Journal of Thermoplastic Composite Materials recent issues

Predicting the Alignment of Ferromagnetic Particles in a Thermoplastic Matrix

Streilen, D., Yarlagadda, S., Gillespie, J. W. — 2008-06-30

This study investigates the use of an external magnetic field to cause the magnetic and physical alignment of ferromagnetic particles in a thermoplastic polymer matrix. The composite selected provides the best alignment involving rare-earth ferromagnetic particles in a polystyrene matrix. The rare-earth particles are able to be effectively aligned due to their high magnetic and physical anisotropy. The time-to align the particles ranged from <5 s at 498 K to approximately 60 s at 398 K. Composites with weight percents ranging from 5 to 25% are studied. A model is developed in order to predict the alignment, and is validated against experimental data. This model predicts the time-to-align based on magnetic torque balancing that would cause alignment with the viscous drag that acts to slow the particle rotation. It is found that the model describing the polymer as a Newtonian fluid follows the same trends and form as the experimental data. Potential sources of differences that prevents close fit to the data are attributed to particle interactions, sample variations, and especially the shear thinning behavior of polystyrene.

Dielectric Relaxation and Thermal Stability of Polycarbonate Doped with MnCl2 Salt

Ayesh, A.S. — 2008-06-30

Polycarbonate (PC)/MnCl₂ composites have been prepared in order to study the influence of MnCl₂ salt on the dielectric properties (resistivity , permittivity ^', dielectric loss ^'', dielectric relaxation time `' and dielectric relaxation process) and thermal stability of PC/MnCl₂ composites. The dielectric study was carried out over a frequency range from 10 Hz to 306 kHz at room temperature as a function of frequency and salt concentration. Permittivity data was fitted in the frequency domain using Yan and Rhodes model in order to estimate the relaxation times for PC composites. As expected, the resistivity of the composites decreases with increasing of salt concentration and frequency. Also, it was found that, addition of MnCl₂ salt to PC host changes the dielectric properties of PC, mainly, broadening dielectric spectra, increases permittivity and dielectric loss, shortening relaxation time and reduces thermal stability of PC and PC composites. Results reveal that the relaxation process of these composites is due to ionic conductivity relaxation with a single relaxation time and not due to viscoelastic relaxation, while in case of pure PC is due to viscoelastic relaxation.

Thermal and Mechanical Properties of PAN- and Pitch-Based Carbon Fiber Reinforced PEEK Composites

Qiang Yuan, , Bateman, S. A., Friedrich, K. — 2008-06-30

Thermal and mechanical properties of different short carbon fibers (CF) reinforced polyether-ether-ketone (PEEK) composites are investigated, where CF is made from polyacrylonitrile (PAN-CF) and pitch (Pitch-CF). The thermal properties of both composites are studied using differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). The crystallinity of PEEK increases with the content of PAN-CF, but it is independent of Pitch-CF content. At the isothermal condition, the crystallite rate of Pitch-CF/PEEK composite is faster than that of PAN-CF/PEEK composites. Dynamic tensile modulus of PAN-CF/PEEK increases with the CF content. An increase of glass transverse temperature with an increase in CF content is found in PAN-CF/PEEK, but not in Pitch-CF/PEEK. The fracture toughness of PAN-CF/PEEK composites increases with CF contents; whereas it remains the same value for Pitch-CF composite. The fracture surface of both composites is analysed using scanning electron microscopy.

Improved Approximations of the Rayleigh Wave Velocity

Pham Chi Vinh, , Malischewsky, P. G. — 2008-06-30

In this article we have derived some approximations for the Rayleigh wave velocity in isotropic elastic solids which are much more accurate than the ones of the same form, previously proposed. In particular: (1) A second (third)-order polynomial approximation has been found whose maximum percentage error is 29 (19) times smaller than that of the approximate polynomial of the second (third) order proposed recently by Nesvijski [Nesvijski, E. G., J. Thermoplas. Compos. Mat. 14 (2001), 356—364]. (2) Especially, a fourth-order polynomial approximation has been obtained, the maximum percentage error of which is 8461 (1134) times smaller than that of Nesvijski's second (third)-order polynomial approximation. (3) For Brekhovskikh—Godin's approximation [Brekhovskikh, L. M., Godin, O. A. 1990, Acoustics of Layered Media: Plane and Quasi-Plane Waves. Springer-Verlag, Berlin], we have created an improved approximation whose maximum percentage error decreases 313 times. (4) For Sinclair's approximation [Malischewsky, P. G., Nanotechnology 16 (2005), 995—996], we have established improved approximations which are 4 times, 6.9 times and 88 times better than it in the sense of maximum percentage error. In order to find these approximations the method of least squares is employed and the obtained approximations are the best ones in the space L²[0, 0.5] with respect to its corresponding subsets.

Thermomechanical Simulation of Infrared Heating Diaphragm Forming Process for Thermoplastic Parts

Labeas, G.N., Watiti, V.B., Katsiropoulos, Ch. V. — 2008-06-30

An innovative methodology for the thermomechanical simulation of the infrared heating diaphragm forming (DF) process is proposed. In the first section of the paper, the heat transfer mechanisms between the infrared (IR) heating lamps and the thermoplastic plate are simulated, and the effect of the various preheating parameters on the heating time and temperature distribution is investigated. In the second section, the mechanical deformation of the thermoplastic component is simulated to enable prediction of heat losses due to the plate contact with the mold. Based on the developed simulation methodology, the main process parameters — e.g., the number, location, and power of IR lamps for optimal preheating; the heat losses during plate deformation; and the minimum required mold temperature throughout the forming phase — are derived for five different thicknesses. The optimization results show that the forming parameters considered influence the heating of the plate in a complex and interactive way; in addition, it is found that with increasing plate thickness, the heating time required to reach the desired temperature also increases.

Wood Fiber Reinforced Polyethylene and Polypropylene Composites with High Modulus and Impact Strength

Qiang Yuan, , Donglyang Wu, , Gotama, J., Bateman, S. — 2008-04-25

Wood plastic composite with high modulus and impact strength were manufactured by combining polyethylene (PE) or polypropylene (PP) with wood fiber (WF) using twin-screw extruder techniques. The advantage of using low melt viscosity polymer matrices is that it enhances the modulus and reduces the overall viscosity of the system. SEM analysis of the composites indicates that the polymer molecules penetrate into the vessels and cracks of the cellulose fiber, which decreases the number of voids and produces a higher density composite with improved mechanical performance. The addition of maleic anhydride-grafted polyolefin as a compatibilizer improves the level of adhesion between the wood fiber and the polyolefin matrix. The impact strength of the composites with compatibilizer is 60% higher than those without. Young's moduli of WF/PE and WF/PP with compatibilizer were 4.4 and 5.4 GPa, respectively, meanwhile the impact strengths of WF/PE and WF/PP were 44 and 24J/m, where the WF content was 50wt%.

Thermal and Mechanical Properties of Wood Flour/Talc-filled Polylactic Acid Composites: Effect of Filler Content and Coupling Treatment

Lee, S.-Y., Kang, I.-A., Doh, G.-H., Yoon, H.-G., Park, B.-D., Qinglin Wu, — 2008-04-25

Wood flour (WF) and talc-filled polylactic acid (PLA) composites are prepared by melt compounding and injection molding. The effects of filler loading and silane treatment, the thermal and mechanical properties of the composites are studied. Loading of WF and WF/talc mixture into neat PLA results in a small decrease in the glass transition and crystalline temperatures of the composites. The use of WF, talc and silane in the composites causes successively larger decreased in the composite crystallinity. The addition of talc and silane to PLA/WF composites improved the tensile modulus. The tensile strength of the composites decreases slightly with the addition of talc, but it considerably improves with the use of 1 wt% silane. Morphological analysis shows improved interfacial bonding with silane treatment for the composites.

Cure Kinetics and Mechanical Properties of Compatibilized Blends of Low Density Polyethylene and Poly Dimethyl Siloxane Rubber

Jana, R.N., Nando, G.B. — 2008-04-25

The cure kinetics of the blends of Low density polyethylene (LDPE) and Polydimethyl siloxane rubber (PDMS) (50 : 50 w/w) with different proportion of ethylene methyl acrylate (EMA) copolymer as an in situ compatibilizer, is studied by differential scanning calorimetry (DSC) and rheometry, using dicumyl peroxide (DCP) as the curing agent. EMA reacts with PDMS to form EMA grafted PDMS (EMA-g-PDMS) which acts as the compatibilizer for the blend systems. The grafting of EMA is confirmed from FT-IR studies. The different kinetic parameters such as reaction enthalpy (H), activation energy (E), frequency factor (Z), and order (n) of the curing reaction are evaluated from the DSC trace. The reaction enthalpy decreases with increasing proportion of EMA in the blends whereas, the activation energy for the curing reaction shows the reverse trend. The order of the curing reaction is found to be of first order. The mechanical properties (e.g., tensile strength, modulus, energy to rupture, etc.) are found to increase with increasing proportion of EMA in the blends and becomes the maximum at 6wt% of EMA, which is taken as the optimum level of EMA for the blend systems. The improvement of mechanical properties of the blend vulcanizates with the EMA content in the blend is due to better dispersion of the blend constituents in presence of the compatibilizer as confirmed from scanning electron microscopy.

Polypropylene Nanocomposites: Effect of Organo-modified Layered Silicates on Mechanical, Thermal & Morphological Performance

Samal, S. K., Nayak, S. K., Mohanty, S. — 2008-04-25

The present article reports the mechanical, thermal and morphological characteristics of polypropylene — maleic anhydride grafted polypropylene —organically modified MMT (PP-PP-g-MAH-OMMT) nanocomposites. PP nanocomposites were prepared by melt mixing in a twin screw extruder followed by injection moulding. Sodium montmorillonite has been organically modified using quaternary ammonium intercalants. A comparative account with commercial quaternary ammonium modified clay; Cloisite 15A has also been presented. Mechanical tests showed considerable improvement in tensile, flexural and impact properties of PP matrix with the incorporation of organically modified nanoclays. Furthermore, the quaternary ammonium intercalants exhibited improved performance with an optimum improvement in compatibilized PP/Cloisite 15A nanocomposites. The morphology of the nanocomposites has been examined using wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM). Morphological findings revealed efficient dispersion of organically modified nanoclays within the PP matrix. PP-g-MAH compatibilized PP/Cloisite 15A nanocomposites displayed finely dispersed exfoliated nanomorphology as compared with other systems. The crystallization, melting behavior and thermal stability of the nanocomposites has been studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) which indicated an increase in crystallization temperature as well as thermal stability of PP matrix in Cloisite 15A nanocomposites. DMA curves also confirmed an increase in storage modulus of PP matrix in the nanocomposites, indicating an increase in the stiffness of the matrix polymer with the addition of organically modified nanoclays.

Effect of EPM-g-MAH on the Flexural and Morphological Properties of Poly(lactic acid)/Organo-montmorillonite Nanocomposites

Chow, W.S., Lok, S.K. — 2008-04-25

Poly(lactic acid) (PLA)/organo-montmorillonite (OMMT) nanocomposites were prepared by using both solution intercalation and melt intercalation methods. Maleic anhydride grafted ethylene propylene rubber (EPM-g-MAH) was used as a toughening agent for the PLA/OMMT nanocomposites. The flexural properties of PLA/OMMT nanocomposites were studied by using three-point bending test (ASTM D790). The structure of PLA/OMMT nanocomposites has been investigated by using a wide-angle X-ray Diffraction (XRD) analysis. The microstructures of the PLA/OMMT nanocomposites were assessed by Field Emission Scanning Electron Microscopy (FESEM). The flexural yield displacement of PLA/OMMT prepared by melt intercalation method was increased by the addition of EPM-g-MAH. FESEM micrographs show that more fibrillated structure could be observed from the fractured surface of PLA/OMMT/EPM-g-MAH nanocomposites prepared by melt intercalation method. XRD results revealed the formation of PLA nanocomposites as the OMMT was intercalated and exfoliated.

Wear Behavior of a Glass Fiber-Reinforced PEI Composite

Vina, J., Garcia, M.A., Castrillo, M.A., Vina, I., Arguelles, A. — 2008-04-25

The wear behavior of a thermoplastic polymer, polyetherimide, and of a composite with this polymer as matrix and a reinforcement of glass fiber fabric has been analyzed. The test was carried out according to the Standard ASTM G99 using a device pin-on-disk. Obviously, the reinforced material has higher wear strength than the nonreinforced material. Also, the evolution of the wear with the temperature has been studied at ambient temperature and at 50, 100, 150, and 200°C. The effect of the temperature is very important because when it was increased the wear was increased, except to 200°C. At 200°C there was an important decrease. The test temperature was measured in the inner of the furnace and when it was 200°C in this zone, the temperature in the contact point was higher and it would be close to glass transition temperature of the polymer (~217°C), this is the reason for an important micro-structural variation in the material.

Properties and Structure of Polypropylene/ Polyethylene-Octene Elastomer/Nano CaCO 3 Composites

Hanim, H., Fuad, M.Y. A., Zarina, R., Ishak, Z.A. M., Hassan, A. — 2008-02-19

Polypropylene (PP)-based nanocomposites were developed by the incorporation of a novel nano-sized precipitated calcium carbonate (NPCC) nanoparticles and polyethylene—octene elastomer (POE). The NPCC filler loading selected were 10 and 15wt.% while the POE contents were varied between 0 and 30wt.%. A slight decrease in the tensile strength of the PP nanocomposites was observed with increasing NPCC content. Results of impact strength indicated that the NPCC filler imparted some toughening effects on the PP and PP/POE blends. Maximum impact strength enhancement was achieved for the PP when blended with 30wt.% POE and filled with 15wt.% NPCC. However, the essential property balance between toughness and stiffness was still lacking in the nanocomposites developed. Differential Scanning Calorimeter results showed that NPCC acted as a nucleating agent for PP, increasing the crystallization temperature of PP by approximately 9°C.

Effect of Nanoclay Content on Void Morphology in Resin Transfer Molded Composites

Hamidi, Y. K., Aktas, L., Altan, M. C. — 2008-02-19

Effects of nanoclay content on morphology and spatial distribution of voids in resin transfer molded nanoclay/E-glass/epoxy composite disks are investigated. Closite^®25A nanoclay loads of 2, 5, and 10wt% are mixed by sonication with a low-viscosity epoxy resin prior to filling the mold cavity containing 13.6% E-glass preform by volume. A disk without nanoclay is also molded. Once the molded composites are cured, voids on radial composite samples are evaluated via microscopic image analysis. The addition of nanoclay is found to result in a significant increase in the apparent viscosity of the clay-epoxy mixture, thus increasing the molding pressure. Void occurrence is observed to increase considerably with increasing nanoclay content, from 2.1% in the composite without nanoclay to 5.1 and 8.3% in the composites molded with 5 and 10wt% nanoclay, respectively. However, the composite with 2wt% nanoclay yields the lowest void content of 0.7%. Voids are observed to be, in average, smaller after the addition of nanoclay at all nanoclay concentrations. Presence of nanoclay in the impregnating resin induces at least 60% reduction in voids located inside fiber tows, which are trapped by the fluid front motion during impregnation. Irregularly shaped voids are also observed to decrease with increasing nanoclay content. A nonuniform void content and morphology is observed radially, which seems to be affected by the flow kinematics as well as possible breakdown and filtration of clay clusters.

Development of HEMP Fiber Reinforced Polypropylene Composites

Hargitai, H., Racz, I., Anandjiwala, R. D. — 2008-02-19

Nonwoven mats from hemp and polypropylene fibers in various proportions are produced and hot pressed to make composite material. The effect of hemp fiber content and anisotropy in the nonwoven mats resulting from the carding technology are examined on the basis of the three-point bending, tensile, and impact properties of the resultant composite materials. Because of the hydrophilic nature and poor dimensional stability of cellulosic fibers due to swelling, the effect of water sorption on mechanical performances is also investigated. Optimal mechanical properties are achieved in composites made from 40 to 50% of hemp fiber by weight. As expected, better mechanical properties are found in the specimens cut from the composite sheets parallel to the direction of carding. A strong decrease in three-point bending properties is noticed after immersing the composite samples in distilled water for 19 days, while the impact strength increased. Double carding of raw materials results in a decreased anisotropy in the composite material.

Effects of Antioxidant and Initiator on the Mechanical Properties of Polypropylene--Aspen Composites

Ruijin Gu, , Kokta, B. V. — 2008-02-19

Studies on the effect of blending method, the introduction method of initiator (dicumyl peroxide, DCP), and the blending time with antioxidant (Irganox) added on the mechanical properties of PP—Aspen composites with and without DCP, respectively are undertaken. An optimum blending time for the composite with Irganox is obtained. The optimum content of Irganox as well as pre-mixing and the final-step feeding-method of DCP are compared to that of conventional method of blending in order to achieve the optimum values of impact and tensile strength properties.

JTCM Reviewers 2005 2007

2007-12-21

Modeling the Behavior of Polymer-layered Silicate Nanocomposites using Factorial and Mixture Designs

Mittal, V. — 2007-12-21

The behavior of polymer-layered silicate nanocomposites is modeled through various factorial and mixtures design methodologies in order to optimize the composite performance and to accurately predict the properties especially for the nonpolar polymer systems. The various factors studied for the factorial design are volume fraction of inorganic clay, cation exchange capacity of the montmorillonite (MMT) substrate, and number of octadecyl chains in the ammonium modification ion exchanged on the clay surface. The constrained mixtures design includes the components as weight percent of polymer matrix, organic modification, and inorganic filler as compared to the total weight of the mixture. The mixtures design for compatibilized nanocomposites is also studied by using the components weight percent of polymer, organically modified clay, and the compatibilizer. The predicted properties from these models narrowly match the experimental results indicating the efficiency of the models to correctly represent the polymer nanocomposites system. The model equations are also used to generate response surfaces to help to achieve the required combinations of the factors or components of the system to obtain optimum composite properties. Unlike conventional models which depend on oversimplified assumptions, which are not applicable in reality, these models do not suffer from these limitations and can still predict the composite properties using a set of simple equations.

Effect of Independent Variables on Mechanical Properties and Maximization of Aspen Polypropylene Composites

Ruijun Gu, , Kokta, B. V. — 2007-12-21

Study on the effect of concentration of maleated polypropylene (MAPP), dicumyl peroxide (DCP), nanoclay (NC), and aspen fiber loading on the mechanical properties of Aspen—PP composites has been undertaken with the objective to protect or increase the impact strength without losing or weakening the tensile strength. The central composite design of Statgraphic plus is used to determine the optimum concentration of additives and to maximize both the impact as well as tensile strength properties to be superior to that of pure PP. Finally, the material price of PP composites with an optimal composition of filler (aspen fiber and NC), coupling agent (MAPP), and initiator (DCP) is compared to that of pure PP and PP reinforced with glass fibers.

Prediction and Optimization of Mechanical Properties of Polypropylene/Waste Tire Powder Blends using a Hybrid Artificial Neural Network-Genetic Algorithm (GA-ANN)

2007-12-21

Blends of Polypropylene (PP) and waste ground rubber tire powder are studied with respect to the effect of ethylene—propylene—diene monomer (EPDM) and polypropylene grafted maleic anhydride (PP-g-MA) compatibilizer content by using the Design of Experiments methodology, whereby the effect of the four polymers content on the final mechanical properties are predicted. Uniform design method is especially adopted for its advantages. Optimization is done using hybrid Artificial Neural Network-Genetic Algorithm technique. A rubber formulary with respect to the four ingredients are optimized having maximum tensile strength and then compared with a blend predicted to have maximum elongation at break. It is concluded that the blends show fairly good properties provided that it has a relatively higher concentration of PP-g-MA and EPDM content. SEM investigations also corroborates with the observed mechanical properties. A quantitative relationship is then shown between the material concentration and the mechanical properties as a set of contour plots, which are then tested and confirmed experimentally to conform to the optimum blend ratio.

Some Experimental and Theoretical Investigations on Fire Retardant Coir/Epoxy Micro-Composites

Misra, R.K., Kumar, S., Sandeep, K., Misra, A. — 2007-12-21

This article reports some experimental and theoretical investigations on fire retardant coir/epoxy micro-composites. The coir fiber is treated with saturated bromine water for increasing the electrical properties and then mixed with stannous chloride solution for improving the fire retardant properties. Only 5% (approximately) of fire retardant filler reduces the smoke density by 25% and the LOI value increases to 24%. The mechanical properties of the coir/epoxy micro-composites are not affected much after incorporation of filler. Flexural strength and flexural modulus of the NET increases tremendously compared to NEU and NE. Multiquadric radial basis function (MQRBF) method is applied for static and dynamic analysis of coir/epoxy micro-composite plate under uniformly distributed load. Damping behavior and natural frequencies are observed in NE, NEU, and NET. MQRBF is applied for spatial discretization and Newmark implicit scheme is used for temporal discretization. The discretization of the differential equations generates greater number of algebraic equations than the unknown coefficients. The multiple linear regression analysis, which is based on the least square error norm, is employed to obtain the coefficients. Simple supported and clamped boundary conditions are considered for verification of present results and they are compared with other existing analytical methods.

Hybrid Glass Fiber-reinforced Thermoplastic Nanocomposites

Houphouet-Boigny, C., Plummer, C. J.G., Wakeman, M. D., Manson, J.-A. E. — 2007-12-21

The feasibility of integrating thermoplastic isotactic polypropylene/ montmorillonite nanocomposite matrices into conventional fiber-reinforced composites has been investigated. Two basic processing routes were considered: long glass fiber (GF)-reinforced composites based on co-wound or co-woven yarns and glass mat reinforced composites. In each case satisfactory impregnation and consolidation were demonstrated, although at high fiber contents, this required increased pressures and/or temperatures in the presence of the montmorillonite. Flexural tests on the glass mat reinforced composites, containing relatively low GF contents, showed the use of a nanocomposite matrix to lead to the significant improvements in bending stiffness and strength.