Study On Dispersion Of Graphene Oxide In Polystyrene And Foaming Behavior Of As-prepared Nanocomposites

Polystyrene (PS) foam is the second most widely used foam. Main blowing agents (CFCs, HCFCs) used for PS foaming always deplete the ozone layer and HFCs causes global warming problem. Carbon dioxide has been indentified as the most promising blowing agent because it is environmentally friendly and non-toxic. However it has high diffusion coefficient and low solubility in PS, leading to control difficult foaming processing. Inorganic particles, especially graphite with a large specific surface area and strong IR absorption, could act as nucleating agents in polymeric foaming processes. The graphite can decrease the Gibbs free energy of nucleation and prevent carbon dioxide from diffusing fast, resulting in the improvement of foaming behavior. Therefore, the good dispersion of graphite in PS is the key problem to improve the foaming properties of PS/graphite.First, We modified PS and graphite, respectively. Second, the synergy and dispersion of the modified GO in PS were studied. Finally, the effect of dispersion on the thermal properties, rheological properties of the PS/GO nanocomposites and their foaming behavior were explored further.1、GO was fabricated by improved Hummers method and the carbon/oxygen molar radio was2.65:1, revealing that its surface contains many-OH and-COOH function groups. PS/GO nanocomposites were also prepared by solution blending using different solvent or concentration. The choice of DMF or an appropriate increase in the concentration is helpful for the dispersion of GO.2、By introducing the polar functional group2VP into PS chain segments, the dispersion of GO was obviously improved. Once TMI that could react with GO was introduced into the PS chain segments, the dispersion of GO was further improved. And better dispersion of GO in PS led to a higher Tg, higher thermal decomposition temperature and higher viscosity of the composites.3、PS and its nanocomposite is foamed by using supercritical carbon dioxide as the blowing agent. The effect of foaming temperature and foaming pressure on foaming behavior were discussed. Under same foaming condition, the order of cell size from largest to smallest is PS> PS/GO> P(St-co-2VP)/GO> P(St-co-TMI)/GO. This indicate that GO act as heterogeneous nucleation agents in PS foaming process; the modification of PS by2VP and TMI is benefit for the improvement of heterogeneous nucleation function. If the temperature ranges from120℃to150℃and the pressure ranges from7.6MPa to20MPa, the cell size of P(St-co-TMI)/GO is smaller than P(St-co-2VP)/GO, and the foaming behavior of P(St-co-TMI)/GO is less sensitive than P(St-co-2VP)/GO. The above results reveal that the better dispersion of GO, the more stable of foaming behavior.