Surface Modification of Reinforcement Fibers for Composites by Acid Treatments

In this study, we investigated the surface modification of reinforcement fibers for composites by acid treatments, including PBO fiber, Kevlar fiber and carbon fiber. The corresponding changes in the surface free energy components were carefully evaluated using a Cahn dynamic contact angle analysis system. In addition, the fiber's surface elemental composition and topography were studied using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The results showed that the surface nitrogen-to-carbon (N/C) and oxygen-to-carbon (O/C) ratios were significantly increased after the treatments. The surface free energy of PBO fiber was increased from 43.3 mJ/m² to 58.5 mJ/m² or by 35% with 60 wt% methanesulfonic acid solution treatment for 36 h. However, the increase with 60 wt% nitric acid solution was only by 14% (to 49.5 mJ/m²) for the same treatment time.     

芳香族聚酰胺纤维改性技术研究进展

芳纶纤维改性技术是当今的研究热点,分析了芳香族聚酰胺纤维目前存在的问题,比较了芳纶纤维的各种改性技术的进展,包括物理改性中的表面涂层技术、等离子体技术、超声浸渍改性技术、γ-射线改性技术,化学改性中的表面刻蚀技术改性、基于酰胺键的化学反应、基于苯环的反应以及功能改性法,并对我国芳纶纤维的工业发展前景做出了展望。     

Unmodified and Modified Surface Sisal Fibers as Reinforcement of Phenolic and Lignophenolic Matrices Composites: Thermal Analyses of Fibers and Composites

Summary: The study and development of polymeric composite materials, especially using lignocellulosic fibers, have received increasing attention. This is interesting from the environmental and economical viewpoints as lignocellulosic fibers are obtained from renewable resources. This work aims to contribute to reduce the dependency on materials from nonrenewable sources, by utilizing natural fibers (sisal) as reinforcing agents and lignin (a polyphenolic macromolecule obtained from lignocellulosic materials) to partially substitute phenol in a phenol‐formaldehyde resin. Besides, it was intended to evaluate how modifications applied on sisal fibers influence their properties and those of the composites reinforced with them, mainly thermal properties. Sisal fibers were modified by either (i) mercerization (NaOH 10%), (ii) esterification (succinic anhydride), or (iii) ionized air treatment (discharge current of 5 mA). Composites were made by mould compression, of various sisal fibers in combination with either phenol‐formaldehyde or lignin‐phenol‐formaldehyde resins. Sisal fibers and composites were characterized by thermogravimetry (TG) and DSC to establish their thermal stability. Scanning electron microscopy (SEM) was used to investigate the morphology of unmodified and modified surface sisal fibers as well as the fractured composites surface. Dynamic mechanical thermoanalysis (DMTA) was used to examine the influence of temperature on the composite mechanical properties. The results obtained for sisal fiber‐reinforced phenolic and lignophenolic composites showed that the use of lignin as a partial substitute of phenol in phenolic resins in applications different from the traditional ones, as for instance in other than adhesives is feasible.

Micrograph of the impact fracture surface of phenolic composite reinforced with mercerized sisal fiber (500 X).     

植物纤维/生物降解塑料复合材料的纤维表面改性研究

综述了植物纤维表面改性的主要方法及特点,其中物理改性包括热处理、静放电处理、蒸汽爆破处理等,化学法改性包括表面接枝法、表面活性剂法、碱处理法、酯化处理法、界面偶联剂法等。最后,讨论了纤维表面改性的发展趋势和研究方向,指出蒸汽爆破处理和低温等离子体处理是未来很有前景的纤维表面改性方法。     

PBO纤维表面改性的研究进展

聚对苯撑苯并双噁唑(PBO)由于其特殊的表层结构,与聚合物树脂基体复合时存在严重的界面不相容性。简要介绍了PBO纤维的结构与性能,综述了化学刻蚀、偶联剂处理、等离子体处理、电晕处理、辐射处理、酶处理、热处理、化学涂层和超临界液体处理等PBO纤维表面改性方法。     

PVA纤维增强水泥基复合材料高温性能研究

对PVA纤维增强水泥基复合材料的高温性能进行研究,分别测试了该材料在经受不同高温后的质量损失、抗压强度以及弯曲韧性,并对其微观结构变化进行了分析.结果表明,相比于普通水泥基材料,PVA纤维增强水泥基复合材料的抗压强度高,变形能力大,抗折强度高,弯曲韧性优越,其中纤维掺量为2％的试块28 d抗压强度达到45.98 MPa,抗折强度可达到14.10 MPa,最大挠度达到0.68 mm;高温处理后掺有PVA纤维的试块完整性良好,没有出现破坏性断裂,只表现为微小裂纹;随着温度的升高,不同纤维掺量砂浆试块的质量损失增大,抗压强度和抗折强度以一定的速率下降,但在800 ℃高温处理后试块仍具有一定的抗压强度和弯曲韧性,纤维掺量为2％的试块的抗压强度能达到18.9 MPa,最大挠度可保持在0.12 mm;根据微观测试可以看出,随着温度的升高,纤维缓慢熔出使试块内部出现相互交错的孔隙通道可有效防止试块高温爆裂,试块内部结构由致密变为松散蜂窝状.     

国内外植物纤维增强水泥基复合材料的研究

自然界广泛存在的植物纤维的形态具有长径比大,比强度高,比表面积大等优点。纤维在抑制混凝土裂缝发展中具有重要的作用,研究开发植物纤维增强水泥基复合材料不仅能降低混凝土的造价,而且有利于环保和可持续发展,具有深远的意义。文章综述了植物纤维的性能与增强作用、在混凝土应用中的研究进展、发展前景和存在的一些问题。     

Modification of Surfaces to Meet Bioadhesive Design Goals: A Review

The modern range of medical devices presents contrasting requirements for adhesion in biological environments. Strong bioadhesion is desired in many circumstances to assure device retention and immobility. Minimal adhesion is absolutely essential in others, where thrombosis or bacterial adhesion would destroy the utility of the implants. A brief review is given of some analytical approaches, based in adhesion science, most useful in addressing these needs. Familiar correlating parameters, such as the critical surface tension, are surprisingly good in predicting bioadhesive outcomes such as tissue integration. The example of dental implants is given to illustrate this correlation. In every case, primary attention must be given to the qualities of the first interfacial conditioning films of bio-macromolecules deposited from the living systems. For instance, fibrinogen deposits from blood may assume different configurations on surfaces of different initial energies, and thus trigger different physiological events. Standard surface modification techniques, such as siliconization, when properly quality controlled can yield improved blood-compatible devices like substitute blood vessels and artificial heart sacs. Promising extensions to new areas of biotechnology are forecast.     

Properties of Glass-Fiber Hybrid Composites: A Review

This paper provides a rigorous literature review in a field of glass-fiber composites. Glass-fiber composite is a type of fiber-reinforced polymer composites. Glass-fiber composite holds good properties such as low density, high strength, and easy processing, so widely used in aerospace, automotive, and construction. Fabrication of glass-fiber composite has been discussed in the present study. Combining the glass-fiber with other fibers into a single polymer matrix results in the development of hybrid glass-fiber composites. The hybridization in glass-fiber composites raised new ideas for future in the field of composites.     

聚酯纤维表面改性的研究进展

随着工业技术和现代科技的发展,聚酯纤维材料的改性和产业应用日益受到人们的关注,并且成为纺织新产品开发的一个重要方向。综述了近年来聚酯纤维等离子体处理、碱处理、胺处理、表面接枝、光化学处理、生物法及微胶囊法等改性技术的研究进展。     

埃洛石/聚合物复合材料界面改性及性能研究进展

综述了埃洛石/聚合物复合材料的增容改性的方法,并分析了增容改性的机理。总结了埃洛石在热塑性树脂如聚丙烯、尼龙6等中的应用,详细探讨了埃洛石/聚合物复合材料在结晶性能、力学性能和热性能等方面提高与改善的原因。展望了埃洛石作为1种无机纳米填料在聚合物基复合材料中的应用潜力与价值。     

PVA纤维表面改性对水泥基复合材料弯曲性能的影响

采用有机硅柔软剂对国产聚乙烯醇(PVA)纤维进行表面改性,并制备了纤维增强水泥基复合材料(PVA-ECC)。采用扫描电子显微镜研究了有机硅柔软剂改性对PVA纤维表面结构的影响,用三点弯曲试验研究了有机硅柔软剂改性的PVA纤维对PVA-ECC复合材料弯曲性能的影响。研究结果表明:随着有机硅柔软剂含量的增加,PVA-ECC的极限弯曲强度和极限跨中挠度均先增加再减小,当有机硅柔软剂质量分数为7%时,极限弯曲强度和极限跨中挠度达到最大值,分别为5.627 MPa和2.123 mm;用ASTM C1609标准分析PVA-ECC三点弯曲韧性,当有机硅柔软剂质量分数为7%时,弯曲韧性达到最大值。     

Chemically Extracted Cornhusk Fibers as Reinforcement in Light‐Weight Poly(propylene) Composites

Flexural, impact resistance, tensile, and sound absorption properties of composites from cornhusk fiber (CHF) and PP have been investigated. The effect of holding temperature, CHF length, CHF concentration, and enzyme treatment of CHF on mechanical properties and the effect of the latter two on sound absorption have been studied. Compared with jute/PP composites, CHF/PP composites have similar impact resistance, 33% higher flexural strength, 71% lower flexural modulus, 43% higher tensile strength, 54% lower tensile modulus, and slightly higher noise reduction coefficient. Enzyme treatment of CHF results in increased mechanical and sound absorption properties.

     

Mechanical Properties of Biodegradable Composites Reinforced with Short Spartium Junceum Fibers before and after Treatments

In the present study, Spartium junceum (SJ) fibers were chemically treated with different concentrations of two coupling agents, silane N [-3 Trimethoxysilyl propyl] ethylene diamine (Z-6020) and stearic acid, in order to improve the mechanical properties of polypropylene/Spartium junceum fibers (PP/SJ) composites. The chemical modification efficiency was verified by FTIR analysis, which showed the appearance of bands around 1260 and 1100 cm^?1 attributed to asymmetric stretching of Si-O-Si linkage and Si-O-Cellulose for (Z-6020) modified SJ fibers. The mechanical properties of the composites prepared from chemically treated Spartium junceum fibers are found to increase substantially compared to those with untreated fibers.     

聚丙烯/云母复合材料改性研究进展

综述了国内外聚丙烯(PP)/云母复合材料改性研究的最新进展,包括改变云母粒径、加入相容剂、表面改性、加入增韧剂等方法。结果认为,各种改性方法均可使PP/云母复合材料的力学性能相对于纯聚丙烯大幅度提高。最后展望了今后PP/云母复合材料研究亟待解决的问题和发展方向。     

Modification of polyamide fiber surfaces by micro-organisms

The properties of some polyamide fibers - polycaproamide (PCA), poly-p-amidobenzimidazole (PABI), poly-p-phenyleneterephthalamide (PPTA), poly-m-phenyleneisophthalamide (PPIA), and polyimide (PI) - treated by different micro-organisms that are abundant in nature (the bacteria Bacillus and Pseudomonas, and the fungi Aspergillus) were studied. The interfacial bond strength between these fibers (untreated and exposed to micro-organisms) and thermoplastic polymers such as polyethylene (PE), polycarbonate (PC), and polysulfone (PSF) was investigated by the single-filament composite and pull-out techniques. If the treatment time is not very long (1-3 weeks), the tensile strength of the fibers does not deteriorate. However, the topography of the surface undergoes considerable changes in some cases. The result of the treatment depends substantially on the chemical nature of the nutrient as well as on the micro-organism species. Two main avenues for fiber modification are possible: (1) decomposition of macromolecules in the surface layer, resulting in surface growth; and (2) adsorption of the metabolic products, which heal surface flaws and alter the chemical nature of the surface. The increase in the interfacial shear strength (IFSS) for the modified fiber-thermoplastic matrix systems was from 15% for the PCA/PE composite to 80% for the PABI/PSF and PABI/PC pairs. This increase was especially marked when a sublayer of a substance specially added to the nutrient, having better compatibility with the matrix, was formed by micro-organisms on the fiber surface.     

Surface Modification of Poly(vinyl alcohol) Fibers

The surfaces of PVA fibers prepared by in situ fibrillation were modified by first crosslinking using glyoxal and then attaching cationic and anionic groups by grafting. Crosslinking prior to modification was beneficial in minimizing the solubility of the fibers in the aqueous medium in which they were modified. Heterogeneous modification techniques were employed so that fiber properties could be preserved. PAA and PDMC were grafted from the PVA microfibrils using the KPS/NaS₂O₃ redox initiating system. Grafting was confirmed by FTIR and NMR spectroscopy. The modified PVA fibers were also analyzed by DSC, TGA, and SEM.

     

Characterization of Interfacial Properties in Fiber-Reinforced Cementitious Composites

For calculating interface properties from pullout tests, a simple theoretical model is proposed. The model enables calculating of the following material parameters: the parameter of shear stiffness of the fiber–matrix boundary layer, the shear bond strength, the frictional bond strength and the specific interfacial fracture energy. These parameters can be determined from the slope of the load-slip curve, the maximum pullout load and the corresponding slip value. Slip-controlled, multiple-fiber pullout tests were conducted in a closed-loop test system. The effects of embedment length of fibers on the model-predicted material parameters were examined. The model predictions were satisfactorily compared with some previously published test data.     

天然纤维及其聚合物基复合材料阻燃改性研究进展

因具有较高的强度和模量、生态环保、价格低廉等特点,天然纤维及其增强复合材料在民用及汽车工业中的高附加值应用越来越多。然而易燃性一直是天然纤维及其增强聚合物基复合材料应用过程中不可避免的诟病,因此相应产品的阻燃研究受到人们越来越多的关注。本文综述了天然纤维及其聚合物复合材料阻燃改性的研究现状,并对其发展和应用前景进行了展望。     

Electrospun CF-PHA Nanocomposites: Effect of Surface Modifications of Carbon Fibers

Biodegradable polyhydroxyalkanoate (PHA) based polymer nanocomposite filled with nanoscale carbon fibers (CFs) were prepared by electrospinning. To enhance the processability and thermal properties of the composites, the carbon fibers were treated with chemical reagents, namely n-octanol, silane coupling agent (KH-550), and nitric acid (HNO₃). The SEM result shows that the composite fibers with nitric acid treated CFs have the finest diameters and many uniform thickness distributions. All surface treatments on carbon fibers have increased the glass transition temperatures and crystallinities of the composites, with nitric acid treatment being the best. The improvements further depended on the volume fraction of the carbon fibers.