Development and physico‐mechanical behavior of LDPE–sisal prepreg‐based composites

Low‐density polyethylene (LDPE)‐coated sisal fiber prepreg was prepared by using solution coating process. These coated fiber prepregs were consolidated to make composites having different weight fraction of sisal fibers in a hot compression‐molding machine. This experimental study reveals that higher loading of sisal fiber up to 57wt% in LDPE–sisal composites is possible by this technique. Mechanical and abrasive wear characteristics of these composites were determined. The tensile strength of composites increased with the increase in sisal fiber concentration. Coating thickness of LDPE was varied by changing the viscosity of LDPE–xylene solution that manifested to different weight fraction of fiber in sisal–LDPE composites. Mechanical, dynamic mechanical, and abrasive wear characteristics of these composites were determined. The tensile strength and modulus of sisal composites reached to 17.4 and 265 MPa, respectively, as compared to 7.1 and 33MPa of LDPE. Storage modulus of sisal composites LD57 reached to 2.7 × 10⁹ MPa at 40°C as compared to 8.1 × 10⁸ MPa of LDPE. Abrasive wear properties of LDPE and its composites were determined under multi‐pass mode; pure LDPE showed minimum specific wear rate. The specific wear rate of composites decreased with the sliding distance. Increase of coated sisal fiber content increased the specific wear rate at all the sliding distances, which has been explained on the basis of worn surface microstructures observed by using SEM. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Experimental investigation of the influence of the compounding process and the composite composition on the mechanical properties of a short flax fiber–reinforced polypropylene composite

Polypropylene (PP) composites containing 20 wt% short flax fibers are prepared, and the process parameters such as throughput, rotational speed, and screw configuration are varied during melt compounding with a corotating intermeshing twin‐screw extruder. The investigations reveal that low rotational speeds, high throughputs, and moderate shear energy inputs by the screw configuration led to an optimum set of mechanical properties. To investigate the influence of different composite compositions on the mechanical properties, composites with fiber contents between 0 and 40 wt% and maleic anhydride‐grafted PP (PP‐g‐MA) contents between 0 and 7 wt% are prepared. Increasing fiber contents enhance the Young's modulus and decrease the elongation at break and the notched impact strength. The tensile strength is barely affected. The addition of PP‐g‐MA increases the tensile strength as well as the elongation at break, whereas the Young's modulus is not influenced. Thus, PP‐g‐MA enhances the adhesion between PP and flax fibers significantly. POLYM. COMPOS., 36:2282–2290, 2015. © 2014 Society of Plastics Engineers     

Influence of interfacial adhesion on the structural and mechanical behavior of PP‐banana/glass hybrid composites

Hybrid composites of polypropylene (PP), reinforced with short banana and glass fibers were fabricated using Haake torque rheocord followed by compression molding with and without the presence maleic anhydride grafted polypropylene (MAPP) as a coupling agent. Incorporation of both fibers into PP matrix resulted in increase of tensile strength, flexural strength, and impact strength upto 30 wt% with an optimum strength observed at 2 wt% MAPP treated 15 wt% banana and 15 wt% glass fiber. The rate of water absorption for the hybrid composites was decreased due to the presence of glass fiber and coupling agent. The effect of fiber loading in presence of coupling agent on the dynamic mechanical properties has been analyzed to investigate the interfacial properties. An increase in storage modulus (E′) of the treated‐composite indicates higher stiffness. The loss tangent (tan δ) spectra confirms a strong influence of fiber loading and coupling agent concentration on the α and β relaxation process of PP. The nature of fiber matrix adhesion was examined through scanning electron microscopy (SEM) of the tensile fractured specimen. Thermal measurements were carried out through differential scanning calorimetry (DSC) and the thermogravimetric analysis (TGA), indicated an increase in the crystallization temperature and thermal stability of PP with the incorporation of MAPP‐treated banana and glass fiber. POLYM. COMPOS., 31:1247–1257, 2010. © 2009 Society of Plastics Engineers     

Comparison between dew‐retted and enzyme‐retted flax fibers as reinforcing material for composites

Two kinds of retted Canadian linseed flax fibers, dew‐retted (F1) and enzyme‐retted flax fibers (F2) were characterized in detail for their applications in composites, such as retting degree, thermal stability, tensile strength, and interfacial behavior in polypropylene (PP) matrix. It's clear from Scanning Electron Micrograph that the aspect ratio of F2 was much higher than that of F1 in the light of their separated elementary fibers in most cases. Instead, the elementary fibers of F1 remained tightly bundled into technical fiber wrapping with more non‐cellulose portions. This reflected its lower retting degree and resulted in its lower thermal stability. Single fiber tensile test and single fiber pull‐out test were used to evaluate the fiber tensile properties and fiber/PP interfacial shear strength, respectively. Better retting degree and fewer damages on F2 endowed F2 better tensile property. Consequently, higher aspect ratio, retting degree, and tensile strength proved F2 to be a kind of better reinforcing material than F1 for composites. POLYM. ENG. SCI., 2012. 2011 published by Society of Plastics Engineers     

Self‐healing and interfacially toughened carbon fibre‐epoxy composites based on electrospun core–shell nanofibres

Dual components of a self‐healing epoxy system comprising a low viscosity epoxy resin, along with its amine based curing agent, were separately encapsulated in a polyacrylonitrile shell via coaxial electrospinning. These nanofiber layers were then incorporated between sheets of carbon fiber fabric during the wet layup process followed by vacuum‐assisted resin transfer molding to fabricate self‐healing carbon fiber composites. Mechanical analysis of the nanofiber toughened composites demonstrated an 11% improvement in tensile strength, 19% increase in short beam shear strength, 14% greater flexural strength, and a 4% gain in impact energy absorption compared to the control composite without nanofibers. Three point bending tests affirmed the spontaneous, room temperature healing characteristics of the nanofiber containing composites, with a 96% recovery in flexural strength observed 24 h after the initial bending fracture, and a 102% recovery recorded 24 h after the successive bending fracture. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44956.     

Preparation and mechanical properties of high‐performance short ramie fiber‐reinforced polypropylene composites

Short ramie fiber (RF) was used to reinforce the polypropylene (PP). The composites were prepared in a twin‐screw extruder followed by injection molding. The experimental results showed that both the strength and the modulus of the composites increase considerably with increasing RF content. The tensile strength and flexural strength are as high as 67 and 80 MPa by the incorporation of ramie up to 30 wt %. To the best of our knowledge, this is one of the best results for short natural fiber‐reinforced PP composites. However, the preparation method in this study is more simple and economic. This short RF‐reinforced PP composites extend the application field for short‐nature fiber‐reinforced PP composites. Morphological analysis revealed that it is the high aspect ratio of the fiber and good interfacial compatibility that result in the high performance of the composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Isolation and characterization of betel nut leaf fiber: Its potential application in making composites

Betel nut leaf fiber (BNLF) is a new finding as cellulosic filler for polymer composites. Its main constituents are 75% α‐cellulose, 12% hemicelluloses, 10% lignin, and 3% others matter, viscosity average molecular weight 132,000 and degree of crystallinity 70%. In the present work, BNLF reinforced polypropylene (PP) composites were prepared using heat press molding method. 5–20 wt% short length fiber is taken for getting benefits of easy manufacturing and the fiber was chemically treated with NaOH, dicumyl peroxide (DCP), and maleic anhydride‐modified PP (MAPP) to promote the interfacial bond with PP. The extent of modification of fiber was assessed on the basis of morphology, bulk density, moisture absorption, thermal, and mechanical properties of untreated fiber, treated fiber, and their reinforcing PP composites. The tensile and flexural strength of composites increase with the increase of fiber loading up to 10 and 20 wt%, respectively. It was also observed that Young's modulus and flexural modulus increase with fiber loading. The thermal degradation behavior of resulting composites was investigated. Among the various treated fibers, MAPP‐treated fiber composite showed best interfacial interactions as well as mechanical and thermal properties. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Water absorption and dimensional stability of short kenaf fiber‐filled polypropylene composites treated with maleated polypropylene

The purpose of this research was to investigate the water absorption behavior and associated dimensional stability of kenaf‐polypropylene‐filled (PP/KF) composites. Composites with different fiber loadings, ranging from 0 to 40 wt %, were prepared with a twin‐screw extruder followed by hot press molding. The influence of the compatibilizer was also studied for PP/KF composite with 5 wt % maleated PP (MAPP). Water absorption testing was carried out at room temperature for 7 weeks. Tensile, flexural, and impact tests were also performed on control, wet, and re‐dried specimens. Increasing the fiber content resulted in higher water absorption and thickness swelling. The inferior mechanical properties of the wet composites were attributed to the effect of water, which deteriorates the interfacial properties of composites. On re‐drying, all properties were almost recovered because of the recovery of interfacial area as evident in scanning electron micrographs. Incorporation of the MAPP significantly improved the compatibility between the fiber and matrix and the mechanical properties of the composites compared with those without MAPP. It also diminished the water absorption as well as the related thickness swelling in the composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

GF/PP复合纱针织物预型件热压成型的压力对复合材料拉伸强度的影响

本文实验研究了热压成型压力对GF/PP复合纱针织物制成的复合材料拉伸强度的影响.研究结果表明,在实验研究的压力范围内随着压力的增大,成型后的复合材料的拉伸强度呈现出先增大后减小的变化趋势.本文从压力的变化对熔融的树脂基体受到的向纤维束内部及纤维束之间渗透的外界推动力和阻力的影响角度分析讨论了产生该变化趋势的原因.     

Improved thermal properties of jute fiber‐reinforced polyethylene nanocomposites

The thermal behavior of chemically modified jute fiber‐reinforced polyethylene (PE) nanocomposites was investigated. Nanocomposites were prepared by hot press molding technique using different fiber loadings (5, 10, 15, and 20 wt%) for both treated and untreated fibers. Jute fibers were chemically modified with benzene diazonium salt to increase their compatibility with the PE matrix. Surface and thermal properties were subsequently characterized. Fourier transform infrared spectroscopy and scanning electron microscopy analysis were used to study the surface morphology. Thermogravimetric analysis (TGA) and differential scanning calorimetry were carried out for thermal characterization. Fourier transform infrared spectroscopy and scanning electron microscopy study showed interfacial interaction among jute fiber, PE, and nanoclay. It was observed that, at optimum fiber content (15 wt%), treated jute fiber‐reinforced composites showed better thermal properties compared with that of untreated ones and also that nanoclay‐incorporated composites showed enhanced higher thermal properties compared with those without nanoclay. POLYM. COMPOS., 38:1266–1272, 2017. © 2015 Society of Plastics Engineers     

Unidirectional hemp and flax EP‐ and PP‐composites: Influence of defined fiber treatments

In some technical areas, mainly in the automotive industry, glass fiber reinforced polymers are intended to be replaced by natural fiber reinforced polymer systems. Therefore, higher requirements will be imposed to the physical fiber properties, fiber‐matrix adhesion, and the quality assurance. To improve the properties of epoxy resins (EP) and polypropylene (PP) composites, flax and hemp fibers were modified by mercerization and MAH‐PP coupling agent was used for preparing the PP composites. The effects of different mercerization parameters such as concentration of alkali (NaOH), temperature, and duration time along with tensile stress applied to the fibers on the structure and properties of hemp fibers were studied and judged via the cellulose I–II lattice conversion. It was observed that the mechanical properties of the fibers can be controlled in a broad range by using appropriate mercerization parameters. Unidirectional EP composites were manufactured by the filament winding technique; at the PP matrix material, a combination with a film‐stacking technique was used. The influence of mercerization parameters on the properties of EP composites was studied with hemp yarn as an example. Different macromechanical effects are shown at hemp‐ and flax‐PP model composites with mercerized, MAH‐PP‐treated, or MAH‐PP‐treated mercerized yarns. The composites' properties were verified by tensile and flexural tests. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2150–2156, 2004     

Fiber hybrid polyimide‐based composites reinforced with carbon fiber and poly‐p‐phenylene benzobisthiazole fiber: Tribological behaviors under sea water lubrication

Fiber hybrid polyimide‐based (PI‐based) composites reinforced with carbon fiber (CF) and poly‐p‐phenylene benzobisthiazole (PBO) fiber of different volume fractions were fabricated by means of hot press molding technique, and their mechanical properties and tribological behaviors under sea water lubrication were systematically investigated in relation to the synergism of CF and PBO fiber. Results showed that the incorporation of CF or PBO fiber improved the tensile strength, hardness, and wear resistance of PI. More importantly, because of the synergistic enhancement effect between CF and PBO fiber on PI matrix, the combination of 10%CF and 5%PBO fiber reinforced PI‐based composite had the best mechanical and tribological properties, showing promising application in ocean environment. POLYM. COMPOS., 37:1650–1658, 2016. © 2014 Society of Plastics Engineers     

Biobased composites prepared by compression molding with a novel thermoset resin from soybean oil and a natural‐fiber reinforcement

Biobased composites were manufactured with a compression‐molding technique. Novel thermoset resins from soybean oil were used as a matrix, and flax fibers were used as reinforcements. The air‐laid fibers were stacked randomly, the woven fabrics were stacked crosswise (0/90°), and impregnation was performed manually. The fiber/resin ratio was 60 : 40. The prepared biobased composites were characterized by impact and flexural testing. Scanning electron microscopy of knife‐cut cross sections of the specimens was also done to investigate the fiber–matrix interface. Thermogravimetric analysis of the composites was carried out to provide indications of thermal stability. Three resins from soybean oil [methacrylated soybean oil, methacrylic anhydride modified soybean oil (MMSO), and acetic anhydride modified soybean oil] were used as matrices. The impact strength of the composites with MMSO resin reinforced with air‐laid flax fibers was 24 kJ/m², whereas that of the MMSO resin reinforced with woven flax fabric was between 24 and 29 kJ/m². The flexural strength of the MMSO resin reinforced with air‐laid flax fibers was between 83 and 118 MPa, and the flexural modulus was between 4 and 6 GPa, whereas the flexural strength of the MMSO resin reinforced with woven fabric was between 90 and 110 MPa, and the flexural modulus was between 4.87 and 6.1 GPa. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Mechanical,thermal and dynamic‐mechanical behavior of banana fiber reinforced polypropylene nanocomposites

Natural fiber‐reinforced nanocomposites based on polypropylene/nanoclay/banana fibers were fabricated by melt mixing in a twin‐screw extruder followed by compression molding in this current study. Maleic anhydride polypropylene copolymer (MA‐g‐PP) was used as a compatibilizer to increase the compatibility between the PP matrix, clay, and banana fiber to enhance exfoliation of organoclay and dispersion of fibers into the polymer matrix. Variation in mechanical, thermal, and physico‐mechanical properties with the addition of banana fiber into the PP nanocomposites was investigated. It was observed that 3 wt% of nanoclay and 5 wt% of MA‐g‐PP within PP matrix resulted in an increase in tensile and flexural strength by 41.3% and 45.6% as compared with virgin PP. Further, incorporation of 30 wt% banana fiber in PP nanocomposites system increases the tensile and flexural strength to the tune of 27.1% and 15.8%, respectively. The morphology of fiber reinforced PP nanocomposites has been examined by using scanning electron microscopy and transmission electron microscopy. Significant enhancement in the thermal stability of nanocomposites was also observed due to the presence of nanoclay under thermogravimetric analysis. Dynamic mechanical analysis tests revealed an increase in storage modulus (E′) and damping factor (tan δ), conforming the strong interaction between nanoclay/banana fiberand MA‐g‐PP in the fiber‐reinforced nanocomposites systems. POLYM. COMPOS., © 2011 Society of Plastics Engineers.     

Flax fiber surface modifications: Effects on fiber physico mechanical and flax/polypropylene interface properties

This study arises on the opportunities of using flax fibers as reinforcement for polypropylene (PP) matrix composites. For this purpose, untreated flax fiber bundles obtained by a retting process have been used. For improving compatibility between flax fiber bundles and PP matrix, fiber surface treatments such as maleic anhydride, maleic anhydride polypropylene copolymer, and vinyltrimethoxy silane have been carried out. On the other hand, alkali treatment has also been carried out for fiber modification. The effect of surface modification on tensile properties of single fibers and also on fiber‐matrix interfacial shear strength (IFSS) has been analyzed. Finally, both optical microscopy and atomic force microscopy have been used for characterizing flax fiber microstructural features. The current study completes previous results to elucidate the influence of treatments on fiber surface and flax fiber‐PP interface. POLYM. COMPOS. 26:324–332, 2005. © 2005 Society of Plastics Engineers.     

Processing–formulation–performance relationships of polypropylene/short flax fiber composites

This work is a comprehensive study of the effect of extrusion process parameters and formulation on the properties of polypropylene (PP)/short flax fiber composites. The parameters that were varied during the twin‐screw extrusion process were screw configuration, revolutions per minute (rpm), extrusion temperature, and flow rate. The effect of the feeding zone location of cellulosic fiber was also considered. This study investigates the effect of the formulation, cellulosic fiber content, the presence of a coupling agent, and of a reactive additive on composite performance. The composites were characterized in terms of morphology and microstructure, fiber length, rheological, thermal, and mechanical properties. Sensibility to humidity and recyclability were also considered. When compared with as‐received PP, the tensile strength of injection‐molded parts increased with cellulosic content by up to 40 vol %, and the tensile modulus increased 3.5 times when a combination of coupling and reactive agents was used. Exposed to controlled humidity of 50% during 1 year, these composites exhibited a very low level of humidity uptake around 0.85 wt %. The processability of these materials using a cast film line and the mechanical properties of extruded sheets are also presented. Furthermore, these materials demonstrate a good recyclability using injection molding by keeping the integrality of their mechanical properties after five reprocessing cycles. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41528.     

制备工艺对亚麻增强热塑性复合材料拉伸力学性能的影响

将增强体亚麻纱线和基体丙纶复丝制成pp/亚麻包覆纱后,进行织造,织物用层合热压法制成复合材料.制备工艺中,包覆纱法对复合材料的拉伸强度最好;麻含量50%的复合材料的拉伸强度达到最佳;当纬纱密度相同时,随着经纱密度的增大经向的拉伸强力和拉伸弹性模量也随之增大,而纬向的却随之减小,当经纱密度相同时,随着纬纱密度的增大,经向的拉伸强力和拉伸弹性模量随之减小,纬向的随之增大.     

Injection molding of long sisal fiber–reinforced polypropylene: Effects of compatibilizer concentration and viscosity on fiber adhesion and thermal degradation

A two‐step process was used to obtain long sisal fiber‐polypropylene (SF/PP)–reinforced thermoplastic composites, using maleic anhydride grafted polypropylene (MA‐g‐PP) as a compatibilizer. At a first stage, modified polypropylenes (mPP) were used for an extrusion impregnation process, for the preparation of composite pellets containing about 70 wt% of SF. SF/mPP pellets with a large aspect ratio were prepared by continuous extrusion impregnation of a continuous SF yarn, using a single screw extruder and an adequate impregnation die. The mPP used were MA‐g‐PP and regular polypropylene (PP), modified by reaction with different amounts of an organic peroxide. The composite pellets were thus dry blended with regular PP pellets in an injection machine hopper, and injection molded to obtain composite tensile specimens with a minimum quantity of modified polypropylene, minimum fiber breakage and thermal degradation, and excellent mechanical properties. It is shown that the fiber breakage is reduced to a minimum, even for recycled composites, due to the presence of the low‐viscosity polymer layer wetting the SF fibers. The bulk composite effective viscosity and the fiber breakage extent and thermal degradation during the injection‐molding step are found to be closely related. Blending with much less expensive mPP at the impregnation stage optimizes the amount of expensive MA‐g‐PP. POLYM. ENG. SCI., 45:613–621, 2005. © 2005 Society of Plastics Engineers     

Surface‐modified talc particles by acetoxy groups grafting: Effects on mechanical properties of polypropylene/talc composites

This article deals with the effects of surface‐modified talc particles on mechanical properties of polypropylene (PP)/talc composites. These materials were prepared by injection molding of PP blended with different concentrations of nontreated and treated talc, under the same processing conditions. Differential thermal calorimetry and scanning electron microscopy were used to assess thermal properties and morphology of the final composites. The reinforcing effect of talc, either treated or nontreated surface, on PP is analyzed through the tensile properties as a function of the mineral content (0–10 wt%). Morphological structure of composites revealed that the talc treatment improved the particle dispersion and distribution within the PP matrix and enhanced the interfacial PP‐talc adhesion. The mechanical properties of these composites, especially the Young modulus, tensile strength and elongation at break, were found to be improved respect to PP‐untreated talc ones. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Thermoset lactic acid‐based resin as a matrix for flax fibers

Thermoset composites were produced from flax fibers and a novel lactic acid (LA)‐based thermoset resin. This resin is based on methacrylated, star‐shaped oligomers of LA. The main purpose of this work was to evaluate whether this resin can be used to produce structural composites from flax fibers. Composites were prepared by spray impregnation followed by compression molding at elevated temperature. The tests showed that composites can be produced with as much as 70 wt% fiber. The composites were evaluated by tensile testing, flexural testing, charpy impact test, dynamic mechanical thermal analysis (DMTA), and low‐vacuum scanning electron microscopy. The ageing properties in high humid conditions were evaluated, the Young's modulus ranged from 3 GPa to 9 GPa in the best case. This work shows that structural composites can be produced from renewable material. It is clear from the results that these composites have properties that make them suitable for furniture, panels, or automotive parts. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011