Fabrication And Mechanical Properties Of Nano Cu/PMMA Microcellular Foams

Nano Copper/PMMA microcellular foamshave the multifunction of lightweightwith compressive capacity, explosion-proof performance and high strength duetoexisting a large amount of microcellular. So they have widely used in the fields ofpackaging, communication and transportation, automobile industry and nationaldefense. In this article, copper nanoparticles were embed in PMMA as theheterogeneous nucleating agent by in situ reduction method. The Copper/PMMAmicrocellular foams were synthesized through supercritical carbon dioxide(ScCO2)foaming technology. In this research, we focus on investigating the influence offoaming conditions on microcellular ’s structure and mass density. The mechanicalproperties at quasi-static and high strain rate were also studied.Firstly, monodispersed copper/PMMA colloids were obtained by in situreduction method which copper chloride dihydrate (CuCl22H2O) used as theprecursor of copper nanoparticles while N, N-dimethyl formamide acted as reducingagent in the absence of any stabilizers. The copper nanoparticles content was easycontrolled by the quantity of copper chloride dihydrate in DMF. The effect of coppernanoparticle content on dispersity of colloids was investigated. When the coppercontent less than10wt.%, the nearly spherical copper nanoparticles have highdispersity with a narrow size distribution. While the content exceed10wt.%, thenearly spherical copper nanoparticles would be agglomeration. So, the copper contentof copper/PMMA nanocomposites can be determined to synthesis Copper/PMMAmicrocellular foams with high foaming efficiency.Secondly, the copper/PMMA nanocomposites were synthesized throughanti-solvent precipitation method and hot pressing molding technology. The Copper/PMMA microcellular foams were synthesized through supercritical carbondioxidefoaming technology. Lewis acid-base theory, which is the theoretical basis ofthe interaction of ScCO2and PMMA was discussed. The adsorbing capacityof CO2inPMMA was measured by gravimetric analysis. The saturation time of foamingprocess was8hours based on the adsorbing capacityof CO2in PMMA. The influenceof saturation temperature and pressure on the adsorbing capacityof CO2was studied. The solubility of CO2in PMMA was increased with higher saturation pressure andlower saturation temperature.Thirdly, the effects of copper content and foaming conditions on copper/PMMAmicrocellular structures were investigated detailedly. With the copper content lessthan5wt.%, the cell size was under5μm and cell density ranged from1011～1012orders of magnitude. The cell density of copper/PMMA microcellular foams wasincreased with lower saturation pressure and higher saturation temperature andshorter foaming time. The cell size of copper/PMMA microcellular foams wasincreased with lower saturation pressure and higher saturation temperature and longerfoaming time. The effects of foaming conditions on copper/PMMA mass density wasalso investigated. The empirical correlations of mass density and foaming conditionswere obtained by a lot of experimental datas. The nucleation efficiency of purePMMA as low asone in a thousand in terms of copper/PMMA microcellular foams.The last part did a tentative exploration on the mechanical properties ofcopper/PMMA microcellular foams at quasi-static loading and high strain rateloading. Thefoams with improved morphologypresentobvious stress plateau regionunder quasi-static loading and stress wave dispersion effect under high strain rateloading. So, the copper/PMMA microcellular foams have a good energy absorptioneffect.