Poly(methyl methacrylate)/montmorillonite nanocomposites prepared by bulk polymerization and melt compounding

This article focuses on structural, thermal, and mechanical properties of nanocomposites in dependence of preparation method and poly(methyl mathacrylate) (PMMA)/organically modified montmorillonite (OMMT) ratio. PMMA/OMMT nanocomposites were prepared by bulk polymerization and by melt compounding. Properties of nanocomposites of the same composition prepared by the two methods were compared. It was observed that nanocomposites prepared via melt compounding at 200°C had a highly oriented structure with lower interlayer spacing values than nanocomposites prepared via bulk polymerization. Two reasons for the observed smaller interlayer spacing obtained by melt compounding were identified. The first is enhanced PMMA penetration and/or formation between layers in the case of bulk polymerization, which was confirmed by determination of stronger interactions between OMMT and PMMA by Soxhlet extraction, infrared spectroscopy, and differential dynamic calorimery. The second reason for smaller interlayer spacing for nanocomposites prepared by melt compounding is organic modifier degradation during melt compounding process, which was confirmed by thermogravimetric analysis. Both reasons lead to the fracture of melt compounded nanocomposites on the OMMT‐polymer interface, which was observed by scanning electron microscopy. For nanocomposites with disoriented structure and larger interlayer spacing prepared via bulk polymerization the fracture occurred in the polymer matrix. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Effect of clay modification on the morphological,mechanical, and thermal properties of polyamide 6/polypropylene/montmorillonite nanocomposites

Polyamide 6/polypropylene (PA6/PP = 70/30 parts) blends containing 4 phr (parts per hundred resin) of organophilic montmorillonite (OMMT) were prepared by melt compounding. The sodium montmorillonite (Na‐MMT) was modified using three different types of alkyl ammonium salts, namely dodecylamine, 12‐aminolauric acid, and stearylamine. The effect of clay modification on the morphological and mechanical properties of PA6/PP nanocomposites was investigated using x‐ray diffraction (XRD), transmission electron microscopy (TEM), tensile, flexural, and impact tests. The thermal properties of PA6/PP nanocomposites were characterized using thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and heat distortion temperature (HDT). XRD and TEM results indicated the formation of exfoliated structure for the PA6/PP nanocomposites prepared using stearylamine modified montmorillonite. On the other hand, a mixture of intercalated and exfoliated structures was found for the PA6/PP nanocomposites prepared using 12‐aminolauric acid and dodecylamine modified montmorillonite. Incorporation of OMMT increased the stiffness but decreased the ductility and toughness of PA6/PP blend. The PA6/PP nanocomposite containing stearylamine modified montmorillonite showed the highest tensile, flexural, and thermal properties among all nanocomposites. This could be attributed to better exfoliated structure in the PA6/PP nanocomposite containing stearylamine modified montmorillonite. The storage modulus and HDT of PA6/PP blend were increased significantly with the incorporation of both Na‐MMT and OMMT. The highest value in both storage modulus and HDT was found in the PA6/PP nanocomposite containing stearylamine modified montmorillonite due to its better exfoliated structure. POLYM. COMPOS., 31:1156–1167, 2010. © 2009 Society of Plastics Engineers     

Temperature and strain rate dependences of yield stress of polypropylene composites reinforced with carbon nanofibers

Polypropylene (PP) nanocomposites filled with 0.1, 0.3, 0.5, and 1.0 wt% carbon nanofiber (CNF) were prepared via melt compounding in a twin‐screw extruder followed by injection molding. The effects of CNF additions on the structure, mechanical and tensile yielding behavior of PP were investigated. TEM and SEM observations showed that CNFs were dispersed uniformly within PP matrix. Tensile test showed that the yield strength and Young's modulus of PP were improved considerably by adding very low CNF loadings. The reinforcing effect of CNF was also verified from the dynamic mechanical analysis. Impact measurement revealed that the CNF additions were beneficial to enhance the impact toughness of PP. The yield stress of the PP/CNF nanocomposites was found to be strain rate and temperature dependent. The yielding responses of PP/CNF nanocomposites can be described successfully by the Erying's equation and a reinforcing index n. The structure and mechanical property relationship of the nanocomposites is discussed. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

A processing-induced clay dispersion and its effect on the structure and properties of polyamide 6

The nanostructures and morphologies of polyamide 6 (PA6)/organoclay nanocomposites prepared by melt compounding have been studied by using X-ray diffraction (XRD) and transmission electron microscopy (TEM). A combination of XRD and TEM indicates that an exfoliated clay morphology dominates at low clay loadings (≤5 wt%) and a mixture of intercalated and exfoliated structures exists at high clay concentrations. It is worth noting, however, that optical microscopy (OM) even shows the presence of large clay agglomerates in samples with higher clay contents. OM images further present an overview of an uneven clay distribution due to the effect of injection molding. The crystalline structure of PA6 is greatly affected by this unevenness in the processing-induced clay dispersion, as evidenced by differential scanning calorimetry (DSC). The thermal dynamic and mechanical properties of PA6 and the nanocomposites have been investigated as a function of clay concentration. The tensile tests show that the degree of dispersion of the nanoclay within the polymer matrix plays a vital role in property improvement. Copyright © 2004 Society of Chemical Industry     

Effects of nanotalc inclusion on mechanical,microstructural, melt shear rheological,and crystallization behavior of polyamide 6‐based binary and ternary nanocomposites

The objective of the study is to investigate the effect of inclusion of nanotalc on the strength properties of polyamide 6 (PA6)‐based binary and ternary nanocomposites. Binary nanocomposites were prepared by melt compounding of PA6 with varying content of nanotalc (1, 2, and 4 wt%). Ternary nanocomposites were prepared by melt compounding of compatibilized blend of PA 6 and ethylene‐co‐butyl acrylate (EBA elastomer) with varying content of nanotalc (1, 2, and 4 wt%). Both the binary and ternary nanocomposites registered a very high improvement in the strength/stiffness‐related properties at lower filler loading of 1 wt%. Phase morphology of the composites studied by SEM, TEM, and XRD revealed the formation of extended brane‐like structures and delaminated talc layers in the binary nanocomposites. The modulus predicted by Halpin‐Tsai and Mooney equation suggests that the composites retained a very good aspect ratio after melt mixing. Orientation effects of nanotalc enhanced the melt flow behavior in the composites. POLYM. ENG. SCI., 50:1978–1993, 2010. © 2010 Society of Plastics Engineers     

Preparation of polypropylene/graphite nanocomposite with the aids of rotating solid‐state mixing and dynamic packing injection molding

In this work, to achieve good dispersion state of graphite in the nonpolar intractable polymer, polypropylene (PP), two specific compounding/molding techniques, rotating solid‐state mixing (RSSM), and dynamic packing injection molding (DPIM), were used during the preparation of PP/graphite nanocomposite. The enhanced dispersion/exfoliation of graphite substance in PP matrix induced by RSSM and/or DPIM treatment was well identified by a combination of polarized optical microscopy, wide‐angle X‐ray diffraction, and scanning electronic microscopy. A comparative analysis indicated that RSSM mainly pulverizes graphite pristine‐particles into tactoids with significantly decreased diameter‐size, while DPIM offers strong melt shear force for exfoliating graphite tactoids into nanosheets whose thicknesses are about tens nanometers and length of 1 micron. Uniform dispersion of graphite nanosheets leaded to substantial increase in heterogeneous crystallization rate and mechanical properties. Our present study proposes a facile effective approach for large‐scale preparation of polymer/graphite nanocomposite with high‐performances. POLYM. COMPOS., 35:1943–1951, 2014. © 2014 Society of Plastics Engineers     

The effect of organoclay on the mechanical properties and morphology of injection‐molded polyamide 6/polypropylene nanocomposites

Nanocomposites containing a thermoplastic blend and organophilic layered clay (organoclay) were produced by melt compounding. The blend composition was kept constant [polyamide 6 (PA6) 70 wt % + polypropylene (PP) 30 wt %], whereas the organoclay content was varied between 0 and 10 wt %. The mechanical properties of the nanocomposites were determined on injection‐molded specimens in both tensile and flexural loading. Highest strength values were observed at an organoclay content of 4 wt % for the blends. The flexural strength was superior to the tensile one, which was traced to the effect of the molding‐induced skin‐core structure. Increasing organoclay amount resulted in severe material embrittlement reflected in a drop of both strength and strain values. The morphology of the nanocomposites was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy‐dispersion X‐ray analysis (EDX), and X‐ray diffraction (XRD). It was established that the organoclay is well dispersed (exfoliated) and preferentially embedded in the PA6 phase. Further, the exfoliation degree of the organoclay decreased with increasing organoclay content. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 175–189, 2004     

Interfacial interactions and performance of polyamide 6/modified attapulgite clay nanocomposites

Attapulgite (AT) clay was firstly treated with sodium polyacrylate (PAS), then polyamide 6 (PA6)/AT nanocomposites were prepared by simple melt compounding. Transmission electron microscope (TEM) and Fourier transform infrared spectrometry (FT‐IR) of treated AT confirm the success of purifying and surface modification of the original AT by PAS. X‐ray diffraction spectra for the nanocomposites show that the microstructure of AT in PA6 matrix is almost unchanged. It indicates that a strong interfacial adhesion exists between AT and PA6 matrix through analyzing fracture surfaces of the nanocomposites, the variation of glass transition temperature (T_g) obtained by dynamic mechanical analysis, and interfacial interaction factors; field emission scanning electron microscopy on the fracture surfaces of the nanocomposites shows that a uniform dispersion of AT is obtained. The above two aspects conform to the improvement of mechanical and thermal properties of the nanocomposites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Effect of clay exfoliation and organic modification on morphological,dynamic mechanical,and thermal behavior of melt‐compounded polyamide‐6 nanocomposites

Polyamide‐6/clay nanocomposites were prepared employing melt bending or compounding technique followed by injection molding using different organically modified clays. X‐ray diffraction and transmission electron microscopy were used to determine the molecular dispersion of the modified clays within the matrix polymer. Mechanical tests revealed an increase in tensile and flexural properties of the matrix polymer with the increase in clay loading from 0 to 5%. C30B/polyamide‐6 nanocomposites exhibited optimum mechanical performance at 5% clay loading. Storage modulus of polyamide‐6 also increased in the nanocomposites, indicating an increase in the stiffness of the matrix polymer with the addition of nanoclays. Furthermore, water absorption studies confirmed comparatively lesser tendency of water uptake in these nanocomposites. HDT of the virgin matrix increased substantially with the addition of organically modified clays. DSC measurements revealed both γ and α transitions in the matrix polymer as well as in the nanocomposites. The crystallization temperature (T_c) exhibited an increase in case of C30B/polyamide‐6 nanocomposites. Thermal stability of virgin polyamide‐6 and the nanocomposites has been investigated employing thermogravimetric analysis. POLYM. COMPOS., 28:153–162, 2007. © 2007 Society of Plastics Engineers     

Melt processing of polyamide 12 and cellulose nanocrystals nanocomposites

The fabrication of nanocomposites of polyamide 12 (PA12) and cellulose nanocrystals (CNCs) isolated from cotton and tunicates is reported. Through a comparative study that involved solution‐cast (SC) and melt‐processed materials, it was shown that PA12/CNC nanocomposites can be prepared in a process that appears to be readily scalable to an industrial level. The results demonstrate that CNCs isolated from the biomass by phosphoric acid hydrolysis display both a sufficiently high thermal stability to permit melt processing with PA12, and a high compatibility with this polymer to allow the formation of nanocomposites in which the CNCs are well dispersed. Thus, PA12/CNC nanocomposites prepared by melt‐mixing the two components in a co‐rotating roller blade mixer and subsequent compression molding display mechanical properties that are comparable to those of SC reference materials. Young's modulus and maximum stress could be doubled in comparison to the neat PA12 by introduction of 10% (CNCs from tunicates) or 15% w/w (CNCs from cotton) CNCs. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42752.     

Nanocrystalline Fe‐Ni alloy/polyamide 6 composites of high mechanical performance made by ultrasound‐assisted master batch technique

The focus of this study is to improve the dispersion state of nanocrystalline (nc) Fe‐Ni particles in polyamide 6 (PA6) matrix and the filler‐matrix interfacial interactions to provide Fe‐Ni alloy/PA6 nanocomposites of remarkable mechanical performance for engineering applications. nc Fe₄₀Ni₆₀ particles were chemically synthesized. Then Fe₄₀Ni₆₀/PA6 nanocomposites of various nanofiller loading were prepared by compounding via a newly modified master batch technique called ultrasound assisted master batch (UMB), followed by injection molding (IM). Their mechanical properties, morphology and structural parameters were characterized and compared with the corresponding properties of Fe₄₀Ni₆₀/PA6 nanocomposites made by solution mixing (SM) and IM. The study reveals that the UMB process is more cost effective and time efficient, simpler and easier to scale up compared with the SM process. In addition, UMB nanocomposites exhibit superior mechanical properties and distinctive morphology compared with the corresponding SM ones. Moreover, structural analyses indicate that physical structural changes occurred in PA6 due to presence of alloy particles are affected differently by the different compounding methods, profound understanding of such phenomenon is focused throughout the article. These distinctive advantages recommend that UMB technique can be of great potential in commercial production of polymer nanocomposites (PNCs). It is concluded that the sonication of nc Fe₄₀Ni₆₀ particles in dilute polymer solution during UMB compounding, a new step that is incorporated for the first time in the master batch process, is mainly responsible for the good wetting between nanoparticles and polymer chains, strong filler‐matrix interactions and consequently the remarkable mechanical performance of UMB PNCs. POLYM. COMPOS., 35:2343–2352, 2014. © 2014 Society of Plastics Engineers     

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.     

Effect of clay on the morphology of blends of poly(propylene) and polyamide 6/clay nanocomposites

PP/NPA6 blends composed of poly(propylene) (PP) and polyamide 6/clay nanocomposites (NPA6) were prepared by twin‐screw extrusion and melt‐drawn into ribbons by a ribbon extrusion process. The influence of clay on the morphology of PP/NPA6 ribbons was investigated by means of field‐emission scanning electron microscopy and optical microscopy. The results show that at low clay content (3, 5 wt%), NPA6 exhibited continuous lamellar structure in PP as pristine PA6 did in a PP/PA6 blend, but at a higher clay content (10 wt%) only ellipsoids or elongated ellipsoids were observed. In order to explain the morphological difference, two factors, ie the compatibilization effect and melt rheology, have been taken into consideration. It has been found that both factors, and probably mainly the variation in melt rheology, were responsible for the morphological difference in the PP/NPA6 blends with different clay contents under the extensional flow field. Copyright © 2004 Society of Chemical Industry     

Location of functionalized-TiO<Subscript>2</Subscript> nanoparticle in an immiscible PP/PA6 blends and its effect on the compatibility of the components

Nanocomposites based on 70/30 (w/w) polypropylene (PP)/polyamide 6 (PA6) immiscible blends and functionalized-TiO₂ nanoparticles were prepared via melt compounding. The influences of TiO₂ on the morphology of nanocomposites were investigated. Scanning electron microscopy results revealed the domain size of the dispersed PA6 phase decreased in presence of functionalized-TiO₂ and the TiO₂ nanoparticles were preferentially located at the PA6 phase and at the interfacial region between PP and PA6, which were ascertained by differential scanning calorimetry. The functionalized-TiO₂ nanoparticles played the compatibilizer for the immiscible PP/PA6 blends, increasing the interaction of the two phases in certain extent. Therefore, a clear compatibiliting effect was induced by the TiO₂ in the immiscible PP/PA6 blends.     

Compounding of nanocomposites by thermokinetic mixing

Nanocomposites have been prepared by melt mixing poly(propylene) (PP) and different levels of a premixed montmorillonite‐organoclay masterbatch (PP/clay concentrate). Melt mixing was achieved using a Gelimat, a high‐speed thermokinetic mixer. The Gelimat system is designed to handle difficult compounding and dispersion applications and can achieve mixing, heating, and compounding of products within a minute. Therefore, the thermal history of the compounded polymer is short, which limits degradation. The structure and properties of the nanocomposites prepared with a Gelimat were compared to ones prepared with a twin‐screw extruder. The structure and properties of PP/clay nanocomposites were compared by TEM, X‐ray diffraction, mechanical testing, and rheological analysis. Results indicate that a better dispersion of the clay can be achieved by thermokinetic mixing when compared to extrusion, resulting in better mechanical properties. Calculations, based on simplifying assumptions, showed that the shear rates generated in a Gelimat are at least one order higher than those generally generated in an extruder. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1557–1563, 2005     

Free‐volume hole properties of two kinds thermoplastic nanocomposites based on polymer blends probed by positron annihilation lifetime spectroscopy

Two type of nanocomposites—an immiscible blend, high density polyethylene/polyamide 6 (HDPE/PA‐6) with organomodified clay, and a compatibilized blend, high density polyethylene grafted with acrylic acid/PA‐6 (PEAA/PA‐6) with organomodified clay—were prepared via melt compounding. X‐ray diffraction and transmission electron microscopy results revealed that the clay was intercalated and partially exfoliated. Positron annihilation lifetime spectroscopy has been utilized to investigate the free‐volume hole properties of two type of nanocomposites. The results show a negative deviation of free‐volume size in PEAA/PA‐6 blend, and a positive deviation in HDPE/PA‐6 blend, and I₃ has a greater negative deviation in compatibilized blend than in immiscible blend due to interaction between dissimilar chains. For nanocomposites based on polymer blends, in immiscible HDPE/PA‐6/organomodified clay system, the variation of free‐volume size with clay content is not obvious and the free‐volume concentration and fraction decreased. While in the case of compatibilized PEAA/PA‐6/organomodified clay nanocomposites, complicated variation of free‐volume properties due to interactions between two phases and organomodified clay was observed. And the interaction parameter β shows the interactions between polymers and organomodified clay. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2463–2469, 2006     

Compatibilizing effect of maleated polypropylene on the mechanical properties and morphology of injection molded polyamide 6/polypropylene/organoclay nanocomposites

Polyamide 6/polypropylene (PA6/PP=70/30 parts) blends containing 4 phr (parts per hundred resin) of organophilic modified montmorillonite (organoclay) were prepared using twin screw extruder followed by injection molding. Maleated polypropylene (MAH-g-PP) was used to compatibilize the blend system. The mechanical properties of PA6/PP nanocomposites were studied through tensile and flexural tests. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to assess the fracture surface morphology and the dispersion of the organoclay, respectively. X-ray diffraction (XRD) was used to characterize the formation of nanocomposites. The thermal properties were characterized by using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The dynamic mechanical properties of PA6/PP nanocomposites were analyzed by using dynamic mechanical thermal analyzer (DMTA). The strength and stiffness of PA6/PP nanocomposites were improved significantly in the presence of MAH-g-PP. This has been attributed to the synergistic effect of organoclay and MAH-g-PP. The MAH-g-PP compatibilized PA6/PP nanocomposites showed a homogeneous morphology supporting the compatibility improvement between PA6, PP and organoclay. TEM and XRD results revealed the formation of nanocomposites as the organoclay was intercalated and exfoliated. A possible chemical interaction between PA6, PP, organophilic modified montmorillonite and MAH-g-PP was proposed based on the experimental work.     

Nanocomposites of polypropylene impact copolymer and organoclays: role of compatibilizers

Nanocomposites of polypropylene impact copolymer and organoclays were prepared using different compatibilizers (polypropylene‐graft‐(maleic anhydride) (PPMA), polyethylene‐graft‐(maleic anhydride) (PEMA) and their mixture) and varying percentages of clay (3 and 6%) in an attempt to obtain balanced mechanical properties. The nanocomposites were prepared by melt compounding and test specimens were prepared by injection molding. Mechanical properties such as tensile, flexural and Izod impact strength are reported. The clay dispersion was investigated using wide‐angle X‐ray diffraction while the phase morphology was characterized using scanning electron microscopy. It is shown that the mechanical properties of the system with mixed PPMA and PEMA compatibilizers showed the best balance of mechanical properties among the nanocomposites explored. Copyright © 2006 Society of Chemical Industry     

Polymer nanocomposites based on needle‐like sepiolite clays: Effect of functionalized polymers on the dispersion of nanofiller,crystallinity, and mechanical properties

Polypropylene (PP)/sepiolite (Sep) nanocomposites are prepared by melt compounding in a mini‐extruder apparatus. The often used maleic anhydride‐modified polypropylene (PP‐g‐MA) is compared with two custom‐made functionalized polymers, PP‐acid and the di‐block copolymer PP‐PEO, with respect to the filler dispersion and filler reinforcement efficiency. For that purpose, morphological and mechanical studies are carried out by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and mechanical tensile tests. In addition, the nanocomposites are characterized by wide‐angle X‐ray scattering (WAXS) and differential scanning calorimetric (DSC) techniques, to assess the effect of the nanofiller on the crystalline structure of the PP matrix nano‐filler. The use of PP‐PEO and PP‐acid resulted in a better nanofiller dispersion compared with traditional PP‐g‐MA‐modified systems. Sepiolite acts as nucleating agent for the crystallization of PP and seems to lead to an orientation of the α‐phase crystals. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Cocontinuous phase morphology for an asymmetric composition of polypropylene/polyamide 6 blend by melt mixing of polypropylene with premelted polyamide 6/organoclay masterbatch

Cocontinuous morphology was obtained for an asymmetric composition of polypropylene/polyamide 6 (70/30 w/w) blend by controlling melt compounding sequence of PP, PA6, and organoclay. Three different compounding sequences were tested: direct melt mixing of all the components, melt mixing of PP with PA6/organoclay masterbatch, and melt mixing of PP with premelted PA6/organoclay masterbatch. Only the third method promotes cocontinuous morphology. In all three cases, organoclay locates preferentially in the PA6 phase and at the interface, although the level of organoclay dispersion is poorer in the case of direct mixing than in the two‐masterbatch approaches. The morphology evolution processes of the three different compounding sequences were investigated and revealed that the main reason for the formation of cocontinuous morphology in the third method is the inhibiting effect of organoclay preincluded in the premelted PA6 phase on phase inversion. The viscosity of PA6 phase and the barrier effect of organoclay were confirmed to be two key factors in promoting cocontinuous structure. Dynamic mechanical analysis shows that the blend having cocontinuous morphology displays higher storage modulus than those having matrix‐dispersed morphology at the same organoclay loading. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011