Study On SiO₂/Cyanate Ester Resin Based Nanocomposites

Cyanate ester (CE) thermosetting polymers have outstanding adhesive, thermal, mechanical and in particular electrical properties. However, cyanate ester are one of the toughest thermosetting polymers, the application they are used in require improving crack resistance. Nano-SiO₂ can effectively enhance the properties of polymer due to its especial surface and interface interaction. In this paper we select nano- SiO₂ to toughen cyanate ester. For obtaining composites of more excellent properties, we apply nano-SiO₂ and liquid polyurethane elastomer (PUR) to to prepare ternary composites . The interaction of components and the properties of the composites are investigatedNanoparticles tend to form agglomerate dut to its size is small, based on the point, an effort has been made to select three different methods to disperse nano- SiO₂ (attrition treatment, coupling agent surface treatment, high-speed homogeneous shearing). Nano-particle dispersion , mechanical and thermal properties of nano-composites under three dispersing methods are characterized by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The characterization results show the distributing of nano- SiO₂ dispersed by three dispersing methods are almost the same. High-speed homogeneous shearing and attrition treatment can improved mechanical and thermal properties of composites, and the properties of the former is better than that of the latter;when nano- SiO₂ was 1wt% , the impact strength and the flexural strength of composites are respectively 35.0% and 12.1% higher than pure CE. However, coupling agent surface treatment decrease mechanical properties of composites, and decomposition temperature is also decreased.SiO₂/CE nano-composites are prepared by a high-speed homogeneous shearing method. The structure of composites is investigated by SEM and transmission electron microscope (TEM). The quasi-static mechanical properties, dynamic mechanical properties (DMA) and TGA of the composites were investigated. The results show that the impact and flexural strengths of the composites obviously increase at the lowcontent of SiO2. The impact strength reaches maximum at 0.3 wt% SiC>2, 75.4% higher than the pure CE. The flexural strength reaches maximum at 0.15 wt% SiO2, 28.0% higher than the pure CE. The strong interfacial interaction between SiO2 and CE determines the improvement of mechanical performance of the composites. The storage modulus and high temperature loss modulus of the composites obviously increase compared with the pure CE, and its glass transition temperature is 31.2°C higher than pure CE with 0.3wt% content of SiO?.The high-speed homogeneous shearing method is applied to prepare ternary composites of CE, nano-SiO2, and liquid polyurethane elastomer (PUR), and the interaction of components and the properties of the composites are investigated. The results show that addition of PUR and nano-SiO2 can synergistically affect the toughness and strength of CE. The improvement of mechanical properties of S1O2/PUR/CE system is mainly due to high interface interaction between SiC>2 and PUR/CE. The storage modulus of SiO2/PUR/CE composites is higher than that of PUR/CE, this indicates that incorporation of SiC>2 into the PUR/CE system remarkably enhances its rigidity and has good reinforcing effects. The loss modulus of SiCb/PUR/CE system is higher than that of PUR/CE system. The improvement of SiCh/PUR/CE in comparison with PUR/CE can also prove introduction of nano-SiCh into PUR/CE system affects physical bonds of the system. The decomposition temperature of SiCh/PUR/CE composites is greatly increased.