Study on Biodegradable High Value-Added Lignin-Based Biocomposites and Their Applications


Student thesis: Doctoral Thesis

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Awarding Institution
Award date11 Jun 2018


Lignin, the second most abundant biopolymer from plants after cellulose, has attracted considerable interest from both academia and industry owing to its low-cost, renewability, biodegradability and biocompatibility. It is the only aromatic biopolymer available from biomass. Recently, high value-added applications of lignin-based biocomposites have been extended to agriculture, fishery, automotive and tissue engineering. In this thesis, novel biodegradable lignin-based biocomposites were prepared, including mixing with gold nanoparticles, grafting with melamine phosphate and decoration with TiO2. Especial attention was paid to the properties of these biocomposites and related applications. Based on the application of lignin-based biocomposites, this thesis will be elaborated from three main aspects:

1)Gold nanoparticles embedded lignin for nonvolatile resistive switching memory. Natural biomaterials are capable of producing biodegradable and/or biocompatible electronic devices for vast applications such as next-generation green data storage. In this chapter, we demonstrate an environment-friendly alkali lignin as a favorable candidate for resistive switching memory storage applications. The resistive memory devices based on gold nanoparticles embedded alkali lignin (Au NPs:lignin) exhibits a typical write-once-read-many-times memory (WORM) resistive switching behavior with a large on-off ratio (> 104), and long data retention characteristics (> 103 s) under low power operation (4.7 V). Au NPs acting as trapping sites in the active layer are responsible for the resistive switching mechanism. The active layer can be fabricated on organic substrates through facile solution-processed methods under normal ambient conditions.

2)Melamine phosphate modified lignin as the sustainable functional flame-retardant filler. Lignin is employed as sustainable flame-retardant filler for polymers due to its high ability of char formation. In this chapter, melamine phosphate modified lignin (MAP-lignin) was synthesized as a bio-based halogen-free flame-retardant agent. MAP-lignin and rice husk ash (RHA) exhibited a good synergistic effect on the flame-retardant property of the poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB) biocomposites. The results revealed that MAP-lignin and RHA could significantly increase the char residue and MAP-lignin had a good miscibility with P34HB. Cone calorimetry data demonstrated that the addition of 30 wt% MAP-lignin and 5 wt% RHA reduced the peak heat release rate (PHRR) and total heat release (THR) of P34HB noticeably by 42.8 and 24.3%, respectively. The enhanced flame retardancy of P34HB biocomposite should be ascribed to the barrier effect of the increased char residue with compact and intact structure, as well as the released gases from the decomposition of melamine.3)Titanium oxide decorated lignin for UV-shielding. It is highly desirable to develop biodegradable UV-shielding films from the renewable resources as the ever-increasing demand from sustainability considerations. In this chapter, TiO2 decorated lignin particles (TiO2@lignin) were synthesized successfully by one-step hydrothermal method in aqueous solution to improve the UV-shielding performance of lignin particles. Then poly(propylene carbonate) (PPC) composite films (thickness of ~ 23 µm) with different contents of TiO2@lignin hybrids were prepared via blade casting method. The UV-vis spectra revealed that the PPC composite film containing 5 wt% TiO2@lignin hybrids could absorb about 90% of UV light in the full UV band (200-400 nm), indicating the TiO2@lignin hybrids had a good UV-shielding property.

By the combination of other biodegradable polymers, such as PLA, P34HB and PPC, the functionalized lignin exhibited potential applications in non-volatile memory device, flame retardant agent and UV-shielding. These approaches endowed low cost lignin with high value-added.

    Research areas

  • High Value-Added, Lignin, Biocomposites, Memory, Flame retardancy, UV shielding