Nadya Dencheva

Manufacturing and properties of aramid-reinforced composites

Fundacao para a Ciencia e Tecnologia (FCT) - post-doctiral grant SFRH/BPD/45252/2008 (to Nadya Dencheva)

Preparation and Properties of Novel In Situ Composite Materials Based on Polyethylene-Polyamide Oriented Blends

The objective of this study is to manufacture and investigate novel nanostructured polymer composites (NPC) based on oriented blends of high-density polyethylene (HDPE) and polyamide 6 (PA6). Conventional polymer processing techniques are used for this purpose including extrusion blending, cold drawing and compression molding. Thus, various polymer blends are prepared comprising 10 and 20 wt% of PA6 and 0-10 wt% of a copolymeric compatibilizer. These blends are cold-drawn to high draw ratios and the oriented strands so produced are further compression molded at various temperatures between the melting points of HDPE and PA6. All NPC obtained are characterized by microscopy techniques, solid state NMR, mechanical tests and wide- and small-angle X-ray scattering from synchrotron. The mechanical and structural data of NPCs are discussed with relation with the polyamide fibrils’ orientation, as well as with the effect of compatibilizer at the matrix-fibrils interface.

Synthesis, characterization, and applications of polyolefin-polyamide micro- and nanofibrillar composites

Abstract This chapter reviews the research on microfibrillar composites (MFCs) based on polyethylene (PE)/polyamide (PA) oriented blends, without and with additional reinforcement by nanoclays. Various topics related to the synthesis, morphological, structural, and mechanical characterization of MFC systems are discussed. Investigations on the structure-properties relationship in neat oriented PA6, PA12 and PA6/nanoclay MFC precursors are important for optimization of the MFC preparation. The mechanical properties in tension, flexure, and impact of PE/PA-based MFC systems are presented. The geometry and orientation of the transcrystalline layer (TCL) forming at the matrix/fibrils interface during the MFC preparation influences the mechanical behavior of MFC. Methods for TCL quantitative evaluation based on electron microscopy and synchrotron X-ray scattering in static and dynamic modes are presented. It is concluded that the knowledge-based transformation of oriented PE/PA blends into MFC can produce useful combination of the strong points of conventional fibrous and clay-reinforced polymer composites avoiding their most important limitations.