Modification Of Unsaturated Polyester Resin By Fumed Silica

Unsaturated polyester resin(UPR) is one of the largest use of resin varieties among composites which are widely used in the field of construction, corrosion, insulation materials.But there are still some shortage in common UPR,such as hard and brittle character after curing, poor toughness, low intensity. So the applications are extremely limited.Therefore, the modification of UPR is significant.Usually, thixotropy level of modified UPR has an important influence on its construction. It is a hot spot to obtain modified UPR which has excellent thixotropy. Fumed silica has nanoscale particles and rich surface hydroxy. It is a preferable reinforcing agent and thixotropic agent of polymer material. This thesis modify UPR with fumed silica and prepare new unsaturated polyester which can meet customers requirements through optimization of formulation and process and comparison difference between domestic and imported fumed SiO2.Firstly, thesis studies a variety physical and chemical properties of fumed SiO2, including the packing density, specific surface area, dispersion, particle morphology, infrared spectroscopy and so on. On this basis, it studies type and content, speed dispersion, dispersion time, a styrene monomer content of fumed SiO2 how to influence the mechanical properties of resin and thixotropy of UPR.The results show that thixotropy of unsaturated polyester resin increase significantly with the increase of the fumed SiO2 content. The effect pecking order for the UPR thixotropic index of different types fumed SiO2 is as follows: N-20 > HL-200 M > HL-200 > A-200 > HL-150. As the unsaturated polyester resin crosslinking agent and diluent, styrene not only can reduce the viscosity of the system, but also to improve thixotropy of system.The thixotropy of UPR increase significantly with the increase of the amount of styrene. The tensile strength and elastic modulus of unsaturated polyester resin increases with the increasing amount of fumed SiO2, dispersion time, the speed of the dispersion. Elongation at break is just the opposite. The reinforcing effect of different types of fumed SiO2 to unsaturated polyester resin is as follow: N-20 > HL-200 M > HL-200 > A-200 > HL-150. The tensile strength and elongation at break of unsaturated polyester resin increase rapidly at first with increasing content of styrene. When the content is more than 32.5%, the tensile strength decreases and the elongation at break rises slowly. It can be found from SEM analysis of tensile fracture: smaller particle size of fumed SiO2, more uniform and dispersed in resin matrix, cross-section showing the fracture toughness.