| Hollow glass microspheres (HGMs) have become a novel type of important energy-saving, clean and light weight multi-functional filler for composites and been widely used in broad fields such as rubber, plastics, coatings, emulsion explosives, oil drilling, aerospace and deep-sea pipelines, due to their characteristics of hollow structure, light weight, good flow properties, low thermal conductivity, sound insulation, low water absorption, chemical stability and low cost. The composites made from polymer matrix and hollow glass microspheres could overcome the limitations of the single components and improve the material performance thus expand the applications. As an inorganic filler, HGM has a great surface polarity, which is imcompatible with the polymer matrix. So it is necessary to modify the surface of HGMs for improving their compatibility and interface adhesion with polymer matrix.As a surface-initiated controlled/ "living" radical polymerization method for surface-graft modification, surface-initiated atom transfer radical polymerization (SI-ATRP) can well control the polymer layer with uniform thickness and high graft density on the inorganic particle surface, so SI-ATRP is a promising surface modification method for inorganic surface.In this thesis, through SI-ATRP, up to 63 wt% polymethylmethacrylate (PMMA) have been successfully polymerized onto the HGM surface. The HGM surface modification was conducted through several sequent procedures of surface activation, surface amino-functionalization with silane coupling agents, introducing surface initiators by amidation reaction and finally grafting PMMA onto the surface via SI-ATRP. Many analytical techniques such as optical microscope, scanning electron microscopy (SEM), diffuse reflectance infrared Fourier transform (DRIFT) and thermo gravimetric analyzer (TGA) were employed to monitor and evaluate the surface modification effect based on two different kinds of HGMs with model SL50 from a domestic factory and S60HS from 3M corporation. The reaction conditions of the first important procedure, surface amino-functionalization with the silane coupling agents, were explored and preliminary optimized, which showed that the alkaline condition of ethanol-ammonia mixed solution well promoted the hydrolysis of the silane coupling agents and the condensation reaction with HGM surface silanol, thus facilitated the surface amino-functionalization and subsequent modification procedures. The HGMs with grafted polymer layer of a uniform thickness were surface hydrophobic and could well dispersed in many kinds of common organic solvents and could infer their good compatibility with many polymer matrixes just like PMMA.Based on some investigations about the preparation conditions, raw materials ratio for the synthesis of polyurethane prepolymers, we preliminarily explored HGM filled polyurethane composites with modified HGM of model S60HS, polyol PEBA2000 and toluene diisocyanate (TDI) via the pre-polymerization, the chain extension reaction and the film-formation curing process. It was found that the modified S60HS (HGM-PMMA) exhibited remarkably improved compatibility and a strong interface adhesion with the polyurethane matrix. The SI-ATRP modified HGMs should be a kind of outstanding fillers with sound insulation and low thermal conductivity and well suitable for polyurethane composites. |
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