Novel preparation and mechanical properties of rigid polyurethane foam/organoclay nanocomposites

A novel method for preparing rigid polyurethane (PU) foam/organoclay nanocomposites was developed through the direct incorporation of an organoclay into PU foam matrices without the addition of any physical or chemical blowing agent. The resultant foams with an appropriate content of the organoclay had a finer cell structure than the pristine PU foams because the organoclay not only acted as a nucleating agent as expected but also acted as a blowing agent of the PU foams; this could be attributed to the bound water between the interlayers of the organoclay. In addition, the incorporation of the organoclay up to 4 phr resulted in improvements in the tensile and compressive strengths, with the maximum values appearing at 2 phr (110 and 152%, respectively). The significant improvement in the mechanical properties could be attributed to the finer cell structure and the increased internal strength of the materials due to the higher degree of hydrogen bonding. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Effect of organoclay on the morphology,mechanical, thermal,and rheological properties of organophilic montmorillonite nanoclay based thermoplastic polyurethane nanocomposites prepared by melt blending

Polymer nanocomposites based on the thermoplastic polyurethane (TPU) and organically modified montmorillonite (OMMT) was prepared by melt intercalation technique using a laboratory internal batch mixer followed by compression molding. Varying amount of organically modified nanoclays (1, 3, 5, 7, and 9 wt%) was added to the TPU matrix to examine the influence of organoclay on nanophase morphology and structure–property relationships. The interaction between TPU matrix and nanofiller was studied by infrared spectroscopy. The morphology of nanocomposites was studied by X‐ray diffraction, transmission electron microscopy, and atomic force microscopy that shows melt mixing by a batch mixer is an effective method for dispersing OMMT throughout the TPU matrix. Thermogravimetric analysis revealed that incorporation of organoclay enhances the thermal stability of the nanocomposites significantly. Differential scanning calorimetry was employed to measure the melting point and glass transition temperature (T_g) of soft segments. The reinforcing effect of the organoclay was determined by dynamic mechanical analysis and physico–mechanical testing. The effects of nanoclay concentration and processing parameters on the dynamic viscoelastic properties of the nanocomposites were studied by a rubber process analyzer using frequency sweep. A significant increase in the viscosity and storage modulus of the nanocomposites was found with the increasing clay content. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Morphology and properties of thermoplastic polyurethane composites incorporating hydrophobic layered silicates

Polyurethane (PU) composites incorporating Cloisite 15A (15A) were prepared via melt compounding and solvent casting. The melt‐compounded composites had better dispersion and a smaller silicate stack size as a result of the higher shear forces associated with twin‐screw extrusion. The PU microphase separation and hard domain order were greater in the melt‐processed materials. At the concentrations of 15A employed in this study (≤7 wt %), the filler did not have an observable effect on the microphase texture of either the solvent‐ or melt‐processed PU. The tensile properties of the melt‐compounded materials were lower than those of their solvent‐cast counterparts because of thermal degradation. The solvent‐cast composite containing a 3 wt % loading of 15A displayed improved tensile strength and elongation, primarily because of plasticization by the silicate organic treatment. The addition of layered silicates with high aspect ratios increased the hysteresis and permanent set of this PU elastomer. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 300–309, 2005     

Thermoplastic vulcanizate nanocomposites based on thermoplastic polyurethane and millable polyurethane blends reinforced with organoclay prepared by melt intercalation technique: Optimization of processing parameters via statistical methods

Statistical approaches including Taguchi design of experiments (DOE), analysis of variance (ANOVA), and multiple linear regression analysis were employed to determine optimum processing conditions for successful preparation of a thermoplastic vulcanizate nanocomposite (TPVNC) based on thermoplastic polyurethane (TPU)/millable polyurethane (MPU) blend reinforced with an organoclay (TPU/MPU/organoclay = 50/50/3 wt/wt/wt) using an internal mixer. Total numbers of mixing layouts were designed by the application of Taguchi's orthogonal array (OA) methodology based on three parameters and three levels in the L₉ selector matrix model. Mechanical properties of all runs were measured and fitted into the statistical software to determine signal to noise (S/N) ratio. Ranks of the parameters were determined based on the delta statistics of the larger is better case of the S/N ratio. The ANOVA parameters were analyzed and percentage contribution of each factor, along with the correlation coefficient of each variable, was measured. The multiple linear regression models for each property were correlated with the parameters through mathematical equations. Fourier transform infrared (FTIR) analysis was performed to examine any interfacial interactions between polyurethane matrix and organoclay. X‐ray diffraction (XRD) analysis and field emission transmission electron microscope (FETEM) were employed to analyze the dispersion of organoclays in the polymer matrix. Field emission scanning electron microscope (FESEM) was employed to observe cryo‐fractured morphology. Dynamic mechanical analysis (DMA) and dynamic shear rheometer (DSR) were used to investigate dynamic mechanical properties and rheological properties of the trials, respectively. Based on all of these characterizations, an optimum processing condition was determined. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of organoclays on the properties of polyurethane/clay nanocomposite coatings

Linear, one‐binding‐site or two‐binding‐site (N⁺) organifiers with two hydroxyl end groups were synthesized, and novel organoclays were prepared through a cation‐exchange reaction between pristine sodium montmorillonite and the synthesized organifiers. After sonication of the as‐prepared organoclay in N,N′‐dimethylformamide for 10 min, the average size of the clay decreased to about 1 μm. The X‐ray diffraction patterns confirmed that the d‐spacing of the silicate layers of the organoclay expanded from 1.1 to about 1.9 nm and the peak intensity decreased with the molecular weight of the organifier increasing. Polyurethane/clay nanocomposites were synthesized by a one‐shot polymerization method. Both intercalated and exfoliated structures of the layered silicates in the polyurethane matrix were observed from transmission electron microscopy micrographs, and the d‐spacing ranged from 4 to 10 nm. The thermal and mechanical properties of the nanocomposite were enhanced by the introduction of the organoclay into the polyurethane matrix. An approximately 40–46°C increase in the onset decomposition temperature, a 200% increase in the tensile strength with a 0.5 wt % clay loading, and a 49% increase in Young's modulus with a 3 wt % clay loading were achieved. The effects of the molecular weight and the number of binding sites of the organifier on the properties of the nanocomposites were also evaluated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Rectorite/thermoplastic polyurethane nanocomposites: Preparation,characterization, and properties

A newly developed kind of layered clay, rectorite (REC), has been used to yield intercalated or exfoliated thermoplastic polyurethane rubber (TPUR) nanocomposites by melt‐processing intercalation. Because of the swollen layered structure of REC, similar to that of montmorillonite, organic rectorites (OREC) can also be obtained through ion‐exchange reaction with two different quaternary ammonium salts (QAS1, QAS2) and benzidine (QAS3). The microstructure and dispersibility of OREC layers in TPUR matrix were examined by X‐ray diffraction and transmission electron microscopy, which revealed not only that the composites with lower amounts of clay are intercalation or part exfoliation nanocomposites, but also that the mechanical properties of the composites were substantially enhanced. The maximum ultimate tensile strength for TPUR/OREC nanocomposites appeared at 2 wt % OREC loading. With increasing OREC contents, the tear strength of the composites increased significantly. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 608–614, 2004     

Microstructure,rheological behavior,and properties of poly(lactic acid)/poly(butylene succinate)/organoclay nanocomposites

Nanocomposites made of poly(lactic acid), poly(butylene succinate), and organically modified montmorillonite were prepared by melt blending in a twin screw extruder. The influence of the organoclay content on nanocomposite properties was investigated. The nanocomposite structure has been characterized by various techniques at different scales. X‐ray diffraction showed an intercalated structure whereas rheological investigations in small amplitude oscillatory shear indicated a partial exfoliation. It was also shown that organoclay was evenly dispersed in the matrix even though some large aggregates were also observed. The mechanical properties of nanocomposites were measured in uniaxial tensile test. Oxygen and water vapor permeability was also characterized. It was shown that dispersed organoclay and aggregates have a direct impact on mechanical properties and permeability. An increase of Young's modulus by 41% and a decrease of permeability by 40% could be obtained with 7 wt % organoclay. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40364.     

Morphology,thermal and mechanical properties of nylon 12/organoclay nanocomposites prepared by melt compounding

Nylon 12 (PA12) nanocomposites with different organoclay loadings were successfully prepared by melt compounding. X‐ray diffraction indicated the dominance of the exfoliated clay morphology throughout the matrix after mixing in a Brabender twin‐screw extruder, in accordance with transmission electron microscopy observations. Thermogravimetric analysis showed that the thermal stability of the PA12 matrix was improved by about 20 °C on incorporation of only 5 wt% clay. Tensile and nanoindentation tests indicated that the elastic modulus and the hardness steadily increased by about 52 % and 67 %, respectively, with a clay concentration up to 5 wt%, while improvements in tensile strength were limited. Impact strength decreased linearly by about 25 % as the clay loading increased (up to 5 wt%), indicating an embrittlement due to clay addition, as evidenced by SEM observation on the fracture surfaces. The embrittling effect may be due to the weak interfacial adhesion between the clay platelets and the polymer matrix. Copyright © 2004 Society of Chemical Industry     

The effect of carbon nanotube hydrophobicity on the mechanical properties of carbon nanotube‐reinforced thermoplastic polyurethane nanocomposites

Double walled carbon nanotubes (DWNT) were functionalized by reacting methanol, dodecylamine, or octadecylamine with a toluene 2,4‐diisocyanate linker through a two‐stage reaction procedure. TGA coupled with FTIR analysis of both the decomposition products and the DWNT samples demonstrated that the functionalization procedure was successful and proceeded as expected for all samples. A preliminary investigation of the reinforcing capabilities of the functionalized DWNT in a thermoplastic polyurethane host polymer was then conducted. Tensile testing of the resultant nanocomposites demonstrated that the octadecylamine functionality provided the greatest enhancement in tensile strength and toughness. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

改性粘土对天然橡胶纳米复合材料形态及流变特性的影响

采用3种有机改性剂分别对无机粘土进行改性,然后通过熔融共混制得了天然橡胶(NR)/有机粘土纳米复合材料。通过热重分析(TGA)和X-射线衍射(XRD)表征了粘土的有机改性程度。用扫描电镜(SEM)和流变手段表征了纳米复合材料的形态和流变特性。结果表明,含有2条长烷基链和含有2个羟乙基官能团的改性剂对粘土具有更好的改性效果,但由于羟乙基官能团具有强极性,与非极性的NR相容性差,导致有机粘土在基体中大量团聚。各纳米复合材料的储能模量在低频区表现出不同程度的"二次平台"或者"上翘",在时间扫描过程中随着时间变化表现出不同的结构演变。     

Influence of organic modification on mechanical properties of melt processed intercalated poly(methyl methacrylate)–organoclay nanocomposites

The influence of organic modifiers on intercalation extent, structure, thermal and mechanical properties of poly(methyl methacrylate) (PMMA)–clay nanocomposites were studied. Two different organic modifiers with varying hydrophobicity (single tallow versus ditallow) were investigated. The nanocomposites were prepared from melt processing method and characterized using wide angle X‐ray diffraction, transmission electron microscopy, thermogravimetric analysis, differential scanning calorimetry (DSC), and tensile tests. Mechanical properties such as tensile modulus (E), break stress (σ_brk), and % break strain (ε_brk) were determined for nanocomposites at various clay loadings. Extent of PMMA intercalation is sufficient and in the range 9–15 Å depending on organoclay and filler loading. Overall thermal stability of nanocomposites increases by 16–30°C. The enhancement in T_g of nanocomposite is merely by 2–4°C. With increase in clay loading, tensile modulus increases linearly while % break strain decreases. Break stress is found to increase till 4 wt % and further decreases at higher clay loadings. The overall improvement in thermal and mechanical properties was higher for the organoclay containing organic modifier with lower hydrophobicity and single tallow amine chemical structure. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Rubber toughening of polyamide 6/organoclay nanocomposites obtained by melt blending

Rubber toughening of polyamide 6 (PA6)/layered‐silicate nanocomposites was investigated. Different systems were prepared via melt blending according to different formulations. Wide‐angle X‐ray diffraction and transmission electron microscopy analyses showed that the nanocomposites had an appreciable degree of exfoliation. A linear elastic fracture mechanics approach was applied to characterize the material fracture behavior in dry conditions, whereas, because of the considerable ductility exhibited by the samples in the wet state, an elastic–plastic approach based on the essential work of fracture methodology was employed. In the absence of rubber, the presence of silicate layers makes the material fracture resistance decrease relative to neat polymer, depending on the degree of humidity. The results showed that the toughening action of rubber strongly depends on the degree of humidity of the material, at least for the rubber contents considered in this study (lower than 10 wt %). In particular, in slightly wet conditions, it was found that the addition of small amounts of rubber increased the fracture resistance of PA6/layered‐silicate nanocomposites without appreciably impairing the material stiffness. Thus, the results indicated that, for the given humidity conditions, a good balance between stiffness and toughness was obtainable by employing a suitable ratio of rubber to layered‐silicate content. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3406–3416, 2006     

Effect of the organoclay preparation on the extent of intercalation/exfoliation and barrier properties of polyethylene/PA6/montmorillonite nanocomposites

Nanocomposites of HDPE matrix and 3 wt % organoclay/PA6 discontinuous phase were prepared in a mixer chamber. These nanocomposites of organoclay, PA6, and HDPE were characterized by X‐ray diffraction, scanning electron and transmission electron microscopy (SEM and TEM). Barrier properties were determined by cyclohexane pervaporation and solubility. The results show that the degree of exfoliation and/or intercalation and the barrier properties depend on a combination of the proper chemical treatment and optimized processing in these polyethylene‐organoclays nanocomposites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Surface‐modifiers of clay on mechanical properties of rigid polyurethane foams/organoclay nanocomposites

Three different surface modifiers, octadecyl trimethyl ammonium (ODTMA), octadecyl primary ammonium (ODPA), and decanediamine (DDA) were used to modify Na⁺? montmorillonite (MMT), and the resultant organoclays were coded as ODTMA‐MMT, ODPA‐MMT, DDA‐MMT, respectively. Rigid PU foams/organoclay composites were prepared by directly using organoclay as the blowing agent without the addition of water. Investigation shows that the morphology of the nanocomposites is greatly dependent on the surface modifiers of clay used in the composites. In detail, DDA‐MMT is partially exfoliated in the PU matrix with the smallest cell size, while two others are intercalated in the PU matrices with smaller cell sizes. The sequence of their cell sizes is pristine PU foams > rigid PU foams/ODTMA‐MMT > rigid PU foams/ODPA‐MMT > rigid PU foams/DDA‐MMT, and the average cell size of rigid PU foams/DDA‐MMT composites decreases evidently from 0.30 to 0.07 mm. Moreover, all rigid PU foams/organoclay composites show remarkable enhanced compressive and tensile strengths as well as dynamic properties than those of PU foams, and the enhancement degree coincides well with the relative extent of internal hydrogen bonding of materials and gallery spacing of organoclay. For example, in the case of rigid PU foams/DDA‐MMT composite, 214% increase in compressive strength and 148% increase in tensile strength compared with those of pure PU foams were observed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Morphology,thermal, and mechanical properties of polyamide 66/clay nanocomposites with epoxy‐modified organoclay

A new kind of organophilic clay, cotreated by methyl tallow bis‐2‐hydroxyethyl quaternary ammonium and epoxy resin into sodium montmorillonite (to form a strong interaction with polyamide 66 matrix), was prepared and used in preparing PA66/clay nanocomposites (PA66CN) via melt‐compounding method. Three different types of organic clays, CL30B–E00, CL30B–E12, and CL30B–E23, were used to study the effect of epoxy resin in PA66CN. The morphological, mechanical, and thermal properties have been studied using X‐ray diffraction, transmission electron microscopy (TEM), mechanical, and thermal analysis, respectively. TEM analysis of the nanocomposites shows that most of the silicate layers were exfoliated to individual layers and to some thin stacks containing a few layers. PA66CX–E00 and PA66CX–E12 had nearly exfoliated structures in agreement with the SAXS results, while PA66CX–E23 shows a coexistence of intercalated and exfoliated structures. The storage modulus of PA66 nanocomposites was higher than that of the neat PA66 in the whole range of tested temperature. On the other hand, the magnitude of the loss tangent peak in α‐ or β‐transition region decreased gradually with the increase in the clay loading. Multiple melting behavior in PA66 was also observed. Thermal stability more or less decreased with an increasing inorganic content. Young's modulus and tensile strength were enhanced by introducing organoclay. Among the three types of nanocomposites prepared, PA66CX–E12 showed the highest improvement in properties, while PA66CX–E23 showed properties inferior to that of PA66CX–E00 without epoxy resin. In conclusion, an optimum amount of epoxy resin is required to form the strong interaction with the amide group of PA66. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1711–1722, 2006     

Morphology and mechanical and viscoelastic properties of rubbery epoxy/organoclay montmorillonite nanocomposites

The morphology and mechanical and viscoelastic properties of rubbery epoxy/organoclay montmorillonite (MMT) nanocomposites were investigated with wide‐angle X‐ray scattering (WAXS), transmission electron microscopy (TEM), tensile testing, and dynamic mechanical thermal analysis. An ultrasonicator was used to apply external shearing forces to disperse the silicate clay layers in the epoxy matrix. The first step of the nanocomposite preparation consisted of swelling MMT in a curing agent, that is, an aliphatic diamine based on a polyoxypropylene backbone with a low viscosity for better diffusion into the intragalleries. Then, the epoxy prepolymer was added to the mixture. Better dispersion and intercalation of the nanoclay in the matrix were expected. The organic modification of MMT with octadecylammonium ions led to an increase in the initial d‐spacing (the [d₀₀₁] peak) from 14.4 to 28.5 Å, as determined by WAXS; this indicated the occurrence of an intercalation. The addition of 5 phr MMTC18 (MMT after the modification) to the epoxy matrix resulted in a finer dispersion, as evidenced by the disappearance of the diffraction peak in the WAXS pattern and TEM images. The mechanical and viscoelastic properties were improved for both MMT and MMTC18 nanocomposites, but they were more pronounced for the modified ones. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 103: 3547–3552, 2007     

Morphologies and mechanical properties of polylactide/thermoplastic polyurethane elastomer blends

To explore a potential method for improving the toughness of a polylactide (PLA), we used a thermoplastic polyurethane (TPU) elastomer with a high strength and toughness and biocompatibility to prepare PLA/TPU blends suitable for a wide range of applications of PLA as general‐purpose plastics. The structure and properties of the PLA/TPU blends were studied in terms of the mechanical and morphological properties. The results indicate that an obvious yield and neck formation was observed for the PLA/TPU blends; this indicated the transition of PLA from brittle fracture to ductile fracture. The elongation at break and notched impact strength for the PLA/20 wt %TPU blend reached 350% and 25 KJ/m², respectively, without an obvious drop in the tensile strength. The blends were partially miscible systems because of the hydrogen bonding between the molecules of PLA and TPU. Spherical particles of TPU dispersed homogeneously in the PLA matrix, and the fracture surface presented much roughness. With increasing TPU content, the blends exhibited increasing tough failure. The J‐integral value of the PLA/TPU blend was much higher than that of the neat PLA; this indicated that the toughened blends had increasing crack initiation resistance and crack propagation resistance. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanical and rheological properties,and morphology of polyamide-6/organoclay/elastomer nanocomposites

The effects of ethylene-methyl acrylate-glycidyl methacrylate (E-MA-GMA) terpolymer and three types of organoclays (Cloisite^® 15A, 25A, and 30B) on mechanical and rheological properties, and morphology of impact modified polyamide-6/montmorillonite ternary nanocomposites were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), parallel disk rheometry, melt flow index measurements, and tensile and impact tests. The materials were prepared by melt blending using a co-rotating twin-screw extruder. XRD and TEM analyses showed that exfoliated-intercalated nanocomposites were formed in both polyamide-6/Cloisite^® 25A and Cloisite^® 30B binary nanocomposites and in ternary systems. SEM micrographs showed that rubber domain sizes were larger in the nanocomposites than in their corresponding polyamide-6/elastomer blends. Generally, tensile strength, Young's modulus, and elongation at break decreased with the addition of elastomer to polyamide-6/organoclay binary nanocomposites. In the melt state, liquid-like behavior of polyamide-6 slightly turned to pseudo solid-like in the binary and ternary nanocomposites. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

UHMWPE/organoclay nanocomposites fabricated by melt intercalation under continuous elongational flow: Dispersion,thermal behaviors and mechanical properties

The preparation of ultra‐high‐molecular weight polyethylene (UHMWPE)/organoclay nanocomposites by continuous elongational flow technique was investigated in a novel eccentric rotor extruder (ERE). The distribution and dispersion morphologies of organo‐modified montmorillonite (OMMT) layers were revealed and observed by ash determination, wide angle X‐ray diffraction and transmission electron microscopy. The thermal and thermal‐mechanical behaviors were characterized by differential scanning calorimeter, thermal gravimetric analysis and dynamic mechanical thermal analysis. The mechanical performances was measured by tensile and impact test. The morphologies of the nanocomposites evidenced that the OMMT layers can be well intercalated or/and exfoliated by UHMWPE matrix, then the fabrication mechanism of intercalated and exfoliated OMMT structures under continuous elongational flow was discussed. The ideal dispersion of OMMT in UHMWPE matrix obviously improved the crystallinity and the mechanical properties at a certain concentration of OMMT loading, indicating that the lower OMMT addition can lead an effective strengthening and toughening for UHMWPE. POLYM. ENG. SCI., 59:547–554, 2019. © 2018 Society of Plastics Engineers     

Preparation,structural development,and mechanical properties of microfibrillar composite materials based on polyethylene/polyamide 6 oriented blends

The preparation of microfibrillar composites (MFCs) based on oriented blends of polyamide 6 (PA6) and high‐density polyethylene (HDPE) is described. By means of conventional processing techniques, the PA6 phase was transformed in situ into fibrils with diameters in the upper nanometer range embedded in an isotropic HDPE matrix. Three different composite materials were prepared through the variation of the HDPE/PA6 ratio with and without a compatibilizer: MFCs reinforced by long PA6 fibrils arranged as a unidirectional ply; MFCs containing middle‐length, randomly distributed reinforcing PA6 bristles; and a nonoriented PA6‐reinforced material in which the PA6 phase was globular. The evolution of the morphology in the reinforcing phase (e.g., its visible diameter, length, and aspect ratio) was followed during the various processing stages as a function of the blend composition by means of scanning electron microscopy. Synchrotron X‐ray scattering was used to characterize selected unidirectional ply composites. The presence of transcrystalline HDPE was demonstrated in the shell of the reinforcing PA6 fibrils of the final MFCs. The impact of the compatibilizer content on the average diameter and length of the fibrils was assessed. The influence of the reinforcing phase on the tensile strength and Young's modulus of the various composites was also evaluated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010