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High Active And UV-resistant Aramid Fibers Through Surface Grafting Of Ce0.8Ca0.2O1.8 And Its Hybrids

Posted on:2016-09-03Degree:MasterType:Thesis
Country:ChinaCandidate:X L ZhuFull Text:PDF
GTID:2191330464952039Subject:Materials Science and Engineering
Abstract/Summary:PDF Full Text Request
Aramid fiber(KF) is a kind of high-tech organic synthesized fiber with high thermal resistance, low density, and high strength. However, it is vulnerable to fracture owing to UV irradiation that resulting in degradation and deterioration of properties, thus the shortened service life will restrict its outdoor application. What’s worse, the high crystallinity and regularity of fiber leads to low surface free energy and lack of active group. As a result, KFs reinforced composites can’t fully exhibit their comprehensive properties. On the other hand, note that flame retardancy has been one keyword of the properties for high performance organic fibers, but few works have been reported. Our work reported in this thesis aims at building a new method to overcome the three bottle-neck problems of KFs while remaining the outstanding thermal and mechanical properties of original KFs, and obtain new high performance KFs with simultaneously improved UV-resistance, high surface activity and flame retardancy.The thesis contains two parts. Firstly, an inorganic particle(Ce0.8Ca0.2O1.8) was synthesized through the soft chemical solution method, which was then grafted on the surfaces of KFs to prepare modified KFs(Ce0.8Ca0.2O1.8@KFs). The structures and properties of Ce0.8Ca0.2O1.8@KFs were systematically investigated. Results show that the high strength and modulus as well as outstanding heat resistance of Ce0.8Ca0.2O1.8 can endow KFs with excellent thermal and mechanical properties; the initial decomposition temperature(Tdi) of Ce0.8Ca0.2O1.8@KFs have been improved by 34.0-66.8o C compared with that of KFs. In addition, Ce0.8Ca0.2O1.8@KFs not only have greatly improved surface wettability due to the presence of-OH groups, but also enhanced UV-resistance. The surface free energies of Ce0.8Ca0.2O1.8@KFs are 1.18-1.43 times of that of KFs; and the retentions of tensile strength of Ce0.8Ca0.2O1.8@KFs reach 88.0-94.5%.Secondly, a new kind of surface modified fibers with hyperbranched polysiloxane/Ce0.8Ca0.2O1.8 hybridized coating(HSi-Ce0.8Ca0.2O1.8), HSi-Ce0.8Ca0.2O1.8@KFs, were prepared through an in-situ methodology. The structures, morphologies and integratedperformance of HSi-Ce0.8Ca0.2O1.8@KFs were intensively studied. Results show that HSi-Ce0.8Ca0.2O1.8 hybrid can effectively improve the tension property and thermal stability of fibers, and which also has a greater improvement in surface activity than Ce0.8Ca0.2O1.8;the Tdi of HSi-Ce0.8Ca0.2O1.8@KF1 has improved by 69.0oC and the surface free energies of HSi-Ce0.8Ca0.2O1.8@KFs are 1.49-1.54 times of that of KFs; Compared with single modifier(Ce0.8Ca0.2O1.8, or HSi), organic-inorganic hybrid modified KFs possess higher UV absorbance and wider absorption range, and thus better UV-resistant performance; the retentions of the tensile strength of HSi-Ce0.8Ca0.2O1.8@KFs reach 91.9-97.4%, higher than those of Ce0.8Ca0.2O1.8@KFs. Besides, HSi and Ce0.8Ca0.2O1.8 in the hybrid exhibit a synergistic effect on flame retardancy for the reason that HSi-Ce0.8Ca0.2O1.8 can form a new structure after absorbing a large amount of heat; the heat release capacity(HRC) and peak heat release rate(PHRR) of HSi-Ce0.8Ca0.2O1.8@KFs are 55.4% and 52.3% of those of KFs,respectively.
Keywords/Search Tags:aramid fiber, Ce0.8Ca0.2O1.8, hyperbranched polysiloxane, surface activity, UV-resistance, flame retardancy
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