Synthesis of Polysulfones and Modification for Epoxy Adhesives
|School||Harbin Engineering University|
|Keywords||polysulfone epoxy adhesives toughening modification thermo-mechanical properties|
Polysulfones (PSF) are members of the high performance thermoplastics which possess noble features such as high strength and stiffness even at elevated temperatures, high continuous use and heat deflection temperatures, excellent resistance to hydrolysis, and acids and bases as well as good dimensional stability even in complex geometric shapes, low susceptibility to environmental stress cracking and extremely high-notched impact strength. Therefore, they can be applied in a variety of fields such as electronic and optical devices, biomaterials, and aerospace materials, ect. A class of thermoset polysulfones can be obtained by reaction of the active groups which can be introduced onto the end or the side of the polysulfone structure, and has good toughness which can overcome the brittleness of thermosetting resin. The performance of epoxy resins can be improved using polysulfones to modify thermosetting resins.Five amine group terminated polysulfones (PSF-NH2) with different molecular weights were synthesized by the reaction from bisphenol-A (BPA),4,4’-Dichloro-diphenylsulfone (DCDPS), and 4-aminophenol. Three carboxyl group terminated polysulfones were prepared by the reaction of BPA, DCDPS, and 4-hydroxybenzoic acid. The products were characterized by fourier transform infrared (FT-IR) and 1H and 13C NMR analyses. The solubility and thermal properties of oligomer were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The effects of molecular weight and dosage of polysulfones on the adhesive properties, mechanical properties, and dynamic thermo-mechanical properties of modified epoxy resin (E-51) using polysulfones as modifiers were studied by universal tensile testing machine and dynamic mechanical analyzer (DMA).Amine group and carboxyl group terminated PSF oligomers have good thermal properties and solubility. The glass transition temperatures (Tg) and char yields at 600℃under air atmosphere of PSF oligomers increased with the increase of molecular weights. For the blending of epoxy resins and amine curing agent with PSF oligomers, PSF can improve the adhesive force and elongation at break because the impact fracture energy was absorbed, transmitted, and dispersed when the plastic deformation was occurred. The little dosage of PSF oligomers with low molecular weight and small grain size can improve the elasticity of modified epoxy resins. On the contrary, much dosage of high molecular weight PSF increase the brittleness of cured system, resulting in the sharp decrease of strength of the product. Amine group terminated PSF oligomers and carboxyl group terminated PSF oligomers have similar properties. Furthermore, PSF oligomers have well processability, and can form homogeneous three-dimensional network with epoxy. The phase separation phenomena can not be observed.