Poly(propylene)/poly(ethylene terephthalate‐co‐isophthalate) blends and glass bead filled composites: Microstructure and thermomechanical properties

Blends of poly(propylene) (PP) and poly(ethylene terephthalate‐co‐isophthalate) (co‐PET) (95/5) with and without compatibilizing agent (maleic anhydride PP), as well as composites of these blends with glass beads (50 wt%) with and without silane coupling agent surface‐treatment, were prepared and studied on a basis of the material microstructure and thermomechanical properties. Infrared and Raman spectroscopy, as well as transmission electron microscopy, displayed evidence of MAPP compatibilizing action for the blend. Differential scanning calorimetry showed a remarkable effect of nucleation rate increase exerted by co‐PET on the PP crystallization. Moreover, glass beads were found to increase the PP nucleation rate slightly. PP crystallinity hardly varied with the composition. Wide angle X‐ray diffraction allowed determination of differences in the orientation of the poly(propylene) b‐axis, with more homogeneous orientations in the presence of both co‐PET and glass beads. MAPP promoted the PP b‐axis orientation. Differences in PP α′ relaxation could be analyzed through dynamic‐mechanical thermal analysis (DMTA). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1841–1852, 2004     

Tribological behavior of Kevlar fabric composites filled with nanoparticles

The friction and wear characteristics of ZnO‐ or montmorillonite‐nanoparticle‐filled Kevlar fabric composites with different filler proportions when sliding against stainless steel pins under dry friction conditions were studied, with unfilled Kevlar fabric composites used as references. The worn surface and transfer film of Kevlar fabric composites were then examined with a scanning electron microscope. It was found that ZnO and montmorillonite as fillers could improve the tribological behavior of the Kevlar fabric composites with various applied loads, and the best antiwear property was obtained with the composites containing 5 wt % ZnO or montmorillonite. This indicated that these nanoparticles could prevent the destruction of Kevlar fabric composites during the friction process. The transfer film established by these nanoparticles during the sliding wear of the composites against their metallic counterpart made contributions to reducing the friction coefficient and wear rate of the Kevlar fabric composites measured in the test. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of poly(etherimide) chemical structures on the properties of epoxy/poly(etherimide) blends and their carbon fiber‐reinforced composites

Poly(etherimide)s (PEIs) with different chemical structures were synthesized and characterized, which were employed to toughen epoxy resins (EP/PEI) and carbon fiber‐reinforced epoxy composites (CF/EP/PEI). Experimental results revealed that the introduction of the fluorinated groups and meta linkages could help to improve the melt processability of EP/PEI resins. The EP/PEI resins showed obviously improved mechanical properties including tensile strength of 89.2 MPa, elongation at break of 4.7% and flexural strength of 144.2 MPa, and good thermal properties including glass transition temperature (T_g) of 211°C and initial decomposition temperature (T_d) of 366°C. Moreover, CF/EP/PEI‐1 and CF/EP/PEI‐4 composites showed significantly improved toughness with impact toughness of 13.8 and 15.5 J/cm², respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of particle size on the properties of Mg(OH)2‐filled rubber composites

A novel nanomagnesium hydroxide powder and three kinds of micro‐Mg(OH)₂, with different particle sizes, were chosen as fillers and mixed with ethylene–propylene–diene monomer rubber (EPDM) to form a series of composites by a traditional rubber‐processing technique. The results showed that the mechanical properties of composites improved with decreasing particle size. The nanocomposites were far stronger than the microcomposites, which also supported the view that rubber reinforcement requires nanoreinforcement. The effect of particle size on the fire resistance of composites was investigated by cone calorimetry and limiting oxygen index analysis, which showed that the particle size of powder had an impact on the fire resistance of composites. For the composites filled with untreated powder, the peak value of heat release rate decreased and T_ign increased with decreasing particle size. In conclusion, the fire resistance of nanocomposites was better than that of microcomposites. Surface modification of particles sometimes substantially improved the mechanical properties of nanocomposites, but had no effect on either the mechanical properties of microcomposites or the fire resistance of nanocomposites and flame retardance. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2341–2346, 2004     

Polypropylene/combinational inorganic filler micro‐/nanocomposites: Synergistic effects of micro‐/nanoscale combinational inorganic fillers on their mechanical properties

Polypropylene (PP) has wide applications in various areas, but its low‐temperature brittleness and low moduli have limited its applications in engineering areas. This article reported micro‐/nanoscale combinational inorganic fillers (CIFs) to reinforce PP‐matrix composites as the first example. The CIFs consisted of plate‐like talc (T), needle‐like wollastonite (W), and nano‐Al₂O₃ (N). The PP/CIFs specimens were fabricated via a process of twin‐screw extrusion and screw‐type injection molding. The mechanical properties and thermal deflection temperature (HDT) of the PP/CIF composites were tested according to the corresponding standards, and the morphologies of the tensile‐fractured sections were observed using FE‐SEM. The PP/WT composites had higher mechanical properties and HDTs than those of either PP/W or PP/T. Small amounts of Al₂O₃ nanocrystals together with WT simultaneously strengthened and toughened the PP‐matrix composites. The PP/WTN composite with 2.6% of nano‐Al₂O₃ had well‐balanced properties, enhanced by a large increment when compared with the PP matrix or PP/WT composites. The enhancements should be attributed to the synergistic effects of the CIFs not only in the aspect of various shapes (plate‐like, needle‐like, and spherical) but also in hierarchical size‐levels (microscale and nanoscale). The novel strategy overcame the limitation of conventional rigid modification and solved the problem of uniform dispersion of nanocrystals in polymer matrices. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Tribological behavior of micrometer‐ and nanometer‐Al2O3‐particle‐filled poly(phthalazine ether sulfone ketone) copolymer composites used as frictional materials

Micrometer‐ and nanometer‐Al₂O₃‐particle‐filled poly(phthalazine ether sulfone ketone) (PPESK) composites with filler volume fractions ranging from 1 to 12.5 vol % were prepared by hot compression molding. We evaluated the tribological behaviors of the PPESK composites with the block‐on‐ring test rig by sliding PPESK‐based composite blocks against a mild carbon steel ring under dry‐friction conditions. The effects of different temperatures on the wear rate of the PPESK composites were also investigated with a ball‐on‐disc test rig. The wear debris and the worn surfaces of the PPESK composites were investigated with scanning electron microscopy, and the structures of the PPESK composites were analyzed with IR spectra. The lowest wear rate, 7.31 × 10^?6 mm³ N^?1 m^?1, was obtained for the composite filled with 1 vol %‐nanometer Al₂O₃ particles. The composite with nanometer particles exhibited a higher friction coefficient (0.58–0.64) than unfilled PPESK (0.55). The wear rate of 1 vol %‐nanometer‐Al₂O₃‐particle‐filled PPESK was stable and was lower than that of unfilled PPESK from the ambient temperature to 270°C. We anticipate that 1 vol %‐nanometer‐Al₂O₃‐particle‐filled PPESK can be used as a good frictional material. We also found that micrometer‐Al₂O₃‐particle‐filled PPESK had a lower friction coefficient at a filler volume fraction below 5%. The filling of micrometer Al₂O₃ particles greatly increased the wear resistance of PPESK under filler volume fractions from 1 to 12.5%. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 993–1001, 2005     

Friction and wear behavior of basalt‐fabric‐reinforced/solid‐lubricant‐filled phenolic composites

To improve the tribological properties of basalt‐fabric‐reinforced phenolic composites, solid lubricants of MoS₂ and graphite were incorporated, and the tribological properties of the resulting basalt‐fabric composites were investigated on a model ring‐on‐block test rig under dry sliding conditions. The effects of the filler content, load, and sliding time on the tribological behavior of the basalt‐fabric composites were systematically examined. The morphologies of the worn surfaces and transfer films formed on the counterpart steel rings were analyzed by means of scanning electron microscopy. The experimental results reveal that the incorporation of MoS₂ significantly decreased the friction coefficient, whereas the inclusion of graphite improved the wear resistance remarkably. The results also indicate that the filled basalt‐fabric composites seemed to be more suitable for friction materials serving under higher loads. The transfer films formed on the counterpart surfaces during the friction process made contributions to the reduction of the friction coefficient and wear rate of the basalt‐fabric composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and properties of some filled poly(vinyl chloride) compositions

Different samples of filled poly(vinyl chloride) (PVC) compositions were formulated from PVC, a polar plasticizer mixture consisting of dioctylphthalate (DOP) and a chlorinated paraffin, and variable proportions of a white filler such as barite, calcium carbonate, kaoline, quartz, or talc; a conductive filler such as High Abrasion Furnace (HAF) carbon black; or a hydrated mineral filler such as aluminium hydroxide, magnesium hydroxide, or calcium hydroxide. Epoxidized soybean oil as a heat stabilizer and sandorin red (BRN) pigment were added. Electrical and mechanical studies show that the incorporation of white fillers produces a plasticized PVC of good electrical insulation character whereas the addition of HAF carbon black produces a sample with some electrical conductivity; both of them have good mechanical properties. Of the hydrated fillers studied aluminium hydroxide has been found to impart the best fire retardancy and good electrical properties for electric wires and cables. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2657–2670, 1999     

Tribological properties of bismaleimide composites with surface‐modified SiO2 nanoparticles

In this article, the surface of SiO₂ nanoparticles was modified by silane coupling agent N‐(2‐aminoethyl)‐γ‐aminopropylmethyl dimethoxy silane. The bismaleimide nanocomposites with surface‐modified SiO₂ nanoparticles or unmodified SiO₂ nanoparticles were prepared by the same casting method. The tribological performance of the nanocomposites was studied on an M‐200 friction and wear tester. The results indicated that the addition of SiO₂ nanoparticles could decrease the frictional coefficient and the wear rate of the composites. The nanocomposites with surface‐modified SiO₂ nanoparticles showed better wear resistance and lower frictional coefficient than that with the unmodified nanoparticles SiO₂. The specific wear rate and the steady frictional coefficient of the composite with 1.0 wt % surface‐modified SiO₂ nanoparticles are only 1.8 × 10^?6 mm³/N m and 0.21, respectively. The dispersion of surface‐modified SiO₂ nanoparticles in resin matrix was observed with transmission electron microscope, and the worn surfaces of pure resin matrix and the nanocomposites were observed with scanning electron microscope. The different tribological behavior of the resin matrix and the filled composites should be dependent on their different mechanical properties and wear mechanism. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and characterization of poly(3‐octylthiophene)/single wall carbon nanotube composites for photovoltaic applications

In situ polymerization of P3OT with SWCNT is carried out in the presence of a FeCl₃ oxidant in a chloroform medium. The characterization of the composites is performed with FTIR, Raman, ¹H‐NMR, UV–Vis, PL spectroscopy, XRD, SEM, TEM, and conductivity measurements. The change (if any) in CC symmetric and antisymmetric stretching frequencies in FTIR, the shift in G band frequencies in Raman, any alterations in λ_max of UV–Vis and PL spectroscopic measurements are monitored with SWCNT loading in the polymer matrix. ¹H‐NMR confirms the wrapping of the polymer on to the SWCNT indicating lack of mobility. The work function values and the optical band gap values also support this view. The in situ polymerization procedure of the donor polymer molecules and the acceptor carbon nanotubes has resulted in enhanced dispersibility and stability of the composites in organic solvents. However, the principal focus of the study is to understand the interaction between the polymer and the SWCNTs, as the interface plays an important role in its application in the photovoltaic cells. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Tensile deformation and fracture mechanism of highly filled high‐density polyethylene/Al(OH)3 composites

The effect of the silicone oil content on the tensile properties and micromechanical deformation of high‐density polyethylene/Al(OH)₃ composites was studied. With an increase in the silicone oil content, the elongation at break and notched Izod impact strength of the composites increased, and the local debonding deformation gradually transformed into homogeneous debonding deformation. A model characterizing the micromechanical deformation process was examined. The increase in the silicone oil content decreased the interaction between the filler particles and the high‐density polyethylene matrix and increased the extension speed of the debonded region, which led to the changes in the tensile properties and micromechanical deformation. A good explanation for the tensile properties and micromechanical deformation was obtained through the model. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1207–1218, 2002     

Tribological and mechanical properties of carbon‐nanofiber‐filled polytetrafluoroethylene composites

The effects of various filler concentrations (0.1, 0.5, 1, 1.5, 2, 2.5, and 3 wt %) on the tribological and mechanical properties of carbon‐nanofiber (CNF)‐filled polytetrafluoroethylene (PTFE) composites were studied. Moreover, the influence of various loads (50, 100, 150, and 200 N) and sliding velocities (0.692 and 1.39 m/s) on the friction and wear behaviors of the PTFE composites was investigated. The results showed that the friction coefficients of the PTFE composites decreased initially up to a 0.5 wt % filler concentration and then increased, whereas the antiwear properties of the PTFE composites increased by 1–2 orders of magnitude in comparison with those of pure PTFE. The composite with a 2 wt % filler concentration had the best antiwear properties under all friction conditions. The friction coefficients of the CNF/PTFE composites decreased with increases in the load and sliding velocity, whereas the wear volume loss of the PTFE composites increased. At the same time, the results also indicated that the mechanical properties of the PTFE composites increased first up to a 1 wt % filler concentration and then decreased as the filler concentration was increased above 1 wt %. In comparison with pure PTFE, the impact strength, tensile strength, and elongation to break of the PTFE composites increased by 40, 20, and 70%, respectively, at a 1 wt % filler concentration. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2430–2437, 2007     

Tribological behavior of poly(ether ether ketone) composites filled with potassium titanate whiskers sliding in different media

The friction and wear properties of poly (ether ether ketone) (PEEK) composites filled with potassium titanate whiskers (PTWs) under alkali, water, and dry conditions were investigated. The wear mechanisms in different lubrication situations were studied on the basis of examinations of the worn and counterpart surfaces with scanning electron microscopy and optical microscopy. The results showed that PTWs could obviously increase the wear resistance and reduce the friction coefficient of the PEEK composites under dry sliding conditions. Only when the PTW content was greater than 35 wt % did the wear resistance and friction coefficient deteriorate. Sliding in water caused increases in the wear rate and friction coefficient of the PEEK composites, and the PTW‐filled PEEK composites showed the highest friction coefficient and wear rate under this lubrication condition. On the contrary, sliding in an alkaline solution, the PTW‐filled PEEK composites showed the lowest friction coefficient and almost the same level of wear resistance as that found under the dry condition. Furrows and abrasive wear were the main mechanisms for the PTW‐filled PEEK composites sliding in water. The transfer onto the counterpart rings was significantly hindered with sliding under water and alkali conditions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

SWCNT induced crystallization in amorphous and semi-crystalline poly(etherimide)s: Morphology and thermo-mechanical properties

In this study we contrast the behavior of an amorphous polyetherimide (ODPA-P3) with that of a semi-crystalline one (BPDA-P3) on introducing single-wall carbon nanotubes (SWCNTs; 0.1–4.4 vol.%). The SWCNTs act as a nucleating agent and induce crystallinity (up to 45%) in amorphous ODPA-P3; in BPDA-P3, the SWCNTs lower the onset of crystallization during thermal imidization, but decrease the overall degree of crystallinity. Tensile tests show that the yield strength is the same for both polyimides up to 0.3% SWCNT loadings. Above this concentration the yield strength for the BPDA-P3 nanocomposites remains constant whereas in the ODPA-P3 nanocomposites it increases from 80 to 126 MPa (1.2 vol.%). In the amorphous PEI, SWCNTs enhance the thermo-mechanical properties (Tg, storage- and elastic modulus, and yield strength), but in the semi-crystalline PEI there are little or no effects on the mechanical performance.     

Lignocellulosic flour‐reinforced poly(hydroxybutyrate‐co‐valerate) composites

Residual lignocellulosic flour from spruce and ground olive stone was used as a natural filler in poly(hydroxybutyrate‐co‐valerate) (PHBV)‐based composites. The morphology and the thermal properties of these composites were investigated by scanning electron microscopy and differential scanning calorimetry, respectively. Lignocellulosic fillers acted as nucleating sites for the crystallization of PHBV and strongly enhanced its degree of crystallinity. Dynamic mechanical analysis and tensile properties of these materials were also studied. A significant reinforcing effect was displayed by dynamic mechanical analysis at temperatures higher than the glass–rubber transition of the matrix. In addition, for low‐particle‐size spruce, a stabilization of the modulus was observed up to 500 K. High‐strain tensile properties did not show any reinforcing effect. This apparent disagreement was explained by the poor adhesion between the hydrophilic lignocellulosic filler and the hydrophobic polymeric matrix. To validate this hypothesis, the experimental data were compared with predicted data involving the percolation concept. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1302–1315, 2003     

Fiber spinning from poly(propylene)–organoclay nanocomposite

SOMASIF ME C16, a filler that enables generation of anisotropic nanoparticles by in situ exfoliation of organic layered silicates, was melt compounded with poly(propylene) (PP) in the presence of maleic anhydride‐grafted PP. Fibers were prepared from this composite by a spinning procedure. The prepared anisotropic fibers were partially oriented by using different drawing ratios. The morphological study showed that the drawing ratio of the fibers particularly influences the level of exfoliation of the SOMASIF ME C16 where the nanoparticles are formed. The layered sheets of the SOMASIF particles are oriented in the direction of the fiber axis. The tensile strength of the filled fibers increases with the increase of drawing ratio much more than that of unfilled PP fibers. This result is accounted for by the formation of exfoliated structures from the nanoparticles of SOMASIF ME C16 by fiber drawing. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 604–611, 2003     

Tribological properties of PBO fabric composites modified by poly (vinyl alcohol)

Friction and wear behaviors of poly (vinyl alcohol) (PVA) modified PBO fabric composites were evaluated in a pin‐on‐disc friction and wear tester, and the relationship between the properties and the structure change resulting from PVA modification were intensively investigated using thermogravimetric analysis (TG) and scanning electronic microscope (SEM) equipped with an energy dispersive spectrometer (EDS). The results indicated that the PVA thin film formed on the fabric surface by chemical crosslinking reaction could improve the antiwear property of the PBO fabric composites efficiently. In argon‐300°C condition, the antiwear property of the PBO fabric composites was improved by 35%, which was due to the improvement of the bonding strength between the fabric and resin and the dispersion of the shear stress induced by the shear creep and plastic deformation of the PVA film in friction. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1313‐1320, 2013     

Effect of chemical treatments on the mechanical,flow, and morphological properties of talc‐ and kaolin‐filled polypropylene hybrid composites

This study was performed with commercially available phenyl trimethoxysilane (PTMS) and neoalkoxytitanate [i.e., neopentyl(diallyl)oxytri(dioctyl)phosphato titanate (LICA 12)] as coupling agents. PTMS and LICA 12 were used to treat talc and kaolin to compare their effects with untreated fillers upon incorporation into polypropylene (PP). Single‐filler PP composites (containing either talc or kaolin) and hybrid‐filler composites (containing a mix of both talc and kaolin) were compounded in a twin‐screw extruder and subsequently injection‐molded into dumbbells. The incorporation of PTMS and LICA 12 slightly decreased the tensile and flexural properties in terms of modulus and strength but increased the elongation at break for both single‐filler and hybrid‐filler composites. There was also a significant improvement in the impact strength of the composites, particularly those treated with LICA 12. The hybrid composites, through the synergistic coalescence of positive characteristics from talc and kaolin with the aid from chemical treatment provided an economically advantageous material with mechanical properties comparable to those of the single‐filler‐filled PP composites. Further investigations on flow and morphological properties were also done to correlate the mechanical properties of the single‐ and hybrid‐filler‐filled PP composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Novel polymer composites based on a mixture of preformed nanosilica‐filled poly(methyl methacrylate) particles and a diepoxy/diamine thermoset system

In this work, a new material based on an epoxy thermoset modified with a thermoplastic filled with silica nanoparticles was investigated. When thermoplastic particles are filled with nanoparticles with unique properties such as high efficiency for absorbing ultraviolet light, electric or magnetic shielding, high electrical conductivity, and high dielectric constants, more than an enhancement of the mechanical properties is expected to be achieved for modified epoxy‐based thermosets. Particles of poly(methyl methacrylate) (PMMA) filled with silica nanoparticles were used to modify a thermoset based on a full reaction between diglycidyl ether of bisphenol A and 3‐(aminomethyl)benzylamine. When the preformed thermoplastic particles were mixed with the reactive constituents of the epoxy system under certain curing conditions in which total miscibility was avoided, uniform particle dispersions could be obtained. The relationships between the composition, morphology (nanoscale and microscale), glass‐transition temperature, mechanical properties, and fracture toughness were considered. Four main results were obtained for consideration of the potential of silica‐filled PMMA as an important modifier of brittle epoxy thermoset systems: (1) a good dispersion of the silica nanoparticles in the PMMA domains, (2) a good dispersion of the silica‐filled PMMA microparticles in the epoxy matrix, (3) the possibility of partial dissolution of the PMMA‐rich domains into the epoxy system, and (4) a slight increase in properties such as the hardness, indentation modulus, and fracture toughness. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Mechanical and thermal properties of talc and calcium carbonate filled polypropylene hybrid composites

The main aim of this work was to study and compare the mechanical and thermal properties of hybrid polypropylene (PP) composites and single‐filler PP composites. With two main types of mineral fillers—calcium carbonate (CaCO₃) and talc—PP composites of different filler weight ratios (talc/CaCO₃) were compounded with a twin‐screw extruder and then injection‐molded into dumbbell specimens with an injection‐molding machine. Tensile, flexural, and impact tests were performed to determine and compare the mechanical properties of the hybrid and single‐filler PP composites. A synergistic hybridization effect was successfully achieved; the flexural strength and impact strength were highest among the hybrids when the PP/talc/CaCO₃ weight ratio was 70:15:15. The nucleating ability of the fillers and its effects on the mechanical properties were also studied with differential scanning calorimetry. Because of the influence of talc as the main nucleating agent, the hybrid fillers showed significant improvements in terms of the nucleating ability, and this contributed to the increase in or retention of the mechanical properties of the hybrid composites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3327–3336, 2004