## 4 Conclusions  
Three different cellulose nanocrystals derived species were compared in their properties, aiming for a possible application in the food packaging sector. All the samples were fully characterized and employed as coatings on different types of plastic films. The main problem to be sorted out was the sensibility of the cellulose nanocrystals to moisture that hampered their incorporation into food \begin{table}
\begin{tabular}{c c c} \hline \hline
**P-CNC\({}_{SO3H}\)-P** & **50\% RH** & **80\% RH** \\ \hline OPP- CNC\({}_{SO3H}\)/PE & \textless{}0.06 & \(1.2\pm 0.25\) \\ \hline OPP- CNC\({}_{SO3H}\)/PLA & \(40\pm 0.15\) & \(320\pm 3.5\) \\ \hline PET- CNC\({}_{SO3H}\)/PE & \(0.25\pm 0.15\) & \(1.107\pm 0.25\) \\ \hline PET- CNC\({}_{SO3H}\)/PP & \textless{}0.06 & \textless{}0.06 \\ \hline
**P-CNC\({}_{COOH}\)-P** & **50\% RH** & **80\% RH** \\ \hline OPP- CNC\({}_{COOH}\)/PE & \textless{}0.06 & \textless{}0.06 \\ \hline OPP- CNC\({}_{COOH}\)/PLA & \(12.41\pm 3.5\) & \(201.11\pm 3.5\) \\ \hline PET- CNC\({}_{COOH}\)/PE & \textless{}0.06 & \textless{}0.06 \\ \hline PET-CNC\({}_{COOH}\)/PP & \textless{}0.06 & \textless{}0.06 \\ \hline
**P-CNC\({}_{COOH}\)-P** & **50\% RH** & **80\% RH** \\ \hline OPP- CNC\({}_{COOH}\)/PE & \textless{}0.06 & \textless{}0.06 \\ \hline OPP- CNC\({}_{COOH}\)/PLA & \(3.78\pm 3.5\) & \(103.55\pm 3.5\) \\ \hline PET- CNC\({}_{COOH}\)/PE & \textless{}0.06 & \textless{}0.06 \\ \hline PET-CNC\({}_{COOH}\)/PP & \textless{}0.06 & \textless{}0.06 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Oxygen permeability of laminated coated-polymers at RH 50–80%, calculated from the mean \(\pm\) standard deviation (\(n=3\)). \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Laminated Polymers** & **P-CNC\({}_{SO3H}\)-P** & **P-CNC\({}_{COOH}\)-P** & **P-CNC\({}_{COOH}\)-P** \\ \hline _Elastic Modulus (N/m)_ & 13,000–36,000 & 14,000–43,000 & 18,000–28,000 \\ \hline Breaking Strength (N/m) & 14–20 & 16–60 & 22–74 \\ \hline _Stiffness (N/m)_ & 650–7000 & 3600–5000 & 3500–8300 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Results of peeling test of laminated coated-polymers. packaging. It was noted that barrier gas properties of cellulose nanocrystals were effective in the absence of humidity, but were compromised in a humid environment. Through this work, it has been shown that the esterification of cellulose nanocrystals has significantly improved the gas barrier, compared to the unmodified ones. In addition, the oxygen permeability of laminated coated-polymers showed very low values, even in high relative humidity (80% RH), which is the confirmation that the lamination has definitely isolated the CNCs coatings from the moisture and that subsequently, it could favor such materials to be used for food shelf-life extension. From the results of the delamination test, it can be observed that the stiffness, elastic modulus and elongation at the end are relevant for all delamination tests of polymers. It is very important to indicate that the lamination of polymers coated with esterified cellulose nanocrystals were the best in terms of reducing the gas permeability, even in higher relative humidity, followed by laminated polymers coated with CNCCOOH and CNCSOSH. Furthermore, sealable plastics selected for the lamination would enable a swift application of CNCs in food packaging, replacing the oil-based materials, such as EVOH and PVDC, that are used today. Such high-performance multi-layer laminates based on a very thin layer of CNCs (\(\approx 1\) um) would imply a paradigm change for the effective development of advanced materials, taking care of environmental protection and the principles of a circular economy. [PERSON], [PERSON], [PERSON] and [PERSON] were all involved in the conceptualization and the methodology of the project, design and realization of experiments, design of the project and analysis of the data as well as in the writing of the paper. [PERSON] was also involved in the supervision and administration of the project and funding acquisition.