The effects of surface modification of microfibrillated cellulose on its dispersion and reinforcement potential in polyolefin composites.

Student thesis: Doctoral ThesisEngineering Doctorate (EngD)

Abstract

Microfibrillated cellulose (MFC) is a highly expanded, high surface area networked form of cellulose-based material. It it is readily available, abundant and cheap. These characteristics alongside with the high modulus and strength of cellulose nanomaterials make it a suitable candidate in the production of nano-scale cellulose based reinforced composites. The main obstacle in the production of performant MFC reinforced polyolefin based composites is the natural incompatibility of the polar cellulose fibrils with the apolar polyolefin macromolecule which lead to filler segregation, phase separation, poor interphase adhesion, reduced filler-matrix interphase, poor stress transfer to the reinforcement fibrils and consequently poor mechanical and impact properties of the composites. This research propose the use of a facile water-based chemistry based on the reaction of MFC with tannic acid and subsequent functionalisation with an alkyl amine to render the surface of the MFC fibrils hydrophobic and enhance the dispersion of the cellulose-based filler into an apolar thermoplastic matrix. The successful production of tannic acid-primary amine reacted MFC was evaluate using Fourier-Transform infrared spectroscopy (FTIR), and the effectiveness of the reaction in producing a hydrophobic form of MFC was evaluated using contact angle measurements. The most suitable processing for the production of the reinforced nanocomposites was selected considering the effect of temperature and compounding process on the filler dispersion in the matrix. The level of dispersion of the compatibilized MFC reinforced composites was evaluated using a variety of spectroscopic and microscopic techniques, the most efficient of which were found to be the Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and the multi-channel Spectral Confocal Laser Scanning Microscopy (SCLSM). The agglomeration of cellulosic filler within the composites was reduced by functionalising the surface of the MFC fibrils with tannic acid and octadecylamine. The resulting composites exhibited an increase in modulus at a high cellulose content.
Date of Award24 Mar 2020
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorSteve Eichhorn (Supervisor)

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