pulps to form three-dimensional thermoformed products.

Sustainable Materials from Organosolv Fibers and Lignin, Kraft Fibers, and Their Blends

“…It can be concluded that organosolv fibers appeared particularly suited for pote thermoformed products that require resistance to we ing, e.g., trays for food packag Materials for food packaging usually include, e.g., fossil low-and high-den polyethylene (LDPE and HDPE). The strength and modulus of LDPE and HDPE roughly between 10 and 30 MPa and 0.3 and 1.0 GPa, respectively [5], which comparable to the mechanical properties obtained in this study (Figure 6). Although elongation of the thermopressed handsheets are considerably lower (<10%) than thos PE materials (>500%), this is not considered a major drawback, as a high stiffnes particularly considered crucial food packaging and trays [46].…”

“…To compare the means of two individual measurements, the two-sided t-test was conducted according to Equations ( 4) and (5) given by Kalpic et al [37]. Here, the variable T was calculated from the sample means X i with standard deviation S i and sample size n i .…”

“…Lignocellulosic fibers, e.g., chemical, chemi-thermomechanical (CTMP), and thermomechanical pulp (TMP), have been extensively explored for thermoformed materials [3][4][5][6]. However, two of the main challenges with lignocellulosic fibers remain, which are the hydrophilicity and lack of water resistance.…”