Effect of chemical treatment on the thermal properties of hybrid natural fiber-reinforced composites

The main objective of this work is to study the effect of chemical treatment on the thermal properties of hybrid natural fiber-reinforced composites (NFRCs). Different chemical treatments [i.e., alkalized and mixed (alkalized+ silanized)] were used to improve the adhesion between the natural fibers (jute, ramie, sisal, and curauá) and the polymer matrix. A differential scanning calorimetry, thermogravimetry, and a dynamic mechanical analysis were performed to study the thermal properties of hybrid NFRC. It was found that the chemical treatments increased the thermal stability of the composites. Scanning electron microscopy images showed that the chemical treatments altered the morphology of the natural fibers. A rougher surface was observed in case of alkali treated fiber, whereas a thin coating layer was formed on the fiber surface during the mixed treatment. However, for some fibers (i.e., sisal and rami), the chemical treatment has a positive impact on the composite properties, whereas for the jute and curauá composites, the best behavior was found for untreated fibers. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47154.     

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.     

A Comparative Study on the Mechanical Properties of Jute and Sisal Fiber Reinforced Polymer Composites

The aim of the present study is to investigate and compare the mechanical properties of raw jute and sisal fiber reinforced epoxy composites with sodium hydroxide treated jute and sisal fiber reinforced epoxy composites. This is followed by comparisons of the sodium hydroxide treated jute and sisal fiber reinforced composites. The jute and sisal fibers were treated with 20% sodium hydroxide for 2 h and then incorporated into the epoxy matrix by a molding technique to form the composites. Similar techniques have been adopted for the fabrication of raw jute and sisal fiber reinforced epoxy composites. The raw jute and sisal fiber reinforced epoxy composites and the sodium hydroxide treated jute and sisal fiber reinforced epoxy composites were characterized by FTIR. The mechanical properties (tensile and flexural strength), water absorption and morphological changes were investigated for the composite samples. It was found that the sodium hydroxide treated jute and sisal fiber reinforced epoxy composites exhibited better mechanical properties than the raw jute and raw sisal fiber reinforced composites. When comparing the sodium hydroxide treated jute and sisal fiber reinforced epoxy composites, the sodium hydroxide treated jute fiber reinforced composites exhibited better mechanical properties than the latter.     

Influence of fiber surface treatment on the properties of sisal-polyester composites

The effect of several chemical treatments, viz. organotitanate, zirconate, silane, and N-substituted methacrylamide, on the properties of sisal fibers used as reinforcement in unsaturated polyester resin (∼50 vol%) was investigated. An improvement in the properties was observed when sisal fibers were modified with surface treatments. Under humid conditions, a decrease of 30 to 44% in tensile and 50 to 70% in flexural strength has been noted. The strength retention of surface-treated composites (except silane) is high compared with untreated composites. It is observed that N-substituted methacrylamide-treated sisal composites exhibited better properties under dry as well as wet conditions. Fractographic evidence such as fiber breakage/splitting and matrix adherence on the pulled-out fiber surface explains such behavior.     

Preparation and characterization of poly(vinyl chloride)/virgin and treated sisal fiber composites

Mechanical property changes, thermal stability, and water absorption capacity of poly(vinyl chloride) (PVC)/sisal fiber composites were assessed with respect to the effect of maleic anhydride chemical treatments of the sisal fiber, for five different sisal fiber contents, varying from 0 to 30% by weight in the composite. The composites prepared with the untreated sisal exhibited higher tensile modulus and hardness than the unloaded resin, while elongation and tensile strength were reduced. The deterioration in the mechanical properties of PVC blended with sisal fiber is attributed to the presence of moisture, interfacial defects at the fiber and polymer interface, and fiber dispersion in the PVC matrix. The amount of absorbed water is a function of the amount of fiber in the composite (F0 = 0 phr, F5 = 0.77 phr, and F20 = 4.83 phr). The comparison of the results of characterization of F5, F20, and F30 formulations prepared with the untreated fibers and the treated ones showed a reduction in absorbed water after the chemical treatment of fiber with maleic anhydride (F0 = 0 phr, F5 = 0.28 phr, and F20 = 2.99 phr), thus improving the mechanical properties of composites prepared with the treated sisal. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3630–3636, 2007     

Sisal fibers treated with NaOH and benzophenonetetracarboxylic dianhydride as reinforcement of phenolic matrix

In this work, composites based on a phenolic matrix and untreated‐ and treated sisal fibers were prepared. The treated sisal fibers used were those reacted with NaOH 2% solution and esterified using benzophenonetetracarboxylic dianhydride (BTDA). These treated fibers were modified with the objective of improving the adhesion of the fiber–matrix interface, which in turn influences the properties of the composites. BTDA was chosen as the esterifying agent to take advantage of the possibility of introducing the polar and aromatic groups that are also present in the matrix structure into the surface of the fiber, which could then intensify the interactions occurring in the fiber–matrix interface. The fibers were then analyzed by SEM and FTIR to ascertain their chemical composition. The results showed that the fibers had been successfully modified. The composites (reinforced with 15%, w/w of 3.0 cm length sisal fiber randomly distributed) were characterized by SEM, impact strength, and water absorption capacity. In the tests conducted, the response of the composites was affected both by properties of the matrix and the fibers, besides the interfacial properties of the fiber–matrix. Overall, the results showed that the fiber treatment resulted in a composite that was less hygroscopic although with somewhat lower impact strength, when compared with the composite reinforced with untreated sisal fibers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Short sisal fiber‐reinforced tire rubber composites: Dynamic and mechanical properties

The world tendency toward using recycled materials demands new products from vegetable resources and waste polymers. In this work, composites made from powdered tire rubber (average particle size: 320 μm) and sisal fiber were prepared by hot‐press molding and investigated by means of dynamic mechanical thermal analysis and tensile properties. The effects of fiber length and content, chemical treatments, and temperature on dynamic mechanical and tensile properties of such composites were studied. The results showed that mercerization/acetylation treatment of the fibers improves composite performance. Under the conditions investigated the optimum fiber length obtained for the tire rubber matrix was 10 mm. Storage and loss moduli both increased with increasing fiber content. The results of this study are encouraging, demonstrating that the use of tire rubber and sisal fiber in composites offers promising potential for nonstructural applications. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 670–677, 2004     

Unsaturated polyester‐toughened epoxy composites: Effect of sisal fiber on thermal and dynamic mechanical properties

In the present study, the mechanical and thermal properties of sisal fiber‐reinforced unsaturated polyester (UP)‐toughened epoxy composites were investigated. The sisal fibers were chemically treated with alkali (NaOH) and silane solutions in order to improve the interfacial interaction between fibers and matrix. The chemical composition of resins and fibers was identified by using Fourier‐transform infrared spectroscopy. The UP‐toughened epoxy blends were obtained by mixing UP (5, 10, and 15 wt%) into the epoxy resin. The fiber‐reinforced composites were prepared by incorporating sisal fibers (10, 20, and 30 wt%) within the optimized UP‐toughened epoxy blend. Scanning electron microscopy was used to analyze the morphological changes of the fibers and the adhesion between the fibers and the UP‐toughened epoxy system. The results showed that the tensile and flexural strength of (alkali‐silane)‐treated fiber (30 wt%) ‐reinforced composites increased by 83% and 55%, respectively, as compared with that of UP‐toughened epoxy blend. Moreover, thermogravimetric analysis revealed that the (alkali‐silane)‐treated fiber and its composite exhibited higher thermal stability than the untreated and alkali‐treated fiber systems. An increase in storage modulus and glass transition temperature was observed for the UP‐toughened epoxy matrix on reinforcement with treated fibers. The water uptake behavior of both alkali and alkali‐silane‐treated fiber‐reinforced composites is found to be less as compared with the untreated fiber‐reinforced composite. J. VINYL ADDIT. TECHNOL., 23:188–199, 2017. © 2015 Society of Plastics Engineers     

Permeability and mechanical property correlation of bio based epoxy reinforced with unidirectional sisal fiber mat through vacuum infusion molding technique

The present investigation is focused to study the permeability of natural fiber during vacuum infusion (VI) process and the effect of the surface treatments of natural fiber, fiber loading direction, resin flow direction and process parameter on the tensile properties of developed composites (sisal/bio based epoxy). The bio based resin exhibits good flow characteristics in NaOH and isocyanate treated fibers which may be attributed to change in polarity. The surface treatments appear to provide an appreciable enhancement in tensile strength through enhanced bonding between fiber and matrix. The longitudinal tensile strength has been found to be higher than that of the transverse direction and the flow along the fiber provides maximum tensile strength. It has also been demonstrated that VI process provides improved mechanical properties as compared to hand‐layup process. Morphological studies of fractured developed composites were performed by scanning electron microscopy (SEM) to understand the de‐bonding of fiber/matrix adhesion. POLYM. COMPOS., 38:2192–2200, 2017. © 2015 Society of Plastics Engineers     

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.     

Influence of fiber treatment on the performance of sisal–polypropylene composites

This article concerns the effectiveness of MAPP as a coupling agent in sisal–polypropylene composites. The fiber loading, MAPP concentration, and fiber treatment time influenced the mechanical properties of the composites. It was observed that the composites prepared at 21 volume percent of fibers with 1% MAPP concentration exhibits optimum mechanical strength. SEM investigations confirmed that the increase in properties is caused by improved fiber‐matrix adhesion. The viscoelastic properties of the treated and untreated composites were also studied. From the storage modulus versus temperature plots, an increase in the magnitude of the peaks was observed with the addition of MAPP and fiber reinforcement, thus showing an improvement in stiffness of the treated composites. The damping properties of the composites, however, decreased with the addition of the fibers and MAPP. The thermal properties of the composites were analyzed through DSC and TGA measurements. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1336–1345, 2004     

Influence of surface treatments on the physicochemical properties of short sisal fibers: Ethylene vinyl acetate composites

Natural fibers (NFs) are rich in cellulose and also they are a low cost, easily renewable source for polymer composites. However, the presence of impurities (waxes, lignin, etc.) and hydroxyl groups produce those NFs with less ability to reinforce polymeric matrices. Short sisal fibers (SSF) were subjected to three different chemical treatments (alkaline, dicumyl peroxide, and silane). Composites of ethylene vinyl acetate (EVA) and chemically modified SSF were prepared by mechanical mixing at the melt state of the polymer matrix (130°C) using a two roll mill. The influences of fiber content and chemical treatment on the mechanical properties of the composites were evaluated. The tensile strength increased for every such treated SSF‐reinforced composite. There was also a noticeable increase in elastic modulus compared with the unfilled matrix. The elongation at break values decreased as the fiber content was increased. Moreover, it was observed that the surface treatment of the SSF improved the fiber dispersion within the EVA matrix. The thermal stability of SSF was analyzed by thermogravimetic analysis. Potentially, the recyclability of the composites might be promising due to the lower specific gravity of NF, accompanied by low cost, and with the added advantage of biodegradability. POLYM. ENG. SCI., 2013. © 2012 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.     

Studies on mechanical properties of sisal fiber/phenol formaldehyde resin in‐situ composites

Phenol formaldehyde resin (PF) reinforced with short sisal fibers (SF) were obtained by two methods, direct‐mixing and polymerization filling. Impact and bending properties of resulting composites were compared. Under the same compression molding conditions, polymerization filled composites showed better mechanical properties than those of direct‐mixed composites. The influences of fiber modifications on the mechanical properties of SF/PF in‐situ (polymerization filled) composites have been investigated. Treated‐SF‐reinforced composites have better mechanical properties than those of untreated‐SF‐reinforced composites. The effects of SF on water absorption tendencies of SF/PF composites have also been studied. In addition, sisal/glass (SF/GF) hybrid PF composites of alkali‐treated SF were prepared. Scanning electron microscopic studies were carried out to study the fiber‐matrix adhesion. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Mechanical and viscoelastic properties of short fiber reinforced natural rubber composites: effects of interfacial adhesion,fiber loading,and orientation

The effect of a two-component dry bonding system consisting of resorcinol and hexamethylene tetramine on the mechanical and viscoelastic properties of short sisal fiber reinforced natural rubber composites has been studied. The studies were conducted with chemically treated and untreated short sisal fibers. Treated fibers impart better mechanical properties to the composites. By mixing with short fibers, the dynamic storage modulus (E') of natural rubber composites was improved. The effects of fiber-matrix adhesion on the mechanical and viscoelastic properties of the composites were investigated. The storage moduli and mechanical loss increased continuously with an increase in fiber loading but decreased with an increase of temperature. The influence of the fiber orientation on the mechanical and viscoelastic properties is discussed.     

Effect of fiber surface treatment on the properties of biocomposites from nonwoven industrial hemp fiber mats and unsaturated polyester resin

Biocomposites were made with nonwoven hemp mats and unsaturated polyester resin (UPE). The hemp fiber volume fraction was optimized by mechanical testing. The effect of four surface treatments of industrial hemp fibers on mechanical and thermal properties of biocomposites was studied. The treatments done were alkali treatment, silane treatment, UPE (matrix) treatment, and acrylonitrile treatment. Bending strength, modulus of elasticity, tensile strength, tensile modulus, impact strength, storage modulus, loss modulus, and tan δ were evaluated and compared for all composites. The mechanical as well as thermal properties of the biocomposites improved after surface treatments. The properties of the above biocomposites were also compared with E‐glass–mat composite. To achieve balance in properties, a hybrid composite of industrial hemp and glass fibers was made. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1055–1068, 2006     

剑麻/钢纤维增强改性酚醛树脂力学和摩擦性能

采用改性酚醛树脂为基体,剑麻/钢纤维混杂为增强纤维,通过辊炼、模压成型工艺制备了剑麻/钢纤维增强酚醛树脂复合材料.研究了剑麻纤维的加入及含量对聚砜改性酚醛树脂复合材料力学性能、摩擦磨损性能及热稳定性能的影响.结果表明:剑麻纤维质量分数为15%、钢纤维为10%时,复合材料的冲击和弯曲强度分别为3.82 kJ/m2和59.6 Mpa,达到最大;随着剑麻纤维含量的增加,复合材料的摩擦系数降低,热稳定性能下降,当剑麻纤维质量分数为10%时,复合材料的摩擦性能优异;复合材料的磨损面呈现黏着磨损和疲劳磨损特征.     

Effect of fiber surface modification on the mechanical properties of sisal fiber‐reinforced benzoxazine/epoxy composites based on aliphatic diamine benzoxazine

Sisal fibers were incorporated into a mixture of benzoxazine and bisphenol A type epoxy resins to form a unidirectionally reinforced composite. Surface modifications of the sisal fibers were carried out with sodium hydroxide, γ‐aminopropyltrimethoxysilane, and γ‐glycidoxypropyltrimethoxysilane. The surface treatments led to changes in the morphology, chemical groups, and hydrophilicity of the fibers. The effect of the fiber surface treatments on the fiber–matrix interfacial adhesion and mechanical properties of the composites were also studied. The results showed that surface treatments with sodium hydroxide and a silane coupling agent led to improved fiber–matrix adhesion; this could be seen in the scanning electron micrographs of the fractured surfaces from mechanical testing and the reduction in the impact strength of the composites made from treated fibers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Studies on thermal degradation and flame retardant behavior of the sisal fiber reinforced unsaturated polyester toughened epoxy nanocomposites

Unsaturated polyester (UP) toughened nanocomposites were prepared using both sisal fibers and montmorillonite clays. The effect of fibers and Cloisite 30B (C30B) nanoclays on the mechanical properties, thermal stability, flame retardant, and morphological behavior of the UP toughened epoxy (Epoxy/UP) were systematically studied. The chemical structures of Epoxy, UP, and Epoxy/UP systems were characterized using Proton Nuclear magnetic resonance (¹HNMR) and Fourier transform infrared (FTIR) spectra. The homogeneous dispersion of nanoclay within the polymer matrix was analyzed using transmission electron microscopy (TEM) and X‐ray diffraction (XRD) analysis. Incorporation of sisal fibers and C30B nanoclays within Epoxy/UP system resulted in an increase in the mechanical, thermal, and flame retardance properties. Thermogravimetric analysis (TGA) has been employed to evaluate the thermal degradation kinetic parameters of the composites using Kissinger and Flynn‐Wall‐Ozawa methods. Cone calorimeter, UL‐94, and LOI tests revealed a reduction in the burning rate of the matrix with the addition of fibers and nanoclays. The results showed that the treated fiber reinforced nanocomposites had higher thermal stability and better flame retardant properties than the treated fiber reinforced composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42068.     

Structural properties and mechanical behavior of injection molded composites of polypropylene and sisal fiber

Composites based on isotactic polypropylene (PP) and sisal fiber (SF) were prepared by melt mixing and injection molding. The melt mixing characteristics, thermal properties, morphology, crystalline structure, and mechanical behavior of the PP/SF composites were systematically investigated. The results show that the PP/SF composites can be melt mixed and injection molded under similar conditions as the PP homo‐polymer. For the composites with low sisal fiber content, the fibers act as sites for the nucleation of PP spherulites, and accelerate the crystallization rate and enhance the degree of crystallinity of PP. On the other hand, when the sisal fiber content is high, the fibers hinder the molecular chain motion of PP, and retard the crystallization. The inclusion of sisal fiber induces the formation of β‐form PP crystals in the PP/SF composites and produces little change in the inter‐planar spacing corresponding to the various diffraction peaks of PP. The apparent crystal size as indicated by the several diffraction peaks such as L_(110)α, L_(040)α, L_(130)α and L_(300)β of the α and β‐form crystals tend to increase in the PP/SF composites considerably. These results lead to the increase in the melting temperature of PP. Moreover, the stiffness of the PP/SF composites is improved by the addition of sisal fibers, but their tensile strength decreases because of the poor interfacial bonding. The PP/SF composites are toughened by the sisal fibers due to the formation of β‐form PP crystals and the pull‐out of sisal fibers from the PP matrix, both factors retard crack growth.