Melt processing and characterization of cellulose fibres based composites and nanocomposites
(2010)
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- Authors
- Supervisors
- Devaux, Jacques
- Abstract
- (en) Cellulose is one of the structural elements of wood, cotton, flax… It has a so-called “microfibrillar” structure made from a meticulous assembly of parallel chains resulting from the biosynthesis of cellulose. Microfibrils have a section of nanoscopic dimension combined with a high length conferring them a high aspect ratio (=length/diameter). They exhibit also interesting mechanical properties (Young’s modulus around 150 GPa), a low density, biodegradability, wide availability, etc. making them quite attractive filler compared to a glass fibre. The objective was to investigate the dispersion of cellulose microfibrils in polymers using melt processing technique. Microfibrils were envisaged to be released from cellulose fibres either during extrusion assisted by water injection under pressure or in suspension via homogenization (producing microfibrillated cellulose or MFC) before extrusion. Limiting cellulose thermal degradation under melt processing conditions was another challenge. The impact of the good specific properties and the gel effect of microfibrillated cellulose on the composite properties were also aimed. In-situ defibrillation during extrusion step was not reasonably reached. However it was shown that high shearing forces improved the dispersion of cellulose fibres in polyolefins. The most spectacular effects came from the water injection under pressure during extrusion. The dispersion of the fibres was enhanced whatever the shear applied. The yellowing of the composites resulting from the thermal degradation of cellulose during processing was reduced. The incorporation of microfibrils in polymers was realized by first defibrillating cellulose by homogenization and then by introducing the dried MFC in the polymer using melt compounding. Addition of surfactant, suspension of polypropylene grafted on maleic anhydride (PP-g-MA) or polyethylene glycol (PEG) to the MFC gel was necessary for preserving microfibrils from agglomeration during drying. Thermal properties of dried MFC were found to be lower than starting cellulose. The anticipated degradation was ascribed to promoted dehydration reactions with as consequence an increase of char. Coating MFC was found to limit the anticipated dehydration reactions. Dispersion of PP-g-MA coated MFC into polyolefins and PEG coated MFC into poly(lactic acid) was obtained and microfibrils and microfibril bundles were located. The efficiency of the dispersion of MFC modified the viscoelastic behavior of the system due to the formation of a percolating network.
- Affiliations
Citations
Quiévy, N. (2010). Melt processing and characterization of cellulose fibres based composites and nanocomposites. https://hdl.handle.net/2078.5/91617