In the successful transition towards a circular materials economy, the implementation of biobased and biodegradable plastics is a major prerequisite. To prevent the accumulation of plastic material in the open environment, plastic products should be both recyclable and biodegradable. Research and development actions in the past few decades have led to the commercial availability of a number of polymers that fulfil both end-of-life routes. However, these biobased and biodegradable polymers typically have mechanical properties that are not on par with the non-biodegradable plastic products they intend to replace. This can be improved using particulate mineral fillers such as talc, calcium carbonate, kaolin, and mica. This study shows that composites thereof with polybutylene succinate (PBS), polyhydroxybutyrate-hexanoate (PHBH), polybutylene succinate adipate (PBSA), and polybutylene adipate terephthalate (PBAT) as matrix polymers result in plastic materials with mechanical properties ranging from tough elastic towards strong and rigid. It is demonstrated that the balance between the Young’s modulus and the impact resistance for this set of polymer composites is subtle, but a select number of investigated compositions yield a combination of industrially relevant mechanical characteristics. Finally, it is shown that the inclusion of mineral fillers into biodegradable polymers does not negate the microbial disintegration of these polymers, although the nature of the filler does affect the biodegradation rate of the matrix polymer.

Bioplastics may solve environmental issues related to the current linear plastic economy, but they need improvement to be viable alternatives. To achieve this, we aimed to add chitin nanocrystals (ChNC) to polylactic acid (PLA), which is known to alter material properties while maintaining a fully bio-based character. However, ChNC are not particularly compatible with PLA, and surface modification with fatty acids was used to improve this. We used fatty acids that are different in carbon chain length (C4–C18) and degree of saturation (C18:2). We successfully used Steglich esterification and confirmed covalent attachment of fatty acids to the ChNC with FTIR and solid-state ¹³C NMR. The morphology of the ChNC remained intact after surface modification, as observed by TEM. ChNC modified with C4 and C8 showed higher degrees of substitution compared to fatty acids with a longer aliphatic tail, while particles modified with the longest fatty acid showed the highest hydrophobicity. The addition of ChNC to the PLA matrix resulted in brown color formation that was reduced when using modified particles, leading to higher transparency, most probably as a result of better dispersibility of modified ChNC, as observed by SEM. In general, addition of ChNC provided high UV-protection to the base polymer material, which is an additional feature that can be created through the addition of ChNC, which is not at the expense of the barrier properties, or the mechanical strength.