## 3 Plastics Used for Food Packaging
### Selected Biodegradable Synthetically Manufactured Polymers
#### 3.2.1 Biomass-derived Chemically Manufactured Polymers
\begin{table}
\begin{tabular}{c c c c c c c} \hline  & \multicolumn{3}{c}{**Permeability**} & \multicolumn{3}{c}{**Mechanical Properties**} \\ \cline{2-7}
**Film Composition** & **O\({}_{2}\)** & **CO\({}_{2}\)** & **H\({}_{2}\)O Vapor** & **Tensile Strength** & **Elongation at Break** & **References** \\ \cline{2-7}  & & **[cm\({}^{3}\)\(\cdot\)mm/(m\({}^{2}\)\(\cdot\)d\(\cdot\)atm)]** & **[g\(\cdot\)mm/(m\({}^{2}\)\(\cdot\)d\(\cdot\)atm)]** & **[MPa]** & **[\%]** & \\ \hline \multicolumn{7}{c}{**Synthetic Polymers**} \\ \hline HDPE & 44–91 & 100 & 0.15 & 32 & 150 & [110, 111] \\  & (20 \({}^{\circ}\)C, 65\% RH) & (23 \({}^{\circ}\)C, 0\% RH) & (38 \({}^{\circ}\)C, 90\% RH) & & 10 & 400 & [110, 111] \\  & 98–183 & & 0.44 & & & & \\  & (23 \({}^{\circ}\)C, 50\% RH) & NR & (38 \({}^{\circ}\)C, 90\% RH) & & & & \\  & 50–200 & 100–1000 & 0.5–2 & 18 & 350 & [111, 112, 113] \\ PE & (23 \({}^{\circ}\)C, 50\% or 0\% RH) & (23-25 \({}^{\circ}\)C, 85\% RH) & & & & \\  & 1–5 & 3–7 & 0.5–2 & 55 & 300 & [111, 112, 113] \\ PET & (23 \({}^{\circ}\)C, 50\% or 0\% RH) & (23 \({}^{\circ}\)C, 75\% RH) & (23 \({}^{\circ}\)C, 85\% RH) & & 55 & 300 & [111, 112, 113] \\  & 50–100 & 200–900 & 0.2–0.4 & & & & \\  & (23 \({}^{\circ}\)C, 50\% or 0\% RH) & (unknown conditions) & (23 \({}^{\circ}\)C, 85\% RH) & 26 & 80 & [111, 112, 113] \\ \hline \multicolumn{7}{c}{**Biomass-derived chemically synthesized materials**} \\ \hline PLA & 3.5–15 & 32.9–72 & 1.6–3.6 & 50.45 & 3 & [110, 114, 115] \\  & (23 \({}^{\circ}\)C, 50\% or 0\% RH) & (23 \({}^{\circ}\)C, 0\% RH) & (38 \({}^{\circ}\)C, 85\% RH) & 50.45 & 3 & [110, 114, 115] \\ \hline \end{tabular}  
* NR: Data not reported.  
\end{table} 
Table 1: Barrier and mechanical properties of selected synthetic polymers and biomass-derived chemically synthesized materials. sports fiber in the PLA-film. Interactions between palm sprout and PLA restrict the water infiltration [118]. The incorporation of lignin in PLA films via simple blending results in a small but significant increase of the oxygen barrier properties, as well as an improved antiradical efficiency that increases with the severity of the heat treatment of the blends [119]. Moreover, the water sorption capacity decreased with an increase of lignin loading from 7 wt% to 15 wt% while tensile strength increased, as shown in a study of [PERSON] et al. [120]. [PERSON] et al. used commercial alkaline lignin and organosolv lignin from almond shells as PLA filler, which greatly improved the thermal stability and increased the elongation at break. Low percentages up to 1% unmodified lignin did not affect the maximum strain, while it was decreased with increasing lignin content at percentages greater than 5% [121]. In addition, kraft and organosolv lignin were examined as nucleating agents, showing that both lignins induce heterogeneous nucleation and increase the crystallization rate in PLA by shortening the crystallization half time and increasing the degree of crystallinity in PLA, while not affecting the processing window of the polymer [122]. One problem when incorporating lignin is its compatibility with PLA, which can be overcome with the addition of triallyl isocyanurate (TAIC), leading to the formation of PLA-TAIC-lignin crosslinked structures as interface, improving the compatibility in the blend and thus the mechanical, thermal, and hydrolytic degradation properties [123]. However, using TAIC, the biocompatibility has to be studied before applying it for food packaging. Another possibility is the introduction of lignin nanoparticles (LNP) into PLA using a Pickering emulsion template method where lignin acts as stabilizer. According to the results of this study, lignin could increase the decomposition temperature by approx. 10%, reduce the light transmission in the UV region, and increase the Young's modulus but also decrease the tensile strength and elongation at break. Moreover, the crystallinity of PLA could be improved with the addition of lignin [124].