Impact fracture behavior of clay-reinforced polypropylene nanocomposites

The micromechanism of plastic deformation during impact loading of polypropylene-clay nanocomposites is examined and compared with the unreinforced polypropylene under identical conditions of processing to underscore the determining role of clay. The addition of clay to polypropylene increases the impact strength in the temperature range of 0 to +70 °C. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and transmission electron microscopy (TEM), wide-angle X-ray diffraction (WAXD) and scanning electron microscopy (SEM) techniques provided an understanding of the micromechanism of plastic deformation in terms of the response of the polymer matrix, nucleating capability of the reinforcement, crystal structure, percentage crystallinity, lamellae thickness, and particle-matrix interface. The enhancement of toughness on reinforcement of polypropylene with nanoclay is associated with change in the primary mechanism of plastic deformation from crazing and vein-type in neat polypropylene to microvoid-coalescence-fibrillation process in the nanocomposite.     

Epoxy/acrylonitrile-butadiene-styrene copolymer/clay ternary nanocomposite as impact toughened epoxy

Epoxy resins have low impact strength and poor resistance to crack propagation, which limit their many end use applications. The main objective of this work is to incorporate both acrylonitrile-butadiene-styrene copolymer (ABS) and organically modified clay (Cloisite 30B) into epoxy matrix with the aim of obtaining improved material with the impact strength higher than neat epoxy, epoxy/clay and epoxy/ABS hybrids without compromising the other desired mechanical properties such as tensile strength and modulus. Impact and tensile properties of binary and ternary systems were investigated. Tensile strength, elongation at break and impact strength were increased significantly with incorporation of only 4 phr ABS to epoxy matrix. For epoxy/clay nanocomposite with 2.5% clay content, tensile modulus and strength, and impact strength were improved compared to neat epoxy. With incorporation of 2.5% clay and 4 phr ABS into epoxy matrix, 133% increase was observed for impact strength. Ternary nanocomposite had impact and tensile strengths greater than values of the binary systems. Morphological properties of epoxy/ABS, epoxy/clay and epoxy/ABS/clay ternary nanocomposite were studied using atomic force microscopy (AFM) phase imaging, scanning electron microscopy (SEM) and wide angle X-ray diffraction (WAXD). New morphologies were achieved for epoxy/ABS and epoxy/ABS/clay hybrid materials. Exfoliated clay structure was obtained for epoxy/clay and epoxy/ABS/clay nanocomposite.     

Polyamide-12 layered silicate nanocomposites by melt blending

Polyamide-12/tetrasilisic fluoromica (PA12-ME100) and polyamide-12/quaternary tallow ammonium chloride modified fluoromica nanocomposites (PA12-MAE) were prepared by melt compounding. The nanocomposite morphology and clay dispersion were investigated using wide angle X-ray diffraction (XRD), scanning electron microscopy (SEM), SEM-energy dispersive X-ray analysis (SEM-EDX), transmission electron miscroscopy (TEM), high resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM). A predominantly intercalated morphology was observed for PA12-ME100, and a very high degree of exfoliation for PA12-MAE. HRTEM showed that the polymer crystallites lie perpendicular to the clay surface. The tensile and flexural properties of the PA12-MAE nanocomposite were significantly enhanced compared to neat polyamide-12, even with the addition of only 4 wt% nanoclay. Furthermore, the elongation at break (%) increased from 180% for polyamide-12 up to >500% for the PA12-MAE nanocomposite. In situ measurement of the heat generated in the test specimens during uniaxial tensile deformation using infra-red thermal imaging showed that the temperature of the dumbbell samples increased from room temperature (23 °C) to as high as 70 °C regardless of the strain rate used. This is considerably above the glass transition temperature (T_g) of PA12-MAE (30 °C), as measured by dynamic mechanical thermal analysis (DMTA). The mechanism of deformation is partially explained in terms of microvoid formation. The shear viscosity of the PA12-MAE nanocomposite determined by dual capillary rheometry was lower than both neat polyamide-12 and PA12-ME100. The reduction in shear viscosity of the nanocomposites was shown, from gel permeation chromatography (GPC) studies, not to originate from polymer degradation during melt blending. The coefficient of thermal expansion, decomposition temperature, and melting and crystallisation temperatures and relative crystalline content of the nanocomposite materials were measured by thermo-mechanical analysis (TMA), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) respectively—properties which can be related to polymer nanoclay interactions.     

The effect of secondary nanofiller on mechanical properties and formulation optimization of HDPE/nanoclay/nanoCaCO3 hybrid nanocomposites using response surface methodology

Mechanical properties were evaluated in high-density polyethylene (HDPE) containing plate-like nanoclay (NC) and particulate nano calcium carbonate (nCaCO₃). A two-step melt mixing method was utilized to prepare nanocomposites withNC/nCaCO₃ hybrid content varying from 7 to 15 wt%. Optimization of the morphological, rheological and mechanical characteristics was carried out via Response Surface Methodology by considering nanofiller loadings and compatibilizer (PE-g-MA) content as independent variables. The findings revealed that a nanocomposite composed of 9 wt% PE-g-MA, 3.5 wt%NC, and 10 wt%nCaCO₃ was optimal. This composition exhibited 50% enhancement in Young's modulus and 8% improvement in yield strength over neat HDPE. Despite the reduced impact strength in all of the prepared nanocomposites, the incorporation ofnCaCO₃ prevented a sudden decrease in the toughness caused by the nanoclay. Further, the fracture behavior observed by scanning electron microscopy (SEM) images suggested that nCaCO₃ activated new toughening mechanisms.     

Studies on mechanical and rheological properties of poly(vinyl chloride) modified with elastomers and rigid organic particles

Chlorinated polypropylene (CPP) as rigid organic particles and chlorinated polyethylene (CPE) as elastomer were used to modify the properties of poly(vinyl chloride) (PVC) by melt blending. Both mechanical and rheological properties of the PVC blends were investigated. The submicroscopic morphology of the blends was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results demonstrate that when the weight ratio of CPE to CPP is about 6 : 1, a sample with the best impact strength and without obvious decline in tensile strength can be obtained. The impact strength correlates well with SEM morphologies, and TEM micrographs in the necking of the tensile specimen indicate that a cold‐drawing deformation of rigid particles happens as reported by T. Kurauchi and T. Ohta (J Mater Sci 1984, 19, 1699). Therefore, a conclusion can be drawn that CPP particles acting similar to elastic particles can toughen PVC, and the cold‐drawing deformation is the primary reason for toughening the PVC blends. In addition, the addition of CPP can promote the processibility of PVC ternary blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2478–2483, 2003     

Influence of compatibilizer on notched impact strength and fractography of HDPE–organoclay composites

The focus of this study was the notched impact property of high‐density polyethylene (HDPE)–organoclay composites and the resultant morphology of impact‐fractured surfaces. Composites with a different organoclay content and degree of organoclay dispersion were compared with neat HDPE under identical conditions. The degree of organoclay dispersion was controlled through the use of a compatibilizer, maleic anhydride grafted polyethylene. It was found that the addition of organoclay can slightly increase the elastic modulus and notched impact strength of the composite. When the level of organoclay dispersion was improved by using compatibilizer, elastic modulus and toughness further increased. A significant increase in yield strength was also notable. The presence of organoclay was found to suppress strain hardening of the matrix during tensile testing. The impact‐fractured surfaces of failed specimens were studied with scanning electron microscopy. The micromechanism for the increased toughness of HDPE–organoclay composites was discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Modeling and optimization of a new impact-toughened epoxy nanocomposite using response surface methodology

This paper reports the development of a high-impact epoxy nanocomposite toughened by the combination of poly(acrylonitrile-co-butadiene-co-styrene) (ABS) as thermoplastic, clay as layered nanofiller, and nano-TiO₂ as particulate nanofiller. Response surface methodology (RSM) was applied for optimization and modeling of the impact strength of epoxy/ABS/clay/TiO₂ quaternary nanocomposite. A second-order mathematical model between the response (impact strength) and variables (ABS, clay and nano-TiO₂ contents) was derived. Analysis of variance (ANOVA) showed a high coefficient of determination value (R ² = 98%). Under optimum conditions, maximum impact strength of 29.2 KJ/m² with 197% increase compared to neat epoxy was experimentally obtained. Also correlation between morphology and impact strength of the nanocomposite was investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD). A dispersion of exfoliated clay platelets, TiO₂ nanoparticles with low agglomeration and ABS nanoparticles was obtained as morphology of the nanocomposite. A new and more effective method for impact toughening of epoxy was introduced. This study clearly showed that the addition of the combination of layered and particulate nanofillers along with ABS as thermoplastic has a considerable enhancement effect on impact strength of epoxy.     

The performances of BMI nanocomposites filled with nanometer SiC

Nanocomposites of bismaleimide (BMI) with different proportions of nanometer SiC were prepared by a high shear dispersion process and casting method at elevated temperature. The mechanical and tribological properties of the nanocomposites were investigated. The bending strength and impact strength of the nanocomposite specimens were determined, and the sliding wear performance of the nanocomposites was investigated on an M‐200 friction and wear tester. The dispersion of nanometre SiC was observed with a transmission electron microscope (TEM), while those of the worn surfaces and transfer films on the counterpart steel ring were observed with a scanning electron microscope (SEM). The experimental results indicate that the nanocomposites exhibited lower friction coefficient and wear loss as well as higher bending and impact strength than BMI resin under the same testing conditions. The lowest wear rate was obtained with the nanocomposite containing 6.0 wt % SiC, while the highest mechanical properties were obtained with the nanocomposite containing 2.0 wt % SiC. The wear mechanism of the nanocomposite is mainly adhesion wear, while that of pure BMI resin is mainly fatigue cracking with plastic deformation. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1246–1250, 2005     

Relationship of fracture behavior and morphology in polyolefin blends

High-density polyethylene (HDPE) and isotactic polypropylene (PP) were mixed either with a stabilizer or with a stabilizer and a compatibilizer in different mixing ratios. The structure and properties of these blends were analyzed by methods such as torsion pendulum measurements, mechanical short time experiments, electron microscopy, and fracture mechanical toughness tests. The results display a strongly increased impact strength in the HDPE/PP blend with compatibilizer within a specific mixing region. The deformation behavior and the mechanism leading to the increased impact strength of the blends were investigated in tensile tests by acoustic emission analysis and scanning electron microscopy: Increased fibrilation and strong strain was registered in the blend with compatibilizer. The impact strength was modeled, using experimentally measured properties such as energy release rate, matrix and inclusion volumes, the impact strength of each component. The inclusion volume that causes plastic deformation was chosen as an additional parameter. The calculated results are in good agreement with the experimental ones.     

Effect of Compatibilizer Type on Properties of 70:30 Polyamide 6/Polypropylene/MMT Nanocomposites

PA6/PP nanocomposites with either polyethylene octene elastomer grafted maleic anhydride (POEgMAH) or PP grafted maleic anhydride (PPgMAH) as compatibilizer were prepared using co-rotating twin-screw extruder followed by injection molding. The mechanical and microstructural properties of the composites were investigated by means of tensile, flexural, and impact testing and by scanning electron microscopy (SEM). X-ray diffraction (XRD) was used to characterize the formation of nanocomposites. The result indicated that the miscibility of PA6/PP nanocomposites was improved with the addition of POEgMAH and PPgMAH. The impact strength of PA6/PP nanocomposite with POEgMAH increased about 5 times higher than uncompatibilized composite. Increment in tensile properties was observed when PPgMAH was used as compatibilizer. XRD results revealed that PA6/PP nanocomposites were successfully formed. Uniform dispersion of PP in matrix were observed through SEM, which showed the improvement of the compatibility between polymers.     

Thermal and mechanical behavior of poly(vinyl butyral)‐modified novolac epoxy/multiwalled carbon nanotube nanocomposites

The effects of poly(vinyl butyral) (PVB) and acid‐functionalized multiwalled carbon nanotube modification on the thermal and mechanical properties of novolac epoxy nanocomposites were investigated. The nanocomposite containing 1.5 wt % PVB and 0.1 wt % functionalized carbon nanotubes showed an increment of about 15°C in the peak degradation temperature compared to the neat novolac epoxy. The glass‐transition temperature of the novolac epoxy decreased with increasing PVB content but increased with an increase in the functionalized carbon nanotube concentration. The nanocomposites showed a lower tensile strength compared to the neat novolac epoxy; however, the elongation at break improved gradually with increasing PVB content. Maximum elongation and impact strength values of 7.4% and 17.0 kJ/m² were achieved in the nanocomposite containing 1.5 wt % PVB and 0.25 wt % functionalized carbon nanotubes. The fractured surface morphology was examined with field emission scanning electron microscopy, and correlated with the mechanical properties. The functionalized carbon nanotubes showed preferential accumulation in the PVB phase beyond 0.25 wt % loading. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43333.     

Blends of poly(vinyl chloride) with acrylonitrile-chlorinated polyethylene-styrene copolymer. II. Mechanical properties

Blends of poly(vinyl chloride) (PVC) and acrylonitrile-chlorinated polyethylene-styrene (ACS) graft copolymer were prepared by melt blending. Mechanical properties were studied by the use of dynamic mechanical analysis (DMA), impact tests, tensile tests, and scanning electron microscopy (SEM). The DMA study showed that PVC is immiscible with chlorinated polyethylene in ACS but partially miscible with poly(styrene-co-acrylonitrile) (25% acrylonitrile content) in ACS. Mechanical property tests showed that there is a significant increase in the impact strength while other good mechanical properties of PVC such as high modulus and high strength remain. SEM observations supported the results of the mechanical properties studies. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 399–405, 1997     

LLDPE/纳米ZnO复合材料的制备与性能研究

将改性纳米ZnO与线型低密度聚乙烯(LLDPE)熔融共混、制备了LLDPE/纳米ZnO复合材料。通过SEM观察纳米ZnO粒子在LLDPE基体中的分散情况;研究了复合材料的力学性能及维卡软化点。结果表明:改性纳米ZnO的加入可提高LLDPE的力学性能和维卡软化点。其中,复合材料的拉伸强度、断裂伸长率、冲击强度、弯曲强度的最大值分别比LLDPE提高了17.00%、13.42%、9.90%、7.04%。     

Synthesis of clay-armored coatable sulfonated polyimide nanocomposites as robust polyelectrolyte membranes

Herein, coatable sulfonated polyimide (SPI) and clay-reinforced SPI membranes SPI-clay 3%, SPI-clay 5%, and SPI-clay 7% were successfully fabricated by one-step high temperature via direct imidization method. The membranes were cast as a coatable thin film using a solution casting method and grafted vermiculite clay nanoparticle were incorporated into the neat SPI as reinforcement by the sonication method. Three different formulated nanocomposite membranes were investigated using different characterization techniques such as Fourier transform infrared spectroscopy as peaks at 1166 and 1227 cm⁻¹ confirmed successful sulfonation. In Proton (¹H) NMR synthesis of SPI confirmed as aromatic proton at 7.3–8.8 ppm depicts successful sulfonation and X-ray diffraction results confirmed the crystalline structure of clay, as its content increased (7%) clear diffraction peak arises at 6 and 25°. Scanning electron microscopy (SEM) provides information about surface morphology of clay reinforced SPI membranes, and SEM micrographs shown uniform dispersion of clay nanofillers and developed easy transfer of electron. Thermogravimetric analysis was performed to investigate the thermal stability of synthesized films, results of thermographs shown degradation in the range of 510–600°C. Different physicochemical parameters employed and their results show the effectiveness of synthesized clay reinforced SPI membranes. Water uptake (WU%) about 0.96%, hydrolytic about 98 h and oxidative stability up to 80°C, ions exchange capacity about 3.16 mmol/g for synthesized clay reinforced SPI membranes. Measurement regarding Dimensional changes was also investigated and dimensional changes (1.557 ∆t/∆l). All these results reveal that the clay-reinforced coatable SPI membranes are a promising material for polymer electrolyte membranes to be used in fuel cell energy applications.     

Preparation of dynamically vulcanized thermoplastic elastomer nanocomposites based on LLDPE/reclaimed rubber

Dynamically vulcanized thermoplastic elastomers nanocomposites (TPV nanocomposites) based on linear low density polyethylene (LLDPE)/reclaimed rubber/organoclay were prepared via one‐step melt blending process. Maleic anhydride grafted polyethylene (PE‐g‐MA) was used as a compatibilizing agent. The effects of reclaimed rubber content (10, 30, and 50 wt %), nanoclay content (3, 5, and 7 wt %), and PE‐g‐MA on the microstructure, thermal behavior, mechanical properties, and rheological behavior of the nanocomposites were studied. The TPV nanocomposites were characterized by X‐ray diffraction, transmission electron microscopy, scanning electron microscopy (SEM), differential scanning calorimeter, mechanical properties, and rheometry in small amplitude oscillatory shear. SEM photomicrographs of the etched samples showed that the elastomer particles were dispersed homogeneously throughout the polyethylene matrix and the size of rubber particles was reduced with introduction of the organoclay particles and compatibilizer. The effects of different nanoclay contents, different rubber contents, and compatibilizer on mechanical properties were investigated. Increasing the amount of nanoclay content and adding the compatibilizer result in an improvement of the tensile modulus of the TPV nanocomposite samples. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of org-titanium phosphonate on the properties of chitosan films

A new type of titanium glycine-N,N-dimethylphosphonate Ti[(O₃PCH₂)₂NCH₂COOH] (TGDMP), with the functional groups –COOH, has been prepared first and then characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Subsequently, chitosan/titanium glycine-N,N-dimethylphosphonate (CS/TGDMP-n) nanocomposite films of various compositions were prepared by solution casting method. The structure, morphology, and properties of nanocomposite films were investigated by FTIR, XRD, scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), and tensile tests. The results showed that the mechanical properties of chitosan films were improved by the incorporation of TGDMP, and the samples kept at moisture environment showed the larger elongation and lower tensile strength than the dried counterparts. In addition, the CS/TGDMP-n films exhibited higher thermal stability and better moisture barrier property than neat CS films.     

Study on the mechanical and morphological properties of toughened polypropylene blends for automobile bumpers

Studies on the use of polyolefin elastomer (POE) and high density polyethylene (HDPE) for toughening polypropylene (PP) to meet the demands of automobile bumpers were conducted. The effect of the basic resin, POE and the influences of the POE amount and HDPE doses on the mechanical properties of the blended composites were discussed. The morphology of impact fracture sections were characterized by scanning electron microscopy (SEM) while the crystalline properties were investigated by DSC. The effect of the composites’ morphology on mechanical properties was also discussed. Results showed that POE could improve the impact strength of PP while the use of HDPE had obvious effects on synergistic toughening. SEM images and DSC data analysis testified to the relationship between morphology, crystallinity and the mechanical properties.     

Amino functionalization of multiwalled carbon nanotubes by gamma ray irradiation and its epoxy composites

In this paper, γ‐ray radiation technique was utilized to simply functionalize multi‐walled carbon nanotube (MWCNT) with amino groups. The successful amino functionalization of MWCNTs (MWCNTs‐Am) was proven and the physicochemical properties of MWCNTs before and after radiation grafting modifications were characterized using FT‐IR, X‐ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The results indicated that the γ‐ray radiation had the visible effects on the surface properties of MWCNTs. The effects of various functionalized MWCNTs on morphological, thermal, and mechanical properties of an epoxy‐based nanocomposite system were investigated. Utilizing in situ polymerization, 1 wt% loading of MWCNT was used to prepare epoxy‐based nanocomposites. Compared to the neat epoxy system, nanocomposites prepared with MWCNT‐Am showed 13.0% increase in tensile strength, 20.0% increase in tensile modulus, and 24.1% increase in thermal decomposition temperature. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers     

Epoxy nanocomposites containing mercaptopropyl polyhedral oligomeric silsesquioxane: Morphology,thermal properties,and toughening mechanism

A novel polyhedral oligomeric silsesquioxane (POSS) containing a mercaptopropyl group [mercaptopropyl polyhedral oligomeric silsesquioxane (MPOSS)] was synthesized via the hydrolytic condensation of γ-mercaptopropyl triethoxysilane in an ethanol solution catalyzed by concentrated hydrochloric acid and was used to modify epoxy–amine networks by a cocuring reaction with diglycidyl ether of bisphenol A (DGEBA). The structure, morphology, and thermal and mechanical properties of these MPOSS/DGEBA epoxy nanocomposites were studied and investigated with thermogravimetric analysis/differential thermal analysis (TGA–DTA), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). From SEM analysis, we observed that the miscibility between epoxy and POSS occurred at a relatively high POSS content, which characterized this mixture as a polymer nanocomposite system. The impact test showed that MPOSS reinforced the epoxy effectively, and the SEM study of the impact fracture surface showed that the fibrous yielding phenomenon observed was an indication of the transition of the brittle stage to a ductile stage and correlated well with the large increases in the impact strength; this was in agreement with the in situ reinforcing and toughening mechanism. The TGA–DTA analysis indicated that the MPOSS/DGEBA epoxy hybrids exhibited lower thermostability at a lower temperature but higher thermostability and higher efficiency in char formation at an elevated temperature. Differential scanning calorimetry showed that the glass transition temperature (T_g) of the MPOSS/epoxy hybrids were lower than that of the neat epoxy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Morphological correlations to mechanical performance of hydroxyapatite‐filled HDPE/UHMWPE composites

Melt mixed and injection molded hydroxyapatite (Hap) filled high‐density polyethylene/ultrahigh molecular weight polyethylene composites were assessed for their thermal, structural, morphological, and mechanical attributes. Differential scanning calorimetry was conducted to analyze the effect of Hap loading on various thermal transitions and their associated enthalpies. The microstructural attributes were characterized by conducting wide angle X‐ray diffraction and scanning electron microscopy (SEM) of cryo‐fractured surface. SEM micrographs of tensile fractured surface revealed the systematic reduction in the size of microfibrils indicating the suppression of local deformation. Improvement in low‐strain mechanical response and flexural properties accompanied with a consistent decrease in strain‐at‐break and toughness was witnessed with increasing Hap content. Toughness aspects were critically discussed in the realms of quasi‐static, dynamic mechanical and sudden impact testing approach. Dynamic mechanical analysis demonstrated the presence of prominent α and γ transitions in the crystalline and amorphous phase respectively. Tensile fractured surface morphologies of the investigated composites revealed a switch‐over from matrix dominated plastic deformation to Hap controlled quasi‐brittle fracture. Thus, our study fundamentally deals with the feasibility of designing polyethylene/Hap composites with superior mechanical properties for biomedical applications, especially for orthopedic implants. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41251.