|
Polylactic acid (PLA) is an important biodegradable polymer materials, is an excellent substitute of petroleum-based plastic. However, the polylactic acid molecule chain, long-chain branched less, low melt strength of the foamed material is difficult to obtain a high magnification. Difficult for the polylactic acid foam drawback polylactic acid system was modified in order to improve its foaming properties. The main study included: the preparation surface graft modification of nano-silica (SiO 2 ), compared silane coupling agent KH560 and bisphenol A epoxy resin graft modification of nano-SiO < / sub>-filled poly (lactic acid) composites; and then change the epoxy-functionalized nano-silica content, various performance nanocomposites nanocomposites with supercritical carbon dioxide as blowing agent in high-pressure applied in the reactor pressure-induced foaming technology, polylactic acid nanocomposite foams. FTIR, TG, DSC, SEM and mechanical properties test method silane coupling agent and epoxy resin modified Hou Nami silica results show that bisphenol A epoxy resin the Hou Nami modified silica surface introduced the epoxy group. Polylactic acid substrate supplemented with 2% of a bisphenol A epoxy resin-modified nano-silica nanoparticles can be preferably dispersed in a resin matrix, evaluated by fractal theory the nano SiO 2 in polyethylene lactic acid in the dispersion effect SiO 2 -g-SM827 fractal dimension smaller SiO 2 -g-KH560 fractal dimension several times without modification SiO 2 fractal dimension greater than 1.5. In addition, the tensile strength, elongation at break, impact strength were increased by 14.52%, 20.71% and 24.77%; nanoparticles Add to also greatly improve the rate of crystallization of the polylactic acid, the degree of crystallinity of 22.92%. Study of polylactic acid foam properties of nano-composite system, the paper using the the microcellular foaming dynamic simulation apparatus and the dumbbell-shaped foam autoclave equipment, supercritical carbon dioxide as a blowing agent, study the saturation temperature of the foaming temperature, the saturation time, crystallization saturation pressure and the pressure release rate of cell morphology, cell size distribution, the impact of the foam density and volume expansion. The study found that with increasing saturation temperature at 145-185 ° C, polylactic acid nano-composite system foam cell diameter decreases first and then increases, cell density and volume expansion increased first and then decreased; 70 - 100 ℃, with the improvement of the foaming temperature, the average cell diameter first decreased and then increased phenomenon; decreases with the saturation time, the average diameter of the cell, the cell density increases, but when the saturation time greater than 2 hours after to extend the saturation time the structure and morphology of the foam has little effect; crystallization so that the average diameter of the foam is reduced, foam density; cell size distribution narrows with increasing saturation pressure, an average diameter of the foam and the foam body decreased density, foam density and volume expansion coefficient is significantly increased, the average diameter of 18MPa under foaming, foam 11.59um cell density of 4.84 × 10 8 cell / cm 3 < / sup>, the density of the foam body 0.13g/cm 3 , the volume expansion ratio of 9.55; average diameter of the foam when the pressure drop rate is decreased by 84.21MPa / s to 11.85MPa / s by 12.32um increased to 31.19um. cell density of 3.17 × 10 8 a / the cm 3 dropped to 2.40 × 10 7 a / cm 3 .
|