From wood to industrial polymeric biomaterials

Sanna Virtanen

Research output: ThesisDoctoral ThesisCollection of Articles

Abstract

Population growth, the dependence on fossil raw materials, and environmental problems caused by oil-based plastics have created a global need to search for alternative materials to replace conventional oil-based materials. Any effort to tackle such challenge, however, needs to meet the principles of sustainable development. Biodegradable and bio-based materials are promising candidates to support related bioeconomy strategies. Here, forest products are key players and, as such, this thesis targets the development of biocomposite materials by utilising wood as renewable source. The introduction of epoxy and silyl functional groups into wood-derived cellulose surface through chemical modification seemed to provide an advantageous route to enhance cellulose nanofibrils (CNF) dispersibility and compatibility with both polyvinyl alcohol (PVA) and polyurethane (PU) polymer matrices. The solution-casted PVA composites were developed by utilising the crosslinking reaction between the hydroxyl groups of PVA and epoxy groups of CNF. Using epoxidised CNF as reinforcement in PVA produced composites with outstanding mechanical properties already at low levels (0.5 to 1.5 wt.%). Additionally, the silylated CNF exhibit potential reinforcing additives already at low loadings in the water- and solvent-based two-component PU coatings by improving their strength, elasticity and abrasion resistance. The adhesion properties of the PU coatings to substrate were still retained when using the silylated CNF as additive. Modified wood-derived CNF provide fundamental improvements to PVA and PU properties, and are not only scientifically interesting but also industrially important. The study also demonstrates that moist, never-dried bleached softwood kraft pulp (BSKP) can be successfully melt compounded with polylactic acid (PLA) without chemical modification, resulting in a composite with enhanced mechanical properties. By using BSKP with relatively high moisture content in feeding, the general drawbacks associated with fibre cutting and degradation of PLA during melt processing were diminished. Also, the expensive and time-consuming stages involved in drying pulp fibres can be curtailed by using this production route. The processability and properties of the PLA/BSKP composites facilitate their future industrialisation and unveil technically and economically feasible applications.
Translated title of the contributionPuusta teollisiin polymeerisiin biomateriaaleihin
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Rojas Gaona, Orlando, Supervising Professor
  • Vuoti, Sauli, Thesis Advisor
Publisher
Print ISBNs978-952-60-8081-9
Electronic ISBNs978-952-60-8082-6
Publication statusPublished - 2018
MoE publication typeG5 Doctoral dissertation (article)

Keywords

  • cellulose
  • chemical modification
  • processing
  • polymer composites

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