Environmental awareness and growing concern about plastic waste and the depletion of non-renewable resources have boosted interest in bio-based polymers in recent years. Although the fraction of bio-based polymers in the global plastics market is still small, the demand and share of bio-based polymers is rapidly increasing. The aim of this dissertation was to prove that fully bio-based long chain cellulose esters have the potential to replace traditional oil-based plastics in selected applications. In this research, the long chain cellulose esters were synthesized with different side chain lengths (C6-C18) and the influence of side chain length on barrier, mechanical and thermal properties was demonstrated. In order to study the differences in pulp reactivity and properties of cellulose esters, the molar mass of commercial softwood dissolving pulp was decreased in a controlled manner by ozone-hydrogen peroxide treatment. This research proved that decreasing cellulose molar mass enabled the synthesis of long chain cellulose esters with better reaction efficiency than with the original cellulose. In addition, both the cellulose molar mass and the degree of substitution could be controlled. The resulting long chain cellulose esters formed transparent, flexible and heat sealable films with good water vapor barrier and mechanical properties. Cellulose esters formed smooth and homogeneous coatings with good adhesions when nanocellulose (CNF) films and virgin kraft papers were coated. The long chain cellulose ester coatings also significantly improved the moisture barrier properties of CNF film and kraft paper – these values decreased linearly as a function of ester chain length up to 50% from non-coated values. These coatings also significantly improved the surface smoothness of CNF films by decreasing nano-roughness. The long chain cellulose ester coatings made the material heat sealable and, in addition, the coatings had no antimicrobial activity, and only few microbes adhered to the surface of these films. These results demonstrate that long chain cellulose ester coatings have potential in future packaging applications where surface smoothness, heat sealability and good water vapor barrier properties are required. Injection molding of long chain cellulose esters and their blends was also studied and the mechanical properties were investigated. The results indicate that thermoplastic long chain cellulose esters are completely processable without any addition of a plasticizer, which is very unusual in the case of cellulose esters. This research proves that these materials have good potential to be used in injection molding applications.
|Translated title of the contribution||Pitkäketjuisten selluloosaestereiden ominaisuudet ja applikaatiot|
|Publication status||Published - 2020|
|MoE publication type||G5 Doctoral dissertation (article)|
- cellulose esters
- barrier properties
- mechanical properties