Direct Melt Mixing Research Articles

Influence of nanocomposite preparation techniques on the multifunctional properties of carbon fabric‐reinforced polystyrene‐based composites with carbon nanotubes

AbstractPolystyrene (PS)‐based and carbon fabric‐reinforced polymers (CFRPs) containing elastomer were prepared using the compression molding technique. PS was also reinforced with two types of carbon nanotubes (CNTs), as received and modified with a silane‐coupling agent. Nanocomposites were fabricated with two different methods, masterbatch dilution, and direct melt mixing. The effect of the nanocomposite preparation technique on the mechanical properties, electrical resistivity, and shape memory behavior of the multilayer composites was investigated. The tensile strength and tensile modulus of the multilayer composite containing CNTs modified with silane coupling agent, and prepared with masterbatch dilution method, increased by 33% and 34%, respectively, compared with the composites prepared with melt mixing. With the masterbatch dilution technique, the electrical resistivity was lower, and slightly increased with surface modification of CNTs. In both preparation techniques, the possible combined effect of CNTs and CF on the thermal and electrical conductivity of the composites led to 100% shape recovery lower than 30 s with electrically actuated bending test.

Study on thermal and mechanical behaviors of polypropylene grade 552R/Cloisite 15A nanocomposites suitable for yarn applications

The investigation of polypropylene (PP)/clay nanocomposites has received considerable scientific and technological attention during the last decades due to their good mechanical and barrier properties. In the present article, the effects of adding Cloisite15A (C15A) nanoclay in polypropylene (PP) were investigated. PP nanocomposites were prepared by a direct melt mixing method. For better dispersion of C15A, 30 wt% of nanoclay masterbatch was first prepared by melt mixing of PP matrix and acrylic acid grafted PP oligomer (PP- g-AA) in a compounder, before being used to produce nanocomposites with 2 and 5 wt% of C15A. The aim of this work was to used nanoclay filled nanocomposites with suitable properties for cable application like good flame-retardant property; improve dye-ability and resilience of polypropylene. The XRD results indicated an intercalated layer structure for nanocomposites, The SEM examination showed satisfactory dispersion of nanoclay in 2 wt% of C15A and some degree of agglomeration in 5 wt% of C15A. DSC analysis indicated that C15A acts as a nucleating agent and increases crystallinity in the nanocomposite. TGA showed with increasing nanoclay, heat resistance was improved and degradation temperatures increased. Limiting oxygen index (LOI) tests showed increased flame retardancy from 25% for neat polypropylene t0 32.2% for nanocomposites of 5 wt% of C15A. The tensile modulus was improved from 423 MPa for neat polypropylene to 474 MPa for nanocomposites with 5 wt% of C15A.This result indicates that increasing C15A content had a suitable effect on the tensile properties. Melt spinning investigation on low oriented yarn (LOY), draw textured yarn (DTY), and fully drawn yarn (FDY) of 2 wt% C15A nanocomposite showed a reduction of linear density for FDY and an increase of the shrinkage. Furthermore, the obtained results for the improvement of dye-ability and compression resilience showed that PP/C15A is appropriate for textile products.

Preparation of thermally conductive polycarbonate/boron nitride composites with balanced mechanical properties

AbstractIn this study, thermally conductive polycarbonate/boron nitride (PC/BN) composites were prepared by masterbatch dilution and direct melt mixing methods, respectively. A comparative study of both microstructure and rheological properties of corresponding composites suggests an improved filler distribution is achieved by masterbatch dilution, which is advantageous to the enhancement of both thermal conductivity and tensile properties at a medium filler loading range. In addition, thermogravimetric analysis indicated that thermal stability of masterbatch diluted PC/BN composites is superior to that of direct melt compounded counterparts. However, the char residue of PC in subsequent composites decreases with increasing filler content, which is believed to be related to the incompatibility between fillers and the matrix, as well as the enhancement of thermal conductivity. This work provides a facile method to prepare thermally conductive composites with balanced mechanical properties.

Evaluation of preventive performance of kaolin and calcium hydroxide nanocomposites in strengthening the outdoor carved limestone

The conservation of ancient Egyptian outdoor carved limestone sculpture is an important issue. This type of artifact is generally exposed to complex weathering processes, and the resulting physico-chemical decay causes unwanted changes in the stone structure and surface. The conservation of carved limestone is a difficult task, requiring the use of materials which need to be compatible to both the original components and those added as part of a previous conservation treatment. The polymeric-nanocomposite materials—which are more and more used on cultural heritage—show promising results for the conservation and preservation of stone monuments, particularly in preventing or reducing future damages. The aims of this study are to characterize limestone used in the outdoor historic sculpture and to examine the efficiency of polymeric nanocomposites in the treatment and preservation of exposed archeological carved limestone. This paper presents a comparative evaluation of the effect of kaolin and calcium hydroxide Ca(OH)2 nanoparticles to both the mechanical and the physico-chemical properties of an acrylic-based copolymer, in order to enhance significantly the polymer properties and its ability to protect and consolidate the weathered outdoor carved limestone. The polymer nanocomposites were prepared by direct melt mixing with a nanoparticle content of 5% (w/v). The stability and efficiency of the consolidation materials were tested by aging artificially the samples under different environmental conditions. The hydrophobic properties and the adsorption of the treatment materials by the stone were analyzed. Moreover, the properties of untreated and treated limestone samples were evaluated comparatively before and after aging by microstructural analysis (the surface morphology was studied using scanning electron microscopy), by measuring the color variances (using spectrophotometry), and by mechanical tests. The results showed that treatment with Ca(OH) nanoparticles/polymer nanocomposite enhanced the durability of stone samples exposed to artificial aging; moreover, it showed higher compatibility in physico-chemical and mechanical properties with the original stone material compared to the samples treated with polymer nanoparticles. The treatment with kaolin nanoparticles/polymer nanocomposite was also effective and showed results second to the Ca(OH) nanoparticles/polymer nanocomposite. The test for hydrophobic properties of both nanocomposites also has a positive outcome and no color change on the surface was observed.

Rheological properties and thermal stability of compatibilized polypropylene/untreated silica composites prepared by water injection extrusion process

In this study, polypropylene/silica (PP/SiO2) composites containing 5 wt% of untreated precipitated silica were compatibilized with different coupling agents like maleic anhydride-grafted polypropylene, glycerol monostearate (GMS), ethylene acrylic acid zinc ionomer and a second polymer phase of polyamide 6 (PA6). The composites were melt-compounded by two different processes: either by direct melt mixing or by dilution of a masterbatch (two-step mixing) in a twin screw extruder using both injected water and high shear stress as a new processing method. The various samples were characterized by Fourier transform infrared spectroscopy (FTIR), thermal analysis, morphological and rheological measurements in order to determine the compatibilizers effects between the matrix and the untreated filler. Hence, atomic force microscopy observations revealed that the untreated silica was dispersed more homogeneously in the presence of PA6 and GMS compatibilizers when water injection is used as one. However, the roughness values are lower in this case. FTIR analysis confirmed the existence of interfacial interactions between OH groups of SiO2 and polar groups of compatibilizers. The storage (G′), loss moduli (G″) and the dynamic viscosity of PP/SiO2 composites increased with the incorporation of PA6. Furthermore, the thermal stability of the compatibilized PP/SiO2 compounds enhanced significantly in the presence of water. An improvement in decomposition temperature of about 50 °C was obtained compared to uncoupled composites.

Structure-property-processing investigation of electrically conductive polypropylene nanocomposites

Abstract This paper investigates the structure-property-processing correlations of electrically conductive polypropylene (PP) nanocomposites. The process parameters and fabrication techniques of PP-based composite materials were studied. Various structures of carbon allotrope-based materials, including synthetic graphite (SG), exfoliated graphene nanoplatelets (xGnP), multi-walled carbon nanotubes (MWCNTs) and carbon black (CB), were used to fabricate the PP-based nanocomposites. The nanocomposites were prepared by either direct melt mixing using an internal mixer or by ball milling of components before the melt mixing process. The electrical and flexural properties were measured. In order to understand the conductivity behavior, both in-plane and through-plane electrical conductivities were measured. The results showed that the incorporation of the xGnP into PP/60 wt.% SG composites resulted in a slight increase of the in-plane conductivities and had a minimal effect on the through-plane conductivities. The addition of MWCNTs and CB to the PP/SG/xGnP composites had a significant effect on the electrical properties and was more pronounced in the case of MWCNTs. The flexural properties of all samples were much lower than those of pure PP. The interface between the filler and the PP matrix and the morphology of the composite materials were observed from the fracture surfaces of the composites using scanning electron microscopy (SEM). In addition, SEM was employed to observe adhesion, microstructural homogeneity, orientation of the xGnP platelets and agglomeration in the composites.

Development of cellulose nanocrystal‐reinforced polylactide: A comparative study on different preparation methods

A masterbatch of polylactide (PLA) containing cellulose nanocrystals (CNCs) prepared via a solution‐cast method was further diluted with neat PLA in the melt state using either a twin‐screw extruder or an internal batch mixer to reach a final CNC content of 4 wt%. For the sake of comparison, a direct melt mixing method was employed to prepare PLA–CNC composites. Then, the efficiency of the preparation methods was assessed by comparing the morphological, rheological and thermomechanical properties of the compounded samples. Scanning electron microscopy showed the disappearance of large agglomerates when using the PLA–CNC masterbatch. Transmission electron microscopy revealed the existence of well‐dispersed CNCs within the PLA matrix at a nanoscale for masterbatch‐based nanocomposites. The rheological properties of the nanocomposites containing the PLA–CNC masterbatch were significantly increased for both steady and small‐amplitude oscillatory shear flow fields, compared to the composites prepared via direct melt mixing. In addition, the masterbatch‐based nanocomposites exhibited pronounced overshoots in the transient start‐up viscosity. The crystalline content of the PLA in the nanocomposites and the crystallization temperature increased when the CNCs were well dispersed, which showed the nucleating effect of the CNCs. In dynamic mechanical thermal analysis, the storage modulus of the nanocomposites increased up to 41 and 128% in the glassy and rubbery regions, respectively. These results show that hydrophilic CNCs can be well dispersed and reinforce PLA using efficient preparation methods. POLYM. COMPOS., 40:E342–E349, 2019. © 2017 Society of Plastics Engineers

Polymer nanocomposites with cellulose nanocrystals made by co‐precipitation

ABSTRACTA premixing method to produce polymer nanocomposites with cellulose nanocrystals (CNCs) is reported. This method involves the dissolution and dispersion of a polymer and CNCs in an organic solvent, co‐precipitation into water, drying of the resulting particles, and subsequent melt processing. The key aspect of the method is that it allows the kinetic trapping of well‐dispersed CNCs in the polymer. Although the nanocomposite must be dried before subsequent melt‐processing, the organic solvent can be removed by extraction in water and recycled, leaving only residual water in the composite, which is easily eliminated. This process presents numerous advantages compared with the time‐consuming solvent casting process, which often suffers from incomplete organic solvent evaporation. As a testbed, polyurethane (PU) composites with up to 30% of CNCs were prepared. These materials were either melt‐processed as produced or used as a masterbatch, i.e., they were diluted via melt‐mixing with neat polymer toward nanocomposites with lower filler content. All nanocomposites prepared using this approach had a homogeneous appearance. They displayed similar mechanical properties as the corresponding reference materials made by solvent casting, and significantly better properties than materials prepared by direct melt mixing. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45648.

Effects of poly(ethylene glycol) on the morphology and properties of biocomposites based on polylactide and cellulose nanofibers

Polylactide (PLA)/cellulose nanofiber (CNF) biocomposites were prepared via solution casting and direct melt mixing. To improve the compatibility, a masterbatch of CNFs and poly(ethylene glycol) (PEG) (1:2) was also prepared. The effects of PEG on the morphology and properties of the biocomposites were investigated. The dispersion/distribution of nanofibers in PLA was improved when the masterbatch was used and the composites were prepared in solution. Substantial effects on the rheological properties of solution-prepared PLA/CNF/PEG composites were observed compared to composites containing no PEG, whereas for melt-prepared composites no significant changes were detected. Increased crystalline content and crystallization temperature were observed for the composites prepared via the masterbatch and solvent casting. The storage modulus of PLA was increased by 42 and 553% at 25 and at 80 °C, respectively, for the solution-based PEG-compatibilized composite containing 2 wt% nanofibers. Also, a better light transmittance was measured for the PLA/CNF/PEG composites prepared in solution.

Natural rubber/graphene oxide nanocomposites via melt and latex compounding: Comparison at very low graphene oxide content

Graphene oxide was produced by the improved Hummers method and characterized by X-ray photoelectron spectroscopy. Graphene oxide was incorporated up to 0.5 part per hundred rubber (phr) in natural rubber through traditional melt mixing and latex precompounding, respectively. Cure behavior of the sulfur-curable natural rubber/graphene oxide nanocomposites was studied in a Monsanto-type vulcameter. Properties of the nanocomposites were determined in dynamic mechanical analysis, static tensile (tensile and tear), and fracture mechanical (J-integral) tests. Unlike for latex precompounding, incorporation of graphene oxide accelerated the vulcanization and reduced its extent for the melt compounded series. Natural rubber/graphene oxide nanocomposites, produced by the latex route, outperformed the melt compounded versions with respect to the hardness, tensile mechanical and fracture mechanical performances. The properties of the former natural rubber/graphene oxide nanocomposites scattered less than those produced using block natural rubber via traditional compounding. The property improvements were attributed to a better dispersion (higher exfoliation and larger aspect ratio) of the graphene oxide layers after latex precompounding compared to the nanocomposites produced via direct melt mixing of block natural rubber.

A slurry compounding route to disperse graphene oxide in rubber

In polymer composites, filler dispersion and interfacial adhesion are two critical factors in determining their properties. To date, it still remains a challenge to achieve uniform filler dispersion and implement interfacial tailoring in rubber composites by direct melt mixing. In this study, we prepared graphene oxide (GO) slurry in acetone via a simple solvent exchange method and modified GO in the slurry. Then the slurry was compounded with nitrile rubber on two-roll mill to produce composites. Morphological and interfacial structural studies revealed that GO was dispersed at nano-scale in the composites, and the dispersion of GO and interfacial adhesion were further improved upon the modification of GO with silane. Consequently, the mechanical properties of the composites were remarkably enhanced by adding GO.

The impact of zinc oxide particle morphology as an antimicrobial and when incorporated in poly(3-hydroxybutyrate-co-3-hydroxyvalerate) films for food packaging and food contact surfaces applications

In this work, zinc oxide (ZnO) micron and nano sized-particles with different morphologies were synthesized by aqueous precipitation and evaluated as antimicrobial agents against foodborne pathogens. The most effective bactericide system was selected to prepare active poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films by three different methods (i) direct melt-mixing, (ii) melt-mixing of preincorporated ZnO into PHBV18 (18mol% valerate content) fiber mats made by electrospinning, and, (iii) as a coating of the annealed electrospun PHBV18/ZnO fiber mats over compression molded PHBV. Results showed that ZnO successfully improved the thermal stability of the PHBV18, being the preincorporation method the most efficient in mitigating the negative impact that the PHBV18 had on the thermal stability, barrier and optical properties of the PHBV films. Similar behavior was found for the coating structure although this film showed effective and prolonged antibacterial activity against Listeria monocytogenes. This study highlights the suitability of the PHBV/ZnO nanostructures for active food packaging and food contact surface applications.

Polyethylene-thermally reduced graphene nanocomposites: comparison of masterbatch and direct melt mixing approaches on mechanical, thermal, rheological, and morphological properties

Two routes of nanocomposite generation, viz., the masterbatch method and direct melt mixing, were compared in the current study in relation with the properties of the polyethylene-thermally reduced graphene nanocomposites compatibilized with functional polymers. Filler dispersion was observed to improve in the masterbatch method due to preferential interactions of compatibilizer with the filler, before melt mixing with the matrix polymer. This also translated into improved mechanical properties as more than two times increment in tensile modulus was observed in the composite HDPE/G/5 EAA/MB (41 %, masterbatch method) as compared to HDPE/G/5 EAA/MM (20 %, melt mixing method). In addition, different compatibilizers also influenced the properties to a different extent owing to their physical interactions with the filler; however, composites generated with masterbatch were always superior in extent of property enhancements. Increasing the compatibilizer content to 10 % also caused varying degrees of matrix plasticization. The storage modulus as well as the complex viscosity of the HDPE/G/5 EAA/MB composite was the highest as compared to HDPE/G/5 EMAZ/MB and HDPE/G/5 EVA-MA/MB composites. HDPE/G/5 EAA/MB and HDPE/G/5 EMAZ/MB composites did not show any decrease in degree of crystallinity as compared to pure polymer, whereas the corresponding composites generated with melt mixing exhibited slight decrease in the crystallinity. The composites were observed to have enhanced thermal stability as compared to HDPE. Five percent EAA-based composites exhibited even higher thermal stability than did HDPE/G composites due to improved filler dispersion. Composites generated with the masterbatch approach had also higher degree of phase mixing than the corresponding melt mixed composites.

Effect of halloysite nanotube on microstructure, rheological and mechanical properties of dynamically vulcanized PA6/NBR thermoplastic vulcanizates

ABSTRACTDynamically vulcanized thermoplastic vulcanizate (TPV) nanocomposites based on polyamide-6 (PA6) and acrylonitrile butadiene rubber (NBR) reinforced by halloysite nanotubes (HNT) were prepared via a direct melt mixing process. The effects of HNT on the physical, mechanical, and rheological properties of nanocomposites were investigated. The prepared PA6/NBR/HNT nanocomposites were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning colorimeter (DSC), dynamic mechanical thermal analysis (DMTA), and rheological measurements. The morphology study of prepared nanocomposites shows that the introduction of HNT into the PA6 phase causes a decrease in the size of NBR droplets. The mechanical measurements revealed that Young’s modulus of TPV nanocomposites increased with the HNT loading up to 54%. DMTA results show that the introduction of 10 wt% of HNT into the PA6/NBR TPV leads to a 30% increase in storage modulus. The rheological measurements revealed that the storage modulus of nanocomposites has an increase of more than 200% in the presence of 7 wt% of HNT loading. Analytical stiffness modeling of Young’s modulus of the TPV nanocomposites was investigated using Hui–Shia and Wu models. Both models have some deviations from experimental results and been modified to predict Young’s modulus of the nanocomposites containing HNT with more precisions. The viscosity behavior of TPV nanocomposites was studied using a Carruea–Yasuda model and showed that the yield stress of nanocomposites increases with higher HNT loadings, indicating the formation of a nanotube network along with NBR phase network.

Influence of functionalized polypropylene on polypropylene/graphene oxide nanocomposite properties

Graphene oxide (GO) derived from oxidation of natural graphite contains many active groups that can interact with a great variety of polar moieties. In this work, polypropylene (PP)/graphene oxide nanocomposites using polypropylene (PP) grafted with amine‐alcohol (PPgDMAE) as compatibilizer were prepared by two different methods. Maleic anhydride grafted PP (PPgMA) was reacted with 2‐[2‐(dimethylamine)‐ethoxy] ethanol (DMAE) in the melt for forming amine‐alcohol functionalized polypropylene (PPgDMAE). Nanocomposites were prepared by two methods. In one method, PP/GO nanocomposite was prepared by direct melt mixing in an internal batch mixer using PPgDMAE as compatibilizer. In another method, a previous mixing of PPgDMAE with GO in hot Xilene was done and then, once the solvent was evaporated, it was incorporated into PP by melt‐mixing. The microstructure and interface enhancement of the prepared composites were analyzed by Fourier transform infrared spectroscopy (FTIR), Raman, X‐ray difraction (DRX) contact angle, scanning and transmission electron microscopy (STEM), mechanical, thermal, and electrical properties measurements. Fourier transform infrared spectroscopy (FTIR) revealed the interaction between GO and PPgDMAE. The loading of GO conducted to enhance the composite mechanical properties attributed to the strong interfacial interactions between GO and PPgDMAE. A significant improvement in mechanical thermal stability and electrical properties was observed when nanocomposites were prepared by the solution blending method compared with melt mixing method. This work suggests a potential application of GO in preparation of high performance PP composites. POLYM. COMPOS., 39:1361–1369, 2018. © 2016 Society of Plastics Engineers

XNBR-grafted halloysite nanotube core-shell as a potential compatibilizer for immiscible polymer systems

Halloysite nanotubes (HNTs) grafted with carboxylated nitrile byutadiene rubber (XNBR) were synthesized via a sol-gel method. The HNTs as an inorganic cores were pre-treated with 3-Glycidoxypropyl trimethoxysilane, then successfully coated with the XNBR as an organic shell. The properties of XNBR-grafted HNTs were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results suggested that the XNBR grafted to the surfaces of HNTs successfully. Then the TPE nanocomposites based on polyamide-6 (PA6) and nitrile butadiene rubber (NBR) containing various XNBR-grafted and pristine HNTs were prepared via a direct melt mixing method. The morphology, mechanical, dynamic mechanical and rheological properties of the prepared TPE nanocomposites were investigated. The results show that the XNBR-grafted HNTs can effectively improve the morphology and mechanical properties of the PA6/NBR TPEs. The morphology study of the prepared nanocomposites show that the effect of XNBR-grafted HNTs on the size reduction of NBR phase is markedly more effective than the pristine HNTs and rose by 50% in the same concentrations. Mechanical measurements show that the Young’s modulus of the TPE nanocomposites rose by 60% in just 7wt% of XNBR-grafted HNT loading. The results indicate that the introduction of HNT/XNBR core-shells into the PA6/NBR TPEs can enhances the interfacial interactions and provides a more fine rubber phase morphology and controlled mechanical properties in comparison with the accordingly TPE nanocomposites containing pristine HNTs.

Impact of non-functionalized and ionic liquid modified carbon nanotubes on mechanical and thermal properties of ethylene- octene copolymer nanocomposites

In this article the development and characterization of composites made from metallocene based ethylene-octene copolymer (EOC) with 38% octene content, non-modified or modified multi walled carbon nanotubes (MWCNTs), covalently functionalised with long chain hexadecyl moiety imidazolium ionic liquid (IL-f-MWCNTs), is presented. The procedure of MWCNTs functionalization is discussed. In order to obtain a good dispersion of the filler, composites with MWCNTs and IL-f-MWCNTs in the concentration range of 0.5-12 wt.% were made by ultrasonication / thermoplastic mixing method. The results indicated improvement in mechanical properties with increase of the filler content. The methodology of the development of EOC matrix nanocomposites with IL-f-MWCNTs showed advantages of the conductive material creation with high mechanical stiffness compared to direct melt mixing of EOC with non-modified MWCNTs. A notable enhancement of thermal stability was observed in case of both pristine MWCNTs and IL-f-MWCNTs containing EOC nanocomposites, which was attributed to scavenging action of the nanofiller. Modification of EOC with IL-f-MWCNTs showed somewhat increased efficiency in enhancing overall thermal stability of the composites because of better dispersion of the nanofiller due to compatibilizing effect of IL modifier.

Isobutylene–isoprene rubber/layered silicate nanocomposites prepared using latex method: Direct casting versus melt mixing after coagulation

In this study, polymer nanocomposites of isobutylene–isoprene rubber blended with sodium–montmorillonite were prepared using latex and co-coagulating methods and their influence on thermal, mechanical, and gas barrier if isobutylene–isoprene rubber composites were compared. The dispersion of the layered silicates in the matrix of the obtained nanocomposites was investigated using transmission electron microscopy and X-ray diffraction. The transmission electron microscopy images revealed both partially exfoliated and intercalated structures for the isobutylene–isoprene rubber/montmorillonite nanocomposite prepared using the latex method and a purely intercalated structure for the sample prepared using the co-coagulating method. The surfactant used in the latex method played an important role in determining the interlayer distance within the silicates in the isobutylene–isoprene rubber/montmorillonite composites, in which the interlayer d-spacing in the silicates increased relative to that for the co-coagulating method after the curing process. The tensile and thermal properties of the isobutylene–isoprene rubber/montmorillonite nanocomposites improved with respect to those of the neat isobutylene–isoprene rubber. The tensile strength and decomposition temperature of the isobutylene–isoprene rubber/montmorillonite composites (5 parts per hundred resin (phr) montmorillonite blended with latex) increased by 100% and 20℃, respectively. The gas-barrier properties of the obtained composites (10 phr montmorillonite blended with latex) even increased by 60% compared with those of the neat isobutylene–isoprene rubber. For the isobutylene–isoprene rubber/clay composites prepared using the co-coagulating method, an observable improvement of the tensile properties was achieved only if the content of the blended clay was greater than 10 phr.

Reinforcement of polyolefins-based nanocomposites: combination of compatibilizer with high shear extrusion process

The structure and properties of polypropylene (IPP) and ethylene propylene copolymer (IEPR) blends filled with nanosilica have been investigated. The nanocomposites were prepared via direct melt mixing using high shear corotating twin screw extruder. The effects of the process as well as adding amaleated-Polyethylene MAPE compatibilizer were assessed by morphology studies, thermal analysis and mechanical testing. From SEM and TEM investigations, a separate dispersion of filler and rubber in the PP matrix prevails in the PP/EPR/SiO2 systems. Encapsulation of the filler particles into the elastomer takes place when MAPE is used, promoting filler/polymer interactions and resulting in a simultaneous improvement in stiffness and toughness. Interestingly, the results indicated that high-shear processing is an effective method to improve the dispersion of the EPR phase and fillers through the matrix. The dispersed phase droplet size was reduced with the increase of the shear rate by varying the screw rotation speed from 300 to 800 rpm, which induces a high shear stress exerted onthe materials. To sum up, what is expected from an efficient compatibilization-process association is the reduction of the dispersed elastomer domains characteristic size, their stabilization by creation of an interphase and thus, enhanced mechanical properties.

Preparation of conductive polyphenylene sulfide/polyamide 6/multiwalled carbon nanotube composites using the slow migration rate of multiwalled carbon nanotubes from polyphenylene sulfide to polyamide 6

ABSTRACTConductive polyphenylene sulfide (PPS)/polyamide 6 (PA6)/multiwalled carbon nanotube (MWCNT) composites having 10–30 wt % PA6 and 1 wt % MWCNTs are prepared by melt mixing at 300°C for 8 min using a high concentration PPS/MWCNT masterbatch approach, and the migration kinetics of MWCNTs from thermodynamically unfavored PPS to favored PA6 was investigated. The morphology of the composites was investigated by field emission scanning electron microscopy and transmission electron microscopy, showing the localization of most MWCNTs in the PPS phase and at the interface, being different from the case of direct melt mixing where non‐conductive materials were obtained with most MWCNTs found in the PA6 phase and at the interface. The electrical resistivity and morphology of the materials as a function of time were investigated, showing that the conductive materials can be prepared within a mixing time of 4–16 min because of the slow migration rate of MWCNTs from PPS toward PA6, and MWCNTs can eventually migrate into the PA6 phase after a long mixing time of 30 min. The slow migration rate of MWCNTs was attributed to the high viscosity ratio of the two phases. This article shows a good example where the migration of MWCNTs was slow enough to control and can be used to prepare conductive polymer blends. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42353.