Date of Award

8-2009

Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Forest Resources

Advisor

Douglas J. Gardner

Second Committee Member

David J. Neivandt

Third Committee Member

Yousoo Han

Abstract

The overall objective of this study was to investigate the influence of microcrystalline cellulose (MCC) filler loading on the mechanical and thermal properties of MCC-filled engineering thermoplastic composites. MCC and engineering thermoplastics (nylon 6 and a polyethylene terephthalate (PET)/polytrimethylene terephthalate (PTT) blend) were chosen as the filler/matrix combination. Engineering thermoplastic composites have attracted much interest over the past several decades due to potentially superior material properties and a wide range of applications such as in automotive, electrical and aerospace materials. MCC is thermally stable compared to other wood constituents and has the advantage of high specific surface area in comparison with conventional cellulose fibers. Because of these properties, MCC can use as a filler in polymer matrices. Differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA) were used to determine thermal properties of the composites. Infrared Spectroscopy (diffuse reflectance infrared Fourier transform (DRIFT)) was also used to identify chemical differences between the neat PET-PTT blend and MCC filled composites. The DSC results indicated that there was not a significant change in the glass transition (Tg) or melting temperature (Tm) of the nylon 6 and PET/PTT blend with the addition of MCC. With increasing MCC content, dynamic mechanical properties improved because of the reinforcing effect of the MCC. The TGA data show that as the MCC filler loading increased, the thermal stability of the composites decreased slightly because of the lower thermal stability of MCC compare to neat nylon 6 and PET/PTT blend. Thermogravimetric analysis also indicated that the MCC did not show significant initial degradation under 300°C, which implies thermal stability so that MCC-filled composites could be used for high temperature circumstances, like in "under the hood" applications in the automobile industry. No significant chemical changes were observed in the DRIFT spectra of the composites. Tensile, flexural and impact tests were used to evaluate the mechanical properties of the composites as well as determining the composite densities. The composites reinforced with higher MCC filler loadings displayed enhanced tensile and flexural properties in comparison with the neat nylon 6 and PET/PTT blend. The Izod impact strength of the composites decreased in comparison with the neat nylon 6 and PET/PTT blend. The density of the composites increased slightly with increased MCC loading.

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