过氧化氢氧化再生纤维素及其阻燃、吸附性能

Preparation and properties of oxidized regenerated cellulose by hydrogen peroxide

以过氧化氢氧化再生纤维素(GC)制备羧基再生纤维素(OGC),表征OGC结构变化及其对阻燃和吸附性能影响机理。通过碱泡预处理能有效提高GC比表面积,增加反应效率,获得羧基含量达15.6%的OGC。FT-IR和13C NMR表征结果说明OGC葡萄糖基环上的C6位伯羟基能被选择性氧化成羧基。随着羧基含量的提高,OGC无定形部分溶解而提高其结晶度,晶型则无显著变化,OGC的热分解温度下降,但是成炭率显著提高。当添加6.25%OGC为成炭剂用于环氧树脂膨胀型阻燃时,氧指数达到27.2,阻燃等级为V0。以火焰原子吸收分光光度法测定结果表明,当羧基含量为15.6%,OGC对铅和铜离子吸附量分别提高14倍和3.5倍,其原因在于氧化改性能显著提高OGC的比表面积和容积率,增加吸附容量。研究结果说明以过氧化氢氧化制备的OGC在阻燃成炭剂以及金属离子吸附领域中具有良好的应用前景。

Hydrogen peroxide was used to oxidize pretreated regenerated cellulose to oxidized regenerated cellulose（OGC） with carboxylic content（CC） ranging from 3.2% to 15.6% depending on the H_2O_2/cellulose molar ratios used, reaction time and the p H. The structure of OGC was characterized by FT-IR, 13 C NMR, SEM,BET and XRD. The results revealed that the primary hydroxyl at C6 site in glucose units of regenerated cellulose was selectively oxidized to carboxyl group by H_2O_2 at the present of copper sulfate, and the notable characteristic peaks of carboxyl groups appeared at 173±2 in the spectra of 13 C NMR. SEM revealed that the pretreated regenerated cellulose by alkali solution would increase the fiber diameter and grooves space, resulting in volume expansion of cellulose, and thereby promoting oxidation reaction. BET surface area（SBET） and adsorption pore volume（Vp） of OGC 15.6 increased from 10.12 m^2·g^（-1） to 62.45 m^2·g^（-1） and 0.0152 cm^3·g^（-1） to 0.0183 cm^3·g-1,respectively. The crystallinity of OGC showed increasing with the increase of CC, which was due to partial loss of the disordered regions during the washing process because of their increased water-solubility. By TG, there was a reduction in thermal stability in parallel with the increase in CC of the samples, while exhibited high char yields. These changes could be attributed to a reduction in degree of polymerization and the increment of CC. The results demonstrated that the cellulose was selectively oxidized to carboxyl group by H2O2, and the properties of OC were depended on the CC. The effect of carbonization agent type on the flame retardant properties of MFAPP/EP was investigated. It revealed that when OGC15.6（6.25%） acted as carbonization agent, the epoxy resin achieved a UL-94 V0 classification with LOI of 27.2%. The flame retardant properties of MFAPP/EP by OGC15.6 were better than those of GC and pentaerythritol. The adsorption capacity of OGC for Cu^（2＋） and Pb^（2＋） ions from aqueous single metal solutions was obtained by analyzing concentration determined by atomic absorption spectroscopy. These samples showed maximum adsorption capacities for Cu^（2＋） and Pb^（2＋） ions ranging from 4.894 to 24.426 mg·g^（-1） and 5.845 to 71.833 mg·g^（-1）, respectively. The OGC15.6 showed larger maximum adsorption capacities than GC. The result illuminated that OGC could be applied to flame retardant EP and metal ions adsorption due to the introduction of carboxylic group.