The Preparation And Properties Of Microcellular Foamed Net Nylon-6 And Nylon-6 Composites Materials

Micro-foaming technology by using chemical or physical blowing agents in the formation of large cells inside the materials, when the cell size reaches the range of5~100 um, it not only reduces the density of materials, but also brings preferable machanical properties. Current techniques for preparation of micro-foaming polyurethane and polystyrene have been studied sufficiently. Nowadays, more and more researchers shift their attentions to nylon microcellular areas, and most of them only foucs on the supercritical foaming technology. However, supercritical foaming need more sophisticated equipment, and the study of preparation microcellular nylon with common equipment is till rarely reported.In this paper, PA6/PP/PP-g-MAH(Polyamide 6/Polypropylene/Maleic Anhydride Grafted Polypropylene) composites was prepared by a twin-screw extruder, and its melting and crystallization characteristics and non-isothermal crystallization kinetics was analyzed with kinetic moldels. The net PA-6 and PA-6 compositesthen was foamed in twin-screw extruders with TSSC chemical foaming agent, respectively. The effect of foaming agents(TSSC), nucleating agents(talc), crosslinked agents(DCP),compatibility agents(PP-g-MAH), screw speed and extrusion temperature on cell morphologies, void fraction, mechanical properties and crystallization behavior were explored by thermal field emission scanning electron microscope(FESEM), density test method, multifunction tensile tester and differential scanning calorimetry(DSC).The study shows that:(1) The PP-g-MAH either accelerates or hindes the crystallization rate of the PA6/PP/PP-MAH composite’s PA6 phase, but it has not effect on the nucleation and growth mechanism of the PA6 phase; both net PA6 and PA6/PP/PP-g-MAH composite’s non-isothermal crystallization kinetics can be well described by Jeziorny and Mo models, but not fit the Ozawa model;(2) For the netPA6, the most important factor affecting the cell diameter, the cell density, and the void fraction was the content of the chemical foaming agent; the minimum cell diameter was 56.84 um, the maximum cell density was 6.21×106 cells/cm3,and the biggest void fraction was 16.20%;(3) The void fraction and cell diameter of the PA6/PP/PP-g-MAH was decreased with the increase content of PP-g-MAH, when the content of the PP-g-MAH was 15 phr, the foamed sample’ cell diameter reaches the minimum 83 um, while the cell density becoming lower;(4) The screw speed has pronounced influence on the foaming properties of the PA6/PP/PP-g-MAH, the cell diamater of the foamed materials increases with the increasing of the screw speed, and when the screw speed was 80 rpm, the obtained sample’s cell diameter can be as small as 80 um, and its cell density can be as large as 6.94×106 cells/cm3;(5) No matter the net PA6 or the PA6/PP/PP-g-MAH micro-foam materials, its tensile stress increased with the relative dengsity increses.