增强齿科树脂的HAp/PMMA纳米复合纤维的制备及其性能

以羟基磷灰石(HAp)纳米颗粒及聚甲基丙烯酸甲酯(PMMA)为主要原料,采用静电纺丝的方法制备了直径均匀、取向良好的HAp/PMMA纳米复合纤维,并通过场发射扫描电镜、傅里叶红外吸收光谱仪、热重分析仪对复合纤维进行了表征。将研磨后的复合纤维作为填料,与微纳米二氧化硅按一定比例填充后,光固化得到齿科复合树脂。力学性能测试表明:填充质量分数为1%的HAp/PMMA复合纤维有效提高了氧化硅基复合树脂的力学性能,其弯曲模量为(8.7±0.7) GPa,弯曲强度为(113.8±5) MPa,压缩强度为(320.1±62) MPa;当复合纤维填充量从质量分数1%提高至3%、5%后,力学强度呈下降趋势。扫描电镜表征显示,当填充量提高后,高分子对填料的浸润性变差,出现部分孔隙及缺陷,导致其力学性能有所下降。     

Experimental Investigation of Mechanical and Morphological Properties of Flax-Glass Fiber Reinforced Hybrid Composite using Finite Element Analysis

The use of cellulosic fibers as reinforcing materials in polymer composites has gained popularity due to an increasing trend for developing sustainable materials. In the present experimental study, flax and glass fiber reinforced partially eco-friendly hybrid composites are fabricated with two different fiber orientations of 0° and 90°. The mechanical properties of these composites such as tensile, flexural and impact strengths have been evaluated. From the experiments, it has been observed that the composites with the 0° fiber orientation can hold the maximum tensile strength of 82.71 MPa, flexural strength of 143.99 MPa, and impact strength of 4 kJ/m². Whereas the composites with 90° fiber orientation can withstand the maximum tensile strength of 75.64 MPa, flexural strength of 134.86 MPa, and impact strength of 3.99 kJ/m². Morphological analysis is carried out to analyze fiber matrix interfaces and the structure of the fractured surfaces by using scanning electron microscopy (SEM). The finite element analysis (FEA) has been carried out to predict the resulting important mechanical properties by using ANSYS 12.0. From the results it is found that the experimental results are very close to the results predicted from FEA model values. It is suggested that these hybrid composites can be used as alternate materials for pure synthetic fiber reinforced polymer composite materials.     

Influence of varying fiber lengths on mechanical,thermal, and morphological properties of MA‐g‐PP compatibilized and chemically modified short pineapple leaf fiber reinforced polypropylene composites

Environmentally benign, low cost and abundantly available short pineapple leaf fibers (PALF), found mostly in the Tropical rain forest climates are ideal materials for manufacture of thermoplastic polymer‐matrix composites. Here, mechanical and thermal properties of composites of maleic anhydride grafted polypropylene (MA‐g‐PP) and chemically modified short PALF are studied as a function of different fiber lengths at 10 vol % fibers loading with fiber orientation in the longitudinal direction. The effects of fiber lengths and fiber loading on the morphological properties are assessed via observations by scanning electron microscopy. Fiber length of 6 mm oriented longitudinally at 10 vol % fibers loading in PP is the optimum and recommended composition, where 73% increase in impact properties, 37% increase in the flexural modulus, 33% increase in flexural strength, and 14% increase in vicat softening temperature are observed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Dynamic mechanical behavior of LCP fiber/glass fiber–reinforced LLDPE composites

Liquid crystalline polymer (LCP) fibers and glass fibers have been used to rein force linear low density polyethylene (LLDPE) by using an elastic melt extruder and the compression molding technique. The impact behavior of hybrid composites of different composition is compared and is explained on the basis of the volume frac tion of the fibers. Addition of glass fibers decreases the Izod impact strength LLDPE. The impact strength of the composites increases when glass fibers are placed by LCP fibers. Dynamic mechanical α and β relaxations are studied and effect of variation of fiber composition on these relaxations is reported in the tem perature range from −50 to 150°C at 1 Hz frequency, a relaxation shifts toward higher temperatures with addition of fibers in LLDPE. Addition of fibers increases the storage modulus of LLDPE.     

Nanofiber‐reinforced polymers prepared by fused deposition modeling

Vapor‐grown carbon fibers (VGCFs), a practical model nanofiber for single‐walled carbon nanotubes, were combined with an acrylonitrile–butadiene–styrene (ABS) copolymer to create a composite material for use with fused deposition modeling (FDM). Continuous filament feedstock materials were extruded from Banbury mixed composites with a maximum composition of 10 wt % nanofibers. Issues of dispersion, porosity, and fiber alignment were studied. SEM images indicated that the VGCFs were well dispersed and evenly distributed in the matrix and that no porosity existed in the composite material following FDM processing. VGCFs aligned both in the filament feedstock and in the FDM traces suggested that nanofibers, in general, can be aligned through extrusion/shear processing. The feedstock materials were processed into test specimens for mechanical property comparisons with unfilled ABS. The VGCF‐filled ABS swelled less than did the plain ABS at similar processing conditions due to the increased stiffness. The tensile strength and modulus of the VGCF‐filled ABS increased an average of 39 and 60%, respectively, over the unfilled ABS. Storage modulus measurements from dynamic mechanical analysis indicated that the stiffness increased 68%. The fracture behavior of the composite material indicated that the VGCFs act as restrictions to the chain mobility of the polymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3081–3090, 2003     

Mechanical behavior of agro‐residue‐reinforced polypropylene composites

In this research, fully environment‐friendly, sustainable and biodegradable composites were fabricated, using wheat straw and rice husk as reinforcements for thermoplastics, as an alternative to wood fibers. Mechanical properties including tensile, flexural, and impact strength properties were examined as a function of the amount of fiber and coupling agent used. In the sample preparation, three levels of fiber loading (30, 40, and 50 wt %) and two levels of coupling agent content (0 and 2 wt %) were used. As the percentage of fiber loading increased, flexural and tensile properties increased significantly. Notched Izod results showed a decrease in strength as the percentage of fiber increases. With addition of 50% fiber, the impact strengths decreased to 16.3, 14.4, and 16.4 J/m respectively, for wheat straw‐, rice husk‐, and poplar‐filled composites. In general, presence of coupling agent had a great effect on the mechanical strength properties. Wheat straw‐ and rice husk‐filled composites showed an increase in the tensile and flexural properties with the incorporation of the coupling agent. From these results, we can conclude that wheat straw and rice husk fibers can be potentially suitable raw materials for manufacturing biocomposite products. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Natural fiber blend—nylon 6 composites

In this study, engineering thermoplastic composites were prepared from natural fiber blend–filled nylon 6. Natural fiber blend from a mixture of kenaf, flax, and hemp fibers were added to nylon 6 using melt mixing to produce compounded pellets. The natural fibers/ nylon6 composites with varying concentrations of natural fibers (from 5 to 20 wt%) were prepared by injection molding. The tensile and flexural properties of the nylon 6 composites were increased significantly with the addition of the natural fiber blend. The maximum strength and modulus of elasticity for the nylon 6 composites were achieved at a natural fiber blend weight fraction of 20%. The Izod impact strength of composites decreased with the incorporation of natural fibers without any surface treatments and coupling agent. The melt flow index (MFI) also decreased with increasing natural fiber blend loading. The results of tensile and flexural modulus of elasticity (FMOE) are in accordance with the rheological data from the MFI measurements. The increase in the tensile and flexural properties indicated that efficient bonding occurred between the natural fibers and nylon 6. No fiber pullout was observed during the scanning electron microscopic analysis of the fracture surfaces. The higher mechanical results with lower density demonstrate that a natural fiber blend can be used as a sufficient reinforcing material for low‐cost, eco‐friendly composites in the automotive industry and in other applications such as the building and construction industries, packaging, consumer products, etc.POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Synthesis of restorative microcapsules having vinyl ester healing medicine for hybrid resin/modified carbon fiber self-healing composites

In this study, we aimed to synthesize restorative microcapsules using aminopropyl triethoxy silane through a combination of both microemulsions with a sol–gel technique and vinyl ester resin used as a healing component. The characteristic features of the microcapsules were analyzed by FTIR, XRD, and SEM and confirmed by the formation of core-shell microspheres with desired properties. The fabricated core-shell microspheres were reinforced into a hybrid resin (vinyl ester (80): epoxy (20)/silane modified carbon fiber composites) using the hand lay-up method. The effect of the microspheres on the mechanical and self-healing properties of composites was investigated. The mechanical test results showed a significant improvement in the flexural and impact strength by approximately 23% and 30%, respectively. The healing property was observed using the flexural test and the results indicated that the recovered strength almost 74% of the composites after initial damage was due to the healing medicine released from the broken portion of the core-shell microspheres that filled and cured the cracked area of the composites.     

Synthesis and characterization of short Grewia optiva fiber‐based polymer composites

Natural fibers, such as Flax, Sisal, Hibiscus Sabdariffa, and Grewia optiva (GO) possess good reinforcing capability when properly compounded with polymers. These fibers are relatively inexpensive, easily available from renewable resources, and possess favorable values of specific strength and specific modulus. The mechanical performance of natural fiber‐reinforced polymers (FRPs) is often limited owing to a weak fiber‐ matrix interface. In contrast, urea–formaldehyde (UF) resins are well known to have a strong adhesion to most cellulose‐containing materials. This article deals with the synthesis of short G. optiva fiber‐reinforced UF polymer matrix‐based composites. G. optiva fiber‐reinforced UF composites processed by compression molding have been studied by evaluating their mechanical, physical, and chemical properties. This work reveals that mechanical properties such as: tensile strength, compressive strength, flexural strength, and wear resistance of the UF matrix increase up to 30% fiber loading and then decreases for higher loading when fibers are incorporated into the polymer matrix. Morphological and thermal studies of the matrix, fiber, and short FRP composites have also been carried out. The swelling, moisture absorbance, chemical resistance, and water uptake behavior of these composites have also been carried out at different intervals. The results obtained lay emphasis on the utilization of these fibers, as potential reinforcing materials in bio‐based polymer composites. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Morphology and mechanical properties of unidirectional sisal– epoxy composites

Plant fibers are of increasing interest for use in composite materials. They are renewable resources and waste management is easier than with glass fibers. In the present study, longitudinal stiffness and strength as well as morphology of unidirectional sisal–epoxy composites manufactured by resin transfer molding (RTM) were studied. Horseshoe‐shaped sisal fiber bundles (technical fibers) were nonuniformly distributed in the matrix. In contrast to many wood composites, lumen was not filled by polymer matrix. Technical sisal fibers showed higher effective modulus when included in the composite material than in the technical fiber test (40 GPa as compared with 24 GPa). In contrast, the effective technical fiber strength in the composites was estimated to be around 400 MPa in comparison with a measured technical fiber tensile strength of 550 MPa. Reasons for these phenomena are discussed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2358–2365, 2002     

A phenomenological study of the mechanical properties of long‐fiber filled injection‐molded thermoplastic composites

Tensile and flexural tests on specimens cut from rectangular injection‐molded plaques show that long‐fiber filled thermoplastic composites are complex, non‐homogeneous, anistropic material systems. Like all fiber‐filled materials, they exhibit through‐thickness nonhomogeneity as indicated by differences between tensile and flexural properties. The in‐plane orientation of fibers in through‐thickness layers causes the material to have in‐plane anisotropic properties. However, these long‐fiber filled materials exhibit an unexpectedly large level of in‐plane nonhomogeneity. Also, the effective mechanical properties of these materials are strongly thickness dependent. The thinnest plaques exhibit the largest differences between the flow and cross‐flow tensile properties. These differences decrease with increasing thickness. A methodology for part design with this class of materials is discussed.     

Polymer-derived ceramic tapes with small and negative thermal expansion coefficients

A polysiloxane filled with ß-eucryptite and/or SiC was used for the processing of polymer derived ceramic tapes. The combination of both fillers in varying proportions allowed to tailor the overall bulk thermal expansion and the flexural strength of the resulting composite materials simultaneously. Incorporation of SiC increased noticeably the flexural strength of the samples and influenced the phase changes resulting from the interactions between the β-eucryptite filler and the polymer derived ceramic matrix. Changes in the phase composition and changes of the unit cell parameters of β-eucryptite because of the formation of solid-solutions with silica originating from the SiO₂ constituent of the polymer derived ceramic matrix were observed by Rietveld refinement. Tapes resulting from this process possess a sufficient mechanical stability and their coefficient of thermal expansion can be adjusted from slightly positive to moderate negative values.     

Morphological and physicomechanical analysis of high‐density polyethylene filled with Salago fiber

The environmental issues associated with the mass discarding of waste plastics in the Philippines have significantly raised for the past decade. However, this country is a home to many natural fibers which necessitates the development of ecofriendly materials to diminish the environmental footprint of polymers. High‐density polyethylene (HDPE) was filled with floured untreated and 5 wt % alkaline‐treated Salago fiber via melt compounding. The physical and mechanical characteristics of both types of composites were measured and compared. The composite filled with 30 wt % untreated fiber became very brittle, showing tensile strength and impact resistance of 15.8 MPa and 4.9 kJ/m², respectively. Alkaline treatment improved the mechanical properties of untreated composites, but not above the value of virgin HDPE. Nevertheless, the flexural strength of treated composites exceeded that of the virgin HDPE. Untreated composites absorbed water twice as the treated ones. Finally, morphological and fractography inspection on tensile and flexural test specimens showed improvement made by treatment on the interfacial adhesion between fiber and thermoplastic, corroborating the results from mechanical properties test. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46479.     

Characteristics of murta bast fiber reinforced epoxy composites

The growing global concern over environment protection has led to the application of natural fiber reinforced polymer composites as alternative materials in manufacturing sectors. Various natural fibers are therefore being explored for reinforcement of polymer matrices. In the present work, murta bast fibers of varying length and weight percent are mixed randomly with the epoxy matrix and the composites are prepared from these mixtures by using the hand lay‐up method. The composites are characterized on the basis of density, thermal gravimetric analysis, infrared spectroscopy, scanning electron microscopy, tensile strength, flexural strength, compressive strength, impact strength, and Rockwell hardness studies. Tensile, flexural, and compressive moduli of the composites are also determined. The tensile strength of the composite was analyzed in the light of the different analytical models. Composites containing 30 weight % fibers of length 25 or 35 mm have the optimum mechanical properties. Murta bast fiber has the characteristics to become a good natural material for reinforcement. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44142.     

Concentration effect of γ‐glycidoxypropyltrimethoxysilane on the mechanical properties of glass fiber–epoxy composites

In this study, glass fibers were modified using γ‐glycidoxypropyltrimethoxysilane of different concentrations to improve the interfacial adhesion at interfaces between fibers and matrix. Effects of γ‐glycidoxypropyltrimethoxysilane on mechanical properties and fracture behavior of glass fiber/epoxy composites were investigated experimentally. Mechanical properties of the composites have been investigated by tensile tests, short beam tests, and flexural tests. The short‐beam method was used to measure the interlaminar shear strength (ILSS) of laminates. The tensile and flexural properties of composites were characterized by tensile and three‐point bending tests, respectively. The fracture surfaces of the composites were observed with a scanning electron microscope. On comparing the results obtained for the different concentrations of silane solution, it was found that the 0.5% GPS silane treatment provided the best mechanical properties. The ILSS value of heat‐cleaned glass fiber reinforced composite is enhanced by ∼59% as a result of the glass fiber treatment with 0.5% γ‐GPS. Also, an improvement of about 37% in tensile strength, about 78% in flexural strength of the composite with the 0.5% γ‐GPS treatment of glass fibers was observed. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Resol–vegetable fibers composites

Vegetable fibers like cotton, sisal, and sugar cane bagasse have been used as reinforcement in a polymeric matrix. Because of its low cost and affinity with lignocellulosic fibers, a phenol‐formaldehyde resin —resol— was selected as the matrix. Composites were prepared by compression molding. The influence of fiber volume fraction‐V_f‐in flexural properties and density of composites has been studied. Cotton and sugar cane bagasse composites present a V_f value at which flexural strength and modulus are maxima. However, sisal composites show a continuous rise in flexural strength and modulus as fiber volume fraction increases, up to 76%, which is the highest concentration studied. Composites made with raw cotton show the highest values of strength and stiffness. The actual density of composites is always lower than theoretical density, due to the presence of voids. Scanning Electron Microscopy reveals a good adhesion between fiber and matrix in the composites. In addition, the flexural properties were analyzed with an efficiency criterion, which relates strength and stiffness with density, and the values obtained were compared with those corresponding to typical structural materials. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1832–1840, 2000     

Properties of bio‐based polymer nylon 11 reinforced with short carbon fiber composites

In this work, micro‐composite materials were produced by incorporating 3‐mm long reclaimed short carbon fibers into bio‐based nylon 11 via melt compounding. A systematic fiber length distribution analysis was performed after the masterbatching, compounding and an injection moulding processes using optical microscopy images. It was found that the large majority of the fibers were within the 200–300 μm in length range after the injection moulding process. The mechanical (flexural and tensile), thermo‐mechanical, and creep properties of the injection moulded materials are reported. We found that an enhancement in flexural and Young's modulus of 25% and 14%, respectively, could be attained with 2 wt% carbon fiber loading whilst no significant drawback on the ductility and toughness of the matrix was observed. The creep resistance and recovery of the nylon 11, tested using dynamic mechanical thermal analysis at room temperature and 65°C, was significantly improved by up to 30% and 14%, respectively, after loading with carbon fiber. This work provides an insight into the property improvement of the bio‐based polymer nylon 11 using a small amount of a reclaimed engineered material. POLYM. COMPOS., 36:668–674, 2015. © 2014 Society of Plastics Engineers     

三维石英织物增强氮化硅基复合材料的制备及其力学性能

以分子结构单元为[SiH2NH]n的全氢聚硅氮烷作先驱体，采用聚合物浸渍裂解法制备了三维石英织物增强氮化硅基复合材料（3DSiO2f／Si3N4）。研究了复合材料的致密化工艺与力学性能。结果表明：全氢聚硅氮烷与石英纤维润湿性好，浸渍效率高，陶瓷产率高；经5个浸渍裂解周期后复合材料密度达1．96g／cm^3，孔隙率为10．9％，复合材料室温弯曲强度为33．5MPa，弹性模量为16．3GPa。由断口形貌看出：材料呈现脆性断裂，无纤维拔出现象，纤维与基体发生了较强的界面结合，基体内部和纤维表面均出现微裂纹。界面结合过强是导致3DSiO2f／Si3N4复合材料力学性能不佳的主要原因。     

Characteristics of banana fibers and banana fiber reinforced phenol formaldehyde composites‐macroscale to nanoscale

Microfibers and nanofibers were prepared from macro banana fibers by a steam explosion process. The fiber surface of chemically modified and unmodified banana fibers was investigated by atomic force microscopy, the studies revealed a reduction in fiber diameter during steam explosion followed by acid treatments. Zeta potential measurements were carried out to measure the acidic property of the fiber surface; the surface acidity was found to be increased from macrofibers to nanofibers. The thermal behavior of macrofibers, microfibers, and nanofibers were compared. Substantial increase in thermal stability was observed from macroscale to nanoscale, which proved the high thermal stability of nanofibers to processing conditions of biocomposite preparation. The composition of the fibers before and after steam explosion and acid hydrolysis were also analyzed using FT‐IR. It was found that the isolation of cellulose nanofibres occurs in the final step of the processing stage. Further macrocomposites, microcomposites, and nanocomposites were prepared and mechanical properties such as tensile, flexural and impact properties were measured and compared. The composites with small amount of nanofibers induces a significant increase in tensile strength (142%), flexural strength (280%), and impact strength (133%) of the phenol formaldehyde (PF) matrix, this increase is due to the interconnected web like structure of the nanofibers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1239‐1246, 2013     

Development and application of triglyceride-based polymers and composites

Triglyceride oils derived from plants have been used to synthesize several different monomers for use in structural applications. These monomers have been found to form polymers with a wide range of physical properties. They exhibit tensile moduli in the 1–2 GPa range and glass transition temperatures in the range 70–120 °C, depending on the particular monomer and the resin composition. Composite materials were manufactured utilizing these resins and produced a variety of durable and strong materials. At low glass fiber content (35 wt %), composites produced from acrylated epoxidized soybean oil by resin transfer molding displayed a tensile modulus of 5.2 GPa, a flexural modulus of 9 GPa, a tensile strength of 129 MPa, and flexural strength of 206 MPa. At higher fiber contents (50 wt %) composites produced from acrylated epoxidized soybean oil displayed tensile and compression moduli of 24.8 GPa each, and tensile and compressive strengths of 463.2 and 302.6 MPa, respectively. In addition to glass fibers, natural fibers such as flax and hemp were used. Hemp composites of 20% fiber content displayed a tensile strength of 35 MPa and a tensile modulus of 4.4 GPa. The flexural modulus was ∼2.6 GPa and the flexural strength was in the range 35.7–51.3 MPa, depending on the test conditions. The flax composite materials had tensile and flexural strengths in the ranges 20–30 and 45–65 MPa, respectively. The properties exhibited by both the natural- and synthetic fiber-reinforced composites can be combined through the production of “hybrid” composites. These materials combine the low cost of natural fibers with the high performance of synthetic fibers. Their properties lie between those displayed by the all-glass and all-natural composites. Characterization of the polymer properties also presents opportunities for improvement through genetic engineering technology. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 703–723, 2001