双醛纤维素的制备及其对纸张强度的增强

目的 采用球磨降低纤维素的结晶度,制备纤维素超细粉体;采用高碘酸钠氧化球磨后的纤维素,制备出双醛纤维素;利用双醛纤维素改善纸张的抗张强度.方法 以微晶纤维素为原料,通过球磨粉碎处理,制备出微晶纤维素超细粉体.利用红外光谱、核磁光谱、X射线衍射和扫描电镜对不同处理时间的样品进行表征;利用高碘酸钠对球磨粉碎后的微晶纤维素超细粉体进行选择性氧化,制备双醛纤维素超细粉体;将双醛纤维素超细粉体加入纸浆中,研究其对纸张强度的影响.结果 微晶纤维素经球磨粉碎后,结晶区被破坏,结晶度下降,会形成大小不一的超细粉状;纸张中双醛纤维素超细粉体的质量分数分别为0.8％和1.0％时,纸张干、湿强度提高到最大;微晶纤维素超细粉体与高碘酸钠的质量比为1:3时,纸张湿抗张强度效果较好,从1.9 N·m/g增加至2.32 N·m/g,提高了22.1％.结论 微晶纤维素超细粉体经高碘酸钠氧化后,纤维表面产生了大量醛基,在抄纸过程中会与纤维表面上的羟基形成半缩醛结构,使纸张的干、湿抗张强度得到改善.     

水溶性PVA纤维接枝硅烷偶联剂及其对纸张的增湿强作用

采用硅烷偶联剂对PVA水溶性纤维进行表面改性,讨论了未改性和改性PVA纤维含量、KH-560添加量对纸张干、湿拉力以及湿强度的影响。研究结果表明PVA纤维经改性后,纸张的各项强度均有大幅提高,同时明显改善了其粘缸粘布行为和分散性。当KH-560添加量为16.6%,改性纤维含量为20%的纸张具有较佳的强度。对比了KH-550与KH-560改性纤维对纸张湿强度的提高效果。扫描电镜能谱显示改性后有Si元素出现,表明含硅支链成功接枝到了纤维表面。而扫描电镜照片则表明,改性后的纤维表面出现了带状分布的浅色颗粒物。原子力显微镜图AFM进一步说明了PVA纤维表面的亲水性基团部分被疏水性支链所取代,可增强纤维间的结合力。     

TEMPO氧化体系对废纸浆纤维的氧化改性

目的利用2,2,6,6-四甲基哌啶氧化物自由基(TEMPO)/NaClO/NaBr氧化体系改善废纸浆纤维成纸的性能。方法以废纸浆为原料,在碱性条件下采用TEMPO/NaClO/NaBr氧化体系对纤维进行选择性氧化,得到不同羧基含量的氧化废纸浆,通过纤维形态分析仪及化学分析法对纤维形态和羧基含量进行分析和测定;将氧化废纸浆、氧化废纸浆与原浆进行抄片和配抄,对手抄片的强度性能进行检测和分析;从经济效益出发,研究氧化体系中TEMPO及NaBr的循环使用次数对纸张强度性能的影响。结果随着NaClO用量的增加,废纸浆纤维的羧基含量增加;纤维长度、宽度和粗度有所降低;纸张抗张强度和环压强度增长较为明显;NaClO和NaBr循环使用2次后纸张的强度性能有所降低,但降低幅度不大。结论TEMPO氧化体系可用于废纸浆的氧化,改善废纸浆的性能。NaClO和NaBr的循环使用能够降低生产成本。     

抗菌纤维素织物的制备及表征

采用高碘酸钠氧化棉织物,在织物表面生成醛基,然后和尿素反应生成席夫碱.经硼氢化钠还原及次氯酸钠溶液漂洗后,织物表面生成了抗菌性的N-氯代酰胺.研究了氯漂工艺对织物上氯含量的影响,考查了织物表面氯胺的可再生性,采用振荡瓶法测试了改性织物的抗菌性.红外光谱测试表明,织物表面的醛基和尿素反应生成了席夫碱;经过硼氢化钠还原和次氯酸钠溶液漂洗后,在织物表面生成了氯胺.改性织物较适宜的氯漂工艺为:20℃、pH 10.0、在0.50％活性氯的次氯酸钠溶液中漂洗15min.织物表面的氯胺具有较好的可再生性.当织物的氯含量≥0.71mg/g时,对大肠杆菌和金黄色葡萄球菌的杀灭率均达到100％.     

环氧氯丙烷对水溶性聚乙烯醇纤维的表面改性及增强机理

采用环氧氯丙烷通过溶胀悬浮多元接枝共聚法对水溶性聚乙烯醇(PVA)纤维进行表面改性,讨论了未改性和改性PVA纤维含量、环氧氯丙烷添加量、干燥温度、干燥时间及PVA纤维水溶温度对纸张干、湿拉力以及湿强度的影响。研究结果表明PVA纤维经环氧氯丙烷改性后,纸张的各项强度均有大幅提高,同时明显改善了其粘缸粘布行为和分散性。当干燥温度为100～110℃,干燥时间为10min,纤维水溶温度为80℃时,纸张具有较佳的强度。红外光谱图证实了环氧基团在原纤维表面的接枝改性反应。扫描电镜图表明PVA纤维经环氧改性后,表面由光滑结构转变为鳞状沟壑结构。原子力显微镜图AFM进一步说明了PVA纤维表面的亲水性基团部分被疏水性环氧基所取代,可增强纤维间的结合力。     

双醛壳聚糖/阳离子淀粉施胶剂的抗油脂性能

目的提高包装纸的环保性及抗油脂性能。方法通过高碘酸钠选择性氧化壳聚糖(CTS)来制备双醛壳聚糖(D-CTS),将双醛壳聚糖与阳离子淀粉(CS)进行复配来制备D-CTS/CS施胶剂,然后将D-CTS/CS施胶剂在手抄纸上进行涂布,测试涂布纸的抗油脂性能。利用表面接触角仪来分析抗油脂的作用机理。结果复合施胶剂中,当双醛壳聚糖质量分数为0.3%,干燥温度为80℃,干燥时间为50 s,p H值为5.5~6.5时,涂布纸抗油脂性能最好,抗油脂指数最高能达到10。结论纸张表面经过该施胶剂处理后,纸张表面静电作用以及成膜性能都得到了提高,从而阻碍了油滴在纸张中的渗透,使抗油脂性能得到了增强。     

硅烷偶联剂及氧化石墨烯二次改性对芳纶纤维界面性能的影响EI北大核心CSCD

为改善芳纶纤维(PPTA)与丁腈橡胶(NBR)复合材料之间的界面强度,采用硅烷偶联剂A172和氧化石墨烯(GO)对芳纶纤维表面进行接枝改性处理,并对处理前后的芳纶纤维进行化学结构、表面形貌及H抽出力分析。利用SEM对抽出纤维表面和橡胶基芳纶纤维复合材料截面进行微观结构分析。结果表明:硅烷偶联剂和氧化石墨烯对芳纶纤维进行二次表面改性后,纤维表面含氧基团增加,化学活性提高,处理后表面存在明显的表层附着物,纤维结构未发生明显损伤且表面粗糙度得到明显改善。每个处理阶段后H抽出力均有提高,且氧化石墨烯二次改性后的芳纶纤维H抽出力提高效果最佳,从18.192 MPa提高到48.748 MPa,芳纶纤维与丁腈橡胶的界面结合力得到了显著提升,从而证实了硅烷偶联剂和氧化石墨烯二次改性芳纶纤维的有效性,为橡胶基芳纶纤维复合材料性能的研究提供了参考。     

氧化细菌纤维素的制备及其表征

目的 通过高碘酸钠氧化制备含醛基的氧化细菌纤维素,并改善细菌纤维素的抗菌性能,为细菌纤维素的综合利用提供新思路.方法 以氧化细菌纤维素中醛基的含量和保留率作为评价指标,通过单因素和正交试验对其进行优化,利用红外光谱仪、扫描电镜对氧化前后的细菌纤维素结构进行表征,以大肠杆菌、金黄色葡萄球菌为实验菌种,探究氧化细菌纤维素的抑菌性能.结果 当高碘酸钠浓度为0.3 mol/L,悬浮液pH为4.0,体系温度为50℃,反应时间为4.0 h时,制备的氧化细菌纤维素的最佳醛基含量为98％(质量分数)、保留率为78％.经氧化后,氧化细菌纤维素存在醛基官能团,其对大肠杆菌、金黄色葡萄球菌产生的抑菌圈直径分别为21.5,23.3 mm.结论 制得了含醛基的氧化细菌纤维素,且其具有较好的抗菌性.     

木质纤维素-聚氨酯共聚型高强度功能纸张的研究

研究了以木质纤维素、聚氨酯为原料合成高强度纸张的方法,并分析了经加工的纸张的物理特性及其表面形态.研究结果表明:木素-TDI-PEG线型遥爪聚合物能够和纸张中纤维素的羟基反应,生成氨基甲酸酯结构,不仅使纸张中的纤维之间产生大量的交联结构,而且把木素与纤维联结起来,从而形成纤维-木素-TDI-PEG四元体系型聚氨酯复合材料,使纸张的耐折度、挺度、耐破度和湿强度等物理指标有了明显的改善,为纸张在包装、建筑等工农业生产中开辟更为广阔的前景.     

氧化石墨烯改性玄武岩纤维及其增强环氧树脂复合材料性能

为了改善玄武岩纤维/环氧树脂复合材料的界面性能,通过偶联剂对氧化石墨烯进行改性,并将改性后的氧化石墨烯引入到上浆剂中对玄武岩纤维进行表面涂覆改性,同时制备了氧化石墨烯-玄武岩纤维/环氧树脂复合材料.采用FTIR表征了氧化石墨烯的改性效果;运用SEM分析了改性上浆剂处理对玄武岩纤维表面及复合材料断口形貌的影响和作用机制.结果表明:偶联剂成功接枝到氧化石墨烯表面;玄武岩纤维经氧化石墨烯改性的上浆剂处理后,表面粗糙度及活性官能团含量增加,氧化石墨烯-玄武岩纤维/环氧树脂界面处的机械齿合作用及化学键合作用增强,界面黏结强度得到改善,玄武岩纤维的断裂强力提高了30.8%,氧化石墨烯-玄武岩纤维/环氧树脂复合材料的层间剪切强度提高了10.6%.     

Effect of fibre curl on the properties of wood pulp fibre-cement and silica sheets

Curl has been induced in unbleached softwood kraft pulp fibres by treatment in the laboratory at 20% consistency in a planetary mixer. Steam treatment of the fibres to set the curl more strongly was found to be detrimental to fibre properties as deduced from handsheet properties. A means of producing two-ply specimens in the laboratory was devised and a tensile test for interlaminar bond strength was developed. The use of curly fibres in reinforced cement and silica sheets gave sheets with improved wet interlaminar bond strengths, relative to sheets prepared from conventionally treated fibres but had little effect on the values of modulus of rupture and fracture toughness.     

氧化微晶纤维素交联壳聚糖复合膜的制备及性能

目的 制备氧化微晶纤维素交联壳聚糖复合膜,并探索交联改性对壳聚糖复合薄膜性能的影响。方法 首先采用高碘酸钠氧化法对微晶纤维素进行氧化处理,制备氧化微晶纤维素,再通过溶液共混流延法制备不同质量分数(0%、1%、3%、5%、7%、9%)的氧化微晶纤维素交联壳聚糖复合薄膜。通过对复合薄膜组分、形貌、力学性能、光学性能、热稳定性及阻隔性能的表征,考察不同含量的氧化微晶纤维素对壳聚糖薄膜各性能的影响。结果 氧化微晶纤维素表面的醛基能与壳聚糖中的氨基发生交联反应,氧化微晶纤维素的加入可以改善壳聚糖薄膜的拉伸强度和断裂伸长率,复合薄膜的拉伸强度和断裂伸长率最大分别达到了43.07 MPa和19.42%;随着氧化微晶纤维素含量的增大,复合薄膜的紫外屏蔽性能增强,水蒸气透过系数增高,但热稳定性未见明显变化。结论 采用氧化微晶纤维素交联改性壳聚糖可以有效改善壳聚糖薄膜的力学性能和紫外屏蔽性能,有助于进一步扩大其包装应用范围。     

Nanogold and nanosilver composites with lignin-containing cellulose fibres

The formation of nanogold and nanosilver composites with cellulose paper fibres and the associated lignin component together with their antimicrobial properties are presented. This follows on from the proprietary technology of Johnston et al. [1] wherein they used nanogold and nanosilver entities in wool fibres to provide novel colourfast colourants in textiles with additional effective antimicrobial and catalytic properties. The nanogold and nanosilver are formed and bound directly onto the unbleached lignin-containing paper fibres without the use of an external linker molecule. For this, the lignin was found to play an essential role and hence the methodology presented is applicable only to cellulose in the form of unbleached kraft fibres and mechanical pulp. The phenol and possibly the aromatic methoxy groups of the lignin are considered to reduce Au³⁺ to Au⁰ and Ag⁺ to Ag⁰, respectively, and bind the nanogold and nanosilver to the fibre surface. SEM images and UV–Visible spectra confirm the formation of nanogold and nanosilver on the fibre surface. Changes in the IR spectra are consistent with the above role of the phenol and methoxy groups. The resulting nanogold—unbleached kraft fibres are purple and the nanosilver—unbleached kraft fibres are yellow due to the surface plasmon resonance effects of nanogold and nanosilver respectively. The nanogold—unbleached kraft fibres and particularly the nanosilver—unbleached kraft fibres exhibit very effective antimicrobial properties at low levels of gold and at very low levels of silver. In this way we have been able to produce novel nanogold paper and nanosilver paper fibres and products which collectively exhibit the properties of the nanomaterials and the fibre substrates in a synergistic way. This provides the opportunity for developing new functional paper products for antimicrobial packaging, medical dressings, and clothing.     

Characterization of TEMPO-oxidized bacterial cellulose scaffolds for tissue engineering applications

Introduction of active groups on the surface of bacterial cellulose (BC) nanofibers is one of the promising routes of tailoring the performance of BC scaffolds for tissue engineering. This paper reported the introduction of aldehyde groups to BC nanofibers by 2,2,6,6-tetramethylpyperidine-1-oxy radical (TEMPO)-mediated oxidation and evaluation of the potential of the TEMPO-oxidized BC as tissue engineering scaffolds. Periodate oxidation was also conducted for comparison. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses were carried out to determine the existence of aldehyde groups on BC nanofibers and the crystallinity. In addition, properties relevant to scaffold applications such as morphology, fiber diameter, mechanical properties, and in vitro degradation were characterized. The results indicated that periodate oxidation could introduce free aldehyde to BC nanofibers and the free aldehyde groups on the TEMPO-oxidized BC tended to transfer to acetal groups. It was also found that the advantageous 3D structure of BC scaffolds remained unchanged and that no significant changes in morphology, fiber diameter, tensile structure and in vitro degradation were found after TEMPO-mediated oxidation while significant differences were observed upon periodate oxidation. The present study revealed that TEMPO-oxidation could impart BC scaffolds with new functions while did not degrade their intrinsic advantages.     

Conformability of wood fiber surface determined by AFM indentation

Mechanical properties of wet fiber surfaces of hardwood chemi-thermo-mechanical pulp and softwood kraft pulp were measured using an AFM as a nanoindetation device. Elastic modulus of wet fiber surfaces was observed in the range of 30 MPa to 1.6 GPa, which is significantly affected by chemical treatment of pulping and bleaching as well as mechanical refining. Plastic yield stress of wet fiber surfaces measured varies from a few MPa to about 100 MPa, and is also highly correlated to chemical and mechanical treatments of these fibers. Plasticity index shows no difference among once-dried hardwood and softwood pulp fibers, but it increases after refining. The dynamic responses of wet fiber surfaces to external loads were evaluated through creep analysis. Even creeps were observed on all wet fiber surfaces, deformation caused by creep is relatively small. The major portion of deformation still comes from instantaneous elastic and plastic deformations. Creep of wet fiber surfaces is a fast dynamic process when subjected to a load change, most of it occurs within several seconds after the initial contact.     

Fabrication and characterization of fully biodegradable natural fiber-reinforced poly(lactic acid) composites

Polymer composites were fabricated with poly(lactic acid) (PLA) and cellulosic natural fibers combining the wet-laid fiber sheet forming method with the film stacking composite-making process. The natural fibers studied included hardwood high yield pulp, softwood high yield pulp, and bleached kraft softwood pulp fibers. Composite mechanical and thermal properties were characterized. The incorporation of pulp fibers significantly increased the composite storage moduli and elasticity, promoted the cold crystallization and recrystallization of PLA, and dramatically improved composite tensile moduli and strengths. The highest composite tensile strength achieved was 121 MPa, nearly one fold higher than that of the neat PLA. The overall fiber efficiency factors for composite tensile strengths derived from the micromechanics models were found to be much higher than that of conventional random short fiber-reinforced composites, suggesting the fiber–fiber bond also positively contributed to the composites’ strengths.     

碳纤维形貌结构对其电化学氧化行为及其复合材料界面性能的影响

通过调控原丝工艺,制备得到形貌结构不同、力学性能相近的PAN基碳纤维(CF),用以模拟碳纤维表面光滑与沟槽结构对其电化学氧化行为的影响。研究表明:原始形貌光滑碳纤维在电化学过程中保持形貌能力较强,相同的电化学氧化强度下,其表面氧碳比高于原始表面粗糙的碳纤维,表明其氧化程度高。X射线光电子能谱(XPS)分峰结果表明,二者表面氧含量差别来自于表面羰基含量的差异。力学性能测试结果表明具有沟槽形貌的碳纤维拉伸强度及拉伸模量提高的幅度较大,其中拉伸强度提高最大值为17.3%。将氧化前后的碳纤维制备成碳纤维增强树脂基复合材料,探讨碳纤维形貌结构对其复合材料界面性能的影响。结果表明:由具有沟槽形貌的碳纤维制备得到的复合材料层间剪切强度(ILSS)较高,表明碳纤维表面物理形貌也是影响复合材料界面的重要因素。     

Autoclaved beaten wood fibre-reinforced cement composites

The need to beat (or refine) wood pulp fibres before using as a reinforcement in cement composites has been re-examined. In the case of Pinus radiata unbleached kraft pulp, it has been confirmed that beating the fibres does contribute to attaining optimum mechanical properties for composites fabricated from such modified fibres.