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Five series of PT-30/organoclay (Cloisite 10A, Cloisite 30B, Nanomer I.28E, Nanomer I.30E and Nanomer I.44PA) composites were prepared and characterized. The dispersion of clay tactoids in PT-30 resin was studied by XRD and TEM. XRD analyses determined that the d-spacings of each nanoclays of these were expanded upon dispersing in the PT-30 matrix versus the as-received clay. TEM micrographs further demonstrated that the intercalation of clay layers by PT-30 occurred during the curing process. Histograms of clay tactoids distributions were generated based on the combination of XRD and TEM results. The glass transition temperatures (Tg) of selected PT-30/clay composites were measured by DSC and compared. Partial clay exfoliation with some resin intercalation was demonstrated. The average flexural strengths and flexural moduli of all composites were obtained using three-point bending tests.

This dissertation includes two parts: Part I “natural fiber/thermoplastic composites” and Part II “studies of organo-clay synthesis and clay intercalation by epoxy resins”. The use of light weight renewable natural materials instead of heavy mineral-based materials is important to generate lighter materials for sustainable human development. Renewable natural fibers have already been used to reinforce thermosetting and thermoplastic polymer composites. The abundance of hydroxyl groups in natural fibers causes two problems: (1) high water moisture uptake and (2) incompatibility with hydrophobic polymer matrices. Surface modifications have been used to solve these problems. In part I of this dissertation, the modifications of wood fiber/flour by acid chlorides and maleated polypropylene were studied. High density polyethylene (HDPE)/wood flour (WF) composites were investigated in Chapter 1 of Part I. Polypropylene (PP)/WF composites were studied in Chapter 2 of Part I. In Chapter 3 of Part I, kenaf/PP composites were explored. Finally, the effect of carbon nanofibers (CNF) and composite blending processes were studied in Chapter 4 of Part I. Composite flexural properties and water absorption properties were evaluated. Flexural strengths and flexural moduli were obtained by four-point bending tests. Micromorphologies were investigated by scanning electron microscope (SEM). Part II presents studies of organo-clay syntheses and the mechanism of clay intercalation by epoxy resins. Ammonium and imidazolium pillaring agents were synthesized and then used to modify clay. A pillaring agent with epoxy functional groups was also synthesized. Clay intercalation by epoxy resins was affected by the epoxy resin polymerization rate, viscosity and temperature. The diffusion rate of monomers and polymers into and out of clay galleries is a function of temperature and a major factor in intercalation. The clay’s degree of nano dispersion in epoxy composites were investigated by TEM. The clay thermostabilites were studied by TGA.

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