氧气等离子体处理对芳砜纶纤维表面性能的影响

用等离子体在氧气环境对芳砜纶(PSA)纤维进行表面改性。分析纤维改性前后断裂强度、摩擦性能和润湿性能的变化。用场发射扫描电子显微镜和X射线光电子能谱仪分析纤维表面的形貌和化学元素变化。结果表明,等离子处理后的芳砜纶纤维,断裂强度变化较小,摩擦性能增强,润湿性能有大幅度提高;纤维表面随处理时间延长粗糙度增加,纤维表面碳元素含量下降、氧元素含量增加,纤维表面极性基团增加。     

表面处理对芳纶纤维物理和机械性能的影响

为了提高界面结合能力,采用空气等离子体对芳纶纤维表面进行改性,通过扫描电子显微镜观察处理前后纤维表面形貌的变化情况,对纤维力学性能及摩擦性能进行测试,优选出最佳处理工艺。进一步研究了纤维表面改性处理方式对纤维集合体力学性能和防刺性能的影响。结果表明:表面改性后芳纶纤维的摩擦系数增大,但强力有所下降,空气等离子体处理最佳条件为50Pa、50W处理5min。芳纶纤维表面经过等离子体改性后,无纺布锥刺的最大压缩载荷同比未处理样品提高了5.27%。     

超声作用对芳纶纤维表面性质的影响

芳纶纤维表面性质是影响其复合材料界面粘接性能的重要因素。本文作者采用超声技术对芳纶纤维表面进行改性处理,研究了超声作用下,芳纶纤维表面化学组成和表面结构的变化。结果表明:超声处理后,纤维表面极性官能团含量增加,比表面积加大,从而改善了芳纶纤维和环氧树脂之间的浸润性。     

常温超声波处理对芳砜纶纤维界面性能的影响

为提高芳砜纶(PSA)纤维表面润湿性和基体界面黏结性能,用超声波在常温下对芳砜纶纤维进行表面改性。研究纤维改性前后润湿性能、界面剪切强度(IFSS)、断裂强度和摩擦性能的变化。用水滴吸收时间和单丝拔抽实验,分析改性前后PSA纤维表面润湿性能和界面剪切强度;并用场发射扫描电子显微镜(FESEM)和X射线光电子能谱仪(XPS)分析纤维表面的形貌和化学元素变化。结果表明,经超声波改性后,PSA纤维的润湿性能大幅提高,水滴吸收时间从大于400s降至13s,且随处理时间增加润湿性能越好;PSA纤维与环氧树脂基体界面黏结性能大幅提高,较未经超声波处理纤维上升44%。同时,经超声波处理后,PSA纤维表面摩擦性能增强;表面氧、氮元素含量分别上升30.2%和18.3%,纤维表面极性基团增加。但是,处理时间过长会使纤维的断裂强度下降幅度加大,综合考虑实验的最佳处理时间为80min。     

PBO纤维表面改性研究进展

综述了目前PBO纤维的表面改性方法,主要包括等离子体处理、表面化学处理、辐射处理、偶联剂处理以及共聚改性的研究进展。分析了各种改性方法的原理并指出各种改性方法的优势及存在的问题。展望了PBO纤维增强复合材料的应用前景,指出今后纤维表面改性仍是PBO纤维增强树脂复合材料的研究重点。     

铬酸氧化法改善超高分子量聚乙烯纤维表面粘接性能

以特定浓度铬酸氧化液对超高分子量聚乙烯(UHMWPE)纤维进行表面氧化改性。通过傅里叶变换红外光谱、X射线光电子能谱、扫描电子显微镜、X射线衍射和力学性能测试分析比较了处理前后纤维的表面官能团变化、形貌结构、结晶性能和力学性能的变化,并采用微脱粘法和拉曼光谱法研究了纤维-树脂复合材料界面剪切强度及微观受力情况。结果表明,UHMWPE纤维经铬酸氧化处理后,纤维表面极性增加,粗糙程度变大;纤维表面处理的最佳条件为55℃、5min;拉曼光谱研究表明,改性后UHMWPE纤维-环氧树脂界面粘接性能较未改性纤维有明显增强。     

连续玄武岩纤维冷等离子改性处理性能研究

采用低温等离子体表面改性处理仪对玄武岩纤维等离子改性,对玄武岩纤维改性前后表面形貌SEM、表面浸润性以及回潮率等的变化进行测试、表征分析。结果表明,未处理的玄武岩纤维表面较为光滑,接触角滞后现象不明显,与树脂基体界面粘结效果不理想,回潮率为0.12%。比较处理时间5min、12min,等离子体改性处理15min刻蚀程度最大,表面最粗糙,回潮率增加到0.83%,而接触角差异达到37.57°,与树脂基体界面粘结效果最好。     

化学改性芳纶纤维增强水泥基复合材料的性能

采用化学改性法对芳纶纤维进行表面处理, 研究了改性前后芳纶纤维对水泥基复合材料强度及抗冲击性能的影响。结果表明: 芳纶纤维的掺入可以提高水泥砂浆的抗折强度和抗冲击性能, 经化学改性后的芳纶纤维增强效果更加明显。当掺杂纤维的体积分数为1.0%时, 化学改性前后芳纶纤维增强水泥砂浆试样与基准砂浆试样相比, 其28天抗折强度分别提高了15.18%和23.85%, 抗冲击韧性分别提高了276.74%和294.54%。采用SEM对芳纶纤维表面微观形貌及试样断口形貌进行了观察, 利用XPS对改性前后芳纶纤维表面元素变化进行了研究, 探讨了芳纶纤维对水泥砂浆的增强机制。      

硅烷偶联剂表面改性玄武岩纤维增强复合材料研究进展

表面改性是增强玄武岩纤维与基体材料之间结合性能的关键。综述了硅烷偶联剂表面改性以及酸、碱刻蚀,等离子处理辅助协同硅烷偶联剂表面改性玄武岩纤维的研究进展,介绍了硅烷偶联剂表面改性玄武岩纤维在聚合物基复合材料中的应用,并对发展趋势进行了展望,同时分析了硅烷偶联剂表面改性玄武岩纤维当前存在的问题。     

木纤维增强不饱和聚酯复合材料的性能研究

采用丙烯酸(AA)对木纤维表面进行改性处理,并对改性后的木纤维进行悬浮性测试。将改性处理后的木纤维与不饱和聚酯树脂复合,制备了木纤维增强不饱和聚酯复合材料,对其进行了拉伸和冲击等力学性能测试。结果表明:木纤维含量对复合材料的力学性能影响很大。随着木纤维含量的增加,复合材料的延伸率和拉伸强度均有所提高;当木纤维含量为15%时,改性处理试剂的最佳浓度为0.15mol/L。此时,材料的延伸率和拉伸强度增加的幅度均趋于平稳,力学性能变化不明显。     

麦草纤维表面化学氧化处理的研究

通过化学氧化,对麦草纤维进行表面改性。初步探索了麦草纤维表面改性的可行性,并对改性剂JB处理前后的麦草纤维进行了ESCA能谱分析,以及麦草纤维／脲醛树脂胶中密度纤维板（MDF）的性能测试。结果表明,所采用的改性方法,提高了麦草纤维表面的极性和反应活性,用改性的麦草纤维制得的中密度纤维板,其力学性能有显著提高。     

Enhanced malachite green removal from aqueous solution by citric acid modified rice straw

In this paper, rice straw was thermochemically modified with citric acid (CA) as esterifying agent. Two introduced free carboxyl groups of esterified rice straw were further loaded with sodium ion to yield potentially biodegradable cationic sorbent. In order to investigate the effect of chemical modification on the cationic dye sorption of rice straw, the removal capacities of native and modified rice straw sorbing a cationic dye (malachite green) from aqueous solution were compared. The effects of various experimental parameters (e.g. initial pH, sorbent dose, dye concentration, contact time) were investigated. For modified rice straw (MRS), the malachite green (MG) removal percentage came up to the maximum value beyond pH 4. For the 250 mg/l of MG solution, the 1.5 g/l or up of MRS could almost completely remove the dye from aqueous solution. Under the condition of 2.0 g/l sorbent used, the percentage of MG sorbed on MRS kept above 93% over a range from 100 to 500 mg/l of MG concentration. The sorption isotherms fitted the Langmuir or Freundlich models. The sorption equilibriums were reached at about 10 h. The sorption processes followed the pseudo-first-order rate kinetics. After chemical modification, the intraparticle diffusion rate constant (k(id)) was obviously increased. The results in this study indicated that MRS was an excellent sorbent for removal of MG from aqueous solution.     

聚乙烯醇乳液改性对汉麻秸秆纤维/水泥基复合材料性能的影响

为解决汉麻秸秆纤维/水泥基复合材料力学性能较差的问题,本文提出采用聚乙烯醇(PVA)乳液对汉麻秸秆纤维/水泥基复合材料进行改性。在优化秸秆纤维的粒径和掺入量后,采用PVA乳液与秸秆纤维和水泥进行共混成型,制备了改性后的汉麻秸秆纤维/水泥基复合材料。研究了不同质量比的PVA乳液对汉麻秸秆纤维/水泥基复合材料的抗折强度、密度、比强度和弯曲韧性的影响,通过含水率、吸水率及红外光谱测试揭示了PVA乳液对汉麻秸秆纤维/水泥基复合材料的改性机制。结果表明:汉麻秸秆纤维粒径为1700 μm及掺入量为12%时,秸秆纤维对汉麻秸秆纤维/水泥基复合材料的增强作用最好。随着PVA乳液质量比的增加,改性后汉麻秸秆纤维/水泥基复合材料的密度逐渐减小,弯曲韧性逐渐提高。当PVA乳液质量比为4.8%时,相较于未改性的汉麻秸秆纤维/水泥基复合材料,改性后的汉麻秸秆纤维/水泥基复合材料抗折强度和比强度分别提高了17.17%和20.50%。通过PVA乳液改性使汉麻秸秆纤维/水泥基复合材料中秸秆纤维与水泥之间的界面得到改善,并缓解了秸秆纤维对水泥水化反应的阻碍作用。      

Artificial neural network (ANN) modeling of dynamic adsorption of crystal violet from aqueous solution using citric-acid-modified rice (Oryza sativa) straw as adsorbent

Rice straw, an abundant, lignocellulosic agricultural residue worldwide, was thermochemically modified with citric acid to develop a biodegradable cationic adsorbent. The morphological and chemical characteristics of rice straw and acid-modified rice straw were investigated by scanning electron microscopy, surface area, and porosity analysis by the BET (Brunauer, Emmett, and Teller) nitrogen adsorption method and Fourier transform infrared spectroscopy. The modification process leads to the increase in the specific surface area and pore size of rice straw. In order to investigate the application potential of the prepared adsorbent to remove a cationic dye (Crystal violet) from its aqueous solution, a continuous adsorption study was carried out in a laboratory scale fixed-bed column packed with acid-modified rice straw. Effect of different flow rates and bed heights on the column breakthrough performance was investigated. Results show that with increasing bed height and decreasing flow rate, the breakthrough time was delayed. In order to determine the most suitable model for describing the adsorption kinetics of Crystal violet in the fixed-bed column system, the Bed Depth Service Time model as well as the Thomas model was fitted to the experimental data. An artificial neural network (ANN) based model for determining the dye concentration in the column effluent was also developed. An extensive error analysis was carried out between experimental data and data predicted by the models using the following error functions: correlation coefficient (R ²), average relative error (ARE), sum of the absolute error (SAE), and χ² statistic test. Based on the values of the error functions, the ANN model was most appropriate for describing the dynamic dye adsorption process.     

环氧氯丙烷改性稻草的制备和表征

稻草秸秆经碱煮预处理后,用环氧氯丙烷在120℃下以甲苯为溶剂反应1～8h。醚化程度用增重率(weight percent gain,WPG)表示。考察反应时间对醚化产率的影响,并采用傅里叶红外变换光谱、X射线衍射分析、热分析和扫描电镜分析,对所制备的环氧氯丙烷改性稻草进行表征。结果表明,预处理后半纤维素和木质素被去除,醚化反应后,稻草样品的结晶度降低,热稳定性略有降低,表面积增大。     

Effect of Silane Coupling Agents on Rice Straw Fiber/Polymer Composites

The effect of coupling agents and electron beam (EB) irradiation dose on the mechanical properties of composites made from rice straw fibers and polymers have been studied. Samples were made by hot pressing of mix composition at 130°C. The pressed samples were subjected to electron beam irradiation dose ranged from 10 to 50?kGy. Increasing the electron beam irradiation dose increased the value of flexural strength, modulus of elasticity and impact strength. It was also observed that, the properties of composites containing γ-aminopropyltrimethoxy silane (A-1100) are lower than those of composites containing N-(2aminoethyl)-3-amino propyltrimethoxy silane (A-700) coupling agents. These are attributed to a hydrogen bonding formation between the amine or protonated amine and the hydroxyl groups of rice straw fibers. The presence of coupling agents in the composites during the EB irradiation process produce a more free radicals which are enough to form a chemical bonding between the rice straw fiber and polymer. The thickness swelling and water absorption values decrease with increasing the EB irradiation dose with presence of coupling agents in the composite.     

Chemical,morphological, and mechanical analysis of rice husk/post-consumer polyethylene composites

Composites were obtained from post-consumer high-density polyethylene (PE) reinforced with different concentrations of rice husk. PE and rice husk were chemically modified to improve their compatibility in composite preparation. Rice husk was mercerized with a NaOH solution and acetylated. The chemically modified fibers were characterized by FTIR and ¹³C NMR spectroscopy. The composites were prepared by extrusion of modified and unmodified materials containing either 5 or 10 wt.% fibers. The morphology of the obtained materials was analyzed by SEM. The chemical modification of the fiber surface was found to improve its adhesion with matrix. Flexural and impact tests demonstrated that PE/rice husk composites present improved mechanical performance comparatively to the pure polymer matrix, on the contrary no benefit is observed in the tensile strength over the pure PE.     

Analyzing the pyrolysis kinetics of rice straw,bagasse, and mixtures thereof and product energy yield

In Taiwan, rice straw and bagasse are major agricultural wastes that are produced in extremely large quantities and volumes and contain high moisture content. Current processing methods remain inadequate; therefore, this study focused on the pyrolysis and relevant analyses of rice straw, bagasse, and mixtures thereof to investigate the feasibility of copyrolyzing rice straw and bagasse for renewable energy generation. Mixtures containing various ratios of bagasse and rice straw were examined through physical, chemical, thermogravimetric, and reaction kinetics analyses. Pyrolysis experiments were conducted to investigate the energy yield of the reaction products. Both bagasse and rice straw contained low ash content, and thermal processing effectively reduced the waste volume and cost of final disposal. A mixture content containing approximately 30 wt% rice straw (potassium content reaching 8.50 g/kg) substantially reduced the activation energies required for copyrolysis reactions, subsequently reducing energies required for thermal processing. The solid char generated from pyrolyzing the bagasse and rice straw mixtures did not decay easily and exhibited high storability and transportability. Moreover, volumetric energy densities substantially increased after pyrolysis. Therefore, copyrolysis is arguably a feasible and effective alternative biofuel conversion method for countries that process large quantities of bagasse and rice straw.     

Novel lignocellulosic hybrid particleboard composites made from rice straws and coir fibers

Novel lignocellulosic hybrid particleboard composites with low cost and high performance using the mixture of rice straws and coir fibers were developed in this work. NaOH (sodium hydroxide) aqueous solution was used to remove the wax and silica layer of rice straw surface. The effects of rice straws/coir fibers (R/C) mass ratios on the physical (thickness swelling) and mechanical (modulus of rupture, modulus of elasticity and internal bond strength) properties of particleboard composites were investigated. The results show that NaOH treatment was an effective method for improving wettability of rice straw surface with smaller contact angles and larger diffusivity–permeability constant. The SEM (scanning electron microscope) observation also gave some evidences such as more rough surface and less number of silica cells after NaOH treatment for improving wettability of rice straw surface. The coir fibers content had a significant negative linear effect on the bending properties and thickness swelling, but a significant positive linear effect on the internal bonding strength due to the lower wax and holocellulose content of coir fiber. When no diisocyanate resin applied, the particleboard composites made with only phenol formaldehyde resin at the optimal R/C ratio satisfied the requirements for load-bearing boards used in dry conditions based on Chinese Standard, indicated that the mixture of rice straws and coir fibers to make high quality particleboard composites was a cost-effective and environment friendly approach.     

Optimization of sodium sulfide treatment of rice straw to increase the enzymatic hydrolysis in bioethanol production

The efficiency of sodium sulfide-assisted alkaline pulping for cellulose preparation from Oryza sativa L. rice straw in Vietnam for enzymatic saccharification was investigated. The response surface methodology was used for the determination of optimal technological parameters of alkaline pulping such as active alkali dosage, temperature and time. The optimal technological parameters were established to be active alkali dosage of 7%, treatment temperature of 100 °C and treatment time of 120 min. At these regimes, a maximal sugar yield of 51.8% (over dry rice straw) was obtained. It meant that the saccharification efficiency up to 97.1% could be achieved by using sodium sulfide-assisted alkaline pretreatment method. Addition of sodium sulfide into alkaline pretreatment resulted in higher sugar yield, higher level of depolymerization of lignin and less loss of cellulose. Moreover, liquid hydrolyzate after enzymatic hydrolysis was analyzed by HPLC to determine the compositions of sugar mixture. The fiber morphology in pretreated biomass solid was also revealed by SEM.