Organo-montmorillonite Nanocomposites Research Articles

The effect of controlled intercalation on the mechanical performances and dimensional accuracy of material extrusion additive manufactured poly(lactic acid)/organo-montmorillonite nanocomposites

Although the material extrusion-based 3D printing (MEX-3DP) has the ability to construct functional complex nanocomposites based on two-dimensional (2D) nanomaterials, however, the interplay of exfoliation degree of 2D materials and MEX-3DP parameters has not been elucidated, which seriously limits the further design and application of MEX-3DP 2D materials towards low-cost device fabrication. In this report, we use the well-studied organo-montmorillonite (MMT) as model materials and systematically studied the effect of various intercalation degrees on the mechanical and geometrical performance of MEX-3DP organo-MMT reinforced poly (lactic acid) nanocomposites. It was elucidated that, different from traditional injection moulding process, the best performance of MEX-3DP samples is obtained from completely exfoliated organo-MMT. The effect of the intercalation degrees is correlated with the melt flowability, thermal expansion and the resulting voids size that essential for MEX-3DP processes. The structure and rheology analysis demonstrate that the high exfoliation degree of 2D materials is essential to compensate the weak interfacial bonding or shrinkage-induced poor mechanical properties. The findings provide a detailed insight into the 2D materials exfoliation on the MEX-3DP quality, which is meaningful for engineers willing to design MEX-3DP functional 2D materials, for next generation disruptive technologies and applications.

The impact of organo‐montmorillonite on rheology and crystalline structure of uncured and cured acrylonitrile‐butadiene rubber/poly(ethylene‐co‐vinyl acetate) nanocomposites

AbstractThe aim of this study was to evaluate the influence of organo‐montmorillonite (OMMT) content on rheology, crystalline structure, and also hardness and tensile properties of uncured and lightly cured acrylonitrile‐butadiene rubber (NBR)/poly(ethylene‐co‐vinyl acetate) (EVA)/OMMT nanocomposites. The nanocomposites containing 0 to 7 wt% OMMT was prepared and then cured with 0.3 wt% dicumyl peroxide. The low‐angle X‐ray diffraction results revealed that curing clearly improved the degree of exfoliation in the materials having high OMMT content. It was found from the hardness and tensile tests that the values of hardness, tensile strength, modulus, and energy at break were higher for the cured nanocomposites than those of the uncured materials in the range of OMMT examined. The results obtained from the Casson plot revealed that the nanofiller played a more effective role in increasing the yield stress of the uncured materials than that of the cured counterparts at a constant OMMT content. The characteristic relaxation time was also progressively increased with OMMT content for the uncured materials; however, the value was higher for the cured materials and it was much less sensitive to the nanofiller content. The I110/I200 peak intensity ratio of EVA calculated from the wide‐angle X‐ray diffraction patterns decreased with increasing in OMMT content for the uncured and cured materials; however, the value was always higher for the cured counterparts.

Poly(lactic acid)/Organo-Montmorillonite Nanocomposites: Synthesis, Structures, Permeation Properties and Applications

Polylactic acid (PLA)/organo-montmorillonite nanocomposites were prepared by the solution casting method using chloroform as solvent. The clays were organically modified by four different modifiers, ternary amine with two alkyl (tallow) tails, primary amine containing silane with a single tail, ammonium salt with a single alkyl (tallow) tail, and ammonium salts with two alkyl (tallow) tails. The structural characterization of the nanocomposite films was performed using Raman spectroscopy and the internal structure of the nanocomposites in the nanometer range was studied using wide-angle X-ray diffraction analysis. All the nanocomposites exhibited superior improvement when compared to neat PLA. Differential scanning calorimetry (DSC) was performed to study the thermal behavior of the prepared composites. Among the used clay types, M24 was the most effective in improving the water vapor and oxygen barrier properties. Water vapor and oxygen permeability of the nanocomposite films were decreased up to 80 and 49% when using M24 clay, respectively. Surface properties of the films were investigated with dynamic contact angle measurements. The migration studies of neat PLA and nanocomposites were performed for three types of food simulants.

Porous lignin based poly (acrylic acid)/organo-montmorillonite nanocomposites: Swelling behaviors and rapid removal of Pb (II) ions

Lignin grafted N, N′-methylene-bisacrylamide (LM) was copolymerized with acrylic acid (AA) to fabricate lignin based poly (acrylic acid) (LBPAA) nanocomposites, and organo-montmorillonite (OrgMMT) was uniformly dispersed in LBPAA by ultrasonic method. The water absorbency in KCl solution was 302.9 g/g for LBPAA/OrgMMT (3 wt% OrgMMT, 43.65 wt% LM, and 53.35 wt% poly(acrylic acid) (PAA)), higher than PAA/OrgMMT (104.5736 g/g), and PAA (131.8 g/g). The Pb2+ adsorption for LBPAA/OrgMMT was demonstrated to be pH-dependent and followed Freundlich multilayer adsorption, with the removal following a pseudo-second-order kinetic model. The Pb2+ absorption capacity of LBPAA (PAA 48.50/48.50 LM)/OrgMMT (3 wt%) was 1.0803 mmol·g−1, the highest among the composites. When the mole ratio of Na+ and Pb2+ was less than 0.21, the Pb2+ adsorption capacity of LBPAA/OrgMMT decreased slightly. The negative ΔG0 indicated that the Pb2+ adsorption process for composite hydrogel and PAA was spontaneous. XPS analysis data indicated that Pb2+ ions formed Pb-O bonds by hydroxyl groups and carboxyl groups for efficient lead ion adsorption. This study demonstrates that LBPAA/OrgMMT can be used as a water retention agent with salt tolerance and as an adsorbent for removing Pb2+ ions from industrial waste water.

Evaluation of the genotoxic potential of modified clays destined to food packaging through the micronucleus assay

Maleated poly(propylene carbonate) (PPC-MA)/organo-montmorillonite (OMMT) nanocomposites were first prepared via melt end-capping poly(propylene carbonate) (PPC) with maleic anhydride (MA) and melt-mixing the PPC-MA with commercial OMMT without and with hydroxyl groups in surfactants: Cloisite 20A (C20A) and Cloisite 30B (C30B), respectively. Intercalated and partially delaminated morphologies were corroborated via X-ray diffraction (XRD) and transmission electron microscopy (TEM). Dynamic mechanical analysis (DMA) revealed that PPC-MA was evidently reinforced by the partially delaminated C30B platelets. From XRD patterns of statically annealed PPC-MA/C20A and PPC-MA/C30B mixtures and Fourier transform infrared (FTIR) results of equivalent nanocomposites, partial delamination of C30B in PPC-MA was confirmed to be relevant to diffusion of PPC-MA molecular chains in C30B galleries, grafting of PPC-MA to C30B platelet surfaces and further separation of C30B platelets.

Preparation and properties of natural rubber/organo-montmorillonite: from lab samples to bulk material

<p>Focusing on application aspects of the rubber nanocomposites and the production and testing of industrial-sized samples, this study was performed in two phases. First, natural rubber (NR)/organo-montmorillonite (OMMT) nanocomposites containing 2–14 phr OMMT were prepared on a laboratory-sized two-roll mill. The vulcanization behavior and mechanical properties of NR/OMMT composites were compared with a referent NR compound containing 60 phr carbon black (N330) as a reinforcing filler. The x-ray diffraction (XRD) analyses showed a predominant intercalated structure for all OMMT nanocomposites. As a result, the organoclay behaved as an effective reinforcement for NR, even at loadings as low as 2 phr. This nanocomposite exhibited an improvement in tensile strength of 29% and in elongation at break of 61% in comparison with the referent NR/N330 compound. With the estimated optimal filler content, in the second phase, bulk NR/OMMT-5/steel samples were successfully produced for dynamic testing. The dynamic moduli were investigated by the method of forced vibrations. Compared to the NR/N 330 samples, NR/OMMT-5 samples showed improved hysteresis, with very low dissipating energy per cycle and significantly reduced Mullins effect.</p>

A study on the effects of organoclay content and compatibilizer addition on the properties of biodegradable poly(butylene succinate) nanocomposites under natural weathering

Biodegradable poly(butylene succinate)/organo-montmorillonite nanocomposites were prepared at different organo-montmorillonite loadings, using maleic anhydride-grafted poly(butylene succinate) as compatibilizer. Poly(butylene succinate) nanocomposites were exposed to outdoor natural weathering for 180 days. Weight loss and decrease in mechanical properties after weathering revealed the degradation of poly(butylene succinate). Natural weathering caused photo-oxidation on poly(butylene succinate), leading to the formation of degraded products, as manifested in Fourier transform infrared spectroscopy. Gel permeation chromatography showed a significant reduction in molecular weight after weathering. It was noted that poly(butylene succinate) nanocomposite exhibited lower degradability as compared to neat poly(butylene succinate), due to the enhanced barrier properties after the addition of organo-montmorillonite. However, the incorporation of maleic anhydride-grafted poly(butylene succinate) increased the degradability. Degree of crystallinity of poly(butylene succinate) reduced after weathering, as shown in differential scanning calorimetry. Scanning electron microscopy analysis revealed fungal and bacterial colonization on the sample surface. In addition, the isolation and identification of bacterial strain were also performed.

Study on thermal stability and flame retardancy of polymer/layered silicate nanocomposites based on POE and POE‐g‐MAH

Ethylene‐octene elastomer (POE)/organo‐montmorillonite (OMT) and maleic anhydride‐grafted POE (POE‐g‐MAH)/OMT composites were prepared through melt mixing and influence of clay dispersion on thermal, dynamic mechanical, and flammability properties were investigated. The results showed that OMT forms intercalated/exfoliated structures in POE‐g‐MAH/OMT and agglomerated structure in POE/OMT microcomposites, resulting in more significant improvements of storage modulus and glass transition temperature in the POE‐g‐MAH/OMT rather than the POE/OMT composites. The POE‐g‐MAH/OMT nanocomposites have better thermal stability and significantly reduced flammability than the POE/OMT microcomposites, which was discussed on the basis of cone colorimeter test of the composites and energy dispersive X‐ray spectrum analysis of the combustion chars. POLYM. ENG. SCI., 54:2911–2917, 2014. © 2014 Society of Plastics Engineers

Functional copolymer/organo-MMT nanoarchitectures: self-assembled core-shell morphology of poly(maleic anhydride-alt-α-olefin)/organo-MMT nanocomposites

This work describes the TEM morphology analysis of amphiphilic alternating copolymers of maleic anhydride (MA) with different α-olefins (1-hexene, 1-octene, 1-dodecene) synthesized by radical-initiated intercalative copolymerization of preintercalated MA···organoclay complexes in the presence of two types of organoclay such as reactive octadecyl amine-montmorillonite (ODA-MMT) and nonreactive dimethyldidodecyl ammonium-MMT (DMDA-MMT). TEM analyses of all the nanocomposites indicate the formation of symmetric or non-symmetric core-shell morphologies. Energy dispersive X-ray spectroscopy analyses were used to study the occurrence of the element in the poly(MA-alt-α-olefin)/organo-montmorillonite nanocomposites. A role of surfactant in these nanosystems insists on alternating copolymer segments with given hydrophobic/hydrophilic balance and surface organo-modifiers of MMT clays. Highly organized self-assembly with symmetric core-shell morphology were formed in nanosystems prepared in the presence of DMDA-MMT clay as compared with ODA-MMT clay-containing nanosystems. The relatively long branched olefin fragments significantly improve image parameters of core-shell morphology where some of the core structures contain accumulated and finely dispersed silicate particles at nano level around 2–25 nm. This observed phenomenon has brought a new approach for future utilization of these nanosystems in controlled drug delivery and anticancer applications with essentially prolonged activity.

Effects of N,N′-Ethylenebis(stearamide) on the Properties of Poly(ethylene terephthalate)/Organo-montmorillonite Nanocomposite

Poly(ethylene terephthalate)/organo-montmorillonite (PET/OMMT) nanocomposites were melt-compounded using twin screw extruder followed by injection molding. N,N′-ethylenebis(stearamide) (EBS) was selected as a dispersing agent to improve the dispersibility and exfoliation of OMMT clay in PET matrix. Morphological properties of the PET/OMMT nanocomposites were examined by using X-ray diffraction analysis, transmission electron microscopy and atomic force microscopy. Thermal properties of the nanocomposites were characterized by using dynamic mechanical thermal analysis. It was found that the OMMT are well dispersed and exfoliated in the presence of EBS. Remarkable enhancement in impact strength and storage modulus of PET/OMMT was achieved by the addition of EBS.

Properties of Poly(Lactic Acid)/ Organo-Montmorillonite Nanocomposites Prepared by Solution Intercalation

Poly(lactic acid)/organo-montmorillonite (PLA/OMMT) nanocomposite films were prepared through solution intercalation using dichloromethane as solvent. X-ray diffraction indicated that organo-montmorillonite (OMMT) was well intercalated and the interlayer spacing d increased by 0.94–1.47 nm. Transmission Electron Microscopy showed that a majority of OMMT was fully exfoliated and uniformly dispersed in the PLA matrix at low filler loading, whereas more intercalated tactoids and aggregates of OMMT existed at high loading. The crystallinity of PLA was hardly changed with the addition of OMMT. Additionally, CO2 permeability and water vapor transmission rate of the composite films were reduced with increasing content of OMMT. At 5 wt% OMMT loading, CO2 permeability and water vapor transmission rate were reduced by 75.8% and 23.9%, respectively. The tensile strength (TS) and Young's modulus of the PLA/OMMT nanocomposites were first enhanced, and then decreased with increasing content of OMMT. Compared with pure PLA, a 83.8% increase in the Young's modulus and a 76.0% improvement in TS were obtained with the addition of 3 wt% OMMT.

Effect of polymer matrix/montmorillonite compatibility on morphology and melt rheology of polypropylene nanocomposites

AbstractIn this study, Ca2+‐montmorillonite (Ca2+‐MMT) and organo‐montmorillonite (OMMT) were modified by three compatibilizers with different degrees of polarity [poly(ethylene glycol) (PEG), alkyl‐PEG, and polypropylene (PP)‐g‐PEG]. PP/MMT nanocomposites were prepared by melt blending and characterized using X‐ray diffraction and transmission electron microscopy. The results showed the degree of dispersion of OMMT in the PP/PP‐g‐PEG/OMMT (PMOM) nanocomposite was considerably higher than those in the PP/PEG/OMMT and PP/alkyl‐PEG/OMMT nanocomposites, which indicated that the dispersion was relative to the compatibility between modified OMMT and PP matrix. Linear viscoelasticity of PP/MMT nanocomposites in melt states was investigated by small amplitude dynamic rheology measurements. With the addition of the modified MMT, the shear viscosities and storage modulus of all the PP/MMT nanocomposites decreased. It can be attributed to the plasticization effect of PEG segments in the three modifiers. This rheological behavior was different from most surfactant modified MMT nanocomposites which typically showed an increase in dynamic modulus and viscosity relative to the polymer matrix. The unusual rheological observations were explained in terms of the compatibility between the polymer matrix and MMT. In addition, the mechanical properties of PP/MMT nanocomposites were improved. A simultaneous increase in the tensile strength and toughness was observed in PP/PMOM nanocomposites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Synthesis and properties of epoxy resin-based acrylated poly (ester-amide)s/silane tailored organo-montmorillonite nanocomposites

Epoxy resin-based unsaturated poly(ester-amide) (UPEA) resins can be prepared by many methods, but in this study, these resins were prepared by the reported method and further acrylation was carried out using acryloyl chloride. Organo-montmorillonite was treated with 3-amino-propyltrimethoxysilane. Nanocomposites composed of UPEA matrix and organically modified clay filler were prepared by hand lay-up. The flexural property of the nanocomposites were determined, and it was found that adding only 3% w/w organically modified clay improved the flexural modulus of UPEA by 35%. Nanocomposites were characterized by x-ray diffraction, differential scanning calorimetry and scanning electron microscopy.

Radiation induced modification of NBR and SBR montmorillonite nanocomposites

Nanocomposites of two different kinds of rubber (acrylonitrile-butadiene rubber NBR and styrene butadiene rubber SBR)/organo-montmorillonite nanocomposites modified by hexadecyltrimethyl ammonium bromide were prepared by the reactive mixing intercalation method in the presence of trimethylolpropane trimethylmethacrylate (TMPTMA). The influence of gamma irradiation on the morphology and properties of the rubber nanocomposites was investigated. Intercalated polar or unsaturated matrices (e.g., NBR and SBR)/OMMT nanocomposites can be obtained, which was confirmed by X-ray diffraction (XRD). The clay layers could be uniformly dispersed in the rubber matrix on the nanometer level. Mechanical tests showed that the nanocomposites had good mechanical properties as compared to the neat composites. The results also showed that the irradiated NBR/OMMT nanocomposites had higher thermal stabilities than irradiated SBR/OMMT nanocomposites.

Biodegradability studies of poly(butylene succinate)/organo-montmorillonite nanocomposites under controlled compost soil conditions: Effects of clay loading and compatibiliser

Biodegradable nanocomposites were prepared from poly(butylene succinate) (PBS) and organo-montmorillonite (OMMT), in the presence of maleic anhydride-grafted PBS (PBS-g-MA) as compatibiliser. The effects of OMMT loading and PBS-g-MA on the biodegradability of PBS nanocomposites were investigated. Soil burial testing was carried out for 180 days in natural organic humus compost soil under controlled conditions. It is noted that the weight loss of nanocomposites was lower than that of neat PBS, due to the enhanced barrier properties after addition of OMMT. However, the addition of PBS-g-MA increased the weight loss of nanocomposite. The mechanical properties of PBS nanocomposites were significantly reduced after the soil burial. Biodegradation of the material was further confirmed by the decreased molecular weight through gel permeation chromatography (GPC), and changes in the chemical structure as verified by Fourier transform infrared (FTIR) spectroscopy. This was supported by the degraded surface of PBS and the nanocomposites observed under scanning electron microscopy (SEM). The effects of biodegradation on the thermal properties were studied through the differential scanning calorimetry (DSC). In addition, the biodegradation rate of the materials was determined by measuring the carbon dioxide (CO2) evolution. The degraded samples were recovered and PBS-degrading bacteria were found to be present in the exposed samples.

Thermal properties and flame‐retardancy of ethylene‐octene copolymer/organ‐montmorillonite nanocomposites

AbstractTwo series of thermoplastic elastomer ethylene‐octene copolymer (POE) composites and maleated ethylene‐octene (POE‐g‐MAH) with organo‐montmorillonite (OMMT) were prepared via melting processing to study their thermal properties and flame‐retardancy. The morphology was studied by transmission electron microscope (TEM). The influence of clay dispersion on thermal and flammability properties was investigated by using thermal gravimetric analysis (TGA) and cone calorimeter. TEM showed that agglomerated structure of OMMT within POE matrix but intercalated/exfoliated structures throughout POE‐g‐MAH matrix. The different dispersion of OMMT resulted in more significant improvements on thermal stability and flame‐retardancy in the POE‐g‐MAH/OMMT nanocomposites compared with POE/OMMT microcomposites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Preferential distribution of clay layers in iPP/OMMT/PEOc ternary nanocomposites

Isotactic polypropylene (iPP)/organo-montmorillonite (OMMT) nanocomposite was modified by poly(ethylene-co-octene) (PEOc). PEOc-rich domains were well dispersed in the iPP matrix, with narrowly distributed size. OMMT layers were well dispersed, mainly intercalated and partially exfoliated. Compared with the case in the binary composites, many OMMT layers were preferential distributed inside and around the PEOc-rich domains in the ternary composite samples, which formed an enhanced OMMT filler network. The reason for the OMMT preferential distribution was considered to be dragged or wrapped by PEOc-rich domains during sample preparation and phase separation.

Phase Morphology and Rheology Behaviors of PTT/POE/OMMT Nanocomposites

The phase morphology and dynamic rheology of poly (trimethylene terephthalate)/maleinized poly (octene-ethylene)/organo-montmorillonite nanocomposites were investigated by using transmission electron microscopy (TEM) and rotational rheometer. The results suggest that some of the OMMT are peeled off and the nanosheets are dispersed evenly in the polymer matrix. When the OMMT content is more than 4%, they are tended to form the aggregates in nanocomposites. The nanocomposites’ melt are pseudo-plastic fluid, and both complex viscosity and shear storage modulus increase with increasing OMMT content due to the interaction between the OMMT and polymers. The nanocomposites’ melt show more elasticity behavior with more OMMT content especially at low shear frequencies.

Crystal Morphology and Thermal Properties of PTT/POE/OMMT Nanocomposites

The crystal morphology, melt-crystallization and mechanical properties of poly (trimethylene terephthalate)/maleinized poly (octene-ethylene)/organo-montmorillonite nanocomposites were investigated by using polarized optical microscopy (POM), differential scanning calorimetry (DSC) and universal material testing machine, respectively. The results suggest that the nanocomposites form smaller or imperfect microcrystallites with lower melting point due to the influence of OMMT components and the nanocomposites have increased crystallization rate because OMMT is an effective nucleation agent. However, the crystallinity decreases because of the thickening effect of OMMT in the composites. The nanocomposite with 2%OMMT has the largest tensile and impact strength.

Dynamic Mechanical Properties and Thermal Stability of PTT/POE/OMMT Nanocomposites

The dynamic mechanical properties, phase morphology and thermal stability of the poly(trimethylene terephthalate)/maleinized poly(octene-ethylene)/organo-montmorillonite nanocomposites (PTT/POE/OMMT) were investigated by using the thermodynamic mechanical analyzer (DMA), transmission electron microscopy (TEM) and thermal gravimetric analyzer (TGA), respectively. The results suggest that the modulus of elasticity of the PTT/POE/OMMT nanocomposite increases, and the glass transition temperature first slightly decreases and then increases with increasing OMMT content because that the TPP plays the role of plasticizer and OMMT plays the role of reinforcing agent. OMMT disperse evenly in the polymer matrix with most of the strip-like sheet morphology. The addition of the OMMT does not apparently affect the thermal stability of the PTT/POE/OMMT nanocomposite.