Some mechanical properties of particulate-filled thermosetting and thermoplastic polymers

A semiempirical, single-parameter equation describes the modulus of particulate systems This equation has been found applicable for thermoplastic/glass bead systems, and it is further verified for particulate thermosetting systems (epoxy and polyester matrices). The temperature effect on the modulus of epoxy/glass bead composites is also analyzed. Crazing characteristics calculated from tensile data of thermoplastic/glass bead composites are summarized and compared with literature results on the corresponding unfilled polymers. The effect of coupling agents and preliminary results on rigid foams are also presented.     

Dynamic mechanical properties of polymer–leather composites

The effects of polymer impregnation, moisture, and lubricant oils on the complex modulus of the grain layer of leather have been studied. The impregnated materials were prepared by introducing a mixture of polyurethane oligomer and vinyl monomers into the grain layer and polymerizing by electron-beam irradiation. Synergism was observed in the interaction of the components of the system and analyzed in terms of the adhesion of the polymer to the collagen fibers.     

Dynamic mechanical properties of some epoxy matrix composites

Dynamic mechanical properties of some epoxy matrix composites have been studied, comparing experimental data with theoretical models. The matrix in all composite samples was Shell Epon 828, a diglycidyl ether of bisphenol A, cured with meta-phenylenediamine. Fibrous composite samples were made with glass and graphite fibers. Particulate composite samples were made with glass microspheres, atomized aluminum, powdered silica, alumina, asbestos, mica, carbon black, and graphite. The dynamic elastic modulus and damping of these samples were measured at temperatures between 85° and 345°K by a free-free flexural resonance technique. The dynamic modulus of parallel fiber composites follows the linear rule of mixtures for low fiber volume fractions; deviations from linearity at higher volume fractions appear to be due to defects caused by the sample fabrication technique. Dynamic moduli of the particulate composites conform, within experimental error, to the static modulus theory of Wu up to filler volume fractions of 0.35 to 0.40. Deviations from Wu's theory at higher volume fractions may be due to agglomeration of filler particles. The damping of particulate composites with quasi-spherical filler particles appears to follow the rule of mixtures. In particulate composites with needle- and flake-type fillers, and in fibrous composites, the fillers are more highly stressed; with more of the strain energy in the low-damping fillers, overall damping is reduced. Damping greater than that attributable to the matrix and filler may be due to slippage at the interface between them. In addition to supporting Wu's theory of the elastic modulus of a particulate composite, this study demonstrates the utility of the nondestructive free-free flexural resonance techniques for obtaining a large body of reliable data in a short time from relatively few small samples. This greatly facilitates the experimental testing of theoretical models and the evaluation of fillers, matrix materials, and fabrication techniques.     

Strain behavior of particulate-filled composites

A theoretical expression has been derived to describe the strain behavior of rigid plastic composites containing spherical filler particles. By combining the predicted ultimate strength values with the appropriate modulus relationship, the complete stress–strain history and corresponding fracture energy may be estimated. The theoretical predictions were compared with experimental values obtained for a general-purpose polyester resin containing spherical glass beads. The influence of silane coupling agents and filler adhesion was also evaluated. Although the experimental values showed considerable scatter, the general trend agreed fairly well with the theoretical predictions.     

Dynamic mechanical properties of pineapple leaf fiber polyester composites

In the recent years, lignocellulosic fibers that originate from a renewable source have been found to provide good reinforcement in polymer matrices. Among the natural fibers, pineapple leaf fiber (PALF) exhibits excellent mechanical properties, besides possessing low density, high stiffness, and low cost. The dynamic mechanical properties, storage modulus (E′), and loss tangent of PALF‐reinforced polyester (PER) composites were evaluated at three frequencies 0.1, 1, and 10 Hz and temperatures ranging from 30 to 200°C. Addition of PALF of 30 mm length (aspect ratio 600) was found to increase the storage modulus leading to a maximum value at 40 wt%. The glass transition temperature (T_g) of the composite of 40 wt% showed a positive shift indicating high polymer/fiber interaction. A new relaxation is observed at 40 wt% showing the presence of a strong interphase at all aspect ratios. SEM photographs of fracture surfaces of composites confirm the results obtained from static and dynamic mechanical analysis. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Dynamic mechanical properties of poly-2-hydroxyethylmethacrylate based composites

The dynamic-mechanical properties of swollen poly-2-hydroxyethylmethacrylate reinforced with PET net and PP fibrillated films are reported. The results indicate that while the shift factors used for the time-temperature superposition are independent of the fillter content, the tan δ is strongly affected by the reinforcement.     

Dynamic mechanical properties of N-phenylnadimide modified PMR polyimide composites

Temperature-frequency dependence of α, β, and γ transitions was determined using a Rheometrics dynamic spectrometer on a series of unidirectional Celion 6000/N-phenylnadimide (PN) modified PMR polyimide composites. The objective was to see if any correlations exist between crosslinked network structure and dynamic mechanical properties. Variation in crosslinked network structures was achieved by altering the polyimide formulation through addition of various quantities of PN into the standard PMR-15 composition. As a control, PMR-15 composite system exhibited well-defined α, β, and γ transitions in the regions of 360, 100, and −120°C, respectively. Their activation energies were estimated to be 232, 60, and 14 kcal/mole, respectively. Increasing the amount of PN concentration caused (a) lowering of the activation energies of the three relaxations, (b) a decrease of the glass transition temperature, and (c) increasing intensities of the three damping peaks, compared to the control PMR-15 counterpart. These dynamic mechanical responses were in agreement with formation of a more flexible co-polymer from PN and PMR-15 prepolymer.     

Dynamic mechanical properties of extruded nylon–wood composites

Dynamic mechanical properties determine the potential end use of a newly developed extruded nylon–wood composite in under‐the‐hood automobile applications. In this article, the dynamic mechanical properties of extruded nylon–wood composites were characterized using a dynamic mechanical thermal analyzer (DMTA) to determine storage modulus, glass transition temperature (T_g), physical aging effects, long‐term performance prediction, and comparisons to similar products. The storage modulus of the nylon–wood composite was found to be more temperature stable than pure nylon 66. The T_g range of the nylon–wood composite was found to be between 23 and 56°C, based on the decrease in storage modulus. A master curve was constructed based on the creep curves at various temperatures from 30 to 80°C. The results show that the relationship between shift factors and temperature follows Arrhenius behavior. Nylon–wood composites have good temperature‐dependent properties. Wood fillers reduced the physical aging effects on nylon in the wood composites. The comparison of the nylon–wood composite with other similar products shows that nylon–wood composites are a promising low cost material for industrial applications. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Dynamic mechanical properties of particle‐reinforced EPDM composites

The dynamic mechanical property of particle‐reinforced ethylene–propylene–diene monomer (EPDM) matrix composites has been studied by using a dynamic mechanical thermal analyzer (DMTA). The individual composite has been reinforced with the various reinforcing particles as follows: silicon carbide particles (SiCps) of 60 μm in average diameter with various volume fractions (i.e., 10–40%); copper (Cu) and aluminum (Al) particles with 20 vol %; and SiCps with 6 and 36 μm in different average diameters with 20 vol % over the total composite volume. It is shown from the experimental results that the dynamic elastic modulus values increase and the composites with 40 vol % SiCps exhibit higher tan δ values through the entire rubbery phase after the glass transition region compared with the composites with lower particle volume percentages. This shows that the composites with 20 vol % Cu particles have the higher dynamic elastic modulus but the lower peak tan δ value than the composites with other particles of 20 vol % do. Scanning electron microscopy results show that the effective particle volume in the composite with Cu particles is higher than the other composites, although the same particle volume fraction of 20% has been used. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1595–1601, 2003     

Dynamic mechanical properties of polypropylene composites filled with ultrafine particles

The dynamic moduli of isotactic polypropylene (PP) filled with ultrafine SiO₂ and micron sized glass particles are measured in the temperature range 30–130°C at frequency 10 Hz. The storage moduli of PP composites, E′_c, increase with filler content and decreasing filler size in the whole range of temperature. The loss moduli of PP composites, E″_c, increase with filler content and decreasing filler size above 40°C. The intensity of the broad despersion which appears at ca. 60°C increases with filler content and decreasing filler size. By assuming that the energy is not dissipated in the effective volume, namely, filler volume plus that of immobilized interfacial region, the effective volume fraction is evaluated from the relative loss modulus, E″_cE″₀ at 60°C. The effective volume fraction increases with filler content and decreasing filler size. The effect of addition of ultrafine particles on the broad dispersion at ca. 60°C resembles the effect of increasing crystallinity of pure PP. It is concluded that the broad dispersion which appeared at ca. 60°C seemed to be assigned to the grain boundary of PP composities or crystalline boundary of pure PP.     

Dynamic mechanical properties of particulates: Application to iron-epoxy composites

The dynamic mechanical properties of composite materials, consisting of an epoxy matrix filled with iron particles, were determined over a temperature range. The storage- and loss moduli were evaluated in a Dynastat apparatus, with the parameters being the volume fraction of filler and the test frequency. A theoretical model was developed for comparing the experimental results with the theoretical predictions. A satisfactory correlation was obtained for the glassy region of the composite.     

On the modulus of three-component particulate-filled composites

Modulus–composition data obtained on a model three-component particulate composite comprising a finely divided dispersed rubber phase and inorganic glass beads in a poly(methyl methacrylate) (PMMA) matrix cannot be represented appropriately in terms of the multicomponent form of the well-known Kerner equation. The data are more nearly in accord with a model based on the assumption that the dispersed rubber phase and the PMMA matrix, taken together, constitute an effective matrix for the glass bead filler. Interparticle interactions are discussed in terms of a maximum packing fraction for each filler species; interspecies interactions are found to be minor for the system studied.     

Dynamic mechanical and mechanical properties of polypropylene/poly(vinyl butyral)/mica composites

Three-component composites consisting of polypropylene (PP) matrix, poly(vinyl butyral) (PVB) modifier, and mica filler at various ratios of matrix to modifies and a constant mica content (30 wt %) were prepared by using two different kinds of PVB, viz., PVB and PVB-P. By correlating with the morphology, the dynamic mechanical and mechanical properties of the composites are studied in detail. PVB component in PP/PVB/mica composites cannot display a reinforcing effect to PP/mica binary composites, while impact strength of the composites are reduced further. It associates with incompatibility between PP and PVB, and as well as higher glass transition temperature of PVB. For PP/PVB-P/mica composites, stiffness decreases and, meanwhile, impact strength increases when PVB-P content is 7 wt %. The improvement of impact strength on PP/mica binary composites at the composition is due to a little affinity between the PP matrix and the plasticizer of PVB-P. Moreover, a minor amount of PP-g-MA in the 63/7/30 PP/PVB/mica composites only acts as an adhesion promoter. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2003–2011, 1997     

Dynamic mechanical properties and correlation with dynamic fragility of sisal reinforced composites

In this study, the reinforcement effect in sisal/polyester composites containing distinct reinforcement content was studied ranging from fragile to strong classification. The results indicate that the reduced storage modulus changes steadily, and the loss modulus and the tan δ peak are broader for composites containing more fiber (dynamically strong composites). As more fiber was incorporated in the resin, lower peak height for the tan delta curve was obtained, which may be indicative of lower energy dissipation due to a greater relative amount of interface. Also, the use of reduced dynamic mechanical curves (similar to dynamic fragility) is an alternative to facilitate the study of the material behavior. POLYM. COMPOS., 36:161–166, 2015. © 2014 Society of Plastics Engineers     

Dynamic mechanical properties of high density polyethylene and teak wood flour composites

The dynamic mechanical properties of high density polyethylene (HDPE) and teak wood flour (TWF) composites at varying volume fraction (Φ _f) of TWF from 0.00 to 0.32 have been studied. In HDPE/TWF composites, storage modulus (E′) decreased at Φ _f = 0.05, then increases with Φ _f; however, values were lower than HDPE up to Φ _f = 0.16, due to a pseudolubricating effect of filler. Loss modulus (E″) values were higher than HDPE in β and α relaxation regions while in γ relaxation region values were marginally equal to HDPE. Tan δ value decreases with Φ _f which may be due to enhanced amorphization and decreased crystallinity of HDPE. In presence of maleic anhydride grafted HDPE (HDPE-g-MAH), E′ values were lower than HDPE/TWF composites. In HDPE/TWF/HDPE-g-MAH, E″ were slightly higher than HDPE/TWF due to slippage of HDPE chains facilitated by the extent of degradation of coupling agent. Tan δ were higher for both systems than the rule of mixture.     

Dynamic mechanical and morphological properties of polycarbonate/multi-walled carbon nanotube composites

Dynamic mechanical and morphological properties of the polycarbonate (PC)/multi-walled carbon nanotube (MWNT) composites were studied by dynamic mechanical thermal analysis (DMTA) and X-ray diffractometry, respectively. For the without annealed PC/MWNT composites containing the higher content of the MWNT (≥7.0 wt%), double tan δ peaks were observed, which could be explained by the phase separation morphology model. For the annealed PC/MWNT composites, a broad single tan δ peak was observed. From the X-ray diffraction of the annealed PC/MWNT composites, it was observed that more regular structure of the PC was obtained, which was consistent with the result of the thermal analysis of the annealed PC/MWNT composites. From the dynamic mechanical properties, thermal analysis, and X-ray diffraction of the annealed PC/MWNT composites, it is suggested that PC/MWNT composites show a broad single tan δ peak and partially crystalline structure of the PC in the PC/MWNT composites by annealing.     

Dynamic mechanical properties of oil palm microfibril‐reinforced natural rubber composites

The dynamic mechanical properties of macro and microfibers of oil palm‐reinforced natural rubber (NR) composites were investigated as a function of fiber content, temperature, treatment, and frequency. By the incorporation of macrofiber to NR, the storage modulus (E') value increases while the damping factor (tan δ) shifts toward higher temperature region. As the fiber content increases the damping nature of the composite decreases because of the increased stiffness imparted by the natural fibers. By using the steam explosion method, the microfibrils were separated from the oil palm fibers. These fibers were subjected to treatments such as mercerization, benzoylation, and silane treatment. Resorcinol‐hexamethylenetetramine‐hydrated silica was also used as bonding agent to increase the fiber/matrix adhesion. The storage modulus value of untreated and treated microfibril‐reinforced composites was higher than that of macrofiber‐reinforced composites. The T_g value obtained for this microfibril‐reinforced composites were slightly higher than that of macrofiber‐reinforced composites. The activation energy for the relaxation processes in different composites was also calculated. The morphological studies using scanning electron microscopy of tensile fracture surfaces of treated and untreated composites indicated better fiber/matrix adhesion in the case of treated microfibril‐reinforced composites. Finally, attempts were made to correlate the experimental dynamic properties with the theoretical predictions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Dynamic mechanical properties of whisker/PA66 composites at high strain rates

PA66 reinforced with potassium titanate whisker (TKW) treated with silane coupling agent were prepared using a twin-screw extruder. The quasi-static and dynamic mechanical properties were investigated. Addition of 40 wt % TKW to PA66 improves all the investigated properties. The high-speed dynamic tests with TKW/PA66 were carried on split Hopkinson pressure bar (SHPB). The loading pulses in SHPB experiments were precisely controlled to ensure that the composite specimens deformed at a nearly constant strain rate under dynamically equilibrated stress during dynamic compression. The constitutive curves and equations at high strain rates have been obtained. TKW/PA66 composites show 20-100% increase on reference modulus and 20% increase on compression strength.     

Dynamic tensile mechanical properties and failure mode of zirconium diboride-silicon carbide ceramic composites

Dynamic indirect tension experiments were performed on zirconium diboride-silicon carbide (ZrB₂−20%SiC) ceramic. Flattened Brazilian disc specimens of ZrB₂−20%SiC were prepared to conduct dynamic tensile tests using the modified Split Hopkinson pressure bar system. The tensile experiments were completed at the range of loading rates from 7.53 to 74.71 GP s⁻¹. The tensile experimental results revealed that the zirconium diboride-silicon carbide ceramic composite is rate-sensitive in terms of the tensile strength and failure mode. The dynamic tensile strength increases linearly with the loading rate and changes from 195 MPa at 7.53 GP s⁻¹ to 654 MPa at 74.71 GP s⁻¹. Moreover, the dynamic tensile strength decreases with the increase in critical fracture time, which conforms to Tuler and Butcher's fracture criterion. In dynamic experiments, a high-speed camera was used to examine the tensile failure process, and fragments were collected to analyze the dynamic tensile failure mechanism. The tensile fracture mode of ZrB₂−20%SiC obviously showed the sensitivity of the loading rate. The fragment size of ZrB₂−20%SiC ceramic decreased but the quantity of fragments increased as the loading rate increased.