PET／无机纳米粒子复合物的制备及性能

将分散处理后的纳米二氧化硅和纳米二氧化钛分别加入对苯二甲酸乙二醇酯的熔体中缩聚,制得聚对苯二甲酸乙二醇酯(PET)／无机纳米粒子复合物,对其结晶性能、热性能和抗紫外性能进行了分析。结果表明:与PET比较,PET／无机纳米粒子复合物的结晶度提高,熔点略有降低,冷结晶温度下降,热结晶温度升高,热稳定性能变化不大;抗紫外性能优良。     

Pickering乳液聚合法制备聚丙烯酸酯涂料印花粘合剂

以NCMC[纤维素纳米晶(CNCs)/羧甲基纤维素(CMC)]为稳定剂,采用Pickering乳液聚合法制备NCMC/聚丙烯酸酯(PA)复合物乳液。以过硫酸钾(KPS)和亚硫酸氢钠(Na HSO3)为引发剂,碳酸氢钠(Na HCO3)为缓冲剂,通过考察单体转化率和凝胶率对乳液聚合条件进行了优化。采用光学显微镜对Pickering乳液的形貌进行观察,通过三相接触角测试对NCMC的表面润湿性进行表征。通过透射电镜(TEM)、扫描电镜(SEM)、热重分析(TGA)及胶膜力学性能测试等对聚合物复合乳液的微观形态和胶膜微观形态、性能进行测试和表征。实验制备的复合乳液可用于制备棉织物涂料印花粘合剂。结果表明:印花后织物具备较好的透气性、滑爽的手感和较高的表观得色量,干摩擦牢度4~5级,湿摩擦牢度4级左右。     

MSF-g-COOH/IFR阻燃复合薄膜的制备及性能研究

以季戊四醇(PEG)和三聚氰胺(MEL)为原料制备一种水溶性膨胀型阻燃剂(IFR),然后采用氯乙酸接枝剑麻纤维素微纤自制纳米纤维素(MSF-g-COOH)为基体,通过抽滤和自组装吸附的方法,制备了一种MSF-gCOOH/IFR阻燃复合薄膜。研究了IFR对MSF-g-COOH薄膜材料阻燃性和热性能的影响,并利用X射线分析仪(XPS)和扫描电子显微镜(SEM)对IFR的合成、MSF-g-COOH/IFR阻燃复合薄膜表面形貌的微观结构以及燃烧后的炭层结构进行分析。结果表明:当IFR自组装吸附在MSF-g-COOH薄膜表面后,MSF-g-COOH/IFR阻燃复合薄膜具有较好的阻燃性和热稳定性;其初始热分解温度相比纯MSF-g-COOH薄膜提高了20℃;经IFR自组装吸附后的MSF-g-COOH/IFR阻燃复合薄膜在燃烧过程中,其表面形成炭支撑保护层,可阻止火势蔓延。     

纳米二氧化钛接枝PMMA/PBMA共聚物的表面改性

以羟丙基甲基纤维素(HPMC)对纳米TiO2进行包覆,然后再将纤维素与甲基丙烯酸甲酯/甲基丙烯酸丁酯(MMA/BMA)进行接枝共聚合,对纳米TiO2的进行表面修饰,对复合粒子进行了表征并观察了粒子的形貌.分析表明在纳米TiO2粒子的表面接枝上了MMA/BMA的共聚物;经过处理的纳米粒子的表面均匀地包覆了一层聚合物;改性后的复合纳米粒子TiO2/HPMC-g-PMMA/PBMA的热分解温度比复合物HPMC-g-PMMA/PBMA的热分解温度高56.9 K.     

细菌纤维素/透明质酸复合材料的生物合成及表征

在培育细菌纤维素(BC)过程中添加不同分子量的两种透明质酸(HA),分别制备出不同的细菌纤维素复合物HA/BC(Mw=3,000)和HA/BC(Mw=300,000)。采用红外光谱、扫描电子显微镜、X射线衍射和热重分析对其结构和性能进行了表征。添加HA后提高了复合物的产量;FTIR结果表明了HA与BC之间存在交联;添加HA增大了BC的热稳定性,而对BC的结晶指数影响不大,且HA/BC(3,000)的性能始终优于HA/BC(300,000);HA(3,000)增大了BC的拉伸强度,而HA(300,000)反而减小了其拉伸强度。结果表明添加小分子量的HA可制备最大热失重温度较高的HA/BC复合物。     

丙烯酸单体接枝纳米纤维素晶须的研究

以K2S2O8为引发剂,在纳米纤维素晶须(NCW)上接枝丙烯酸单体(AA),制备出丙烯酸接枝改性的纳米纤维素晶须.通过傅立叶变换红外光谱(FTIR)、透射电镜(TEM)、热重分析(TGA)等测试方法对接枝产物的性能进行了分析,并采用电导滴定的方法计算了接枝率以及表面取代基团含量.研究了反应条件对接枝率和接枝效率的影响.结果表明,在引发剂浓度为4 mmol/L,引发时间为5 min,纳米纤维素晶须与丙烯酸单体摩尔比为1: 1.5,反应时间为6 h的条件下,得到了接枝率为14.09%的丙烯酸接枝纳米纤维素晶须.实验证明,在NCW上可以接枝上丙烯酸,接枝率为14.09%的产物与NCW具有相似的表面形貌和热性能;TEM分析可知,接枝产物的分散性得到了提高;表面取代基团含量测试表明,接枝产物表面上的亲水性分散基团含量比NCW增加了5倍以上.     

丙烯酸单体接枝纳米纤维素晶须

以K2S2O8为引发剂,在纳米纤维素晶须(NCW)上接枝丙烯酸单体(AA),制备出丙烯酸接枝改性的纳米纤维素晶须。通过傅立叶变换红外光谱(FTIR)、透射电镜(TEM)、热重分析(TGA)等测试方法对接枝产物的性能进行了分析,并采用电导滴定的方法计算了接枝率以及表面取代基团含量。研究了反应条件对接枝率和接枝效率的影响。结果表明,在引发剂浓度为4mmol/L,引发时间为5min,纳米纤维素晶须与丙烯酸单体摩尔比为1∶1.5,反应时间为6h的条件下,得到了接枝率为14.09%的丙烯酸接枝纳米纤维素晶须。实验证明,在NCW上可以接枝上丙烯酸,接枝率为14.09%的产物与NCW具有相似的表面形貌和热性能;TEM分析可知,接枝产物的分散性得到了提高;表面取代基团含量测试表明,接枝产物表面上的亲水性分散基团含量比NCW增加了5倍以上。     

纳米纤维素晶须-壳聚糖/聚乙烯醇复合膜性能与细胞相容性

以椰壳纤维为原料,制备了纳米纤维素晶须,用硅烷偶联剂对纳米纤维素晶须进行改性,将改性后纳米纤维素晶须与壳聚糖、聚乙烯醇共混,采用溶液浇铸法制备了改性纳米纤维素晶须-壳聚糖/聚乙烯醇复合膜。采用FTIR、DSC、TG、XRD和SEM对改性纳米纤维素晶须-壳聚糖/聚乙烯醇复合膜的结构、热性能、结晶行为和形貌进行表征与分析,对复合膜的力学性能和水接触角进行测试,将成纤维细胞L929接种到复合膜上,对其进行细胞相容性实验。结果表明,添加改性纤维素晶须,能够使壳聚糖/聚乙烯醇复合膜的热性能、结晶行为和力学性能提高,成纤维细胞在复合膜上具有较好的黏附和生长,制备的纳米纤维素晶须-壳聚糖/聚乙烯醇复合膜具有良好的综合性能和细胞相容性。     

阳离子壳聚糖对纸的增强和助滤作用

增加纸的强度和改善纸料的滤水性以提高生产效率是造纸生产中的重要课题.本文研究了阳离子壳聚糖及其与羧甲基壳聚糖或羧甲基纤维素组成的聚电解质复合物对纸的抗张强度和纸料滤水性的影响,探讨了阳离子壳聚糖与钠基改性膨润土配合提高纸料滤水性的效果.实验结果表明,壳聚糖季铵盐与羧甲基壳聚糖或羧甲基纤维素的复合比例(质量比)分别为0.43和1.2时,聚电解质复合物的浊度最高.聚电解质复合物的加入有效的增加了纸张的抗张强度和滤水性能.阳离子壳聚与羧甲基壳聚糖复合物的增强和助滤效果最好,当其相对于纸浆的加入量为1％时,纸的抗张强度提高了27.69％,纸料的叩解度下降了35.9％.阳离子壳聚糖与膨润土组成的助滤体系可以显著降低纸浆的叩解度,特别是当阳离子化壳聚糖用量较少时,其助滤效果更好.     

乙酸酯化法表面改性纳米纤维素及其性能表征

在超声波辅助作用下,研究通过乙酸酯化法对纳米纤维素进行表面改性,并采用傅里叶变换红外光谱仪(FTIR)、场发射透射电子显微镜(FETEM)等对其表面化学结构、晶体结构及宏观和微观形貌进行分析。研究表明:根据Fischer酯化反应原理,通过一步催化酯化法可制得功能化修饰纳米纤维素;修饰改性后的纳米纤维素(E-CNCs)和纳米纤维素(CNCs)形貌相同,均呈棒状,宽度在10～100 nm之间,酯化反应主要发生于无定形区,而对纤维素晶区结构破坏较小,仍有天然纤维素的特征结构,E-CNCs取代度为0.47时,结晶度仍能达到80.16%。     

Chain confinement in electrospun nanocomposites: using thermal analysis to investigate polymer-filler interactions

We investigate the interaction of the polymer matrix and filler in electrospun nanofibers using advanced thermal analysis methods. In particular, we study the ability of silicon dioxide nanoparticles to affect the phase structure of poly(ethylene terephthalate), PET. SiO₂ nanoparticles (either unmodified or modified with silane) ranging from 0 to 2.0 wt% in PET were electrospun from hexafluoro-2-propanol solutions. The morphologies of both the electrospun (ES) nanofibers and the SiO₂ powders were observed by scanning and transmission electron microscopy, while the amorphous or crystalline nature of the fibers was determined by real-time wide-angle X-ray scattering. The fractions of the crystal, mobile amorphous, and rigid amorphous phases of the non-woven, nanofibrous composite mats were quantified by using heat capacity measurements. The amount of the immobilized polymer layer, the rigid amorphous fraction, was obtained from the specific reversing heat capacity for both as-spun amorphous fibers and isothermally crystallized fibers. Existence of the rigid amorphous phase in the absence of crystallinity was verified in nanocomposite fibers, and two origins for confinement of the rigid amorphous fraction are proposed. Thermal analysis of electrospun fibers, including quasi-isothermal methods, provides new insights to quantitatively characterize the polymer matrix phase structure and thermal transitions, such as devitrification of the rigid amorphous fraction.     

Preparation of treelike and rodlike carboxymethylated nanocellulose and their effect on carboxymethyl cellulose films

In this work, carboxymethyl cellulose (CMC) with low substitution degree, followed by different posttreatments, was applied to prepare treelike CMC nanofibrils (CMCNFs) and rodlike CMC nanocrystals (CMCNCs), and their performance in CMC composite film was evaluated simultaneously. From transmission electron microscopy results, it was found that the treelike CMCNCFs exhibited a lager aspect ratio compared to the rodlike CMCNCs. As for reinforcing CMC film, 4 wt% was the best adding amount, at this time, the tensile strength of CMC/CMCNFs and CMC/CMCNCs composite films was increased by 72.1% and 47.3%, respectively. Moreover, adding these nanofillers to CMC also could enhance the thermal stability of composite films slightly, while the transmittance of composite films was reduced at the same time. In addition, CMC/CMCNFs film was designed as a packaging box to determine its performance. Therefore, this study could reveal the differences of properties for composites with different types of nanocellulose and provide a foundation for further application of nanocellulose.     

Comparative study of polystyrene/chemically modified wheat straw composite for green packaging application

The recalcitrant nature of native wheat straw (WS) biomass results from cellulose, lignin, hemicellulose and some amount of protein embedded together in a composite structure causing poor adhesion to a polymer matrix composite. Adequate pre-treatment can curtail the recalcitrance structure of WS and enhance the susceptible cellulose area to synthesize a green composite. This paper examined the effect of various chemical pre-treatment procedures in improving surface morphology of wheat straw. Moreover, polystyrene (PS), PS (60 wt%)/native WS (40 wt%), PS (60 wt%)/NaOH-treated WS (40 wt%), PS (60 wt%)/HCl-treated WS (40 wt%), and PS (60 wt%)/H2SO4-treated WS (40 wt%) composite films were prepared using solution casting method. The changes in crystalline structure, hydrophobicity, water vapor migration rate, and thermal and mechanical stabilities of synthesized bio-composites were examined. From the results it can be concluded that the alkali-treated WS is highly compatible with the PS and can be used to synthesize a biodegradable composite film for various industrial green packaging applications.     

CMC-g-PAA/APT/HA复合高吸水性树脂的制备与溶胀性能

以羧甲基纤维素(CMC)为基质,丙烯酸(AA)为单体,凹凸棒黏土(APT)和腐植酸(HA)为复合组分,采用水溶液聚合法制备了羧甲基纤维素接枝聚丙烯酸/凹凸棒黏土/腐植酸(CMC-g-PAA/APT/HA)环境友好复合高吸水性树脂,用红外光谱(FTIR)进行了结构表征。考查了APT和HA含量对树脂吸水倍率和吸水速率的影响,研究了树脂在不同pH溶液中的溶胀行为以及反复吸水性能。试验结果表明,APT和HA通过其表面的活性基团参与了接枝共聚反应,在体系中引入HA和APT能够显著提高复合高吸水性树脂的吸水能力。在HA含量为5%(质量分数),APT含量为30%(质量分数)时,树脂可达到最优吸蒸馏水倍率为582g/g。该复合高吸水性树脂在pH值在4～11范围内时具有较高的吸水性能,表现出优异的pH稳定性。经过5次反复溶胀后,该复合吸水树脂仍能达到424g/g的吸水倍率,较不含APT和HA样品提高了近44%。     

Properties of a semi-crystalline and an amorphous thermotropic liquid crystalline polymer

The physical properties, thermal stability, rheology and tensile properties of a commercial semi-crystalline and an amorphous thermotropic liquid crystalline polymer (TLCP) have been investigated. Analysis by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) confirm the presence of a small melting endotherm and a glass transition in the former material. The as-received amorphous TLCP exhibits no obvious melting endotherm and a strong glass transition is detected. The flow and tensile properties of the semicrystalline polymer are dominated by the presence of the crystalline to nematic transition temperature. The properties of the amorphous TLCP appear to be governed by increasing mobility afforded by increasing temperature. Based on flow behaviour and further DSC analysis it has been shown that under appropriate annealing conditions the as-received amorphous TLCP can develop solid crystalline order.     

Fabrication and characterization of composite sol-gel coatings on porous ceramic substrate

Highly porous ceramic materials were coated using a composite sol-gel method. Alumina powder is dispersed in a silica sol-gel solution and then dip-coated on the substrate. The resulting coatings present a composite microstructure in which crystalline alumina grains are linked to each other by an amorphous silica phase. In this work, we show that, by accurately controlling the sol-gel parameters (water, solvent and silica precursor (TEOS) ratio, pH and ageing time of the sol) and also the powder grain size distribution it is possible to obtain crack-free thick films (more than 20 μm in one step). These coatings present good adherence to the substrate, decrease the roughness and also close the surface porosity of the substrate. Coating mechanical properties have been evaluated thanks to micro-indentation measurements and linked to coating structural evolution with the thermal treatment temperature.     

Experimental study on carboxymethylation of cellulose extracted from Posidonia oceanica

The production of carboxymethylcellulose (CMC) from bleached cellulose pulps obtained from Posidonia oceanica was explored. The optimal reaction conditions were studied for the carboxymethylation of cellulose in organic liquids. The carboxymethylation reaction was carried out with NaOH and monochloroacetic acid (MAC) as the reagent. Different alcohols were compared in terms of the degree of substitution (DS). The highest DS was obtained with n‐butanol. For this alcohol, the effects of the temperature, alkali concentration, and MAC concentration were studied. The reaction was also carried out in three consecutive steps. The resulting CMC had a DS of about 2.75. The functionalization of cellulose was checked using FTIR spectroscopy and ¹³C‐NMR. The X‐ray analysis showed that the crystalline structure of cellulose decreased when the DS increased and the structure was totally amorphous in high DS material. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1808–1816, 2006     

Hybrid Polyamide/Silica Nanocomposites: Synthesis and Mechanical Testing

A hybrid inorganic‐polymer composite was formed through nanosize silica filler particles (< 30 nm) that were incorporated inside a nylon‐6 matrix. The composite was microtomed and examined with TEM which revealed that the silica particles were well dispersed and non‐aggregated. Optimization of the synthesis conditions relied on appropriate choice of organic solvent and pH control. Crystallinity of the composite was examined with XRD and showed the silica phase remains amorphous while the polyamide phase was semi‐crystalline. Compared to pure nylon‐6, mechanical tests on the hybrid composite showed an increase in impact toughness, an increase in E‐modulus as a function of filler percentage, and a strain‐at‐break of > 0.5.     

Surface and pore structure modification of cellulose fibers through cellulase treatment

The surface and pore structure of cellulose fibers have a significant impact on the properties and performance in applications. Cellulase enzymatic hydrolysis of cellulose fibers can result in changes to the surface and pore structure, thus providing a useful tool for fiber modification. This research characterizes these changes using various test methods such as fiber dimension, water retention value (WRV), hard‐to‐remove (HR) water content, freezing and nonfreezing bound water content, polymer adsorption, and crystallinity index. For a high‐dosage cellulase treatment (600 U/g dry solid), the fiber length was significantly decreased and the fibers were “cut” in the cross direction, not in the axial direction. The swelling capacities as measured by the WRV and HR water content increased for the high‐dosage treatment. Three independent measurements (nonfreezing bound water, polymer adsorption, and crystallinity index) are in good agreement with the statement that the amorphous regions of cellulose fibers are a more readily available substrate relative to crystalline regions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3833–3839, 2007     

BaO-Al2O3-B2O3-SiO2玻璃/SiO2高膨胀低温共烧陶瓷研究

用BaO-Al2O3-B2O3-SiO2玻璃与二氧化硅复合的方法制备了高膨胀系数低温共烧陶瓷。实验首先制备一组玻璃材料,通过热膨胀测试、DTA等方法研究了玻璃的热学性能,然后用玻璃与石英、方石英和鳞石英晶体按一定比例复合制得高膨胀低温共烧陶瓷。通过烧结试验、XRD等分析方法研究了复相陶瓷材料的烧结收缩性能、晶相组成、热膨胀系数和介电常数。结果表明:50%BaO-7.5%Al2O3-30%B2O3-12.5%SiO2玻璃具有较低的转变温度(520℃)。该玻璃与鳞石英晶体以1:1的比例复合,850℃/10min烧结可以获得热膨胀系数为12.18×10-6K-1、介电常数为5.37的低温共烧陶瓷。