改性微晶纤维素的制备及其对填充丁苯橡胶性能的影响II 改性棉纤维素对填充丁苯橡胶性能的影响

研究了微晶纤维素(MCC)和改性微晶纤维素(MMCC)的用量对丁苯橡胶(SBR)硫化胶物理机械性能的影响,以及分别填充20phrMCC和MMCC的SBR复合材料的耐磨性和动态力学性能分析。结果表明,当MCC和MMCC的用量都为20phr时,硫化胶有最大的拉伸强度,分别为15.3MPa和19.0MPa;填充MMCC的SBR复合材料的磨耗体积比填充MCC的降低了41%;填充20phr的MCC和MMCC的SBR具有相似的玻璃化温度。     

Mechanical properties of biodegradable composites from poly lactic acid (PLA) and microcrystalline cellulose (MCC)

Biodegradable composites were prepared using microcrystalline cellulose (MCC) as the reinforcement and polylactic acid (PLA) as a matrix. PLA is polyester of lactic acid and MCC is cellulose derived from high quality wood pulp by acid hydrolysis to remove the amorphous regions. The composites were prepared with different MCC contents, up to 25 wt %, and wood flour (WF) and wood pulp (WP) were used as reference materials. Generally, the MCC/PLA composites showed lower mechanical properties compared to the reference materials. The dynamic mechanical thermal analysis (DMTA) showed that the storage modulus was increased with the addition of MCC. The X‐ray diffraction (XRD) studies on the materials showed that the composites were less crystalline than the pure components. However, the scanning electron microscopy (SEM) study of materials showed that the MCC was remaining as aggregates of crystalline cellulose fibrils, which explains the poor mechanical properties. Furthermore, the fracture surfaces of MCC composites were indicative of poor adhesion between MCC and the PLA matrix. Biodegradation studies in compost soil at 58°C showed that WF composites have better biodegradability compared to WP and MCC composites. The composite performances are expected to improve by separation of the cellulose aggregates to microfibrils and with improved adhesion. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2014–2025, 2005     

微晶纤维素胶体的流变性研究

本文研究了微晶纤维素肢体的流变性质．微晶纤维素肢体为触变性流体，它的贮存稳定性、热稳定性和酸碱稳定性优于羧甲基纤维素．按Ostwade幂方程式算出它的触变系数及按Green－Weltmann方程式算出它的时间融变系数和拆散触变系数都比较大。     

微晶纤维素的研究进展

微晶纤维素具有独特的尺寸结构,其基质纤维素丰富价廉、可再生降解并具有良好的生物相容性,是天然高分子材料的重要分支.微晶纤维素的制备方法主要有酸水解法和酶解法;微晶纤维素除在传统行业有广泛应用外,还在增强复合、生物医学和光电科学等新兴领域有重要应用.最后对微晶纤维素的未来发展进行了展望和期待.     

微晶纤维素的微细结构研究

研究了各种纤维素材料及不同酸浓度水解制成的微晶纤维素的聚合度，并用X-射线衍射法研究结晶度、结晶形态、晶粒尺寸和颗粒大小；用透射电镜（TEM）观察颗粒形状和大小，发现不同纤维素材料达到平衡聚合度（LODP）的盐酸浓度略有不同；在酸水解过程中纤维素的结晶形态、晶粒尺寸和颗粒大小基本不变，而且用X-射线衍射及TEM测出的颗粒不是纤维素晶粒，而是微原纤。     

微晶纤维素的羧甲基化反应

纤维素通过特殊的化学物理手段处理后，得到的微晶纤维素在有机溶剂中能很好地分散开，且所需要的有机溶剂的量较少。对其反应条件的探索表明，用微晶纤维素来进行羧甲基化反应，碱化和醚化时间较短，且一氯醋酸的利用率较高；用异丙醇作溶剂比乙醇作溶剂反应效果好。产物用1H－NMR研究表明，取代基在2位、3位和6位上的分布较均匀。     

抗凝血硫酸化微晶纤维素的制备

以微晶纤维素(MC)为原料,采用氯磺酸-DMF硫酸化方法制备了具有抗凝血活性的硫酸微晶纤维素钠盐Na-MCS,并研究了以提高产物抗凝血活性为目标的工艺,即在常温条件下向原料MC中加入适量的浸润试剂DMF,并在真空下搅拌浸润;在盐水冰浴中制备氯磺酸-DMF酯化试剂;将适量酯化试剂加入已浸润的MC中搅拌反应;调节反应产物的pH值,在去离子水中透析,减压浓缩后真空干燥。     

High yield production of microcrystalline cellulose by a thermo-mechano-solvolytic treatment

By thermally treating a commercial cellulose in ethylene glycol, celluloses of controlled low degree of polymerization, DP_r = 1000 to 70, can be derived. Two general behaviors are observed in the range studied. At first, the depolymerization reaction is predominant down to a DP equal to 130. Beyond this level, the depolymerization process leads to extensive solubilization of the cellulose. The treated celluloses have been analyzed by X-ray diffraction, FTIR, TGA, elemental analysis and enzymatic hydrolysis. No chemical change of the cellulose could explain the two different behaviors. A physical modification in the form of depolymerization and destructuration is suspected.     

Preparation of microcrystalline cellulose from rice straw under microwave irradiation

Crude cellulose was isolated from rice straw and then converted into microcrystalline cellulose (MCC) via partial hydrolysis. Both the isolation and partial hydrolysis were carried out under microwave. Rice straw was successively pretreated with alkaline and acid solutions before hydrolysis. Lignin and silica were almost removed but partial removal of hemicellulose in dilute alkali solution, and the residual hemicellulose was further removed in dilute acid solution. The total removal rates of hemicellulose, lignin and silica reached up 92.0%, 98.5%, and 96.8%, respectively. The cellulose content of 93.6 wt % in MCC was given by partial hydrolysis of crude cellulose isolated from rice straw. The comparison between microwave irradiation and traditional heating method was also investigated. Compared to traditional heating method, similar results were obtained while milder conditions, including shorter time and lower temperature, were required. An effective microwave‐assisted and energy‐efficient methodology using rice straw as the alternative source of cellulose fiber was developed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44901.     

Silicified microcrystalline cellulose based pellets and their physicochemical properties

Silicified microcrystalline cellulose (SMCC), Prosolv SMCC 50 was used as spheronization aid to manufacture pellets by extrusion and spheronization. Different ratios of SMCC to lactose were used to manufacture pellets using appropriate levels of water as liquid binder. Avicel PH101 based pellets were also manufactured for comparison of their physical properties. The ratio of liquid binder to spheronization aid was critical to produce pellets of desired size and shape. Extrudates composed of 20% aid could withstand only smaller spheronization force in order to be shaped into pellets. The successful products fulfilled the quality of pellets such as narrow size distribution and spherical in shape. The highest surface tensile strength was observed in pellets with equal ratio of lactose to SMCC while pellets having 20% aid disintegrated rapidly within 15 min. Furthermore, Prosolv SMCC 50 based pellets possessed a stronger surface tensile strength when compared with Avicel PH101 based pellets. In conclusion, Prosolv SMCC 50 has showed to be a good spheronization aid for extrusion and spheronization when used in the range of 20 to 80% content. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43829.     

微晶纤维素超临界水解糖化的研究

于420℃的盐浴温度下,在80 g水中分别加入1～5 g的微晶纤维素,进行了纤维素超临界水解产糖的研究.结果表明随着固液比的增大,还原糖和己糖含量均升高,但液化率下降,最大还原糖质量浓度为13.05 g/L,对应的己糖质量浓度为7.12 g/L,液化率50.6%,己糖产率为11.4%,电镜图片显示水解残渣的表面有大量的孔洞,同时形成了大量的球状颗粒.     

乙醇再生微晶纤维素的分级及其结构表征

在微晶纤维素（MCC）的Na OH/尿素溶液中加入不同质量的无水乙醇进行分级沉降，得到分级再生微晶纤维素。通过黏度法测定了再生微晶纤维素的聚合度，采用FTIR、XRD、XPS、TG和SEM对再生微晶纤维素的结构、结晶度、热稳定性和形貌进行了表征。结果表明，随着分级次数的增加，再生微晶纤维素的聚合度逐渐降低，3次分级后微晶纤维素的聚合度由MCC的203降至77；微晶纤维素形貌由表面光滑的棒状纤维结构变为粗糙多孔的结构；再生微晶纤维素的晶型由MCC的Ⅰ型转变为Ⅱ型，3次分级后微晶纤维素的结晶度由MCC的65.58%降至32.05%。分级再生微晶纤维素的自由羟基增加，参与成键的羟基减少；再生微晶纤维素的热稳定性随着分级次数的增加而降低，3次分级后初始分解温度由MCC的310℃降至257℃。     

Impact of water absorption on the creep performance of epoxy/microcrystalline cellulose composites

Recently, considerable effort has been made to study cellulose/epoxy composites. However, there is a gap when it comes to understanding the post-conditioning anomalous effect of moisture uptake on their mechanical and dynamic-mechanical properties, and on their creep behavior. In this work, up to 10.0 wt% microcrystalline cellulose (MCC) was incorporated into epoxy resin by simple mixing and sonication. Epoxy/MCC composites were fabricated by casting in rubber silicone molds, and rectangular and dog-bone test specimens were produced. The moisture uptake, dynamic mechanical, chemical, tensile, and creep behavior were evaluated. The incorporation of MCC increased the water diffusion coefficient. The changes in storage modulus and glass transition temperature, combined with Fourier-transform infrared spectroscopy analysis, evidenced that water sorption in epoxies causes both plasticization and additional resin crosslinking, although the latter is prevented by the addition of MCC. The creep strain of the composites increased by 60% after conditioning, indicating that plasticization induced by water sorption plays an important role in the long-term properties of the composites.     

粗纤维素酶液对微晶纤维素酶解的影响因素

栗生灰黑孔菌多被用于产漆酶的研究,很少有利用其纤维素酶的报道。为了降低在纤维素水解中纤维素酶的使用成本,利用栗生灰黑孔菌发酵制备的粗纤维素酶液,以微晶纤维素为底物模型,研究粗纤维素酶液水解微晶纤维素的最佳pH、温度和最佳表面活性剂助剂种类及浓度,并对不同表面活性剂存在条件下的纤维素酶解动力学、紫外和荧光光谱进行了研究。结果表明,粗纤维素酶水解微晶纤维素的最佳条件为pH 4.8,温度50℃,最佳表面活性剂助剂为吐温80,添加剂量为1.12mg/g底物;吐温80的添加可提高粗纤维素酶解的最大反应速度常数V_max,降低米氏常数K_m;表面活性剂改变了纤维素酶的紫外和荧光最大吸收峰,酰胺Ⅰ带和酰胺Ⅲ带的谱峰,可能通过与纤维素酶中的氨基酸残基发生反应影响了纤维素酶的结构,进而影响了微晶纤维素的水解反应。该研究为进一步降低纤维素水解成本提供了理论指导。     

Radiation degradation of microcrystalline cellulose in solid status

Pulverization and degradation are important pretreatment procedures in producing bio‐ethanol from cellulose. In this study, microcrystalline cellulose (MCC), a pure α‐cellulose, was degraded by γ‐irradiation. The average degree of polymerization, content of reducing sugar, crystalline structure, and molecular structure were investigated to elucidate the radiation effect on the degradation of MCC. The results manifested that γ‐ray destroyed part of the chemical bond and hydrogen bond, leading to the degradation of cellulose and increasing of the reducing sugar content. According to the Fourier transform infrared result, radiation degradation led to the formation of reductive carbonyl group. Meanwhile, radiation had slight influence on the crystalline structures of MCC. Therefore, the radiation degradation procedure is expected to benefit the further proceedings such as ultrafine treatment and enzyme hydrolysis of cellulose. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Enhanced mechanical properties of epoxy composites using cellulose micro- and nano-crystals

Epoxy polymers are commonly utilized in structural applications due to their high bearing capacity and excellent chemical resistance. However, their inherent brittleness poses a significant challenge for their use in high shock and fracture strength products. To address this shortcoming, fillers can be incorporated into the polymer during preparation. In this study, we aimed to investigate the effect of incorporating cellulose-based fillers, namely cellulose nanocrystals (CNCs) and microcrystalline cellulose (MCC), on the mechanical properties of epoxy polymer composites. The study evaluated the impact of various factors, including filler concentration, particle size, and moisture content, on the mechanical properties of the composites. The results demonstrated that the incorporation of CNC or MCC powders at concentrations below 5% could enhance the mechanical properties of the resulting epoxy composites without adversely affecting their surface and thermal properties. The maximum tensile strength and fracture toughness of the filler-based epoxy composites were achieved at 2 and 4 wt% for CNCs and MCC, respectively. CNCs with a smaller particle size distribution were found to be much more effective than MCC in improving the mechanical properties of the epoxy composites. Furthermore, utilizing dried fillers resulted in a higher improvement in tensile strength, which was achieved at lower filler concentrations.     

Effect of cellulose nanofibers and acetylated cellulose nanofibers on the properties of low‐density polyethylene/thermoplastic starch blends

The aim of this study was to evaluate the effect of cellulose nanofibers (CNFs) and acetylated cellulose nanofibers (ACNFs) on the properties of low‐density polyethylene/thermoplastic starch/polyethylene‐grafted maleic anhydride (LDPE/TPS/PE‐g‐MA) blends. For this purpose, CNFs, isolated from wheat straw fibers, were first acetylated using acetic anhydride in order to modify their hydrophilicity. Afterwards, LDPE/TPS/PE‐g‐MA blends were reinforced using either CNFs or ACNFs at various concentrations (1–5 wt%) with a twin‐screw extruder. The mechanical results demonstrated that addition of ACNFs more significantly improved the ultimate tensile strength and Young's modulus of blends than addition of CNFs, albeit elongation at break of both reinforced blends decreased compared with the neat sample. Additionally, biodegradability and water absorption capacity of blends improved due to the incorporation of both nanofibers, these effects being more pronounced for CNF‐assisted blends than ACNF‐reinforced counterparts. © 2018 Society of Chemical Industry     

木薯淀粉基十二烷基糖苷的制备及其表面性能

以木薯淀粉为糖源,在浓硫酸的催化作用下采用转苷法制备木薯淀粉基十二烷基糖苷（APG）,考察淀粉与乙二醇反应过程中反应体系糖浓度的变化规律,探讨反应温度、反应时间、催化剂用量、醇糖比等诸因素对十二烷基糖苷制备反应的影响,研究产品的表面性能。实验结果显示,在乙二醇糖苷的反应过程中,还原糖的浓度变化呈现先增大后降低的趋势;十二烷基糖苷的制备最佳反应条件为反应温度115℃,反应时间4h,催化剂用量0.8%,醇糖比为3.5∶1;制备的淀粉基十二烷基糖苷的表面张力为25.9 mN/m,临界胶束浓度（cmc）约为0.05%。     

微晶纤维素模板法制备纳米二氧化钛及表征

以TiCl4为原料,微晶纤维素为模板,制备了具有微晶纤维素特征形貌的纳米二氧化钛。借助透射电子显微镜、环境扫描电子显微镜、傅里叶变换红外光谱、X射线衍射、热重分析等分析方法对样品进行表征,探讨纳米二氧化钛的形成机理。结果表明:在500℃焙烧得到准球形锐钛矿纳米二氧化钛,粒径为15 nm;在700℃和900℃焙烧分别得到夹有金红石型的锐钛矿和红晶石型纳米二氧化钛,并且随着焙烧温度的升高,纳米二氧化钛晶型由锐钛矿逐渐转变成金红石型,其粒径增大,烧结加剧致使形貌变得更不规则。700℃焙烧产物在紫外光下对罗丹明B具有较佳的光催化降解性能。     

载甲钴胺香蕉纤维素微晶/PLGA介孔材料的制备及性能研究

从香蕉树皮中提取香蕉纤维素微晶，将甲钴胺、香蕉纤维素微晶和乳酸-羟基乙酸共聚物(PLGA)制备成载甲钴胺香蕉纤维素微晶/PLGA介孔材料。运用SEM、比表面积及孔径分析仪（BET）、热重-质谱联用仪(TG-MS)和FTIR对产物进行了表征；采用紫外分光光度计对载甲钴胺介孔材料进行了载药率、包封率、体外释放度测定。红外谱图分析表明，所制备的香蕉纤维素微晶的主要成分为纤维素；BET法测定结果表明，载甲钴胺香蕉纤维素微晶/PLGA介孔材料的平均孔直径[4V(孔体积)/A(表面积)]为17.89nm；TG-MS结果表明，载甲钴胺香蕉纤维素微晶/PLGA介孔材料分解温度约为300℃；体外释放实验表明，该材料对甲钴胺有较好的控释作用，药物释放遵循零级释放动力学方程。