Comparative Chemical Analysis of the Rind and Pith of Totora (Schoenoplectus californicus) Stems

ABSTRACT

Totora (Schoenoplectus californicus (C.A. Mey.) Soják) is a sedge that grows in lakes and marshes in America and some of the Pacific Islands. The hypothesis tested was that the rind and pith of totora stems have different chemical characteristics. A higher ash content on the pith (7.81% vs. 6.36%) may indicate strategies of the plant to reinforce the aerenchyma tissue and clarify the storage mechanism of compounds by bio mineralization. Almost double acid-insoluble lignin content in the rind (16.42% vs. 8.90%) may indicate the potential optimization of industrial procedures such as paper production by using specific tissues of the plant.     

Mechanical Behavior of Ensete ventricosum Fiber Under Tension Loading

The mechanical behavior of Ensete ventricosum fibers, expressed as the dependency of tension force in relation to the elongation, was determined for fibers with gauge length 50 mm and transformed into general linear mathematical model describing dependency of tension stress and strain. The average rupture force (10.88 ± 1.11) N, rupture stress (390.33 ± 21.96) MPa, rupture strain (0.021 ± 2 · 10^–5), and volume energy (3.39 ± 0.22) J m^?3 were also determined at this conducted study. Using image analyses, it was determined that the cross section of Ensete ventricosum fiber has circle shape and its dimension was specified. From the study, it implies that Ensete ventricosum fiber, with respect to its mechanical behavior under tension loading having regard to its density and to the fact that it is environmentally friendly, biodegradable and recyclable, could be used as a perspective construction material of the future. Determined model of mechanical behavior could be applied as background for further research focused on the Ensete fiber application.     

Preparation of Polyimide Fiber/Thermoplastic Resin Composites with Improved Mechanical Properties

As a high-performance material for preparing composite materials, polyimide fibers suffer from many potential drawbacks, including poor bonding with other substrates, which results in composite materials with poor mechanical properties. Therefore, this study proposed a simple and rapid technique for obtaining loose, porous polyimide fiber papers by implementing a wet method using equal amounts of polyimide fiber and polyimide fiber paper as reinforcements, respectively. The polyimide resin-based composite materials were prepared by hand lay-up and hot pressing. The results showed that the paper-based reinforcement exhibited high porosity and the fibers were arranged with a uniform pore size distribution. The tensile properties, bending performance, and interlaminar shear performance of the paper-based composite improved by 130%, 108%, and 34.5%, respectively, compared to those of the fiber-based counterpart. The factors affecting the mechanical properties of the composites were analyzed based on the fiber length, fiber beating or lack thereof, and the basis weight of the paper. The increased uniformity of the polyimide fiber paper changed the ordering of the fibers and resolved drawbacks such as difficult dispersion, uneven pore size distribution, and poor mechanical properties related to single fibers in the resin-based composite material.     

剑麻纤维/聚丙烯复合材料物理力学性能的研究

研究了剑麻纤维(SF)的预处理方法、长度和含量对剑麻纤维/聚丙烯(SF/PP)复合材料物理力学性能的影响,采用扫描电子显微镜(SEM)对复合材料的冲击断面进行微观结构分析.实验结果表明:SF经过碱处理和蒸汽爆破处理后,复合材料的冲击强度分别提高了70%、76%;当SF的长度为5～8 mm、含量为20%时复合材料的冲击强度达到最大为21.99 kJ/m2;SF含量为50%时弯曲强度、弯曲弹性模量与纯PP相比提高了27.5%、41.1%;熔体流动速率和吸水率随SF含量的增加变化明显.     

纤维增强对镁基复合板物理力学性能的影响

以玻璃纤维为增强材料,以镁基无机矿物质为基体材料,制备了新型纤维增强镁基无机复合板.研究了短切纤维、纤维网格布以及短切纤维结合纤维网格布3种增强方式对镁基复合板的物理力学性能和耐湿热性能的影响.结果表明,纤维增强方式对镁基无机复合板的密度、含水率、吸水率等性能影响较小,对复合板的力学性能和耐湿热尺寸稳定性影响较大,采用...     

短炭纤维增强酚醛树脂基石墨复合材料力学性能

以短炭纤维（Cf）为增强相,超细石墨（Gr）为填充组分,热固性酚醛树脂（PF）为基体,采用热模压法制备Cf—PF／Gr复合材料。使用万能材料试验机测定材料弯曲强度,利用扫描电子显微镜观察其断口形貌。研究了树脂、炭纤维含量及纤维空气氧化处理对Cf-PF／Gr复合材料力学性能的影响。研究结果表明：随着PF含量减少,复合材料弯曲强度降低,当PF含量小于20％时,材料力学性能明显变差;Cf含量增加,材料弯曲强度呈先增大后减少趋势,当纤维质量分数为4％时,材料弯曲强度达到极大值57MPa;炭纤维空气氧化处理能够明显改善纤维与基体的界面状态,提高复合材料弯曲强度。     

PBO纤维纸基复合材料的热老化及高温力学性能研究

本研究采用湿法成形技术制备了聚对苯撑苯并二噁唑（PBO）纸,将其浸渍聚酰亚胺（PI）树脂后,得到PBO纤维纸基复合材料（PBO/PI),随后对PBO/PI进行300℃的老化,并在300℃下测试了其拉伸性能。将PBO/PI与模拟蜂窝格壁的间位芳纶浸渍纸（PMIA/PI）进行对比,分析了老化和高温对PBO/PI和PMIA/PI力学性能的影响。结果表明,在300℃的高温老化下,由于材料微裂纹的产生及扩展,二者拉伸强度均呈下降趋势,但老化前后PBO/PI的强度均比PMIA/PI更强。动态力学性能显示,老化前后PBO/PI的储能模量大于PMIA/PI的储能模量,说明PBO/PI的刚性比PMIA/PI大,在高温下仍不易发生变形。在300℃的高温拉伸测试下,PBO/PI的拉伸强度和保持率均比PMIA/PI要高。PBO/PI在常温及300℃高温下的力学性能均优于PMIA/PI,PBO纤维制备的复合材料可用于需要高的抗变形和热稳定性的承重结构和蜂窝部件中。     

真丝在氯化钙溶液中的分纤举动与力学性能

采用氯化钙、水的二元体系及氯化钙、水、乙醇的三元体系分别对桑蚕丝进行溶解处理，探讨了桑蚕丝在溶解过程中丝纤维的微观形态结构和力学性能变化。研究表明，随着丝纤维的溶解，纤维表面出现较为明显的分纤举动，同时纤维内部大分子的聚集态结构发生变化，分子间的结合力减弱，强伸力下降。     

硬脂酸-CaCO3协同改性对植物纤维/聚乳酸复合材料力学性能的影响

以硬脂酸、CaCl₂、NaHCO₃和NaOH为原料,对植物纤维进行硬脂酸-CaCO₃协同改性,在纤维表面沉积CaCO₃颗粒和疏水的硬脂酸钙层,并通过造纸法制备改性植物纤维/聚乳酸(PLA)复合材料。结果表明,协同改性生成的硬脂酸钙包裹了CaCO₃颗粒并覆盖在植物纤维表面,提高了纤维的疏水性,复合材料的力学性能随c(硬脂酸)∶c(NaHCO₃)的增加而先增加后减小;反应温度对复合材料强度影响较小;复合材料的抗张指数和耐破指数随c(NaOH)∶c(NaHCO₃)的增加而先增加后减小,耐折度则持续减小;最佳改性条件为：c(硬脂酸)∶c(NaHCO₃)∶c(NaOH)=4∶6∶6、反应温度75℃,此时制备的复合材料抗张指数、耐破指数和耐折度分别为51.0 N·m/g、3.56 kPa·m²/g、244次。     

聚芳酯纤维绝缘纸的制备及性能研究

以聚芳酯短切纤维为原料,通过机械剪切得到微纤,通过湿法分散微纤辅助真空抽滤制备聚芳酯纤维原纸,再经过热压得到聚芳酯纤维纸。研究了不同热压温度对聚芳酯纤维纸的力学性能、和介电性能等的影响。结果表明,当热压温度为260℃时,聚芳酯纤维纸的力学性能和电气强度达到最高,抗张强度和弹性模量分别为65 MPa和1.32 GPa,电气强度达到43.1 kV/mm。同时具有较高的热稳定性,较低的介电常数和介电损耗。     

微胶囊机械性能表征方法的研究

为了对微胶囊机械性能进行定性及定量的分析,利用实验室常用的紫外可见分光光度计、抗压强度机、显微硬度仪和电子天平,研究了四种表征方法。以实验室自制的酚醛环氧树脂微胶囊为例,进行表征后发现：使用紫外可见分光光度计,借助胶囊破裂前后的吸收光谱变化,可对包有隐性染料的微胶囊进行间接定性表征;使用抗压强度机可对紧密堆积的微胶囊块进行直接定量表征;使用显微硬度仪和电子天平可实现对单个微胶囊进行直接定量表征。四种不同表征方法实现了对单个、多个微胶囊的定性和定量表征。     

提取方法对玉木耳膳食纤维结构特征和功能特性的影响

以玉木耳为实验材料,采用碱提取法和酶提取法提取玉木耳的不溶性膳食纤维和可溶性膳食纤维,比较两种提取方法对其结构特征、理化性质和功能特性的影响。扫描电子显微镜分析表明,酶法提取的纤维具有更疏松和更复杂的结构。傅里叶变换红外光谱测定表明所有样品都显示出典型的糖吸收峰。X射线衍射分析表明酶法提取的膳食纤维具有较低的结晶度。热重分析表明碱法提取的膳食纤维具有更高的热稳定性。酶法提取的膳食纤维持水力（10.68～20.79 g/g）、持油力（2.05～3.72 g/g）、膨胀力（2.85～12.14 mL/g）、葡萄糖（4.92～7.95 μg/g）和胆固醇吸附能力（3.89～8.19 mg/g）均显著高于碱法提取的膳食纤维,对α-淀粉酶（45.43%～66.71%）和胰脂肪酶（21.50%～36.52%）也有更强的抑制作用。结果表明,玉木耳膳食纤维可作为一种功能性食品成分,本研究为进一步探究玉木耳的营养价值提供了理论依据。     

竹炭纤维与粘胶纤维性能对比分析

通过对竹炭纤维的截面结构、力学性能、细度、摩擦性能、耐酸碱性、质量比电阻等性能的比较分析,为合理使用竹炭纤维和粘胶纤维提供了一定的理论依据。结果表明,竹炭纤维的细度离散度较粘胶纤维小,纤维均匀、可纺性好;竹炭纤维的吸湿性、断裂强度、初始模量明显大于粘胶纤维,其摩擦性能、比电阻等性能与粘胶纤维接近。     

沉析纤维尺寸效应对PET纸结构与性能的影响

本研究对自制聚对苯二甲酸乙二醇酯(PET)沉析纤维进行筛分处理,并与PET短切纤维混抄成纸,探讨了沉析纤维的尺寸效应对PET纸结构、机械及电气性能的影响。结果表明,筛分目数为100、含量50%的PET沉析纤维成纸性能最好,PET纸匀度指数达94,抗张指数56.2 N·m/g,撕裂指数42.9 mN·m~2/g,层间结合强度79.4 N·m/g,耐压强度9.51 kV/mm。     

小麦纤维对小麦淀粉热力学及流变学特性的影响研究

利用快速黏度分析仪(RVA)、差示扫描量热仪(DSC)、流变仪(DHR)和扫描电镜(SEM)测定添加小麦纤维对小麦淀粉糊化特性、热力学特性、流变学特性和微观结构的影响。结果表明,随小麦纤维添加量的增加,小麦淀粉崩解值和回生值显著降低,表明小麦纤维抑制了小麦淀粉凝胶的老化;在4℃环境下储藏7d后,其老化焓值随小麦纤维添加量增加显著降低,抗老化性显著提升;添加不同浓度小麦纤维的淀粉糊为假塑性流体,小麦淀粉凝胶均为弱凝胶;小麦淀粉凝胶微观结构显示小麦纤维添加使小麦淀粉凝胶的表面更加完整、结构更加致密。由此表明小麦纤维对小麦淀粉凝胶老化有显著抑制作用。     

Thermal and Mechanical Behavior of the Coir Powder Filled Polyester Micro-Composites

ABSTRACT

Reinforcement of micro- or nano-fillers is the new key technique to enhance the mechanical properties of polymers. The present work pertaining to the thermo-mechanical behavior of micron range coir filler reinforced polyester matrix composites. The polyester micro-composites are manufactured by hand lay-up method in which the reinforcement is coir micro-fillers, which are uniformly dispersed in the polyester matrix. The following testing and characterizations were performed to predict the thermo-mechanical behavior of the micro-composites and pristine polymer: tensile and flexural tests, Dynamic Mechanical Analysis (DMA), and Field Emission Scanning Electron Microscopy (FESEM). The mechanical properties of micro-composites were attained highest when the filler reinforcements were maximum. Dynamic light scattering (DLS) particle size analysis shown the size distribution of coir micro-particles and the avg. size of coir micro-particles was 0.255 µm.     

粘胶基调温纤维基本力学性能研究

为研究粘胶基调温纤维的力学性能,采用不同的试验方案对丝维尔纤维、Outlast粘胶纤维及相关纤维的基本力学性能进行了测试分析。     

纤维长度对芳纶纤维纸结构和力学性能的影响

讨论芳纶纤维长度对纸页结构和力学性能影响。研究表明,纸页紧度随着纤维长度增加而降低,平均孔径随着纤维长度增加而增加;抗张强度、伸长率、耐破度在长度是1～4mm时,随着纤维长度的增加而增加,4mm以后变化不太明显;撕裂度在1～6mm范围内,都是随着长度的增加而增加。     

竹纤维增强尼龙复合材料动态机械热分析

对竹纤维增强尼龙复合材料动态机械性能进行研究.结果表明,竹纤维增强尼龙复合材料存在玻璃态、高弹态、粘流态,玻璃化转变和流动转变区域.粘流态的温度与界面改性处理、纤维用量的关系不大,与基体呈现粘流态的温度有关.经界面改性处理,竹纤维增强尼龙复合材料的玻璃化转变温度比尼龙-6基体高,且随着纤维含量的增加而提高.复合材料的储能模量、损耗模量比尼龙-6基体高.采用扫描电镜分析了复合材料的界面微观结构.     

Cissus Populnea Fiber - Unsaturated Polyester Composites: Mechanical Properties and Interfacial Adhesion

ABSTRACT

Mechanical (flexural, hardness, and impact) properties and interfacial adhesion of acetic anhydride (AC) and ethylene diamine tetraacetic acid (EDTA) treated Cissus populnea fiber-unsaturated polyester (UPR) composites was investigated because of poor durability of the natural fiber-UPR composite applications. UPR composites were prepared with untreated and optimally treated fiber using hand-lay-up technique. Optimization of mechanical properties and interfacial adhesion between the fiber and UPR were determined using response surface methodology and fiber pull-out method, respectively. AC and EDTA treated fibers improved the flexural and hardness properties and interfacial adhesion at reduced impact strength. This is corroborated with morphology of the composites.