协同改性处理对剑麻增强HDPE复合材料力学性能的影响

植物纤维和树脂的界面相容性差一直制约着天然纤维复合材料的发展和应用。分别对剑麻纤维(SF)进行了碱-偶联协同处理和碱-接枝协同处理,并利用双螺杆挤出机制备了SF/高密度聚乙烯(HDPE)复合材料。观察了剑麻纤维表面以及复合材料断面的微观形貌,表征了改性前后纤维基团的变化,研究了协同改性处理对剑麻纤维及其复合材料力学性能的影响。结果表明,碱-偶联协同处理的改性效果更好,剑麻纤维与HDPE的相容性得到明显改善,复合材料最大拉伸强度和弯曲强度相对于未改性纤维复合材料分别提高18.64%和20.25%。     

改性剑麻纤维增强聚乳酸复合材料热性能研究

依据丙交酯配位开环反应原理,在剑麻纤维表面接枝上聚乳酸分子支链进行表面改性,并与未处理、碱处理表面改性对比,研究了表面改性方法对剑麻纤维热性能的影响。使用熔体共混模压成型工艺制备了改性剑麻纤维增强聚乳酸复合材料,并研究了不同表面改性方法对复合材料热性能的影响。结果表明,剑麻纤维的加入使得复合材料的热稳定性略有降低,其中碱处理略高于未处理,而接枝处理降幅最大。同时,纤维的加入有利于复合材料异相成核,提高结晶度,其中以接枝剑麻纤维的促进作用最为突出。     

表面处理对剑麻纤维性能及与淀粉相容性的影响

采用碱处理、硅烷偶联剂处理以及两者复合的处理方法对剑麻纤维进行表面改性,研究了不同处理方法对剑麻纤维的性能以及剑麻纤维/淀粉复合材料界面粘结性能的影响。通过傅立叶变换红外光谱仪、热重分析仪、扫描电子显微镜和万能试验机对不同处理的剑麻纤维进行表征,使用拔出实验测试剑麻/淀粉复合材料的界面粘结情况,并采用二参数威布尔模型计算拉伸强度和界面剪切强度。结果表明,所有处理方法都能提高剑麻纤维的热稳定性和界面剪切强度。与未处理纤维相比,碱处理后的剑麻纤维与淀粉的界面剪切强度最高,为2.011 MPa,提高了19%。     

表面处理对剑麻纤维布/不饱和树脂材料性能影响

采用碱、高锰酸钾及热对剑麻纤维布进行了表面处理,并由真空辅助树脂传递模塑成型(VARTM)工艺制备了剑麻纤维布增强不饱和聚酯树脂复合材料。通过对复合材料的力学性能及吸水性的测试,研究了不同剑麻纤维布表面处理对其不饱和聚酯树脂复合材料性能的影响。结果表明:经过碱处理,复合材料的拉伸、弯曲,冲击强度提高最大,可分别提高26.5%,16.5%和22.6%,吸水率降低了47.5%。对剑麻纤维布进行表面处理可使复合材料的界面性能得到改善,力学性能提高,吸水性降低。     

洋麻纤维的表面改性及其在聚丙烯基复合材料中的应用

采用碱处理、偶联剂处理以及碱–偶联剂复合处理对洋麻纤维进行表面改性,然后将其与聚丙烯(PP)纤维复合,采用非织造–模压工艺制备了PP/洋麻纤维复合材料。研究了上述3种表面改性方法对洋麻纤维强度及其复合材料弯曲与剪切性能的影响,并采用扫描电子显微镜(SEM)研究了洋麻纤维表面改性前后的形貌变化及其与PP基体之间的界面结合状况。结果表明,表面改性后洋麻纤维的拉伸强度均降低,但复合材料的弯曲强度及层间剪切强度均提高,表明这3种改性方法均提高了洋麻纤维与PP之间的界面结合强度;碱处理可去除纤维表面的果胶成分,使纤维束变得松散,使复合材料的弯曲强度及层间剪切强度分别较未表面改性时提高了21%和169%,但弯曲弹性模量降低了21%;偶联剂处理则使复合材料的弯曲强度,弯曲弹性模量和层间剪切强度较未表面改性时提高了23%,7%和160%;碱–偶联剂复合处理兼顾了碱处理和偶联剂处理的优点,使复合材料弯曲强度、弯曲弹性模量和层间剪切强度分别较未表面改性时提高了26%,18%和572%,综合性能最佳。SEM结果表明,碱–偶联剂复合处理后,复合材料中纤维与树脂之间的界面结合较好。     

碱处理对剑麻纤维增强聚乳酸可降解复合材料性能的影响

以剑麻纤维(SF)和聚乳酸(PLA)为原料,通过注塑成型工艺制备了剑麻纤维增强聚乳酸可降解复合材料。研究了连续碱处理剑麻纤维(CASF)和未改性处理剑麻纤维(USF)在不同含量时对复合材料力学性能、吸水性及可降解性能的影响。结果表明:剑麻纤维的质量分数会显著影响复合材料的力学性能、吸水性和降解性能。相较于未改性处理剑麻纤维(USF),碱处理剑麻纤维(CASF)可以进一步提高复合材料的力学性能,降低复合材料的吸水率,延缓剑麻纤维增强可降解树脂基复合材料的降解速率,且酶降解法相较于土埋法降解能够显著加快复合材料的降解速率。当剑麻纤维含量为20%时,CASF/PLA复合材料的拉伸强度、弯曲强度和弯曲模量相较于纯PLA和USF/PLA分别提高了32.71%、10.08%;19.63%、12.11%;97.33%、12.40%;其冲击强度相较于纯PLA提高了71.19%。     

剑麻纤维接枝改性对其增强PLA复合材料性能影响

通过紫外光在剑麻纤维表面接枝甲基丙烯酸甲酯(MMA),利用改性后的剑麻纤维与聚乳酸(PLA)熔融共混制备纤维增强复合材料。结果表明:改性后的剑麻在1 729.9cm-1处出现明显的羰基吸收峰。当MMA质量分数为60%,光照时间为4min时,其改性剑麻纤维制备的复合材料拉伸强度、弯曲强度和冲击强度达到最优,与未改性剑麻纤维复合材料相比分别提高了37.53%,34.82%,79.45%。改性后的剑麻纤维在PLA基体中分散较好,嵌入到PLA基体中,相界面模糊。     

剑麻纤维的表面改性及其复合材料的研究进展

简述了剑麻纤维的组成、结构及力学性能,并总结了剑麻纤维表面改性的几种方法,包括物理方法：热处理、酸碱处理、有机溶剂处理;化学方法：改变表面张力、界面偶合、表面接枝聚合。同时论述了剑麻纤维的表面改性对复合材料力学性能的影响。     

剑麻纤维／酚醛树脂复合材料研究

本文采用碱处理、硅烷偶联剂处理、化学接枝和热处理等物理化学方法，对剑麻纤维进行改性。研究了改性后短剑麻纤维／酚醛树脂复合材料的弯曲性能、无缺口冲击强度和布氏硬度，借助扫描电子显微镜观察了复合材料的弯曲断口形貌，并研究了剑麻纤维的不同处理方法对复合材料耐水浸泡性的影响。结果表明：剑麻纤维经硅烷偶联剂处理后，能有效改善刚性的剑麻纤维与脆性的酚醛树脂基体之间的粘结，从而提高了复合材料的综合力学性能，剑麻     

蔗渣纤维表面改性及其对聚乙烯醇/淀粉复合材料性能的影响

采用碱处理法、接枝法对蔗渣纤维表面进行改性,并用正交试验优化蔗渣与氨基三乙酸接枝共聚反应的工艺条件。利用傅里叶变换红外光谱、扫描电子显微镜、电子式万能试验机表征了处理前后蔗渣纤维的表面结构和表面形貌、聚乙烯醇(PVA)/淀粉复合材料断面形貌及拉伸强度。结果表明:碱处理法和接枝法改性有效提高了蔗渣纤维的表面活性,碱处理和接枝处理蔗渣与PVA/淀粉复合材料的拉伸强度分别提高了30.7%和96.7%。     

An investigation of sound absorption coefficient on sisal fiber poly lactic acid bio‐composites

In this research, the mechanical, acoustical, thermal, morphological, and infrared spectral properties of untreated, heat and alkaline‐treated sisal fiber‐reinforced poly‐lactic‐acid bio‐composites were analyzed. The bio‐composite samples were fabricated using a hot press molding machine. The properties mentioned above were evaluated and compared with heat‐treated and alkaline‐treated sisal fibers. Composites with heat‐treated sisal fibers were found to exhibit the best mechanical properties. Thermo‐gravimetric analysis (TGA) was conducted to study the thermal degradation of the bio‐composite samples. It was discovered that the PLA‐sisal composites with optimal heat‐treated at 160°C and alkaline‐treated fibers possess good thermal stability as compared with untreated fiber. The results indicated that the composites prepared with 30wt % of sisal had the highest sound absorption as compared with other composites. Evidence of the successful reaction of sodium hydroxide and heat treatment of the sisal fibers was provided by the infrared spectrum and implied by decreased bands at certain wavenumbers. Observations based on scanning electron microscopy of the fracture surface of the composites showed the effect of alkaline and heat treatment on the fiber surface and improved fiber‐matrix adhesion. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42470.     

The influence of chemical surface modification on the performance of sisal‐polyester biocomposites

This article concerns the effectiveness of various types and degrees of surface modification of sisal fibers involving dewaxing, alkali treatment, bleaching cyanoethylation and viny1 grafting in enhancing the mechanical properties, such as tensile, flexural and impact strength, of sisal‐polyester biocomposites. The mechanical properties are optimum at a fiber loading of 30 wt%. Among all modifications, cyanoethylation and alkali treatment result in improved properties of the biocomposites. Cyanoethylated sisal‐polyester composite exhibited maximum tensile strength (84.29 MPa). The alkali treated sisal‐polyester composite exhibited best flexural (153.94 MPa) and impac strength (197.88 J/m), which are, respectively, 21.8% and 20.9% higher than the corresponding mechanical properties of the untreated sisal‐polyester composites. In the case of vinyl grafting, acrylonitrile (AN)‐grafted sisal‐polyester composites show better mechanical properties than methyl‐methacrylate (MMA)‐grafted sisal composites. Scanning electron microscopic studies were carried out to analyze the fiber‐matrix interaction in various surface‐modified sisal‐polyester composites.     

剑麻纤维与晶须混杂增强聚丙烯复合材料

采用熔融共混和注塑成型方法制得了剑麻短纤维(SF)和CaSO4晶须混杂增强聚丙烯(PP)复合材料，研究了复合材料的热性能、微观结构和力学性能。结果表明，晶须提高了复合材料的热稳定性，阻碍了PP的结晶，降低了复合材料中PP相的结晶度和结晶速率；SF和晶须提高了复合材料的模量和韧性，但由于混杂增强复合材料弱界面键合的制约，晶须的高强性能并没有在复合材料中充分表现出来。     

Relationship between processing and properties of biodegradable composites based on PCL/starch matrix and sisal fibers

Biocomposites were produced using polycaprolactone and starch as matrix, and sisal fibers as reinforcement. The matrix is a biodegradable commercial product called MaterBi‐Z, which is based on a polycaprolactone and starch system. The relationship between processing conditions and properties is reported. An alkaline treatment was performed in order to improve the adhesion and the compatibility of the fiber with the matrix. The effect of the treatment on the tensile properties and morphology was determined. Fiber content enhances the tensile properties of the biodegradable composite. The experimentally observed tensile properties (modulus and tensile strength) of short sisal fiber reinforced MaterBi‐Z matrix composites with different fiber loading are compared with the existing theories of reinforcement. SEM photomicrographs of the fractured composite surfaces are also analyzed.     

Effect of cloisite 30B clay and sisal fiber on dynamic mechanical and fracture behavior of unsaturated polyester toughened epoxy network

This study examined the dynamic mechanical properties of sisal fiber reinforced unsaturated polyester (UP) toughened epoxy nanocomposites. The chemical structures changes in Epoxy, UP and UP toughened epoxy (Epoxy/UP) systems were characterized by Proton Nuclear magnetic resonance (¹HNMR) spectroscopy. The morphological alterations of the nanocomposites were analyzed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The untreated, chemically treated fibers, nanoclays, and the fiber reinforced Epoxy/UP nanocomposites were confirmed by FTIR spectrometer. The obtained mechanical results showed that alkali‐silane treated fibers improve the tensile strength (96%) and flexural strength (60%) of the Epoxy/UP nanocomposite than that of Epoxy/UP blend due to the strong interfacial bonding between the sisal fiber and matrix. The fracture toughness (K_IC) and fracture energy (G_IC) of treated sisal fiber reinforced DGEBA/UP/C30B nanocomposites found to be higher than that of untreated sisal fiber nanocomposites. The dynamic mechanical analysis (DMA) reveals that the fiber reinforced Epoxy/UP nanocomposites contains 30 wt% treated fiber and 1 wt% nanoclays, exhibits the highest storage modulus and better glass transition temperature (T_g) among the other kind of systems. The surface morphology of the fibers, fractured surface of the resins and composites were confirmed by scanning electron microscope (SEM). POLYM. COMPOS., 37:2832–2846, 2016. © 2015 Society of Plastics Engineers     

Effect of interface modification on the mechanical properties of polystyrene‐sisal fiber composites

The effect of interface modification on the mechanical (tensile, impact and flexural) properties of polystyrene–sisal fiber composites was investigated. The interface modification was performed by treatment of sisal fibers with benzoyl chloride, polystyrene maleic anhydride (PSMA), toluene diisocyanate (TDI), methyl triethoxy silane and triethoxy octyl silane. These interface modifications improve the compatibility of hydrophilic sisal fiber with a hydrophobic polystyrene matrix and change the tensile, impact and flexural properties of the composite, but to varying degrees depending on the fiber modification. The treated fibers were analyzed by spectroscopic techniques. Scanning electron microscopy was used to investigate the fiber surface, fiber pullout, and fiber‐matrix interface.     

Some structural aspects of sisal fibers

A critical account has been presented of the recent investigation on the chemical modification of lignocellulosic sisal fibers. The molecular structure of the paracrystalline cellulose, which forms the major constituent of the fiber, was studied by x-ray diffraction technique. Scanning electron microscope examination of the multicellular structure, surface topology, and fracture morphology of the fiber was carried out. The mechanical properties of the sisal ultimate cell and the “technical” fiber have been investigated by means of a microextensometer and an Instron tensile tester, respectively.     

剑麻增强醋酸纤维素复合材料的制备与性能研究

对剑麻(SF)进行乙醚化处理以改性纤维结钩和性能,得到改善纤维(ASF)。并通过挤出、模压工艺制备了剑麻增强醋酸纤维索(CA)复合材料。从纤维长度、结钩、热性能等力一面研究改性和加工工艺对SF的影响,同时研究了复合材料的力学性能。研究结果表明,SF和ASF使复合材料的拉伸性能和弯曲性能都得到了一定的增强。尽管ASF/CA复合材料在强度和模量上比SF/CA复合材料硝有逊色,但是由于ASF与基体相容性提高、柔韧性改善,从而其ASF/CA复合材料在断裂伸长率和冲山性能上优于SF/CA复合材料。     

Surface modification of polyimide fibers by novel alkaline–solvent hydrolysis to form high‐performance fiber‐reinforced composites

We modified polyimide (PI) fibers by a novel hydrolysis approach and fabricated PI‐fiber‐reinforced novolac resin (NR) composites with enhanced mechanical properties. We first used an alkaline–solvent mixture containing potassium hydroxide liquor and dimethylacetamide (DMAc) for the surface modification of the PI fibers. The results indicate that the surface roughness and structure of the PI fibers were controlled by the hydrolysis time and the content of DMAc. With the optimized hydrolysis conditions, the tensile modulus of modified PI fibers improved 15% without compromises in the fracture stress, fracture strain, or thermal stability. The interfacial shear strength between the modified PI fibers and NR increased 57%; this indicated a highly enhanced interfacial adhesion. Finally, the tensile and flexural strengths of the composites increased 72 and 53%, respectively. This research provides an effective method for the surface modification of PI fibers and expands their applications for high‐performance composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46595.