Extension of the use of cellulose nanowhiskers in composite materials

Hossain, Kazi Md Zakir (2014) Extension of the use of cellulose nanowhiskers in composite materials. PhD thesis, University of Nottingham.

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Abstract

This thesis explores the use of cotton derived cellulose nanowhiskers (CNWs) in composite materials in the form of nanocomposite films, surface modified polymer fibres and also in self-reinforced (SR) composites.

Cellulose nanowhiskers (CNWs) were produced from cotton via sulphuric acid hydrolysis process and blended with polylactic acid (PLA) to produce CNW-PLA and was added to hydroxyethyl cellulose (HEC) to manufacture CNW-HEC nanocomposite films. The aggregated morphology and hydrophilicity of CNWs, hydrophobicity of PLA and the solvent used (Chloroform) played a major role in creation of voids within the CNW-PLA nanocomposites. In addition, the aggregated morphology of the CNWs also influenced the surface roughness and light transparency properties of the CNW-HEC films. Improvement in the mechanical, thermal and thermomechanical properties for both types of nanocomposites was achieved due to the reinforcing effect of the rod-like nanowhiskers. An increase in the crystallinity of the nanocomposites indicated that the CNWs induced crystallisation in the matrices. Incorporation of CNWs also had a significant influence on accelerating the degradation profile of the CNW-PLA nanocomposites and reducing the swelling capacity and initial swelling rate for the CNW-HEC films.

PLA fibres were also produced with varying diameters (11 µm to 38 µm) via a melt drawing process employing increasing take-up velocities. A higher degree of chain orientation as well as an increase in crystallinity for the thinner fibres was achieved due to strain-induced crystallisation. The variation in PLA fibre diameter also revealed a noticeable influence in their mechanical and moisture absorption properties at various humidity levels. Further, the hydrophobic and smooth surface of the PLA fibres was coated with various blends of CNWs (65 to 95 wt%) and polyvinyl acetate (PVAc) to impart roughness, where PVAc acted as a binder. An increase in tensile modulus and moisture absorption properties were achieved for the CNW/PVAc coated PLA fibres. These surface modified PLA fibres were aligned to produce unidirectional (UD) fibre mats prior to hot compaction (at 95oC) to manufacture SR PLA composites. Incorporation of CNW/PVAc within the SR PLA composites revealed an increase in their flexural and ductile properties compared to the control composite.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Rudd, C.D.
Ahmed, I.
Thielemans, W.
Keywords: Cellulose fibers, nanocomposites (Materials)
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Faculties/Schools: UK Campuses > Faculty of Engineering > Department of Mechanical, Materials and Manufacturing Engineering
UK Campuses > Faculty of Engineering
Item ID: 13910
Depositing User: EP, Services
Date Deposited: 10 Dec 2014 12:01
Last Modified: 13 Sep 2016 12:03
URI: http://eprints.nottingham.ac.uk/id/eprint/13910

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