Effect of Chemical Treatment and Fiber Loading on Mechanical Properties of Borassus (Toddy Palm) Fiber/Epoxy Composites

The aim of the present study was to investigate and compare the mechanical properties of untreated and chemically modified Borassus fiber–reinforced epoxy composites. Composites were prepared by the hand lay-up process by reinforcing Borassus fibers with epoxy matrix. To improve the fiber-matrix adhesion properties, alkali (NaOH) and alkali combined with silane (3-aminopropyltriethoxysilane) treatment of the fiber surface was carried out. Examinations through Fourier transform-infrared spectroscopy and scanning electron microscopy (SEM) were conducted to investigate the structural and physical properties of the Borassus fibers. Tensile properties such as modulus and strength of the composites made with chemically modified and untreated Borassus fibers were studied using a universal testing machine. Based on the experimental results, it was found that the tensile properties of the Borassus-reinforced epoxy composites were significantly improved as compared with the neat epoxy. It was also found that the fiber treated with a combination of alkali and silane exhibited superior mechanical properties to alkali-treated and untreated fiber composites. The nature of the fiber/matrix interface was examined through SEM of cryo-fractured samples. Chemical resistance of composites was also found to be improved with chemically modified fiber composites.     

聚丙烯/锡氟磷酸盐玻璃复合材料的结构与性能

锡氟磷酸盐玻璃(Pglass)具有较低的玻璃化转变温度,在常规聚合物加工温度窗口内具有熔融流动性,是一种新型的无机类聚合物玻璃。本文采用双螺杆挤出机制备了聚丙烯(PP)/Pglass有机聚合物/无机玻璃复合材料,并对其相形貌、界面性能、流动性能、结晶性能、力学性能和热稳定性能进行了研究。结果表明:Pglass以微米级颗粒分散在PP基体中,且两相之间界面明显、相容性较差。Pglass的添加使复合材料的熔体剪切粘度降低。Pglass的存在促进了基体PP的结晶。复合材料的弹性模量随着Pglass含量的增加而增加。Pglass提高了复合材料的热稳定性。     

Mechanical Properties and Chemical Resistance of Short Tamarind Fiber/Unsaturated Polyester Composites: Influence of Fiber Modification and Fiber Content

In the present work, tamarind fibers were extracted from ripened fruits by the water retting process. Using these fibers as reinforcement and unsaturated polyester as matrix, composite samples were prepared by the hand lay-up technique. The effect of chemical surface treatments (alkali and silane) of tamarind fibers on the mechanical properties, chemical resistance, and interfacial bonding was studied. The mechanical properties of the composites with surface modified fibers were found to be higher than those with unmodified fibers. Morphological studies indicated improvement of interfacial bonding by alkali and silane coupling agent treatments of the fibers. The composites were found to be resistant to many chemicals.     

热塑性碳纤维复合材料界面研究

综述了热塑性碳纤维复合材料界面研究的新进展。指出由于热塑性复合材料基体树脂是高聚物,熔体牯度很大,很难均匀地分布在增强纤维之中并与纤维形成良好浸溃,存在界面结合不良的问题,因此对其界面优化设计要有一个新的认识。界面上没有化学键结合,界面结合不良,但只靠短化学键的连接,界面结合也不良,必须有一个强韧结合的界面,既有强结合又具有界面松弛能力,同时又能与高聚物基体融合的界面缓冲层的优化设计。对于Plueddemann偶联剂的概念中偶联剂“必须成为树脂的一部分”,作者认为最好的方法是就是树脂本身,即它既与纤维化学键键合,又与树脂良好相容,界面匹配。这将是热塑性复合材料界面层设计的一种新方法。     

Effect of Fiber Volume Fraction on the Flexural Properties of Unidirectional Carbon Fiber/Epoxy Composites

In this study, the effect of fiber content on the flexural property of continuous carbon fiber/epoxy composites was investigated. Samples with four different fiber volume fractions, 50, 60, 70, and 80 vol.%, were fabricated. For comparisons, cast epoxy resin was also prepared. It was observed that the flexural strength and modulus of this material are enhanced with increasing fiber volume fractions in the range of 50–70 vol.%. Results show that the carbon fiber/epoxy composites possess the largest fracture force and displacement when the fiber volume fraction is 70 vol.%, which is mainly attributed to the effective stress transfer of fibers. This can restrict crack tip propagation and blunt the crack tip, then consume abundant deformation energy and result in an increase of fracture work. On the other hand, poor flexural property was observed when the sample with high fiber volume fraction (80 vol.%) was tested. Three different types of failure modes were observed according to the fiber content.     

The influence of matrix crystallinity,filler grain size and modification on properties of PLA/calcium carbonate composites

Thermal and mechanical properties of polylactide (PLA) composites with different grades of calcium carbonate, 40 nm and 90 nm nanoparticles, and also with submicron particles, unmodified and modified with calcium stearate or stearic acid, obtained by melt mixing, were compared. Films with amorphous and crystalline matrices were prepared and examined.T_g of PLA in the composites remained unaffected whereas its cold crystallization was enhanced by the fillers and predominantly depended on filler content. Filling decreased thermal stability of the materials but their 5% weight loss temperatures well exceeded 250 °C, evidencing stability in the temperature range of PLA processing. The amorphous nanocomposites with modified nanoparticles exhibited improved drawability and toughness without a significant decrease of tensile strength; nearly two-fold increase of the elongation at break and tensile toughness was achieved at 5 wt% content of the modified nanofiller. Lack of surface modification of the filler, larger grain size with an average of 0.9 μm, and matrix crystallinity had a detrimental effect on the drawability. However, the presence of nanofillers and crystallinity improved tensile modulus of the materials by up to 15% compared to neat amorphous PLA.     

Structures and properties of the compression-molded istactic-polypropylene/talc composites: Effect of cooling and rolling

Talc-loaded isotactic polypropylene (iPP) composites with various contents of talc were fabricated by compression molding, following slow- and fast-cooling processes, to obtain slow-cooled samples (SCS) and fast-cooled samples (FCS), respectively. Lamellar thickness of the α-crystal of iPP in the SCS is observed to be larger than that in the FCS by X-ray diffraction study. Rolled fast-cooled samples (RFCS) were also prepared at 25 °C in order to examine the crystal growth of iPP. An epitaxial growth mechanism of the α-crystal of iPP from the talc crystal is proposed. Surface of talc-loaded FCS appears with a smaller particle size than that of talc-loaded SCS and RFCS as observed by a scanning electron microscope. Young’s modulus and tangent modulus of FCS are found lower than those of SCS with the addition of talc up to 20 wt% and higher above this concentration, except microhardness which is higher in SCS at all contents of talc. From thermal studies, talc-loaded SCS and FCS are found to show higher melting temperature than the neat samples. Effect of cooling and rolling on the structures and properties of the fabricated composites are elaborately discussed.     

狼尾草特性及狼尾草/PP复合材料性能研究

对狼尾草茎秆进行拉伸性能测试和长径比测量、并进行X射线衍射图谱、红外光谱和热重分析,分别以三种粒径(40目、60目、80目)狼尾草茎秆纤维为填充材料,以聚丙烯(PP)为基体材料,使用模压成型工艺制备三种不同粒径的狼尾草/PP复合材料。对制备的复合材料进行了接触角测量、吸水性能和力学性能测试,并用扫描电子显微镜(SEM)观察了复合材料拉伸断面微观结构。结果表明:狼尾草茎秆纤维素类型为I型,相对结晶度为44%;40目、60目和80目三种目数狼尾草/PP复合材料24h吸水厚度膨胀率分别为7.7%、4.2%和4.4%;其中40目狼尾草/PP复合材料有较好的结合界面和较好的力学性能,其拉伸强度、弯曲强度、弯曲模量和冲击强度分别为10.47MPa、15.98MPa、1.9GPa和3.7kJ/m²。由此得知,40目狼尾草/PP复合材料力学性能最好,但吸水性较强;60目狼尾草/PP复合材料具有较好的力学性能和一定的抗吸水性,综合性能最佳。     

碳纤维三向织物/环氧树脂复合材料的制备与力学性能

选择不同纱线间距[即二经(纬)纱之间的中心距]尺寸的碳纤维三向织物,采用热压成型技术制备了碳纤维三向织物/环氧树脂复合材料.研究了纱线间距及样品裁剪角度等对力学性能的影响,并与碳纤维二向织物/环氧树脂复合材料的力学性能进行对比.结果表明,随着纱线间距尺寸从2 mm增加到6 mm,0°方向断裂强度从221. 7 MPa下降到148. 1 MPa,撕裂强力从1000 N下降到600 N; 90°方向断裂强度从50. 0MPa下降到22. 1 MPa,撕裂强力从330 N下降到100 N;顶破强力从424 N下降到216 N.这些力学性能的逐渐降低是单位面积的碳纤维增强体含量减少和织物的孔洞增大共同作用的结果.纱线间距为2 mm的碳纤维三向织物复合材料在0°(以纬纱为基准),30°,45°,60°和90°方向的断裂强度分别为221. 7,48. 5,44. 3,227. 7和50. 0 MPa,即断裂强度在0°和60°方向大于在30°,45°及90°方向.由三向织物的编织原理可知,0°与60°方向完全相同,因此其断裂强度相似,且样品中有一组纱线与外加载荷平行,对形变破坏具有一定的约束作用,而...     

高性能环氧树脂/碳纳米管复合物的热分析研究

用差示扫描量热仪(DSC)、热失重分析仪(TGA)和动态力学热分析仪(DMTA)研究了多壁碳纳米管(MWNTs)/高性能4,4′-二氨基二苯甲烷四缩水甘油环氧树脂(TGDDM)/4,4′-二氨基二苯基砜(DDS)复合物的热性能.Kissinger和Flynn-Wall-Ozawa的非等温固化动力学研究发现,随着MWNTs含量的增加,复合物固化反应的活化能先减小后增大.TGA研究表明,MWNTs的添加对环氧树脂热稳定性影响很小.碳纳米管填充到TGDDM/DDS体系后,复合物的储存模量随着MWNTs含量的增加而增大,而玻璃化温度却随之减小.     

导热膨胀石墨/聚醚酰亚胺复合材料的制备与性能

利用膨胀石墨(EG)经高温处理后比表面积大的特点, 以膨胀石墨作为导热填料, 通过球磨和热模压方法制备了膨胀石墨/聚醚酰亚胺(PEI)导热复合材料, 并对其加工过程、 微观形貌、 热性能和导热性能进行了研究. 结果表明, 球磨处理可以打破膨胀石墨的“泡沫”状态并减少石墨纳米片间的间隙, 热压可以诱使和促进石墨纳米片沿着水平方向排列和取向, 从而显著提升了复合材料的平面内导热性能. 当膨胀石墨在复合材料中的质量分数为20%时, EG/PEI复合材料的面内导热系数为2.38 W?m^?1?K^?1. 与PEI相比, 复合材料导热系数的增幅约为12倍. 所制备的EG/PEI复合材料均具有良好的散热能力、 较好的热稳定性和较高的储能模量, 是一种综合性能优异的导热材料.     

PVA-SiO_2复合物改性棉纤维及其吸油性能

首先以棉纤维为主要原材料,通过一步浸渍将聚乙烯醇-二氧化硅粒子(PVA-SiO_2)复合物涂覆在棉纤维表面;然后对其进行疏水改性,制得一种超疏水吸油材料。通过扫描电子显微镜(SEM)和水接触角(WCA)测试对改性纤维的表面结构及润湿性进行了分析表征。研究了PVA和SiO_2纳米粒子的质量分数对纤维吸油性能的影响,并评价了改性纤维的疏水性、润湿耐受性、吸油速率和重复使用性能。结果表明:棉纤维经过PVA-SiO_2复合物涂覆后具有稳定的超疏水性,吸油量比改性前显著提高,对正己烷、甲苯和氯仿的吸油量分别提高了47%、18.6%和26.2%。     

纳米ATO改性聚丙烯腈纤维的研究

采用高导电率的纳米粉体ATO(SnO2·Sb2O3)为抗静电剂,从6种不同类型的分散剂中筛选出聚乙烯亚胺,通过设计正交实验探索出最佳工艺组合,将纳米ATO稳定均匀地分散于去离子水中,将该悬浮液作为聚丙烯腈纤维纺丝过程的预热浴,来改善聚丙烯腈纤维的抗静电性,研究了ATO用量、添加位置等对纤维抗静电性能、力学性能的影响。     

Properties of Low Density Polyethylene/Polypropylene Blends

ABSTRACT

The role of di-cumyl peroxide (DCP) as compatibilizer in low density Polyethylene/Polypropylene (LDPE/PP) blends has been explored. Mixtures with varying LDPE/PP ratio were prepared in a Brabender plasticorder and tested for their mechanical properties and calorimetric response. Then peroxide was added at concentrations up to 0.5%, and the mechanical properties of the these new blends were measured. Also, the mixing torque, melt flow index and gel content of the above products were recorded as a function of peroxide concentration. It was found that the incorporation of DCP restricts the thermoplastic characteristics of the melt, which was primarily attributed to branching which occurs in LDPE. This results in an enhancement in the adhesive bonding between the two polymers mainly due to chain entanglements. This was further supported by the fact that mechanical properties of the treated blend were significantly improved.     

Mechanical Properties and Dynamic Mechanical Analysis of Thermoplastic-Natural Fiber/Glass Reinforced Composites

The mechanical properties and dynamic behavior of thermoplastic composites based on polypropylene/glass fibers and polypropylene/natural fibers (i.e. kenaf, hemp, flax) are presented. A survey is given on some aspects, crucial for the use of these composites in structural and non-structural components such as their vibration-damping response, in relation to the composite compaction level and the manufacturing procedure. In order to investigate a wide vibration frequency range, including acoustic frequencies, different testing techniques, both with forced and free vibrations, were applied. A comparison between natural fiber and glass fiber reinforced laminates is presented. Compaction levels, allowing to obtain the best compromise between mechanical performance and damping response, are investigated.     

Preparation and properties of gluten/calcium carbonate composites

Environment friendly thermosetting composites were prepared by blending wheat gluten （WG） as matrix, calcium carbonate （CaCO3） as filler and glycerol as plasticizer followed by compression molding the mixture at 120 ℃ to crosslink the WG matrix. Morphology observation showed that the CaCO3 particles were finely dispersed in matrix. Incorporation of CaCO3 up to 10 wt% into the composites caused Young＇s modulus and tensile strength to increase markedly. On the other hand, the moisture absorption and elongation at break decreased slightly.     

Thermal and mechanical interfacial properties of the DGEBA/PMR-15 blend system

In this work, the blend system of diglycidyl ether of bisphenol A and PMR-15 polyimide is investigated in terms of thermal and dynamic mechanical interfacial properties of the casting specimens. The thermal stabilities are studied by thermogravimetric and thermomechanical analyses, and the dynamic mechanical properties are carried out by dynamic mechanical analysis. The results show that the thermal stabilities based on the initial decomposition temperature, the integral procedural decomposition temperature, and the glass transition temperature are increased with increasing PMR-15 content. The crosslinking density (rho) of the blend system is increased at 10 phr of PMR-15, compared with that of neat epoxy. Mechanical interfacial properties measured in the context of critical stress intensity factor and critical strain energy release rate show similar behaviors with E(a) and rho, probably due to the increase in intermolecular interactions or hydrogen bondings in polymer chains.     

Tensile properties,thermal and morphological analysis of thermoplastic polyurethane films reinforced with multiwalled carbon nanotubes

The paper reports on thermal, tensile and morphological properties of thermoplastic polyurethane (TPU) based films obtained by melt-compounding and chill-roll extrusion. Composite films containing up to 1 wt% of multiwalled carbon nanotubes (MWNTs) are characterized in terms of thermal properties, tensile behavior and morphological issues taking the neat TPU film as the reference material.     

超高相对分子质量聚乙烯纤维

超高相对分子质量聚乙烯是一种重要的高性能纤维 ,本文介绍了该纤维的制备、结构、性能以及应用等方面的研究情况。     

Processing of Thermal Sensitive Materials – a Case Study for Wood Plastic Composites

Summary. The influence of processing parameters, e.g. throughput and temperature, of the compounding step of wood plastic composites was investigated in this work. The effects on the mechanical properties as well as the influence on the colour of the produced composites were correlated with the different processing parameters. The composites showed a wide range of good processability, only at high temperature and low throughput strong darkening occurred, as well as a loss of tensile strength was found for these samples.