水溶性PVA纤维对包装纸增强作用的研究

在高强度包装纸抄造过程中,使用水溶性PVA纤维做增强剂,研究了水溶性PVA纤维的添加量、加入方式、磨浆条件对增强效果的影响.结果表明,添加水溶性PVA纤维后,纸张抗张强度显著提高,裂断长提高幅度为18.8%～45.8%,撕裂指数、耐破指数也有不同程度的改善.研究确定了水溶性PVA纤维的最佳使用条件为:PVA60用量为6%,两段磨浆,程序升温干燥,此时抄片各项强度指标有不同程度的提高,裂断长提高45.8%,撕裂指数提高32.9%,耐破指数提高17.3%.研究表明水溶性PVA纤维是一种有效的纸张增强剂,制备的高强度纸包装材料生物降解性能好,是真正的绿色包装材料.     

液体直接染料纸张染色效果的影响因素

探讨了硫酸铝及其用量、液体直接染料的种类和用量、浆料种类和打浆度等因素对液体直接染料纸张染色效果的影响。结果表明,加入适量的硫酸铝可以改善染色效果,硫酸铝对阴离子直接染料比对阳离子直接染料染色效果的改善更大;黄色染料可显著提高纸张的b*值,而L*值、a*值会有不同程度的减小;红色染料可显著提高纸张的a*值,而L*值、b*值会有不同程度的减小;红色染料对L*值的减小程度比黄色染料大;棕色染料可增加纸张的a*值、b*值,但同时L*值会有所降低;黑色染料可大幅度降低纸张的L*值,但同时a*值、b*值均会有一定程度的减小;直接染料对漂白化学浆的染色比未漂浆的染色效果更好;打浆度高的浆料有利于染色。     

速生桉木硫酸盐浆氧脱木素工艺的优化

对卡伯值为17．1的速生桉木硫酸盐浆进行了氧脱木素各影响因素的研究。结果表明，用碱量、温度、氧压和时间对氧脱木素后纸浆的性质均有明显的影响。从氧脱木素后纸浆的脱木素程度和黏度的变化考虑，该速生桉木硫酸盐浆较适宜的氧脱木素工艺条件为：浆浓10％，用碱量2％，MgSO4用量0．2％，反应温度100℃，反应时间60min，氧压0．5MPa。     

纤维素酶酶解苇浆纤维微观结构和结晶结构的变化

采用红外光谱(IR)、X射线衍射分析和扫描电镜对在纤维素酶解进程中苇浆纤维素大分子的结构及纤维形态的变化进行了研究.研究结果表明,纤维素酶酶解进程中,纤维素大分子的晶型没有改变,但结晶度呈现周期性变化,微晶尺寸略有降低.在酶解初期,纤维素酶不仅作用于纤维素无定形区,也开始作用在纤维素结晶区表面;在酶解中、后期,纤维素酶对纤维素结晶区和无定形区的作用呈现周期性变化.纤维素酶解过程中纤维表面呈现周期性"剥皮"现象,并且在纤维表面出现孔洞和沟槽,在孔洞处纤维易断裂,导致纤维长度和粗度的降低.     

XPS、AFM和ToF-SIMS的工作原理及在植物纤维表面分析中的应用

介绍了先进的表面分析仪器化学分析电子能谱(XPS)、原子力显微镜(AFM)、含飞行时间分析器的二次离子质谱仪(ToF-SIMS)的工作原理,回顾了近年来它们在植物纤维表面分析中的成功应用,综合利用XPS、AFM及ToF-SIMS方法,可分析和解决制浆造纸过程中的现象和问题。     

Promoted cell proliferation and mechanical relaxation of nanocomposite hydrogels prepared in cell culture medium

Nanocomposite hydrogels (NC gels) were synthesized through in situ polymerization of N-isopropylacrylamide (NIPAm) in the hectorite clay suspension made from cell culture medium Dulbecco’s modified Eagle medium (DMEM). Cell cultured on these NC gels (D-NC gels) surface proliferated faster compared with that on the NC gels synthesized in water due to the nutrients in the D-NC gels. Cells attached and proliferated faster on the D-NC gels with higher modulus. In addition, cell sheets with good viability spontaneously detached from the gel surface by lowering temperature. Their tensile elongation at break was higher than 7 and the true strength σ_true was up to 800 kPa. The stress–strain curves of the D-NC gels were described quantitatively with the Mooney–Rivlin equation. A stretched exponential stress equation was adopted to express the stress relaxation of the D-NC gels with an average relaxation time τ (～10² s) estimated from data fitting, showing a broad distribution (polydispersity k ～ 0.4). The τ value, which was used in simulation for the tensile creep compliance of the D-NC gels, became shorter with increasing clay concentration due to the decrease in the network chain length. The relaxation process was similar to the natural articular cartilage. This work provides a facile way to produce hydrogels with improved cell compatibility and satisfactory mechanical properties for biomedical applications.     

Compositional analysis and projected biofuel potentials from common West African agricultural residues

In recent years the focus on sustainable biofuel production from agricultural residues has increased considerably. However, the scientific work within this field has predominantly been concentrated upon bioresources from industrialised and newly industrialised countries, while analyses of the residues from most developing countries remain sparse. In this study the theoretical bioenergy potentials (bioethanol and biogas) of a spectrum of West African agricultural residues were estimated based on their compositions. We analysed 13 of the most common residues: yam peelings, cassava peelings, cassava stalks, plantain peelings, plantain trunks, plantain leaves, cocoa husks, cocoa pods, maize cobs, maize stalks, rice straw, groundnut straw and oil palm empty fruit bunches. The yam peelings showed the highest methane and bioethanol potentials, with 439 L methane (kg Total Solids)⁻¹ and 0.61 L bioethanol (kg TS)⁻¹ based on starch and cellulose alone due to their high starch content and low content of un-biodegradable lignin and ash. A complete biomass balance was done for each of the 13 residues, providing a basis for further research into the production of biofuels or biorefining from West African agricultural residues.     

Effects of periodically alternating temperatures on performance of single-chamber microbial fuel cells

Practical applications of microbial fuel cells (MFCs) for wastewater treatment are usually operated over a wide range of temperature, especially day–night temperature difference. Here, MFCs at alternating temperatures were compared with those at constant temperatures. MFCs at 6/18 °C reached a steady-state voltage of 0.41 ± 0.05 V at 6 °C and 0.36 ± 0.04 V at 18 °C, which were lower than that of MFCs at 18/30 °C (0.42 ± 0.01 V at 18 °C and 0.47 ± 0.02 V at 30 °C). MFCs at 18/30 °C produced the highest power density of 2169 ± 82 mW m⁻² at 30 °C, even higher than that of MFCs at constant temperature 30 °C. Moreover, MFCs at 6/18 °C and 18/30 °C obtained a comparable coulombic efficiencies (94.6 ± 5.2%, 83.2 ± 4.1%, respectively) compared with MFCs at constant temperatures (86.3 ± 7.3% at 18 °C and 84.1 ± 5.5% at 30 °C). These results demonstrate that MFCs could be successfully adapted for use under day–night temperature difference conditions.     

聚乙烯亚胺对白泥预处理及其加填对AKD施胶影响的研究

本文研究了聚乙烯亚胺(PEI)对白泥预处理后一些基本性能变化和用于加填时对施胶性能的影响。研究表明,通过不同pH值的PEI和机械处理白泥后,在粒径<10μm时,白泥的体积分数增大了9.37%-56.82%,而在10-30μm和>30μm的粒径范围内,白泥的体积分数都在减小。同时,预处理白泥加填后体系的Zeta电位值比未经处理白泥加填后体系的Zeta电位值小,体系变得不稳定。而预处理前后的白泥用于纸张加填时,经过预处理过程的白泥加填后施胶度比空白组PEI0的施胶度降低了56.60%-103.59%。     

乙醇浓度对桉木片醇水抽提预处理液成分的影响

采用回转式密封炉在醇水体系下对桉木片进行抽提预处理,分别采用3种不同浓度(醇/水比1/4、1/2、1/1)的混合液制备了不同的抽提物。对过滤后的抽提液首先进行糖分测定;其次将抽提液经冷冻干燥、苯/甲醇溶解、风干处理后,进行亲脂性化合物的测定;着重考察了乙醇/水体系中乙醇的浓度对预处理抽提液成分相对含量的影响。结果表明,抽提液中总含糖量分别为1.597mg/L、1.641mg/L、1.679mg/L,占物料总质量比例分别为5.39%、5.54%、5.66%,其中木糖的含量最高,三种样品均在78%以上;定性测得的预处理实验中抽提液亲脂性化合物为烷烃类、酯类和胶质类化合物,并且分子量大;主要的化合物为2,4’,5-三甲基二苯甲烷,2,6,11-三甲基-十五烷,十七烷,2,6,10,14-四甲基-十六烷,十九烷,槲皮素,二十六烷。