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The aim of this work is to study the mechanical behavior of a hybrid composite based on polyester thermoset matrix reinforced by a mixture of Luffa (LF) and Glass (GF) fibers. The whole volume fraction of the fibers was limited to 20 vol% in which the LF fraction was varied from 5 vol% to 20 vol%. Composites plates were prepared using the resin transfer molding (RTM) method. The morphology was studied by scanning electron microscopy (SEM), and the mechanical properties of the composites were characterized using tensile, three points’ flexural tests and hardness. Obtained results have shown that the mechanical properties of the hybrid composites were superior to those of polyester/LF composite. The mechanical properties depend on the GF fraction and on the organization of GF and LF sheets in the composite. The analytical modeling of tensile properties showed that the mechanical behavior of these hybrid composites is better described by the model of Hirsch with an adjustable value between 0.37 and 0.55. In addition, the water absorption behavior of these hybrid composites was also investigated during 200 h.

Oil palm fiber reinforced high density polyethylene (HDPE) composites which can be used in several applications (mechanical part, fiber panel, etc.) were manufactured by twin-screw extrusion followed by compression molding. In particular, the effect of coupling agent (maleated polypropylene, MAPP) concentration (0, 2, 4 and 6 wt.%) was investigated for 30 and 40 wt.% oil palm fiber. Scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FT-IR), dynamic mechanical thermal analysis (DMTA) and mechanical testing (tension and impact) were carried out to determine the effect of fiber and compatibilizer contents. The results showed that compatibilized composites have increased stiffness due to enhanced interfacial adhesion between the fibers and the matrix, as well as better homogeneity (better fiber dispersion) due to chemical bonding. The optimum MAPP content was found to be 4% for the range of conditions tested.

Polyamide 6 (PA6) and acrylonitrile butadiene styrene blend reinforced by graphene nanosheets (GNs) nanocomposites were prepared by batch system followed by hot compression to get samples for different tests. A low amounts of graphene were used (1, 2, 3, 4 wt%), with this selected loading range, the mechanical properties (Young's modulus) have increased linearly with GNs contents. However, it is observed stability in the tensile strength. The electrical and rheological properties are well characterized and have shown that the evolution of the properties runs through a threshold loading charge. The results are related to the blends morphology, and SEM images showed selective preferential localization in the polyamide 6 phase. Moreover, the presence of GNs in the blends has reduced the surface tension between the two polymers. POLYM. COMPOS. 37:998–1006, 2016. © 2014 Society of Plastics Engineers

In this work, Almond Shells (ASs) particles are used as reinforcement in a thermoplastic matrix as polypropylene (PP). Composites containing Almond Shells (ASs) particles with and without compatibilizer (maleic anhydride grafted polypropylene; SEBS-g-MA) for various particle content (5, 10, 15, 20, 25, 30 wt.%) was investigated by means of studying their mechanical, thermal and rheological properties. The composites were prepared in a twin-screw extruder and assessed by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), tensile testing and Dynamic Mechanical Analysis (DMA). Results show a clear improvement in mechanical and rheological properties from the use of Almond Shells particles in the matrix without and with maleic anhydride compatibilizer, corresponding to a gain in Young’s modulus of 56.2% and 35% respectively, at 30 wt.% particle loading. Thermal analysis revealed that incorporation of particle in the composites resulted in increase in the initial thermal decomposition temperatures.

Doum palm fibers are an environmentally friendly reinforcement in polymer composites. Their mechanical properties and abundance allow its use as an innovative material composite. In this paper doum fibers were alkali treated to clean their surface and enhance polymer fibers interaction. Tensile and rheological properties were investigated to see the effect of fibers content on the composites properties. Also, comparative composites were processed to assure a good wettability between fibers and the polymer with the use of a coupling agent as styrene–(ethylene–butene)–styrene three-block copolymer grafted with maleic anhydride (SEBS-g-MA). Results shows that tensile properties was enhanced when fiber were added to the polymer and has enhanced more with the use of coupling agent. A gain of 70% and 77% in the Young’s modulus at 30 wt.% fibers content for the binary and ternary composites, respectively. And a gain of 18% in tensile strength at 10 wt.% fibers content for the ternary composites. Moreover, dynamic mechanical thermal analyses were carried out in order to compare the changes of the properties with frequency, fibers loading, temperature and compatibilizer.

This paper deals with the mechanical and thermal properties of clay and pine cone fibers reinforced polypropylene hybrid composite at a total weight percent of 30. To enhance charges wettability within the polymer, a coupling agent was added and a mercerization treatment was carried out to the fibers. Tensile, torsional, hardness tests were conducted for these composites to evaluate the impact of hybrid charges. The tensile properties results indicate that the Young’s modulus has increased for whole systems reaching a gain of 80%, while tensile strength remained stable with the use of both charges. For torsional and hardness characterizations of such hybrid composite, an increase in the torsional resistance is noted with clay addition when hardness properties were in decrease at high clay loading. Thermal degradation decreases with the addition of fibers which is normal with the addition of a low degradation temperature charge.

A new benzimidazolium derivative, the benzimidazolium- N,N ′-hexadecane-2-hydroxy-ethyl bromide (Bz) featuring two geminal hexadecyl hydrophobic buttress has been synthesized and used for the functionalization of sodium montmorillonite (MMT-Na) via cationic exchange process. The resulting benzimidazolium-modified MMT (MMT-Bz) exhibits a large d -spacing of 3 nm between silicate layers and shows a high thermal stability compared to the commonly used clay modified alkyl ammonium salts (cloisite 20A and cloisite 20B). MMT-Bz was incorporated in high density polyethylene (HDPE) matrix via melt mixing method to produce HDPE/MMT-Bz nanocomposites. The microstructure and the morphology of these nanocomposites were studied by X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The dispersion state of the organoclay within HDPE was monitored by UV–Vis spectroscopy and melt rheology. A more homogeneous dispersion or a greater content of the MMT-Bz in the matrix produced stronger solid-like and non-terminal behavior in the nanocomposites. Tensile properties and thermal stability were evaluated and discussed on the basis of the amount of clay incorporated within the nanocomposites. The intercalated structure in the nanocomposites, resulting from both the better dispersion/distribution of clay nano-platelets and their strong interaction with the polymer chains, provides the driving force to significantly enhance the HDPE properties.

Moroccan hemp is a cellulosic fiber obtained from the north of Morocco. Their use as reinforcement in thermoplastic matrix composite requires a knowledge of their morphology and structure. In this paper the Moroccan hemp fiber was alkali treated to remove waxes and noncellulosic surface components. Fiber/matrix adhesion was assured by the use of a styrene-(ethylene-butene)-styrene three-block copolymer grafted with maleic anhydride (SEBS- g -MA) as a compatibilizer. Scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FT-IR), Thermogravimetric analysis (TGA), tensile and torsional tests were carried out for hemp fibers polypropylene composite and the compatibilized composite at different fiber content. Thus, the binary composite PP/hemp fibers (Alk) and ternary system with maleic anhydride indicate clearly an improved adhesion of the fiber to the matrix as results of the good interaction at the interface. A gain of 50% on the Young’s modulus of PP/hemp 25 wt.% without coupling agent and 74% on the PP/hemp 20 wt.% composite with the coupling agent were found. Tensile strength curve shows a remarkable stabilization when the coupling agent was used.

Mechanical properties of alfa, coir and bagasse fibers reinforced polypropylene (PP) composites have been investigated. In order to improve the composite’s mechanical properties, fibers were alkali treated before compounding to remove natural waxes and other non cellulosic compounds. The mechanical properties of the composites obtained with these three fibers were found to be superior to those of the neat polymer. Addition of various amount of reinforcement fibers yielded noticeable increases in both tensile and flexural modulus as well as the torsion parameter. 56–75% increases in tensile modulus were observed by the use of alfa, coir and bagasse while the flexural modulus increased by 30–47% when compared to neat PP. An increase in torsion modulus is also observed when the fiber content exceeds a threshold level. A power law model was developed using an experimental data to calculate the torsion modulus of fiber-reinforced composites at various fiber loading and frequencies.

Polymer composite materials with vegetable fibers were an attractive field for many industries and researchers, however, these materials required the issues of compatibility between the fibers and the polymeric matrix. This work evaluates the thermal and mechanical properties of Doum-fibers reinforcing a low density polyethylene (LDPE) composite to follow the effect of adding fibers into polymer matrix. Doum-fibers were Alkali treated to clean the fiber surface and improve the polymer/fibers adhesion. The Doum-fibers were compounded in LDPE matrix at various contents and extruded as continuous strands. An enhance on mechanical properties of composites was found, a gain of 145% compared to neat polymer at 30 wt.% fiber loading in Young’s modulus, a gain of 135% in flexural modulus at 20 wt.% fiber loading and a gain of 97% in torsional modulus at 0.1 Hz. Thermal properties were evaluated and the results show a slight decrease with increase of added Doum.

Pine cone fibers are a cellulosic material readily available and can be used as reinforcement in a thermoplastic-based composite. A solid knowledge of their fibrillar morphology and structure is required to evaluate their usefulness as a substitute to other abundant natural fibers. Pine cone fibers were alkali treated prior usage to remove waxes and non cellulosic surface component. Fiber–matrix adhesion was assured by both a styrene–(ethylene–butene)–styrene triblock copolymer grafted with maleic anhydride (SEBS-g-MA) and a linear block copolymer based on styrene and butadiene compatibilizer. Scanning Electron Microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction, Thermogravimetric analysis (TGA), tensile and torsional tests were employed for Pine cone polypropylene composite and compatibilized composite at different fiber content. Results show a clear improvement in mechanical properties from the use of both alkali treated Pine cone and Pine cone compatibilized with maleic anhydride, a gain of 43% and 49% respectively in the Young’s modulus, as a results of improved adhesion between fibers and matrix at the interface.

Graphene oxide nanosheets (GOn)/PVDF nanocomposite films were prepared by solution casting method with various GOn contents. GOn were obtained via sonication of bulk graphite oxide in dimethylformamide (DMF). Due to the strong and specific interaction between carbonyl group ( C O) in GOn surface and fluorine group ( CF 2 ) in PVDF, the GOn were homogeneously dispersed and distributed within the matrix. The chosen approach for preparation and the high compatibility between GOn and PVDF result in the formation of purely piezoelectric β-polymorph at only 0.1 wt.% GOn content. Below that content a mixture of β and α-polymorph is observed. The Young's modulus and tensile strength of PVDF were respectively increased by 192% and 92% with the addition of 2 wt.% GOn. The thermal stability of PVDF polymer was also significantly increased with increasing of GOn loading. The as-obtained flexible nanocomposite films with such low GOn content can be used as active materials in the field of piezoelectric applications.

To improve interactions between carbon nanotubes (CNTs) and poly(vinylidene fluoride) (PVDF) matrix, multiwalled CNTs (MWCNTs) were successfully coated with amphiphilic polyvinylpyrrolidone (PVP) using an ultrasonication treatment performed in aqueous solution. It was found that PVP chains could be attached noncovalently onto the nanotubes' surface, enabling a stable dispersion of MWCNTs in both water and N,N-dimethylformamide. PVP-coated MWCNTs/PVDF nanocomposite films were prepared by a solution casting method. The strong specific dipolar interaction between the PVP's carbonyl group (CO) and the PVDF's fluorine group CF2 results in high compatibility between PVP and PVDF, helping PVP-coated MWCNTs to be homogenously dispersed within PVDF. Fourier transform infrared and X-ray diffraction characterization revealed that the as-prepared nanocomposite PVDF films exhibit a purely β-polymorph even at a very low content of PVP-wrapped MWCNTs (0.1 wt%) while this phase is totally absent in the corresponding unmodified MWCNTs/PVDF nanocomposites. A possible mechanism of β-phase formation in PVP-coated MWCNTs/PVDF nanocomposites has been discussed. Furthermore, the tensile properties of PVDF nanocomposites as function of the content in PVP-coated MWCNTs were also studied. Results shows that the addition of 2.0 wt% of PVP-coated MWCNTs lead to a 168% increase in Young's modulus and a 120% in tensile strength. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

Nanocomposites of poly(vinylidene fluoride) (PVDF) with chemically reduced graphene nanosheets (GNs) were prepared by melt mixing method and their structure and morphology characterized by SEM analysis. The addition of GNs in the PVDF matrix resulted in changes of the crystallization and melting behaviors. Furthermore, increasing GNs content led to improved thermal stability of the PVDF nanocomposites in air and nitrogen, as well as significant increase in tensile and flexural properties. The nanocomposites' rheological behavior is also affected by the GNs' content. Using oscillatory rheology to monitor the GNs' dispersion, it was found that as the GNs loading increase, the Newtonian behavior disappears at low frequency. This suggests a viscoelastic behavior transition from liquid-like to solid-like, with greater GNs content and more homogeneous dispersion resulting in a stronger solid-like and nonterminal behavior. By using the melt mixing method to disperse GNs, the properties of PVDF are enhanced due to the better dispersion and distribution of GNs throughout the matrix. This improvement could broaden the applications for PVDF nanocomposites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

In this work, high density polyethylene (HDPE) was compounded with chemically treated coir fiber using a heated two roll mill. Three chemical treatments denoted silane, sodium hydroxide (NaOH) and dodecane bromide (C12) were selected to improve the interface adhesion between fibers and polyethylene matrix. The mechanical properties of these composites were evaluated and compared against those of neat polymer and untreated fibers composites. A fixed fiber loading of 20 wt.% was used in all composites. A chemical analysis using Fourier Transform Infrared spectroscopy (FTIR) was performed to see the extent of chemical modification of the fibers. Results have shown that tensile and torsional modulus exhibited a significant increase when compared to the neat HDPE. A notable increase in the Young’s modulus was observed when C12 and silane were used, corresponding to 120% and 70%, respectively. The composites’ ductility was also evaluated by the plastic stored energy and showed a noted increase when C12 and silane were used, an increase of 55% with C12 treatment and 23% when silane treatment was used. Such results promise many applications for composite materials.

The interest in using natural fibers as reinforcement for thermoplastic polymers was attracted several studies covering both material science and green technology. The use of plant fiber requires the issue of compatibility between matrix and fibers. This study treat the effect of chemical modification (alkali treatment, etherification treatment and esterification treatment) on the Alfa fiber surface, and its impact on mechanical and thermal properties of composites. To this end, the percentage of fibers was fixed at (20 wt.%), and to evaluate the effect of each chemical modification in Alfa reinforced polypropylene (PP), based on the mechanical and thermal properties of composites. Composites containing chemically modified Alfa fibers were found to possess improved mechanical and thermal properties when compared to non-treated composite. The highest improvement in Young’s modulus was observed with esterified fibers, with a 35% increase. Thermal stability is best increased using etherification-treated fiber, with gains in the temperature up to 80 °C.

In this work, the development and the mechanical characterization of a doum textile composite based on a polypropylene matrix were carried out. Mechanical and rheological tests were effectuated, to illustrate the effect of woven fibers on the mechanical and viscoelastic properties at 0°, 15°, 30°, and 45° directions. The woven fibers were treated and the matrix was melted to a coupling agent to assure compatibility between the fibers and the polymer. The composites with long fiber are generally used as film and the main properties is the tensile. In this study, our goal was to improve the tensile properties. Results have shown that tensile properties exhibited a significant increase when compared to the polypropylene. However, it was observed that the stress direction has no influence on the thermal properties of the composite. Also, this article evaluates models that predict the stiffness of the composites at different stress directions to be compared to the experiments. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4347–4356, 2013