Poly(p-phenylene-2,6-benzobisoxazole) (PBO) fiber is currently one of the best-performing organic fibers; however, its low UV aging resistance limits its use. To improve the UV aging performance of PBO fibers, a novel PBO-Fe-PDA fiber was created by depositing a biomimetic structure of polydopamine (PDA) on the surface of PBO fibers with the transition metal ion Fe3+ as the active center. The surface morphology and elemental composition of PBO-Fe-PDA fibers were investigated. It was revealed that Fe3+ formed a coordination bond structure with the oxazole ring, and PDA was successfully loaded onto the surface of PBO-Fe fibers. After UV aging, the crystallinity and crystallographic orientation of PBO fibers significantly decrease, microcrystals inside the fibers slip, and the size of microvoids in the fibers rises. As a result, the strength of PBO fibers was significantly decreased after UV aging. The anti-UV aging capacity of PBO-Fe-PDA fibers, on the other hand, has been enhanced, as evidenced by a slight drop in crystallinity and crystallographic orientation and a significant decrease in the size growth of internal microvoids in the fibers after UV aging. The tensile strength retention of PBO-Fe-PDA fibers after UV aging increased by 93.13% when compared to PBO fibers without altering the fibers’ initial strength. The testing results show that this surface modification method is simple to employ and extends the service life of PBO fibers significantly.
Zheng Cheng,Can Chen,Jieyang Huang,Teng Chen,Yang Liu,Xiangyang Liu
The nondestructive functionalization of aramid fiber is an important research direction. In this study, a kind of benzimidazole-contained aramid fiber, Poly- p -phenylene-benzimidazole-terephthalamide (PBIA) fiber, was modified by the coordination of benzimidazole unit in fiber structure with Fe 3+ . Further, the coordinatively unsaturated sites of Fe 3+ endow the modified fiber with active sites for the grafting of PEI. Model compound of PBIA unit, PBA, was utilized to confirm the whole process of modification. In comparison with that of the untreated fiber, the IFSS value of fiber with PEI grafted has an increase by 47%, owing to the chemical bond formed on the fiber/epoxy interface and the better wettability of resin to fiber. In all, the study presents a nondestructive functionalization of aramid fiber and can be employed in the modification of other benzimidazole-contained substrates.
Fe(III)-coordinated mesoporous silica adsorbents functionalized with different loadings of ethylenediamine groups were prepared by a new NH 4 F-assisted co-condensation method and impregnation of Fe 3+ cations. Various characterization techniques, e.g. XRD , SEM, TEM, ICP-MS, elemental analysis , FT-IR spectroscopy, and nitrogen adsorption–desorption, were utilized to investigate the effect of functionalization degrees of adsorbents on their chemical composition, surface chemistry, pore structures and phosphate adsorption capacities in detail. In the batch adsorption tests, the functionalized adsorbents with increasing loadings of ethylenediamine groups possessed markedly enhanced adsorption capacities, although there was a gradual loss of ordered mesostructures accompanied. The adsorption isotherms were represented better by using Langmuir model than Freundlich model, which indicated the presence of monolayer adsorption. In particular, for the resulting adsorbent prepared with 0.5:1 M ratio of AAPTS and TEOS, the maximum phosphate capture capacity calculated from Langmuir model is 20.7 mg P/g. In the kinetic study , the phosphate adsorption followed pseudo-second-order equation well with a correlation coefficient of 0.999, suggesting the adsorption process be chemisorption . The phosphate adsorption efficiency of prepared adsorbent was highly pH-dependent and the high removal of phosphate was achieved within the pH between 3.0 and 6.0. The presence of Cl − and NO 3 - exhibited small impacts on the phosphate adsorption by using our synthesized absorbent; whereas, there were significantly negative effects from HCO 3 - and SO 4 2 - on the phosphate removal. In 0.010 M NaOH, more than 90% of the absorbed phosphate anions on the spent adsorbent could be desorbed, suggesting the absorbent with a capacity of regeneration.
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