| Oriented porous graphene-polymer materials are equipped with significant anisotropic pore structure and properties,thus the superior mechanical,electrical and thermal properties of graphene merge with inexpensive and better flexibility of polymer that inspire a wave of research in oriented filter adsorption,sound and shock adsorption.Freeze-casting is the main method for preparing oriented porous materials,in which the pore and lamellar structure are extremely affected by solid content and components in the dispersion for freezing.However,few work has reported the synergistic effect of various factors on the pore structures and performance,most of which have centered on the single role of solid content or freezing rate on porosity.On the basis of numerous studies have focus only on the porosity of materials but neglect the design of pore or lamellar structure,sulfonated graphene(SG)was chosen here as main component and highly oriented layered porous graphene-polymer composites(SG-CMC/PVA composites)were successfully prepared through directional freeze-casting method by adding sodium carboxymethylcellulose(CMC)and polyvinyl alcohol(PVA)respectively.Besides,the pore structure was regulated and laminated materials of S-CP-PF were also fabricated by immersing and curing phenol formaldehyde resin(PF)in such SG-CMC/PVA composites.The main research contents are as following:(1)Solid content and relative weight ratio of different components in dispersion were regulated to analyse the effect of various components and intermolecular interactions on ice crystal growth and pore/lamellar structures.The porosity of SG-CMC/PVA composites decreases and the irregular macropores exhibited on radial section gradually transform into a “honeycomb” structure with the increase of solid content.More importantly,owing to the existence of hydrogen bond,and the differences in molecular volume and intrinsic characteristic of components,the pore structure of SG-CMC/PVA samples could be destroyed and display more fragments on the cross section.Nevertheless,the increase of weight ratio of CMC could highlight the lamellar structure and obtain smoother and tighter layers.(2)The relationship between pore structure,composition and performance was established based on the mechanical,electrical properties of SG-CMC/PVA composites.Highly oriented lamellar structure of SG-CMC/PVA composites account for their anisotropy feature in various properties.The increase of solid content,the weight ratio of SG or CMC in dispersion could generally improve the axial compression strength,brittleness,electrical and thermal conductivity of such samples,whereas the radial properties are more susceptible to the porosity and bridges between layers.Thus,SG-CMC/PVA-4 and 3SG-CMC/PVA-6 composites respectively convey the lowest electrical conductivity(Radial resistance: 4.17 G? Axial resistance: 2.23G?)and the highest thermal conductivity(0.051 W/m·k).Besides,the swelling ratio and adsorption capacity of samples are mainly depend on the porosity,molecular crosslinking networks and the affinity of samples to solvents,in which SG-CMC-PVA-2 composite indicates the most remarkable equilibrium swelling ratio and adsorption capacity of 3524% and 25.2 ml·g-1.(3)A series of significant anisotropic S-CP-PF composites with significantly improved mechanical strength were obtained by using PF to regulate the pore structure of SG-CMC/PVA composites.And the porosity of porous composite obviously decreases as the immersion-curing proceeds which results in the improvement of mechanical strength.Thus,the axial compressive and flexural strength of S-4C1P-4PF(Four immersion-curing processes)respectively achieve the maximum of 80.5 MPa and 43.6MPa.Additionally,S-4C1P-4PF also shows favourable flame retardant and resonant sound absorption. |
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