In situ dynamic vulcanization process in preparation of electrically conductive PP/EPDM thermoplastic vulcanizate/expanded graphite nanocomposites: Effects of state of cure

In situ melt dynamic vulcanization process has been employed to prepare electrically conductive polypropylene (PP)/ethylene–propylene–diene rubber (EPDM) (40/60 wt %) thermoplastic vulcanizates (TPVs) incorporated by expanded graphite (EG) as a conductive filler. Maleic anhydride grafted PP (PP‐g‐MAH) was used as compatibilizer and a sulfur curing system was designed and incorporated to vulcanize the EPDM phase during mixing process. Developed microstructures were characterized using scanning electron microscopy (SEM), melt rheomechanical spectroscopy (RMS), X‐ray diffraction (XRD), and transmission electron microscopy (TEM) and were correlated with electrical conductivity behavior. For comparison, another class of TPV/EG nanocomposites was fabricated using a commercially available PP/EPDM‐based TPV via both direct and masterbatch melt mixing process. Conductivity of the nanocomposites prepared by in situ showed no significant change during dynamic vulcanization till the mixing torque reached to the stationary level where micro‐morphology of the cured rubber droplets was fully developed, and conductivity abrupt was observed. In situ cured nanocomposites showed higher insulator to conductor transition threshold (3.15 vol % EG) than those based on commercially available TPV. All electrically conductive in situ prepared TPV nanocomposites exhibited reinforced melt elasticity with pseudosolid‐like behavior within low frequency region in dynamic melt rheometry indicating formation of physical networks by both EG nanolayers and crosslinked EPDM droplets. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Structure and electrical properties of grafted polypropylene/graphite nanocomposites prepared by solution intercalation

A novel process was developed to prepare electrically conducting maleic anhydride grafted polypropylene (gPP)/expanded graphite (EG) nanocomposites by solution intercalation. The conducting percolation threshold at room temperature (Φ_c) of the nanocomposites was 0.67 vol %, much lower than that of the conventional conducting composites prepared by melt mixing (Φ_c = 2.96 vol %). When the EG content was 3.90 vol %, the electrical conductivity (σ) of the former reached 2.49 × 10^?3 S/cm, whereas the σ of the latter was only 6.85 × 10^?9 S/cm. The TEM, SEM, and optical microscopy observations confirmed that the significant decrease of Φ_c and the striking increase of σ might be attributable to the formation of an EG/gPP conducting multiple network in the nanocomposites, involving the network composed of particles with a large surface‐to‐volume ratio and several hundred micrometers in size, and the networks composed of the boards or sheets of graphite with high width‐to‐thickness ratio and particles of fine microscale or nanoscale sizes. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1864–1869, 2003     

Interfacially compatibilized poly(lactic acid) and poly(lactic acid)/polycaprolactone/organoclay nanocomposites with improved biodegradability and barrier properties: Effects of the compatibilizer structural parameters and feeding route

Nanocomposites with enhanced biodegradability and reduced oxygen permeability were fabricated via melt hybridization of organomodified clay and poly (lactic acid) (PLA) as well as a PLA/polycaprolactone (PCL) blend. The nanocomposite microstructure was engineered via interfacial compatibilization with maleated polypropylene (PP‐g‐MA). Effects of the compatibilizer structural parameters and feeding route on the dispersion state of the nanolayers and their partitioning between the PLA and PCL phases were evaluated with X‐ray diffraction, transmission electron microscopy, and scanning electron microscopy. Although highly functionalized PP‐g‐MA with a low molecular weight was shown to be much more effective in the intercalation of PLA and the PLA/PCL blend into the clay gallery spaces, composite samples compatibilized by high‐molecular‐weight PP‐g‐MA with a lower degree of maleation exhibited lower oxygen permeability as well as a higher rate of biodegradation, which indicated the accelerating role of the dispersed nanolayers and their interfaces in the enzymatic degradation of PLA and PLA/PCL matrices. This evidenced a correlation between the nanocomposite structure and rate of biodegradation. The size of the PCL droplets in the PLA matrix was reduced by nanoclay incorporation, and this revealed that the nanolayers were preferentially wetted by PCL in the blend. However, PCL appeared as fine and elongated particles in the microstructure of the PLA/PCL/organoclay hybrids compatibilized by higher molecular weight and less functionalized PP‐g‐MA. All the PLA/organoclay and PLA/PCL/organoclay hybrids compatibilized with high‐molecular‐weight PP‐g‐MA displayed a higher dynamic melt viscosity with more pseudo solid‐like melt rheological responses, and this indicated the formation of a strong network structure by the dispersed clay layers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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     

Rheological behaviors of glass bead‐ and wollastonite‐filled polypropylene composites modified with thermoplastic elastomers

Steady‐ and oscillatory‐shear rheological behaviors of polypropylene/glass bead (PP/GB) and PP/wollastonite (PP/W) melts modified with thermoplastic elastomers, poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene) copolymer (SEBS) and the corresponding block copolymer grafted with maleic anhydride (SEBS‐g‐MA), were examined by means of a parallel‐plate rheometer. With adding the elastomers (SEBS and SEBS‐g‐MA) and fillers (spherical GB and acicular W) to PP, viscosity especially at low shear rates and shear‐thinning flow behavior at high shear rates were pronounced as evidenced quantitatively by Carreau–Yasuda (CY) parameters, but Cox–Merz analogy became weakened. Besides, melt‐elasticity in terminal region and relaxation time (t_c) in crossing point increased, indicating an enhancement in quasi‐solid behavior of molten PP. Comparing with the elastomers, rheological behaviors of molten PP were more influenced with adding the rigid fillers, especially with W due to distinct acicular shape of W particles. SEBS‐g‐MA elastomer more affected rheological behaviors of the ternary composites than SEBS elastomer, implying that SEBS elastomer and the filler particles behaved individually (i.e., development of separate microstructure) in (PP/GB)/SEBS and (PP/W)/SEBS ternary composites, but core‐shell microstructure developed with strong interfacial adhesion by adding SEBS‐g‐MA elastomer, and the filler particles encapsulated with the thick SEBS‐g‐MA elastomer interlayer (i.e., core‐shell particles) acted like neither big elastomer particles nor like individual rigid particles in melt‐state. Moreover, effects of SEBS‐g‐MA elastomer reached a maximum on rheological behaviors of (PP/W)/SEBS‐g‐MA ternary composite, indicating a synergy between core‐shell microstructure and acicular W particles. Correlations between oscillatory‐shear flow properties and microstructures of the blends and composites were evaluated using Cole–Cole (CC), Han–Chuang (HC), and van Gurp–Palmen (vGP) plots. COMPOS., 2012. © 2012 Society of Plastics     

Polypropylene/clay nanocomposites: An innovative one‐pot process

This work discloses a novel one‐pot preparation method of polypropylene (PP)/clay nanocomposites with high degree of clay delamination and improved thermal, mechanical and rheological properties. The in situ simultaneous synthesis of carboxylate clay from native clay and ionomer of PP‐graft maleic anhydride (PP‐g‐MA) through trihydrate sodium acetate addition, combined with water injection in the extrusion process, appears to be a valuable alternative to the use of organoclay for producing PP/PP‐g‐MA/clay nanocomposites. The influence of PP‐g‐MA graft content, and of its ionomer form, onto the clay dispersion has been especially investigated. PP‐g‐MA of low graft content is compared to a home‐made highly grafted PP‐g‐MA synthesized in the presence of N‐bromosuccinimide (NBS). The nanocomposites prepared by combining the use of NBS‐mediated PP‐g‐MA, trihydrate sodium acetate and water injection exhibit the highest clay dispersion. Thermal, rheological, and mechanical properties of the nanocomposites have been measured. POLYM. COMPOS., 36:644–650, 2015. © 2014 Society of Plastics Engineers     

The physical and mechanical properties of beta‐nucleated polypropylene/montmorillonite nanocomposites

Polypropylene (PP) and polypropylene/polypropylene‐g‐maleic anhydride/ organomontmorillonite (PP/PP‐g‐MA/OMMT) nanocomposites were modified with 0.05 to 0.3% (w/w) of the aryl amide β‐nucleator to promote the formation of hexagonal crystal modification (β‐phase) during melt crystallization. The nonisothermal crystallization behavior of PP, PP/PP‐g‐MA/OMMT and β‐nucleated PP/PP‐g‐MA/OMMT nanocomposites were studied by means of differential scanning calorimetry. Structure‐property relationships of the PP nanocomposites prepared by melt compounding were mainly focused on the effect and quantity of the aryl amide nucleator. The morphological observations, obtained from scanning electron microscopy, transmission electron microscopy and X‐ray diffraction analyses are presented in conjunction with the thermal, rheological, and mechanical properties of these nanocomposites. Chemical interactions in the nanocomposites were observed by FT‐IR. It was found that the β‐crystal modification affected the thermal and mechanical properties of PP and PP/PP‐g‐MA/OMMT nanocomposites, while the PP/PP‐g‐MA/OMMT nanocomposites of the study gained both a higher impact strength (50%) and flexural modulus (30%) compared to that of the neat PP. β‐nucleation of the PP/PP‐g‐MA/OMMT nanocomposites provided a slight reduction in density and some 207% improvement in the very low tensile elongation at break at 92% beta nucleation. The crystallization peak temperature (T_cp) of the PP/PP‐g‐MA/OMMT nanocomposite was slightly higher (116°C) than the neat PP (113°C), whereas the β‐nucleation increased the crystallization temperature of the PP/PP‐g‐MA/OMMT/aryl amide to 128°C, which is of great advantage in a commercial‐scale mold processing of the nanocomposites with the resulting lower cycle times. The beta nucleation of PP nanocomposites can thus be optimized to obtain a better balance between thermal and mechanical properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Reduced percolation concentration in polypropylene/expanded graphite composites: Effect of viscosity and polypyrrole

With the goal to obtain material combining electrical and thermal conductivity at low filler loadings, composites based on polypropylenes (PP) and expanded graphite (EG) have been prepared. The effects of matrix viscosity and of coating the EG particles with polypyrrole (PPy, EG/PPy = 37.5/62.5 by weight) on the EG dispersibility and formation of percolation structures have been analyzed. When increasing the EG amount from 6 to 8 wt %, the electrical conductivity of PP/EG composites increased by 7–9 orders of magnitude, independent of matrix viscosity. When EG‐PPy is added, percolation was observed between 8 and 12 wt % EG‐PPy (3 and 4.5 wt % EG) in case of PP with higher viscosity and 6 wt % EG (2.25 wt % EG) in case of PP with lower viscosity, exhibiting a strong synergistic effect of EG and PPy in the latter case. In contrast, PPy does not contribute to reduction of thermal percolation concentration. Thermal percolation is observed at 8 wt % EG in PP/EG composites, but no percolation was found in PP/EG‐PPy composites with EG‐PPy contents of up to 20 wt %, corresponding to 7.5 wt % EG. Analyzing the melt rheology it becomes clear that the contribution of PPy to the formation of a filler network is strongly dependent on the matrix viscosity. The comparison of thermal, electrical and rheological percolation reveals that PPy participates in electron transport reducing the electrical percolation but not to heat transport. Overall, we found a good correlation between electrical, thermal, and melt rheological percolation concentrations. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41994.     

Influences of compatibilizers on rheology and mechanical properties of propylene random copolymer/styrene‐ethylene‐butylene‐styrene block copolymer/organic‐montmorillonite nanocomposites

Propylene random copolymer (PPR)/styrene‐ethylene‐butylene‐styrene block copolymer (SEBS)/compatibilizer/organic‐montmorillonite (OMMT) quaternary nanocomposites and PPR/compatibilizer/OMMT ternary nanocomposites were prepared via two‐stage melt blending and influences of compatibilizers, maleic anhydride (MA) grafted styrene‐ethylene‐butylene‐styrene copolymer (SEBS‐g‐MA), poly(octene‐co‐ethylene) (POE‐g‐MA), or propylene block copolymers (PPB‐g‐MA), on rheology and mechanical properties of the nanocomposites were investigated. The results of X‐ray diffraction measurement and transmission electron microscopy observation showed that OMMT layers were mainly intercalated in the nanocomposites except for the mainly exfoliated structure in the quaternary nanocomposites using POE‐g‐MA as compatibilizer. The nanocomposites exhibited pseudo‐solid like viscoelasticity in low frequencies and shear‐thinning in high shear rates. As far as OMMT dispersion was concerned, POE‐g‐MA was superior to SEBS‐g‐MA and PPB‐g‐MA, which gives rise to the highest viscosities in both the ternary and quaternary nanocomposites. The quaternary nanocomposites containing POE‐g‐MA were endowed with balanced toughness and rigidity. It was suggested that a suitable combination of compatibilizer and SEBS was an essentially important factor for adjusting the OMMT dispersion and distribution, the rheological and mechanical performances of the nanocomposites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of functionalized SWCNTs on microstructure of PP‐g‐MA/OMMT/f‐SWCNTs nanocomposite

The aim of this work was to study the effect of functionalized single‐walled carbon nanotubes (f‐SWCNTs) on the microstructure of PP‐g‐MA/organic modified montmorillonite (OMMT)/f‐SWCNTs ternary nanocomposite. Pristine SWCNTs were chemically modified by maleic anhydride to improve the interaction between PP‐g‐MA and nanotubes. The dispersion states of OMMT in the different nanocomposites were investigated by wide angle X‐ray diffraction. The morphologies of the nanocomposites were characterized by scanning electron microscopy. Crystallization behaviors of nanocomposites were studied through differential scanning calorimetry and polarizing optical microscopy. Different than the PP‐g‐MA/OMMT binary nanocomposite, in which the OMMT is mainly in an exfoliated state, the ternary PP‐g‐MA/OMMT/f‐SWCNTs nanocomposite exhibits mostly intercalated OMMT. Furthermore, in the ternary nanocomposite, the crystallization of polymer is mainly induced by f‐SWCNTs rather than by OMMT. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Melt processing and characterization of multicomponent polymeric nanocomposites containing organoclay

Nylon 6 (Ny)/polypropylene (PP)/maleated polypropylene (PP‐g‐MA)/organoclay/wollastonite composites were prepared by melt processing. The polymers' composition was kept constant ([70PP/30Ny]/4PP‐g‐MA). Melt compounding was conducted using a twin‐screw extruder in three different methods: (1) simultaneous incorporation of the components into the compounding equipment, (2) preparation of [Ny6/clay] concentrate, and then in a second step, mixing the other components with the concentrate, and (3) mixing of PP with wollastonite and clay followed by the addition of Ny6 and PP‐g‐MA in the second step. Injection‐molded specimens were characterized in tension, scanning electron microscopy, X‐ray diffraction (XRD), and differential scanning calorimetry. The sequence of component addition greatly influences the structure and properties of the composites. Enhanced mechanical properties were achieved when the two‐step mixing procedure was used for the PP/Ny6/PP‐g‐MA/clay system (method 2) and also for the PP/Ny6/PP‐g‐MA/clay/wollastonite system (method 3). The XRD pattern of the PP/Ny6/PP‐g‐MA/clay nanocomposites produced by the two‐step mixing method does not show a characteristic basal reflection of the pristine organoclay, indicating a predominately exfoliated structure of clay. POLYM. COMPOS., 28:417–424, 2007. © 2007 Society of Plastics Engineers     

Effects of carbon nanofibers on the fracture,mechanical, and thermal properties of PP/SEBS‐g‐MA blends

Polypropylene/maleated (styrene‐ethylene‐butadiene‐styrene) (PP/SEBS‐g‐MA) blends reinforced with 0.2–2.5 wt% carbon nanofibers (CNFs) were prepared by injection molding. The structure, thermal, mechanical, and fracture behaviors of PP/SEBS‐g‐MA blends and their nanocomposites were studied. Wide‐angle X‐ray diffraction (WAXD) results showed that the SEBS‐g‐MA and/or CNF additions do not induce a structural change of PP. Tensile measurements showed that the Young's modulus and tensile yield strength increase with the increasing filler content. Izod impact and essential work of fracture test results demonstrated that CNFs are beneficial to improve the impact strength and specific essential work of fracture of PP/SEBS‐g‐MA blends. Therefore, tough PP‐nanocomposites can be achieved by melt‐blending low fractions of CNFs and appropriate elastomer contents. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Melt rheological properties of polypropylene–maleated polypropylene blends. I. Steady flow by capillary

Melt rheological properties of blends of polypropylene (PP) and PP grafted with maleic anhydride (PP‐g‐MA) are studied using a capillary rheometer. A pseudoplastic flow behavior is observed. The pseudoplasticity of the melt reduces with an increase of PP‐g‐MA content and/or temperature. The PP‐g‐MA component in the blend acts as decreasing melt viscosity, especially in the lower shear rate region, while the addition of PP‐g‐MA to PP does not cause obvious increase of die swell ratio. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1641–1648, 1999     

Effect of processing conditions on the formation of polypropylene/organoclay nanocomposites in a twin screw extruder

Polypropylene (PP)/organoclay (Cloisite^©20A) nanocomposites are prepared via direct melt intercalation in a co‐rotating twin screw extruder. Maleic anhydride (MA)‐grafted PP (PP‐g‐MA) is used as a compatibilizer to improve the dispersion of the clay. The formulation used to prepare the nanocomposites is fixed and is equal to 80/15/5 (PP/PP‐g‐MA/Cloisite^©20A), expressed in mass fraction. The objective of the present study is to investigate the effects of processing conditions as well as screw profile upon the formation of PP nanocomposites. The parameters studied are the feed rate and the screw speed, which are varied independently, from 4.5 to 29.0 kg/h and from 100 to 300 rpm, respectively. The state of dispersion is quantified by wide angle X‐ray diffraction (WAXD), transmission electron microscopy, and rheological measurements. WAXD results show that the nanocomposites obtained in different conditions have an intercalated structure, with an increase in interlayer spacing. However, this interlayer spacing is globally unaffected by processing parameters. On the opposite, the proportion of exfoliation, estimated by rheological measurements, is depending on operating conditions (screw speed and feed rate). It increases when the feed rate decreases and the screw speed increases. Investigations on the state of dispersion along the screw profile are also presented. They show that no evolution of intercalated structure is observed along the screws and that screw geometry is only efficient in particular extrusion conditions to delaminate clay platelets. Numerical simulations of the twin screw extrusion process, using the software Ludovic^©, put in evidence that the total strain is a key factor for characterizing the level of exfoliation in the nanocomposites. POLYM. ENG. SCI. 46:314–323, 2006. © 2006 Society of Plastics Engineers     

Polypropylene/clay nanocomposites prepared by in situ grafting‐melt intercalation with a novel cointercalating monomer

Polypropylene (PP)/clay nanocomposites were prepared by melt‐compounding PP with organomontmorillonite (OMT), using maleic anhydride grafted polypropylene (PP‐g‐MA) as the primary compatibilizer and N‐imidazol‐O‐(bicyclo pentaerythritol phosphate)‐O‐(ethyl methacrylate) phosphate (PEBI) as the cointercalating monomer. X‐ray diffraction patterns indicated that the larger interlayer spacing of OMT in PP was obtained due to the cointercalation monomer having a large steric volume and the d‐spacing further increased with the addition of PP‐g‐MA, as evidenced by transmission electron microscopy. Thermogravimetric analysis revealed that the PEBI‐containing PP nanocomposites exhibited better thermal stability than PEBI‐free PP composites. Dynamic mechanical analysis demonstrated that the storage modulus was significantly enhanced, and the glass transition temperature (T_g) shifted slightly to low temperature with the incorporation of clay for PP/OMT hybrids. PEBI‐containing PP/OMT composites gave a lower T_g value because of the strong internal plasticization effect of PEBI in the system. Cone calorimetry showed that the flame‐retardancy properties of PP nanocomposites were highly improved with the incorporation of PEBI. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effects of different compatibilizers on the rheological,thermomechanical, and morphological properties of HDPE/LLDPE blend‐based nanocomposites

The influence of two different compatibilizers and their combination (maleic anhydride grafted high density polyethylene, HDPE‐g‐MA; maleic anhydride grafted linear low density polyethylene, LLDPE‐g‐MA; and 50/50 wt % mixture of these compatibilizers) on the rheological, thermomechanical, and morphological properties of HDPE/LLDPE/organoclay blend‐based nanocomposites was evaluated. Nanocomposites were obtained by melt‐intercalation in a torque rheometer in two steps. Masterbatches (compatibilizer/nanoclay 2:1) were obtained and subsequently diluted in the HDPE/LLDPE matrix producing nanocomposites with 2.5 wt % of nanoclay. Wide angle X‐ray diffraction (WAXD), steady‐state rheological properties, and transmission electron microscopy (TEM) were used to determine the influence of different compatibilizer systems on intercalation and/or exfoliation process which occurs preferentially in the amorphous phase, and thermomechanical properties. The LLDPE‐g‐MA with a high melt index (and consequently low viscosity and crystallinity) was an effective compatibilizer for this system. Furthermore, the compatibilized nanocomposites with LLDPE‐g‐MA or mixture of HDPE‐g‐MA and LLDPE‐g‐MA exhibited better nanoclay's dispersion and distribution with stronger interactions between the matrix and the nanoclay. These results indicated that the addition of maleic anhydride grafted polyethylene facilitates both, the exfoliation and/or intercalation of the clays and its adhesion to HDPE/LLDPE blend. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1726–1735, 2013     

Improved melting strength of polypropylene by reactive compounding with ultrafine full‐vulcanized polybutadiene rubber (UFBR) particles

Ultrafine full‐vulcanized polybutadiene rubber (UFBR) in particle sizes of ca. 50–100 nm has been used for modifying mechanical and processing performances of polypropylene (PP), and PP‐g‐maleic anhydride (PP‐MA) has been used as a compatibilizer for enhancing the interfacial adhesion between the two components. The results show that PP/UFBR possesses rheological behaviors such as highly branched PP when UFBR content in blends reaches 10 wt%, while in contrast, the much low content of UFBR combining small amount of PP‐MA endows the material with rheological characteristics of high melt strength materials like highly branched PP. The mechanism accounting for the rheological behaviors of binary blends and effectiveness of PP‐MA on PP/UFBR blends has been proposed. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Effects of compounding procedure on morphology development,melt rheology,and mechanical properties of nanoclay reinforced dynamically vulcanized EPDM/polypropylene thermoplastic vulcanizates

New nanocomposite thermoplastic vulcanizates (TPVs) comprising dynamically cross‐linked nanoscale EPDM rubber particles dispersed throughout the polypropylene (PP) matrix have been prepared by both batch and continuous melt blending of PP with EPDM in the presence of vulcanizing ingredients, nanoclay and maleated EPDM (EPDM‐g‐MA) as compatibilizer. X‐ray diffraction, linear melt viscoelastic measurement, and tensile mechanical behavior results revealed that the developed microstructure is strongly affected by the type of the melt compounding process as well as the route of material feeding. When EPDM phase was precompounded with a vulcanizing agent, nanoclay, and EPDM‐g‐MA prior to the melt blending with PP, not only nanosize cross‐linked rubber particles appeared uniformly throughout the PP continuous phase, but also the melt blending leads to the significant enhancement of the mechanical properties compared with counterpart samples prepared by one‐step melt mixing process. Also better dispersion of nano layers in the rubber compound before melt blending with PP results in higher mechanical properties of the resulted TPV. POLYM. ENG. SCI., 56:914–921, 2016. © 2016 Society of Plastics Engineers     

Study on dispersion and intercalation of organoclay in PP and PP‐g‐MA matrices

Understanding the complex mechanism of dispersion and intercalation of the clay tactoids can allow us to control the final morphology, homogeneity, and the macroscopic properties of clay nanocomposites. The objective of this work is a multiscale study of the dispersion state of PP/organoclay and PP‐g‐MA/organoclay composite. The microscopic investigation, WAXS diffractograms, rheological analysis, and mechanical properties were used to characterize the dispersion of organoclay in PP and PP‐g‐MA matrices during melt blending in two different shear rates. The morphological results show a system of aggregating intercalated clay particles which disperse by increasing mixing time with a strain‐controlled process and a very quick intercalation process in early mixing times for PP‐g‐MA/organoclay nanocomposite, while PP/organoclay samples only form microcomposites. The relative network modulus of these intercalated particles as a function of mixing time was obtained; and the tensile modulus of nanocomposite samples were compared with Halpin‐Tsai model prediction. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers     

New generation layered nanocomposites derived from ethylene‐co‐vinyl acetate and naturally occurring graphite

New ethylene‐co‐vinyl acetate (EVA, with 60% vinyl acetate content) based nanocomposites were prepared with graphites modified by various techniques and a commercially available expanded graphite (EG). The infrared spectra and the surface energy measurements indicated better oxidation and higher surface energy of the graphite modified by mixed acids followed by high temperature treatment (GO). Interlayer space and surface area were increased as a result. EG possessed higher surface area. GO was found to distribute in finer tactoids of average thickness of 25 nm in the matrix, as compared with the unmodified graphite (UG), having average tactoid thickness more than 40 nm along with aggregation. EG also showed finer dispersion in the EVA matrix with some network formation. The dynamic mechanical and the mechanical properties were superior at the 2 wt % concentration of the GO, beyond which the improvement was less, possibly because of aggregation of GO. Greater EVA‐GO interaction at 2 wt % concentration was also supported from the swelling analysis, thermal conductivity, and the thermo‐oxidative degradation data of the hybrid composites. The melt viscosity was lower at 2 wt % GO concentration. EG based nanocomposites registered similar properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008