Fabrication, Thermal and Mechanical Characterization of Silicon Carbide-Expancel Nanocomposite

Abstract

A novel sonochemical method is developed to infuse silicon carbide nanoparticles (SiC) into expandable thermoplastic micro-spheres (Expancel) containing acrylonitrile and methylacrylonitrile polymer. Expancel micro-spheres consists a drop of liquid hydrocarbon encapsulated by a gas proof thermoplastic polymeric shell. These micro spheres expand ∼4 to 5 times of their original size (10μm) and drastically decrease it’s density from ∼1000kg/m3 to ∼30kg/m3, when exposed to the heat. To fabricate nanocomposite foam the Expancel microspheres were first dispersed in hexane along with known percentage of SiC nanoparticles and irradiated with high intensity ultrasonic horn for about 30min at room temperature. The excess n-hexane is removed using a high vacuum for 12h and heating at 60°C for 1h successively. The dry powder is transferred into a rectangular stainless steel mold and the mold is heated to ∼190°C at a heating rate of 10°C for 30 min using a MTP-14 programmable compression molding under a pressure of ∼ 3000lbs. The test coupons were cut precisely from the panels to carry out thermal, morphological and mechanical characterizations. The as-prepared nanophased foam samples were characterized by scanning electron microscopy (SEM), thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The SEM studies have shown that the SiC are well dispersed over the entire volume of the matrix with minimal, agglomeration. The foam cells structures are well ordered and uniform in size and spherical in shapes. The TGA and DSC analyses indicate that the nanophased foam materials are thermally more stable than the corresponding neat systems. Compression tests have been carried out for both nanophased and neat foams systems. Test results show a significant increase in compressive strength and modulus of the nanophased foams over the neat system. This enhancement in compressive properties has been observed repeatedly for multiple batches. Details of the synthesis procedure, thermal and mechanical characterization are presented in this paper.