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     

Effect of Organoclays on Nonisothermal Crystallization Kinetics of Poly (trimethylene terephthalate) Nanocomposite

Non-isothermal crystallization kinetics, melting behavior of virgin PTT and PTT nanocomposites were investigated using differential scanning calorimetry with the Avrami equation. Mechanical properties of PTT/clay nanocomposite is also described with Einstien and Guth model. The rate of crystallization and half time required for crystallization increases with increasing the cooling rate for both virgin PTT and PTT/clay nanocomposites. Virgin PTT shows the double melting behavior which changes to single melting point in prances of C30B nanoclays in the case of PTT/C30B nanocomposites. Incorporation of loading of organoclays increases the activation energy (E_a) in PTT matrix and optimum E_a was observed in PTT/C30B-based system.     

Influences of Functionalized Nanoclays on Morphology and Mechanical Properties of Polyvinyl Alcohol-Based Composites by Twin-Screw Extruder

Polyvinyl alcohol-based nanocomposites filled with different weight percentage of functionalized nanoclays were prepared by melt processing with a twin-screw extruder. The effective incorporation of amine-modified bentonite nanoclays in the PVA matrix leads to the increase in thermal stability, stress–strain properties. The effect of the addition of functionalized nanoclays in PVA matrix exhibits intercalated nanocomposite structure. The thermal decomposition (T_d) temperature of the composites increases up to 30°C, than pristine PVA. The morphology influences were studied by TEM. These clay nanocomposite films could be useful for wound dressing material and for enhancing the moisture absorbance properties.     

Biodegradable PBAT/Starch Nanocomposites

Starch-based biodegradable banocomposites of poly(butylene adipate-co-terephthalate) [PBAT] and organically modified nanoclays were prepared using melt intercalation technique in Haake Torque Rheocord 9000. Two different organically modified nanoclays Cloisite C20A and Cloisite C30B at various wt% (1, 3, 5) have been used for fabrication of nanocomposites. Starch was gelatinized to prepare thermoplastic starch (TPS) for increasing the compatibility with the PBAT matrix. Subsequently, films of PBAT/TPS blends at various TPS contents (10, 20, 30, 40) wt% and PBAT/TPS Organoclay biodegradable blend nanocomposites at different wt% of nanoclays were prepared using solvent casting method. The interfacial region between the biodegradable polymer matrix and the clays were also modified with grafting of Maleic anhydride (MA) with PBAT chains, during melt blending through two stage reactive extrusion process. Mechanical tests revealed an increase in tensile modulus and elongation at break with the incorporation of 30 wt% TPS and C30B nanoclay to the tune of 44.45% and 776.9% as compared with PBAT matrix. PBAT/TPS30 wt%/C30B3wt% shows maximum tensile modulus and elongation at break due to intercalation of silicate layers resulting from similarity in the surface polarity and interactions of C30B with TPS. Morphology of PBAT/TPS30%/C30B3% biodegradable blend nanocomposite studied using WAXD and SEM indicated intercalation and improved dispersion of TPS within PBAT with incorporation of C30B. Dynamical mechanical analysis of PBAT/TPS/C30B biodegradable blend nanocomposite revealed an increase of storage modulus and glass transition temperatures of PBAT with addition of nanoclays. Further Biodegradation test also confirmed higher biodegradability of PBAT in presence of TPS and C30B.     

Effect of processing conditions on the structural morphology of PP–EP/EVA/organoclay ternary nanocomposites

The effect of processing conditions on the morphology of heterophasic PP–EP/EVA/organoclay ternary nanocomposites was examined. The nanocomposites were prepared in a co-rotating twin screw extruder with different screw configurations and incorporation methods. Three different sizes of EVA granules were used. The results obtained by X-ray scattering (WAXD) and electronic microscopy (TEM) showed an increase in d spacing value of the clay associated with the polar interactions between the vinyl acetate of EVA and the surface of the nanoclays. In addition, some chains of the non-polar copolymer PP–EP may have become intercalated into the clay galleries as a result of polymer diffusion induced by shear stress during melt mixing. An increase in surface area of EVA granules resulted in a more homogenous clay dispersion and intercalation. The morphologic changes resulted in an increase in heat distortion temperature (HDT) and flexural modulus of the ternary nanocomposites.     

Poly(lactic acid) and layered silicate nanocomposites prepared by melt mixing: Thermomechanical and morphological properties

Poly(lactic acid) (PLA) nanocomposites were prepared by melt mixing technique in a Haake batch mixer. The clay dispersion within the PLA matrix during melt mixing was well explained through the morphological characterization. Morphological characterizations were studied by X‐ray diffraction and transmission electron microscopy. The exfoliation/intercalation of the clay particles within the polymer matrix during melt mixing depends on the mixing torque generated during the preparation of nanocomposites. The significance of processing temperature and the mixing time in melt mixing were studied for PLA/C93A and PLA/C30B nanocomposites. The structure and properties of the nanocomposites were also characterized by differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, and mechanical properties by standard tensile testing. The incorporation of nanoclays into the PLA matrix enhanced the mechanical properties and thermal stability of the PLA nanocomposites. This may be due to the reinforcing effect of nanoclays within the polymer matrix. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Using a β-Cyclodextrin-functional Fe3O4 as a Reinforcement of PLA: Synthesis,Thermal, and Combustion Properties

In this work, Fe₃O₄ nanoparticles were chemically grafted with β-cyclodextrin (β-CD@Fe₃O₄). Fe₃O₄ nanoparticles were modified using N,N-dimethylformamide as a solvent, β-cyclodextrin as a modifier, and 3-glycidoxypropyltrimethoxysilane as a coupling agent at room temperature. The obtained modified Fe₃O₄ were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis techniques. β-CD@Fe₃O₄ was incorporated into a poly(lactic acid) matrix to prepare new green nanocomposites with modified properties. β-CD@Fe₃O₄ showed good dispersion in the poly(lactic acid) matrix and thermal and combustion properties of the nanocomposites were improved.     

Effect of Clay Types on the Mechanical,Dynamic Mechanical and Morphological Properties of Polypropylene Nanocomposites

In the present investigation Polypropylene–Maleic anhydride grafted polypropylene–organically modified MMT (PP-MAPP-OMMT) nanocomposites were prepared by melt mixing in a twin screw extruder followed by injection molding. The effect of clay chemistry and compatibilizer on the properties of the nanocomposites has been studied. Sodium montmorillonite has been organically modified using quaternary and alkyl amine intercalants. A comparative account with commercial quaternary ammonium modified clays i.e Cloisite 20A, Cloisite 15A and Cloisite 30B has been presented. Storage modulus of PP matrix also increased in the nanocomposites, indicating an increase in the stiffness of the matrix polymer with the addition of organically modified nanoclays. The morphology of the nanocomposites has been examined using wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM). Morphological findings revealed efficient dispersion of organically modified nanoclays within the PP matrix. MAPP compatibilized PP/Cloisite 15A nanocomposites displayed finely dispersed exfoliated nanomorphology as compared with other systems.     

Impact modification of poly(trimethylene terephthalate)/polypropylene blend nanocomposites: Fabrication and characterization

A poly(trimethylene terephthalate) (PTT)/polypropylene (PP) blend and the nanocomposites were prepared with and without the addition of a compatibilizer precursor [maleic anhydride grafted polypropylene (MAPP)]. A reactive route was used for the compatibilization with the addition of MAPP during melt blending in a batch mixer. Organically modified nanoclays were used as nanoscale reinforcements to prepare the blend nanocomposites. Mechanical tests revealed optimum performance characteristics at a PTT/PP blend ratio of 80 : 20. Furthermore, incorporation of nanoclays up to 3 wt % showed a higher impact strength and higher tensile strength and modulus in the blend nanocomposites compared to the optimized blend. The nanocomposite formation was established through X‐ray diffraction and transmission electron microscopy (TEM). Thermal measurements were carried out with differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC thermograms revealed an increase in the crystallization temperature in the presence of the nanoclays in the blend system containing Cloisite 30B. TGA thermograms also indicated that the thermal stability of blend increased with the incorporation of Cloisite 30B. Furthermore, dynamic mechanical analysis measurements showed that the Cloisite 30B nanocomposite had the maximum modulus compared to other nanocomposites. TEM micrographs confirmed an intercalated morphology in the blend nanocomposites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of compatibilizer and organoclay content on structure,thermal, and mechanical properties of poly(butylene succinate)/(Ethylene acrylic acid)/Organoclay nanocomposites

Poly(butylene succinate) (PBS)/(ethylene acrylic acid) (EAA)/organoclay nanocomposites were prepared by using the melt intercalation technique. EAA was used as compatibilizer and organoclay was used as inorganic filler. X‐ray diffraction and transmission electron microscopy results indicated the addition of compatibilizer led to a large increase in basal spacing of nanocomposites and better overall dispersion of organoclay in the PBS matrix. However, the basal spacing was found to be invariant as the organoclay content increased. The differential scanning calorimetry analyses revealed that the incorporation of the organoclay and EAA and the variation of organoclay content altered the melting behavior and crystallization properties of PBS. Storage and loss modulus of virgin matrix increased with the incorporation of organoclay and EAA, and a maximum for the nanocomposite with 9 wt% organoclay. Moreover, the glass transition temperatures also increased for the various organoclay‐containing samples. Mechanical properties showed an increase with the incorporation of organoclay and EAA. The 5 wt% organoclay‐filled PBS gave the highest tensile strength and notched Izod impact strength among all the composites. Further increments in organoclay loading reduced the tensile strength and notched impact strength of nanocomposites, which was thought to be the result of agglomeration. However, increments in clay loading enhanced the flexural strength and flexural modulus of nanocomposites, with a maximum at 9 wt% organoclay. J. VINYL ADDIT. TECHNOL., 23:219–227, 2017. © 2015 Society of Plastics Engineers     

Structures and Performance of White Clay-Filled Isotactic-Polypropylene Composites Prepared by Double-Molding Techniques

Various contents of Bangladeshi white clay (WC)-filled Isotactic polypropylene (iPP) composites were fabricated by double-molding techniques. Scanning electron micrographs shows a good impact between iPP matrix and fillers. X-diffraction and IR spectroscopic measurements reveal that inclusion of fillers develops an additional γ-crystal along with the α- and β-crystals that are merely observed in the neat iPP. Young's modulus and microhardness are found to increase with increasing WC content. Thermal analyses represent a considerable increase of thermal stability of the composites with filler addition. Appearance of new crystalline phase by filler inclusion and performances of the composites are discussed in detail.     

Dispersion of nanoclays with poly(ethylene terephthalate) by melt blending and solid state polymerization

Melt intercalation of clay with poly(ethylene terephthalate; PET) was investigated in terms of PET chain mobilities, natures of clay modifiers, their affinities with PET, and nanocomposite solid state polymerization (SSP). Twin screw extrusion was used to melt blend PET resins with intrinsic viscosities of 0.48, 0.63, and 0.74 dL/g with organically modified Cloisite 10A, 15A, and 30B montmorillonite clays. Clay addition caused significant molecular weight reductions in the extruded PET nanocomposites. Rates of SSP decreased and crystallization rates increased in the presence of clay particles. Cloisite 15A blends showed no basal spacing changes, whereas the basal spacings of Cloisite 10A and Cloisite 30B nanocomposites increased after melt extrusion, indicating the presence of intercalated nanostructures. After SSP these nanocomposites also exhibited new lower angle X‐ray diffraction peaks, indicating further expansion of their basal spacings. Greatest changes were seen for nanocomposites prepared from the lowest molecular weight PET and Cloisite 30B, indicating its greater affinity with PET and that shorter more mobile PET chains were better able to enter its galleries and increase basal spacing. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and characterization of nylon 6/clay nanocomposites prepared by ultrasonication and in situ polymerization

Nylon 6 nanocomposites were prepared by the in situ polymerization of ε‐caprolactam with ultrasonically dispersed organically modified montmorillonite clay (Cloisite 30B®). Dispersions of the clay platelets with concentrations in the range 1–5 wt % in the monomer were characterized using rheological measurements. All mixtures exhibited shear‐thinning, signifying that the clay particles were dispersed as platelets and forming a “house of cards” structure. Samples with Cloisite concentrations above 2 wt % showed a drop in viscosity between the initial shearing and repeated shearing, indicative of shearing breaking down the initial “house of cards” structures formed on sonication. DMTA measurements of the samples showed an increase in the β‐relaxation temperature with increasing clay concentration. The bending modulus, at temperatures below T_g, showed an increase with increasing clay concentration up to 4 wt %. X‐ray diffraction measurements showed that all nylon 6/Cloisite 30B samples were exfoliated apart from the 5 wt %, which showed that some intercalated material was present. The nylon crystallized into the α‐crystalline phase, which is the most thermodynamically stable form. Preference for this form may be a consequence of the long time associated with the postcondensation step in the synthesis or the influence of the platelets on the nucleation step of the crystal growth. DSC measurements showed a retardation of the crystallization rate of nanocomposite samples when compared with that of pure nylon 6, due to the exfoliated clay platelets hindering chain movement. This behavior is different from that observed for the melt‐mixed nylon 6/clay nanocomposites, which show an enhancement in the crystallization rate. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Use of acrylic based surfmers for the preparation of exfoliated polystyrene–clay nanocomposites

Two polymerizable cationic surfactants, (11-acryloyloxyundecyl)dimethyl(2-hydroxyethyl)ammonium bromide (hydroxyethyl surfmer) and (11-acryloyloxyundecyl)dimethylethylammonium bromide (ethyl surfmer), were used for the modification of montmorillonite (MMT) clay. The modification of MMT dispersions was carried out by ion exchange of the sodium ions in Na⁺-MMT by surfactants in aqueous media. Modified MMT clays were then dispersed in styrene and subsequently polymerized in bulk by a free-radical polymerization reaction to yield polystyrene–clay nanocomposites. An exfoliated structure was obtained using the ethyl surfmer-modified clay, whereas a mixed exfoliated/intercalated structure was obtained using the hydroxyethyl surfmer-modified clay. Nanocomposite structures were confirmed by small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The nanocomposites exhibited enhanced thermal stability and an increase in glass transition temperature, relative to neat polystyrene. The nanocomposites also exhibited enhanced mechanical properties, which were dependent on the clay loading. Intercalated polystyrene–clay nanocomposites were obtained using the non-polymerizable surfactant-modified clay (cetyltrimethylammonium bromide). Nanocomposites made from mixtures of surfmer-modified and CTAB-modified clays were also prepared, showing intermediate properties. However, when the nanocomposites were prepared in solution only intercalated morphologies were obtained. This was attributed to the competition between the solvent molecules and monomer in penetrating into clay galleries. These nanocomposites also exhibited enhanced thermal stability relative to the virgin polystyrene prepared by the same method. Similar temperatures of degradation (at 50% decomposition) were found for these nanocomposites relative to those prepared by bulk polymerization.     

Influence of nanoclays on electrical and morphological properties of thermoplastic polyurethane/multiwalled carbon nanotube/clay nanocomposites

Nanocomposites of thermoplastic polyurethanes (TPUs), multiwalled carbon nanotubes (MWCNTs) and clays were prepared via melt processing using polyether‐ and polyester‐based TPUs, MWCNTs, and organically modified nanoclays (Cloisite C30B and C25A). Coaddition of clays and MWCNTs to TPU nanocomposites increased their electrical conductivities above those without any clay. Nanoclay alone is shown to produce no effect on electrical conductivity. TEM results show that the coaddition of nanoclay affects the nanocomposite morphology by changing the MWCNT distribution. Clay C25A and MWCNTs were observed to form network structures in the nanocomposites, resulting in improved electrical conduction. Interaction between MWCNTs and clays as well as an increase in nanocomposite viscosity caused by the coaddition of clays may influence the morphology change. Most of the nanocomposites containing both MWCNTs and clay exhibited higher dielectric constants, indicating higher electrical conductivities. Tensile properties investigations confirmed the reinforcing effects of the MWCNTs and clays. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of modified layered silicates on the confined crystalline morphology and thermomechanical properties of poly(ethylene oxide) nanocomposites

In this work, poly(ethylene oxide) (PEO)/organoclay nanocomposites with three different types of nanoclays (Cloisite 30B, Somasif JAD400, and Somasif JAD230) were prepared by melt mixing with a laboratory kneader followed by compression molding. The nanocomposites were characterized by atomic force microscopy and scanning electron microscopy. Their crystallization behavior on a hot stage was investigated with polarized optical microscopy. The size and regularity of the spherulites of the PEO matrix were altered significantly by the incorporation of Cloisite 30B, but there was not as much variation with the other two clays. The dynamic viscoelastic behavior of the PEO/organoclay nanocomposites was assessed with a strain‐controlled parallel‐plate rheometer. The effects of clay modification on the thermomechanical and rheological properties were addressed. The reinforcing effect of the organoclay was determined with dynamic mechanical analysis and tensile testing. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Morphological and Functional Expression of Fibroblast on Poly(lactide-co-glycolide)/β-Tricalcium Phosphate/Nature Bone

The in-vitro biocompatibility of degradable and bioactive composites consisting of poly(lactide-co-glycolide) (PLGA), β-tricalcium phosphate (β-TCP), and nature bone (NB) was investigated by culturing fibroblasts on the PLGA/β-TCP/NB substrates, and the cell morphology, proliferation, alkaline phosphatase (ALP) activity, and von Kossa mineralization were evaluated. The results showed that the incorporation of β-TCP and NB benefited fibroblasts attachment and the fibroblasts cultured on the PLGA/β-TCP/NB composite substrates spread better as compared to those on the pure PLGA after culturing for different times. MTT assay showed that the fibroblasts cultured on the PLGA/β-TCP/NB extraction revealed a higher proliferation rate than those on the pure PLGA extraction. ALP and von Kossa assay indicated that β-TCP and NB could promote biomineralization in vitro. All of the results showed that the addition of β-TCP and NB into PLGA could stimulate fibroblasts to proliferate and differentiate.     

Mechanical response and rheological properties of polycarbonate layered‐silicate nanocomposites

The effect of clay loading on the mechanical behavior and melt state linear viscoelastic properties of intercalated polycarbonate (PC) nanocomposites was investigated. At low frequencies, the linear dynamic oscillatory moduli data revealed diminished frequency dependence with increasing nanoclay loading. The 3.5 and 5 wt% clay nanocomposites exhibited dramatically altered relaxation behavior, from liquid‐like to pseudo‐solid–like, compared to the pure PC and the 1.5 wt% clay nanocomposite. Thermal degradation of PC resulted from the melt compounding of organo‐modified nanoclays was evident from the reduction in the glass transition temperature and molecular weight of the PC nanocomposites. These nanocomposites also exhibited a significant decrease in the extent of tensile elongation and ductility with respect to the nanoclay incorporation. A concomitant decrease in the rheological properties at high frequencies was also observed, and was consistent with the lowering of the molecular weight of PC, particularly near or above the percolation threshold of nanoclay. These nanocomposites, nevertheless, exhibited elastic‐plastic deformation in compression, regardless of nanoclay content. Polym. Eng. Sci. 44:825–837, 2004. © 2004 Society of Plastics Engineers.     

Poly(lactic acid)–layered silicate nanocomposites: The effects of modifier and compatibilizer on the morphology and mechanical properties

Poly(lactic acid) (PLA) based nanocomposites were prepared to investigate the effects of types of nanoclays. Five different organically modified nanoclays (Cloisites^®15A, 25A, and 30B, and Nanofils^®5 and 8) were used. Two rubbery compatibilizers, ethylene‐glycidyl methacrylate (E‐GMA) and ethylene‐butyl acrylate‐maleic anhydride, were used in the nanocomposites as compatibilizer‐impact modifier. The degree of clay dispersion, the chemical compatibility between the polymer matrix and the compatibilizers, and changes in the morphology and mechanical properties of the nanocomposites were investigated. The mechanical properties and the morphological studies showed that the interactions between the different compatibilizers and PLA resulted in different structures and properties; such that the dispersion of clay, droplet size of the compatibilizer, and tensile properties were distinctly dependent on the type of the compatibilizer. Compatibility between C25A, C30B, and E‐GMA resulted in the best level of dispersion, leading to the highest tensile modulus and toughness among the compositions studied. In the mentioned nanocomposites, a network structure was formed owing to the high reactivity of the epoxide group of GMA towards the PLA end groups resulting in high impact toughness. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42553.     

Preparation and characterization of high performance exfoliated montmorillonite/silicone rubber nanocomposites with enhanced mechanical properties

Highly exfoliated and intercalated silicone rubber (SR) nanocomposites based on natural montmorillonite (Cloisite Na⁺) and organically modified montmorillonite (Cloisite 30B and Cloisite 20A) were successfully prepared by melt‐mixing technique. Dispersion of the nanoclays in the rubber nanocomposites was subsequently investigated. As indicated by the X‐ray diffraction (XRD) analysis, intercalation, and exfoliation of the clay particles in the nanocomposites was achieved at less than 8 parts per hundred (phr) rubber by weight, irrespective of the initial interlayer spacing of the nanoclay particles. Both Cloisite Na⁺ and Cloisite 30B were spontaneously transformed into exfoliated microstructures during the vulcanisation stage. Overall, the use of the nanoclays in silicone rubber improved the Young's modulus, tensile strength, and elongation at break by more than 50% as compared with the control rubber. In addition, this work provided a fresh insight into the way intercalated and exfoliated morphologies affect mechanical properties of silicone rubber nanocomposites. It was shown that the exfoliated Cloisite Na⁺ yielded outstanding mechanical properties with low hysteresis at the same loading of the exfoliated Cloisite 30B and intercalated Cloisite 20A organoclays. As expected, the formation of crosslinks affected the mechanical properties of the rubber vulcanizate significantly. POLYM. ENG. SCI., 53:2603–2614, 2013. © 2013 Society of Plastics Engineers