Degraded Paper: Stabilization and Strengthening Through Nanocellulose Application

Figures & data

Figure 1. Brittle and fragile historical paper from mechanical wood pulp breaks and crumbles into pieces when wrinkled.

Figure 2. Application of nano cellulosic suspension on historical newspaper with a film applicator.

Table 1. List of standards, technical data, equipment, and suppliers used for analytical methods.

Analytical method	Standard	Technical data	Equipment	Supplier
Microscopy		Jenoptik ProgRes® SpeedXT core 3, Software Jenoptik ProgRes® CapturePro 2.10	Polarization microscope, Filter I3 Blue excitation BP 450–490, Blocking Filter LP 515	Jenoptik AG, Germany
pH of suspensions		pHC101 Electrode	HQd Portable Metre	Hach Lange GmbH, Switzerland
Conductivity of suspensions		CDC401 Electrode	HQd Portable Metre	Hach Lange GmbH, Switzerland
Rheology of suspensions		Physica MCR with a DG26.7 double gap cylinder	Rheometre	Anton Paar Switzerland AG, Switzerland
pH of paper samples	ISO 6588-1: 2012	Metrohm 827 pH lab	pH-metre	Metrohm AG, Switzerland
Tensile strength	EN ISO 1924-2: 2008, EN 20187: 1993	zwickiLine Z 2.5	Tensile testing machine	ZwickRoell GmbH & Co. KG, Germany

Figure 3. Folding machine used for standardized folding of the paper samples according to Bansa-Hofer.

Table 2. Testing parameters for measurement of tensile strength.

Test length at starting position	180.0 mm
Speed at starting position	400 mm/min
Pre-load	None
Test speed	20 mm/min
Turn-off threshold	50% Fmax
Upper force limit	500 N
Power threshold for breaking test	0.5% Fnom

Table 3. pH-values of CNF and CNC suspensions from 0.5–3 wt%.

Table 4. Conductivity in μs/cm of CNF and CNC suspensions from 0.5–3 wt%.

Table 5. Apparent viscosities of CNF 0.5–3 wt% in H₂O at increasing shear rates of 1–1000 [1/s].

Table 6. Apparent viscosities of CNC 0.5–3 wt% in H₂O at increasing shear rates of 1–1000 [1/s].

Table 7. Apparent viscosities of CNF 0.5–3 wt% in H₂O:EtOH at increasing shear rates of 1–1000 [1/s].

Table 8. Apparent viscosities of CNC 0.5–3 wt% in H₂O:EtOH at increasing shear rates of 1–1000 [1/s].

Figure 4. Historical paper from mechanical wood pulp untreated (top left), coated with Japanese paper 4 gm² (top right), coated with CNC 3 wt% (bottom left) and CNC 3 wt% + CNF 0.5 wt% (bottom right). The thin fibres of the Japanese paper are slightly veiling the writing in the text area. The coating with CNF and CNC has no negative effect on the appearance of the paper or the printed areas.

Figure 5. After treatment with CNC 3 wt%, the brittle and fragile historical paper still breaks at the creases after wrinkling but doesn’t disintegrate into tiny pieces as the untreated paper. A strengthening of the paper structure has been achieved by the treatment with nanocellulose. At the same time, the coating with an amount of CNC as high as 3 wt% is visible just as a distinct gloss on the paper surface.

Table 9. Fluorescence micrographs of cross sections of Whatman® no.1 untreated (a1 and a2) and treated with CNC 1 wt% marked with RBITC, respectively immersed (b1 and b2) and coated (c1 and c2). On the left column, dark field transmitted visible light images. On the right, dark field images excited with blue light.

	No filter	UV filter I3 Blue
Whatman® no. 1
Whatman® no. 1 + CNC & RBITC (immersed)
Whatman® no. 1 + CNC & RBITC (coated)

Figure 6. Measurement results of tensile strength for Whatman® paper treated with CNF and CNC.

Figure 7. Measurement results of tensile strength for historical newspaper treated with CNF and CNC.