Investigation Of Microstructure Of Polymer/layered Silicate Nanocomposite By Positron Annihilation

In this dissertation, the microstructure and other properties of a series of polymer layered silicate nanocomposites are systematically studied by Positron Annihilation Lifetime Spectroscopy (PALS) and other experimental methods. The free volume properties , Structural transition and crystallization behavior are discussed. The main results are as follows:1. Positron annihilation lifetime spectroscopy has been applied to study microstructure for epoxy-montmorillonite nanocomposite containing different content of montmorillonite, including the characteristics of free volume and interfacial layer, and the correlation between the positron annihilation parameters and the mechanical strength of the composite. It is observed that the o-Ps lifetime T₃ and it's intensity I₃ all decrease when the composite contains 2% montmorillonite, while the intensity of the second lifetime I₂ increases. A good correlation between I₂ and flexural strength is found, which indicates that the interfacial interaction plays an important role in determining the flexural strength.2. A new computing program-MELT has been applied to study the distributable of the second lifetime intensity. It shows that when the composite contains 2% montmorillonite, the parameter δ = 21.082ps (δ = FWHM/2.355) is the maximal., which confirms that more interface has been formed for the content 2% montmorillonite.3. The structural transitions of HDPE/ rectorite nanocomposite are studied as a function of temperature. It is observed that the inflection points of o-Ps lifetime increase differently, so the structural transition temperature increase differently too.4. Using XRD technology, the crystallization behavior of HDPE/ rectorite nanocomposite is discussed. It shows that the rectorite layer can facilitate crystallization and increase the crystallization degree.