Study On The Preparation Of Polymer/Inorganic Hybrid Fibers By Sol-Gel Method

Polymer/inorganic hybrid material is a kind of new composite, which has both merits of organic polymer material and inorganic material. Polymer/inorganic hybrid fiber combines merits of hybrid materials with fiber materials, whcih implies important theoretical significance and has vast application vistas.In this paper, a series of hybrid sols and hybrid fibers based on polymer/silica/(titania) were prepared by Sol-Gel and drawing method. The viscosity and spinnability of the hybrid sols were researched, the preparation, mechanism, microstructure, and property of the hybrid fibers was investigated systemically. The main investigations are compiled below.1. A series of hybrid sols of PVA/SiO₂, PAA/SiO₂, PAN/SiO₂, Sucrose/SiO₂, HPMC/SiO₂ and PVA/SiO₂/TiO₂ were prepared with tetraethorylsilane(TEOS) and tetrabutylorthotitanate(TBOT) as raw materials by Sol-Gel method respectively, and the change rules in viscosity versus aged time and spinnability of which were studied. The results showed that the hybrid sols were similar to SiO₂ sols in viscosity change rules, that is, three distinct change rate stages of viscosity were found in all the sols, the characteristic of which was changed slowly, quickly and drastically, respectively. Among these, in the second stage, polymers in the hybrid sols were almost linear molecules with proper molecular weight, and the hybrid sols were spinnable. The conclusion provided experimental foundations for the research on preparation of hybrid fibers.2. The hybrid mechanism, chemical structure and performance of PVA/SiO₂ hybrid fibers were researched. The results showed that PVA was linked with silica by Si-O-C bonds, which formed by the condensation between -OH groups of PVA and the hydrolysates of TEOS, the performance of resistance to heat and to water of PVA were improved greatly, the crystallinity of PVA was limited by SiO₂ networks, and the hybrid fibers were amorphous. The results will afford a new route of modification of PVA fibers.3. The hybrid mechanism, chemical structure and performance of PVA/SiO₂/TiO₂ hybrid fibers were studied. The results showed that spinnability of the hybrid sols were improved gradually with increasing of PVA content, and the hydrolysis time of the hybrid sols decreased markedly with increasing of TBOT content. In the interior of the hybrid fibers, the distribution of polymer and silica-titania was very homogeneous, the hybrid fibers had better resistance to heat and to water. The results are of important reference value for the preparation and modification of PVA/SiO₂ hybrid fibers.4. Continuous PAA/SiO₂ hybrid fibers were prepared by co-condensation reaction of TEOS and vinyl triethorylsilane(VTEOS) and Sol-Gel polymerization in situ processes. The hybrid mechanism, chemical structure and performance of PAA/SiO₂ hybrid fibers were researched. The results showed that the PAA/SiO₂ hybrid sol possesses well spinnability when its viscosity become 1400-3000mPa·s, the fibers had smooth appearance and their diameters were symmetric with well transparency, PAA were linked with SiO₂ networks by chemical bonds via coupling agents, and the hybrid fiber had good resistance to heat and to water. The results will suggest a new method for modification of water soluble polymers, especially, in heat resistance and water resistance.5. SiC fiber is a kind of excellent reinforcer for high performance composites, which has similar insulating constant and electric resistivity to glass fiber, similar strength and modulus to carbon fiber, and superior heat-oxidation resistance than carbon fiber and aromatic fiber. It has been widely used in high-technical areas as aviation, spaceflight and atomic energy industry. Continuous sucrose/SiO₂ hybrid fibers were prepared via Sol-Gel method by drawing, the feasibility of using it as a new candidate for the precursor of continuous SiC fiber was investigated preliminary. The results showed that sucrose was linked with silica by chemical bonds, in the interior of the fibers, homogeneous and amorphous networks were formed, and after the hybrid fibers had been heated to 800℃, co-existence of silica and micro-crystals of graphite were formed. Up till now, no reports about this research have been found. And this research will provide theoretical basis for new route of SiC fiber.6. Two kinds of hybrid sols of PAN/SiO₂ were prepared via sols blend and Sol-Gel in-situ polymerization respectively. The hybrid mechanism, the spinnability of the two kinds of hybrid sols and structures of the hybrid fibers prepared were researched. The results indicated that the chemical structures, the micro-morphology and the performance of the hybrid fibers were influenced greatly by their preparation method and conditions. Among these, CN groups hydrolyzed in the hybrid fibers via in-situ polymerization, and the interior structures of the hybrid fibers via in-situ polymerization were more homogeneous, the structure of PAN could be well kept via sols blend, and both of the hybrid fibers had better resistance to heat than pure PAN. The results will provide theoretical basis for the development of PAN fibers with good performance, especially, in heat-resistance.7. HPMC/SiO₂ hybrid sols were prepared via Sol-Gel method with TEOS and HPMC as raw materials and KH570 as coupling agent. In the basis of investigation on the spinnability of the hybrid sols and the structure and performance of HPMC/SiO₂ hybrid fibers, gradient HPMC/SiO₂ hybrid fibers were prepared with silica gel fiber and HPMC/SiO₂ hybrid sols as raw materials. The influences of viscosity on the micro-morphology and on formation of the gradient HPMC/SiO₂ hybrid fibers were investigated. The results indicated that the preparation of gradient hybrid fiber was greatly influenced by the viscosity of the hybrid sol, the gradient hybrid fiber could be well prepared when the viscosity of HPMC/SiO₂ hybrid sol was kept at about 6000mPa·s. The results provide a new idea for the preparation of gradient hybrid fiber.