Adhesion and Stability of Nanocellulose Coatings on Flat Polymer Films and Textiles

Renewable nanocellulose materials received increased attention owing to their small dimensions, high specific surface area, high mechanical characteristics, biocompatibility, and compostability. Nanocellulose coatings are among many interesting applications of these materials to functionalize different by composition and structure surfaces, including plastics, polymer coatings, and textiles with broader applications from food packaging to smart textiles. Variations in porosity and thickness of nanocellulose coatings are used to adjust a load of functional molecules and particles into the coatings, their permeability, and filtration properties. Mechanical stability of nanocellulose coatings in a wet and dry state are critical characteristics for many applications. In this work, nanofibrillated and nanocrystalline cellulose coatings deposited on the surface of polymer films and textiles made of cellulose, polyester, and nylon are studied using atomic force microscopy, ellipsometry, and T-peel adhesion tests. Methods to improve coatings’ adhesion and stability using physical and chemical cross-linking with added polymers and polycarboxylic acids are analyzed in this study. The paper reports on the effect of the substrate structure and ability of nanocellulose particles to intercalate into the substrate on the coating adhesion.


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NFC and NCC films were deposited (spin-coated) on the surface of the polymer-coated on the CL, PET and PA 6,6 coated Si-wafers; and (iv) Protocol 4: NFC and NCC aqueous dispersions 142 were mixed with P(GMA-OEGMA) copolymer, spin-coated on the CL, PET and PA 6,6 coated 143 Si-wafers. In all cases, the nanocellulose coatings were annealed after the deposition at 120 °C for 1 h.

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The NFC and NCC coatings were prepared first using Protocol 1. We discovered a poor

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The stability of the deposited NFC and NCC films in an aqueous environment was estimated 177 with a simple test. The coated samples were exposed to 50 C aqueous solution at stirring for 1 h.

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Comparing the AFM images of the film before and after exposure to the aqueous medium in most 179 cases did not reveal changes in the film morphology ( Figure 5). For these nanocellulose coatings, we

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Changes in film thickness of the NFC and NCC coatings in all cases, with exceptions of 204 untreated PET substrates, after rinsing in water are reported in Table 1

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The analysis of the experimental data shows that the most common mechanism of coating 212 degradation is partial delamination. Only for the PET substrate, we observed almost a complete 213 adhesive detachment of the nanocellulose. The result shows that the nanocellulose coating has the 214 lowest adhesion to the PET surface and the strongest interaction with the PA 6,6 surface among the 215 synthetic polymers. NCC coatings demonstrate a higher adhesion to different CL substrates than 216 NFC coatings. It is likely due to the denser packed NCC particles in the coating in contrast to NFC 217 fibers, and hence, a lower swelling of the coating. The addition of PEI and P(GMA-OEGMA)

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improves the stability of the coatings. The latter effect is likely due to the switching from the 219 adhesive defoliation mechanism to the partial delamination of the film.

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Notably, the film is much more stable on PET and PA 6,6 substrates when the coating is mixed 221 with P(GMA-OEGMA). We may speculate that the major strengthening contribution of the

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We may speculate about the following mechanism of the improvement of the stability of the

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The outcomes changed for the peel tests using fabrics instead of films made of the same 283 polymers. NCC binding is stronger than NFC for all cases (compare Figure 9 and Figure 10). We This result was in conflict with the experiment in water (Table 1) Table 2.

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The result indicates that warp and weft density for cotton fabrics are substantially higher than those

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The mean flow pore diameter of the cotton and nylon fabrics also shows the highest values with 319 broader pore size distribution in nylon fabric. This is another factor correlating with the uptake of distribution shows that the majority of the pores are less than ∼100 µm, and for the PET fabric, the 326 pore size range is between ∼5 and ∼50 µm. The pore size distribution of the cotton, polyester, nylon,

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The spectra were presented using absorbance mode (-logR/Ro). The resolution for all the 435 infrared spectra was 4 cm -1 , 120 scans for each spectrum.