Abstract

Layered silicate clays have been used for decades as filler materials to enhance mechanical and thermal properties of polymers. Recently, efforts have focused on separating the layers of the clay with the purpose of forming clay-polymer nanocomposites. Investigations have been addressing the enhancement of mechanical and thermal properties of these materials. In this study, 5wt% of commercial montmorillonite clay (Cloisite Na+) and organically-modified montmorillonite (OMMT) clays (Cloisite 15A and Cloisite 30B) were compounded with nylon6. Nylon6/layered silicate nanocomposites were fabricated using melt compounding and solution compounding techniques. Nanoindentation, x-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), melt flow index (MFI) and transmission electron microscopy (TEM) analyses were carried out in order to elucidate the effect of the processing conditions and the organic modifier on the structure and properties of the formed nanocomposites. At a preliminary stage, melt compounding of nylon6 and Cloisite 30B was carried out at 230°C, 250°C and reprocessed at 250°C in an attempt to elucidate the role of processing temperature and the melt viscosity in exfoliation and dispersion of silicate layers during melt compounding. It was found that processing at 250°C yields superior exfoliation and dispersion while reprocessing results in full exfoliation and uniform dispersion of silicate layers. Nylon6/Na+, nylon6/15A, and nylon6/30B nanocomposites were produced by melt compounding at 250°C via single-screw extrusion. Nylon6/30B nanocomposite showed fully exfoliated and well dispersed silicate layers, which resulted in superior mechanical ii behavior (modulus and hardness) measured by nanoindentation. The lack of organic modifier in Nylon6/Na+ and the presence of a non-polar organic modifier in nylon6/15A nanocomposites, led to minor enhancements in their mechanical behavior compared to the neat polymer. Nylon6/Na+, nylon6/15A, and nylon6/30B nanocomposites were also produced by solution compounding. Nylon6/30B and nylon6/15A nanocomposites were found to have superior mechanical behavior compared to nylon6/Na+ nanocomposite. This believed to be due to the effect of the organic modifier in increasing the inter-gallery distance of clays and thus allowing the polymer to intercalate the clay galleries leading to full exfoliation. The effect of ball milling on the structure and the mechanical behavior of solution-compounded nanocomposites was investigated. It was found that although, under certain conditions, ball milling leads to exfoliation of silicate layers, a significant deterioration in the mechanical behavior of the formed nanocomposites was noticed, which is believed to, possibly, be due to a decrease in the aspect ratio of silicate layers due to their fragmentation during ball milling. The melt viscosity of the composite and the type of the organic modifier of the clay were found to be determinative factors in controlling the degree of delamination and dispersion during melt compounding. For the case of solution compounding, the presence of the organic modifier (regardless of its type) is found to be the primary factor in controlling delamination during solution compounding.

School

School of Sciences and Engineering

Degree Name

MS in Mechanical Engineering

First Advisor

Esawi, Amal

Committee Member 1

Ramadan, Adham

Document Type

Thesis

Rights

The American University in Cairo grants authors of theses and dissertations a maximum embargo period of two years from the date of submission, upon request. After the embargo elapses, these documents are made available publicly. If you are the author of this thesis or dissertation, and would like to request an exceptional extension of the embargo period, please write to thesisadmin@aucegypt.edu

Download

Share

COinS