Dynamic mechanical properties of sisal fiber reinforced polyester composites fabricated by resin transfer molding

The dynamic mechanical properties of sisal fiber reinforced polyester composites fabricated by resin transfer molding (RTM) were investigated as a function of fiber content, frequency, and temperature. Investigation proved that at all temperature range the storage modulus (E′) value is maximum for the composites having fiber loading of 40 vol%. The loss modulus (E″) and damping peaks (tan δ) were lowered with increasing fiber content. The height of the damping peaks depends upon the fiber content and the fiber/matrix adhesion. The extent of the reinforcement was estimated from the experimental storage modulus, and it has been found that the effect of reinforcement is maximum at 40 vol% fiber content. As the fiber content increases the T_g from tan δ curve showed a positive shift. The loss modulus, storage modulus, and damping peaks were evaluated as a function of frequency. The activation energy for the glass transition increases upon the fiber content. Cole–Cole analysis was made to understand the phase behavior of the fiber reinforced composites. Finally, attempts were made to correlate the experimental dynamic properties with theoretical predictions. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Dynamic mechanical properties of oil palm fiber/phenol formaldehyde and oil palm fiber/glass hybrid phenol formaldehyde composites

The dynamic mechanical properties of oil palm fiber reinforced phenol formaldehyde (PF) composites and oil palm/glass hybrid fiber reinforced PF composites were investigated as a function of fiber content and hybrid fiber ratio. The dynamic modulus of the neat PF sample decreases with decrease in frequency. Glass transition attributed with the α relaxation of the neat PF sample was observed around 140°C. Tanδ values and storage modulus show great enhancement upon fiber addition. The value increases with increase in fiber content. The loss modulus shows a reverse trend with increase in fiber loading. Incorporation of oil palm fiber shifts the glass transition towards lower temperature value. The glass transition temperature of the hybrid composites is lower than that of the unhybridized composites. The highest value of mechanical damping is observed in hybrid composites. Storage modulus of the hybrid composites is lower than unhybridized oil palm fiber/PF composite. A similar trend is observed for loss modulus. Activation energies for the relaxation processes in different composites were calculated. Activation energy is increased upon fibrous reinforcement. Complex modulus variations and phase behavior of the composites were studied from Cole‐Cole plots. Finally, master curves for the viscoelastic properties of the composites were constructed on the basis of time‐temperature superposition principle. POLYM. COMPOS., 26:388–400, 2005. © 2005 Society of Plastics Engineers     

Short polyethylene terephthalate fiber (PET) reinforced NBR rubber composites

Acrylonitrile-butadiene rubber (NBR) has been reinforced with different content of PET up to 25 phr. Vulcanization of prepared composites as will as the unreinforced ones have been induced by ionizing radiation of accelerated electron beam of varying dose up to 150 kGy. Evaluations of the vulcanized composites have been followed up through the measurement of mechanical, physical and thermal properties. Also, scanning electron microscope (SEM) was performed. Mechanical properties, namely tensile strength (TS) and hardness were found to increase with the increase of irradiation dose as well as the increase in the content of PET up to 25 phr. Also, elongation at break (ε _b) was found to decrease with the increase of irradiation dose; however, the decrease in ε_b is not consistence with the increase in fibers loading. Young’s modulus (E) and tensile modulus at 25% elongation (E25) were found to increase with the increase of irradiation dose and fiber loading up to 20 phr. Also, the volume fraction of swollen rubber increases as irradiation dose and/or fiber content increased; it was more influenced by irradiation rather than fiber loading. Anisotropic swelling increased with irradiation and fiber loading up to 20 phr. SEM photomicrograph showed that irradiation causes adhesion between PET fiber and NBR where less pulling out and less pitting on the surface were observed. The thermal properties of the composite irradiated at 100 kGy reveal that the activation energy (E _a) increases up to 10 phr fiber content. When the composite that contains 10 phr fiber irradiated at doses higher than100 kGy, Ea decreased.     

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.     

Mechanical properties of surface‐treated banana fiber/polylactic acid biocomposites: A comparative study of theoretical and experimental values

Current study evaluates the effect of fiber surface treatments on the mechanical properties of banana fiber (BF) reinforced polylactic acid (PLA) biocomposites. Experimental results indicate increase in tensile modulus and strength upon surface treatments of BF with various silanes (APS and Si69) and NaOH. Approximately, an increase of 136% in tensile strength and 49% in impact strength was obtained in case of biocomposites with Si69‐treated BF compared with the untreated BF biocomposites. Also, experimentally determined mechanical modulus of untreated and surface‐treated BF biocomposite has been compared with the mechanical modulus calculated using various micromechanical models. Models such as Hirsch's, modified Bawyer and Bader's, and Brodnyan model showed good agreement with the experimentally determined results. Similarly, other models like Halpin‐Tsai, Nielson modified Halpin‐Tsai, and Cox's model also have been tried for the comparative study with the experimental data. Surface modification of BF showed increased interfacial adhesion between the fiber and the matrix which was evident from lowered difference between the experimentally and theoretically derived mechanical modulus. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Mechanical and thermal properties of bamboo fiber reinforced polypropylene/polylactic acid composites for 3D printing

In this article, a kind of degradable composite was prepared from bamboo fiber (BF), poly lactic acid (PLA), and polypropylene (PP). The mechanical and thermal properties were characterized by the universal testing machine, thermogravimetric analysis, differential scanning calorimetry. In order to improve the compability between BF and polymer matrix several modification on the surface of BF were explored and compared. Moreover, a compatibilizer (maleated PP) was applied to further increase compatibility between the fiber and matrix. It is found that the thermal stability of BF/PP/PLA composites decreased with the increase of maleated polypropylene (MAPP) content. When 5% MAPP was used the tensile strength, flexural strength, and impact strength of composites reached 33.73, 47.18 MPa, and 3.15 KJ/m², with an increase by 13, 11.7, and 23.5%, respectively, compared with the composites without MAPP. The improvement of mechanical properties is attributed to the fact that irregular grooves and cracks induced by the modification of BF facilitate the infiltration of polymer into fiber due to the strong capillary effect. Furthermore, BF/PP/PLA composites are potential to be used in 3D printing. POLYM. ENG. SCI., 59:E247–E260, 2019. © 2018 Society of Plastics Engineers     

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     

Application of sustainable treatments to fiber surface for performance improvement of elastomeric polyurethane reinforced with basalt fiber

In order to overcome compatibility leakage between composite phases, which is a significant challenge in multidimensional composite applications, it is crucial to optimize the chemical nature of additives. The surface of basalt fiber (BF) was chemically enriched via biobased epoxy resin sizing and functional silanization process to improve its interfacial adhesion to the ecograde elastomeric polyurethane (EPU) matrix. The surface properties of BF were examined with the help of scanning electron microscopy X-ray spectroscopy (SEM/EDX) and Fourier-transformed infrared spectroscopy (FTIR) analyses. Impacts of surface modifications were compared based on mechanical, morphological, thermomechanical, and melt-flow behaviors of composites involving pristine and modified BF. Findings revealed that surface-modified BF inclusions improved the tensile strength and Shore-hardness values of composites. Tensile strength of EPU raised from 27.1 to 37.1 MPa after compounding with epoxy-sized BF. Additionally, the resin-coated BF incorporation exhibited a two-fold increase in the tensile modulus of EPU. Thermomechanical response of EPU exhibited an increasing trend by BF inclusions regardless of treatment type. Glass transition temperature of EPU shifted to 5 units higher value with modified BF loadings. SEM investigations confirmed the increased interfacial interaction between the EPU matrix and surface-sized BF. The chemically enriched surface of BF improves composite performance by improving adhesion at the EPU-BF interface. The results of this study confirmed that enhanced interfacial adhesion led to performance improvements for BF-loaded EPU composites.     

Effect of layering pattern on dynamic mechanical properties of randomly oriented short banana/sisal hybrid fiber–reinforced polyester composites

Dynamic mechanical test methods have been widely employed for investigating the structures and viscoelastic behavior of polymeric materials to determine their relevant stiffness and damping characteristics for various applications. Randomly oriented short banana/sisal hybrid fiber–reinforced polyester composites were prepared by keeping the volume ratio of banana and sisal 1 : 1 and the total fiber loading 0.40 volume fraction. Bilayer (banana/sisal), trilayer (banana/sisal/banana and sisal/banana/sisal), and intimate mix composites were prepared. The effect of layering pattern on storage modulus (E′), damping behavior (tan δ), and loss modulus (E″) was studied as a function of temperature and frequency. Bilayer composite showed high damping property while intimately mixed and banana/sisal/banana composites showed increased stiffness compared to the other pattern. The Arrhenius relationship has been used to calculate the activation energy of the glass transition of the composites. The activation energy of the intimately mixed composite was found to be the highest. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2168–2174, 2005     

Mechanical and dynamic mechanical analysis of hybrid composites molded by resin transfer molding

This work aims to evaluate the performance of glass/sisal hybrid composites focusing on mechanical (flexural and impact) and dynamic mechanical analyses (DMTA). Hybrid composites with different fiber loadings and different volume ratios between glass and sisal were studied. The effect of the fiber length has also been investigated. The densities of the composites were compared with the theoretical values, showing agreement with the rule of mixtures. The results obtained in the flexural and impact analysis revealed that, in general, the properties were always higher for higher overall reinforcement content. By DMTA, an increase in the storage and loss modulus was found, as well as a shift to higher values for higher glass loading and overall fiber volume. It was also noticed an increase in the efficiency of the filler and the calculated activation energy for the relaxation process in the glass transition region. The fiber length did not significantly change the results observed in all analyses carried out in this work. The calculated adhesion factor increased for higher glass loadings, meaning the equation may not be applied for the system studied and there are other factors, besides adhesion influencing energy dissipation of the composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The effect of fiber concentration on mechanical and thermal properties of fiber‐reinforced polypropylene composites

A novel composite material consisting of polypropylene (PP) fibers in a random poly(propylene‐co‐ethylene) (PPE) matrix was prepared and its properties were evaluated. The thermal and mechanical properties of PP–PPE composites were studied by dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) with reference to the fiber concentration. Although, by increasing PP fiber concentration in PPE, no significant difference was found in melting and crystallization temperatures of the PPE, the storage, and the tensile and flexural modulus of the composites increased linearly with fiber concentrations up to 50%, 1.5, 1.0, 1.3 GPa, respectively, which was approximately four times higher than that for the pure PPE. There is a shift in glass transition temperature of the composite with increasing fiber concentration in the composite and the damping peak became flatter, which indicates the effectiveness of fiber–matrix interaction. A higher concentration of long fibers (>50% w/w) resulted in fiber packing problems, difficulty in dispersion, and an increase in void content, which led to a reduction in modulus. Cox–Krenchel and Haplin–Tsai equations were used to predict tensile modulus of random fiber‐reinforced composites. A Cole–Cole analysis was performed to understand the phase behavior of the composites. A master curve was constructed based on time–temperature superposition (TTS) by using data over the temperature range from −50 to 90°C, which allowed for the prediction of very long and short time behavior of the composite. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2260–2272, 2005     

Rheological characterization of PP/jute composite melts

The present article summarizes an experimental study on the molten viscoelastic behavior of PP/jute composites under steady and dynamic mode. Variations in melt viscosity and die swell of the composites with an increase in shear rate, fiber loading, and coupling agent concentration have been investigated using capillary rheometer. It was observed that with the addition of fibers and MAPP, the melt viscosity of the composites increased due to improved fiber‐matrix interfacial adhesion. Further, the dynamic viscoelastic behavior, measured using parallel plate rheometer, revealed an increase in the storage modulus (G′), indicating higher stiffness in case of fiber‐filled composites as compared with the virgin matrix. Time–temperature superposition was applied to generate various viscoelastic master curves. The fiber‐matrix morphology of the extrudates was also examined using scanning electron microscopy, which corroborated the findings of rheological properties. The treated composites displayed uniform distribution of fibers within the PP matrix with lesser surface irregularities. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1476–1484, 2006     

Effect of alkali‐resistant glass fiber on polypropylene/polystyrene blends: Modeling and characterization

Alkali‐resistant glass fiber (GF) reinforced polypropylene (PP)/polystyrene (PS) blends were prepared by melt mixing in a Thermo Haake Rheochord mixer. Variation in thermal and mechanical properties with the addition of glass fibers into the polypropylene/polystyrene blends was investigated. The characterization of PP/PS/GF composites was done by dynamic mechanical analysis (DMA), thermogravimetric analysis, scanning electron microscope, and transmission electron microscope. The experimentally observed tensile properties of glass fiber reinforced PP/PS blends were compared with various published models. It was found that the experimental results agree well with Hui‐ Shia and series models. DMA tests revealed an increase in storage modulus with fiber loading confirms the greater degree of stress transfer from the matrix to the fiber. TEM micrographs reveal that the glass fibers are located at the interface between the blend components. POLYM. COMPOS., 37:398–406, 2016. © 2014 Society of Plastics Engineers     

Effect of surface treatments of banana fiber on mechanical,thermal, and biodegradability properties of PLA/banana fiber biocomposites

Poly lactic acid (PLA)/Banana fiber (BF) biocomposites were fabricated employing melt blending technique followed by compression molding. BF were surface‐treated by NaOH and various silanes viz. 3‐aminopropyltriethoxysilane (APS) and bis‐(3‐triethoxy silyl propyl) tetrasulfane (Si69) to improve the compatibility of the fibers within the matrix polymer. Mechanical tests revealed an increase of tensile strength to the tune 136% and impact strength to 49% as compared with the untreated biocomposite. Thermal properties of the composites have been evaluated using DSC and TGA. DSC thermograms revealed an increase in the melting transitions thus revealing effective fiber/matrix interface. The thermal stability in the biocomposites also increased in case of banana fiber treated with Si69. Viscoelastic measurements using DMA confirmed an increase of storage modulus and low damping values in the silane treated biocomposites. Biodegradation studies in the biocomposites have been investigated in B. cepacia medium through morphological and weight loss studies. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Polymerization compounding composites of nylon‐6,6/short glass fiber

Nylon‐6,6 was grafted onto the surface of short glass fibers through the sequential reaction of adipoyl chloride and hexamethylenediamine onto the fiber surface. Grafted and unsized short glass fibers (USGF) were used to prepare composites with nylon‐6,6 via melt blending. The glass fibers were found to act as nucleating agents for the nylon‐6,6 matrix. Grafted glass fiber composites have higher crystallization temperatures than USGF composites, indicating that grafted nylon‐6,6 molecules further increase crystallization rate of composites. Grafted glass fiber composites were also found to have higher tensile strength, tensile modulus, dynamic storage modulus, and melt viscosity than USGF composites. Property enhancement is attributed to improved wetting and interactions between the nylon‐6,6 matrix and the modified surface of glass fibers, which is supported by scanning electron microscopy (SEM) analysis. The glass transition (tan δ) temperatures extracted from dynamic mechanical analysis (DMA) are found to be unchanged for USGF, while in the case of grafted glass fiber, tan δ increases with increasing glass fiber contents. Moreover, the peak values (i.e., intensity) of tan δ are slightly lower for grafted glass fiber composites than for USGF composites, further indicating improved interactions between the grafted glass fibers and nylon‐6,6 matrix. The Halpin‐Tsai and modified Kelly‐Tyson models were used to predict the tensile modulus and tensile strength, respectively.     

Effects of wheat straw fiber content and characteristics,and coupling agent concentration on the mechanical properties of wheat straw fiber‐polypropylene composites

Wheat straw fiber‐polypropylene (PP) composites were prepared to investigate the effects of wheat straw fiber content (10, 20, 30, 40, and 50 wt %), fiber size (9, 28, and 35 mesh), and maleic anhydride grafted polypropylene (MAPP) concentration (1, 2, 5, and 10 wt %) on the static and dynamic mechanical properties of the wheat straw fiber‐PP composites in this study. The tensile modulus and strength of the composites increased linearly with increasing wheat straw fiber content up to 40%, whereas the elongation at break decreased dramatically to 3.78%. Compared with the composites made of the longer wheat straw fiber, the composites made of the fines (>35 mesh) had a slightly higher tensile strength of 31.2 MPa and tensile elongation of 5.39% at break. With increasing MAPP concentration, the composites showed an increase in tensile strength, and the highest tensile strength of 34.0 MPa occurred when the MAPP concentration reached 10 wt %. As wheat straw fiber content increased from 0 to 40%, the flexural modulus of the composites increased gradually from 1335 to 3437 MPa. The MAPP concentration and wheat straw fiber size distribution had no appreciable effect on the static flexural modulus of the composites. The storage flexural modulus of the composites increased with increasing wheat straw fiber content. The scanning electron microscopy (SEM) observation on the fracture surface of the composites indicated that a high wheat straw fiber content (>30 wt %) resulted in fiber agglomeration and a reduction in interfacial bonding strength. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A comparative study on mechanical properties and water absorption behavior of fiber‐reinforced polypropylene composites prepared by OCC fiber and aspen fiber

Fiber‐reinforced polymers have received considerable attention from industry in recent years. Due to the sharp ecological damage, worldwide shortage of trees in many areas and the global demand for fibrous material, there has been growing interest in the use of recycled wood fiber as an alternative or substitute fiber source. The present study investigates the tensile, flexural, Izod impact, and water absorption behavior of Old Corrugated Container (OCC) and aspen (AS) reinforced polypropylene (PP) composites as a function of fiber content. The surface of AS and OCC fibers was modified through the use of MAPP coupling agent. From the studies it was found that mechanical properties increase with increase in fiber loading in both cases. However the addition of wood fibers resulted in a decrease in impact strength of the composites. The water absorption property at varying fiber loading were evaluated and found maximum for the OCC/PP composites. The weight gains for all specimens were less than 3.5%. Finally, the results showed the usefulness of OCC fiber as a good alternative and reinforcing agent for composite. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Dynamic mechanical properties of cotton/polypropylene commingled composite systems

The dynamic mechanical properties of cotton/polypropylene (PP) commingled composite system was studied with reference to the fiber content, chemical treatments with potassium permanganate and maleic anhydride modified PP, processing conditions and applied frequency. Side by side commingling of matrix and reinforcing fibers was adopted for the fabrication of composite laminates as they provide the shortest melt flow distance during the melting of matrix fibers. This method can also be used for the recycling of textile wastes. The storage modulus was found to increase with the fiber content across a range of temperatures. The loss factor was found to decrease with the increase in fiber content while the glass transition temperature increases. The chemical treatments increase the value of storage modulus. A master curve was constructed and also made a comparison between the experimental results and the theoretically predicted values. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Interfacial,dynamic mechanical,and thermal fiber reinforced behavior of MAPE treated sisal fiber reinforced HDPE composites

The present article summarizes an experimental study on the mechanical and dynamic mechanical behavior of sisal fiber reinforced HDPE composites. Variations in mechanical strength, storage modulus (E′), loss modulus (E″), and damping parameter (tan δ) with the addition of fibers and coupling agents were investigated. It was observed that the tensile, flexural, and impact strengths increased with the increase in fiber loading up to 30%, above which there was a significant deterioration in the mechanical strength. Further, the composites treated with MAPE showed improved properties in comparison with the untreated composites. Dynamic mechanical analysis data also showed an increase in the storage modulus of the treated composites The tan δ spectra presented a strong influence of fiber content and coupling agent on the α and γ relaxation process of HDPE. The thermal behavior of the composites was evaluated from TGA/DTG thermograms. The fiber–matrix morphology in the treated composites was confirmed by SEM analysis of the tensile fractured specimens. FTIR spectra of the treated and untreated composites were also studied, to ascertain the existence of type of interfacial bonds. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3306–3315, 2006     

Mechanical properties and water absorption of fiber‐reinforced polypropylene composites prepared by bagasse and beech fiber

The present study investigates the tensile, flexural, notched Izod impact, and water absorption properties of bagasse and beech reinforced polypropylene (PP) composites as a function of fiber content. The surface of fibers was modified through the use of maleated polypropylene (MAPP) coupling agent. From this study, it was found that mechanical properties increase with an increase in fiber loading in both cases. However, the addition of wood fibers resulted in a decrease in impact strength of the composites. The water absorption property at varying fiber loading was evaluated and found maximum for the BA/PP composites. The weight gains for all specimens were less than 7%. In general, the results showed the usefulness of bagasse fiber as a good alternative and reinforcing agent for composite. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009