Incorporation Of Clay Research Articles

Micro-structural, thermal, and mechanical properties of injection-molded glass fiber/nanoclay/polypropylene composites

Hybrid composites of PP/NC/GF were prepared by extrusion and injection molding. Molded specimens were analyzed by XRD, SEM, and TEM, together with characterization of thermal and mechanical properties. XRD results revealed that the interaction between NC particles and the PP matrix results in intercalation of the polymer chains, which increases the clay interlayer distance. TEM results revealed NC particle intercalation. TGA results showed that the incorporation of clay into the GF composite improves the thermal stability of the material. The initial thermal decomposition temperatures also shifted to higher values. Incorporation of GF into PP lowers the tensile strength of the binary composite, indicating poor fiber–matrix interfacial adhesion; however, introducing NC increased the strength of the ternary composites. Tensile modulus was enhanced with the incorporation of GF and further increased with an introduction of NC. Flexural strength and flexural modulus are both enhanced with an increase in fiber loading. The addition of clay nanoparticles further improved these properties.

Structurally Enhanced Hydrogel Nanocomposites with Improved Swelling and Mechanical Properties

In this work, structurally enhanced hydrogel nanocomposites based on 2-acrylamido-2 methyl propane sulfonic acid (AMPS)-acrylamide (AAM) copolymer with high hydrophilic group content were prepared by in-situ copolymerization by using different types of clay (montmorillonite, mica and halloysite). Nanocomposite hydrogels were characterized by Fourier-Transform Infrared Spectroscopy (FTIR) and X-ray diffraction (XRD) analyses and determination of swelling degrees of the samples. Mechanical properties of the samples were also investigated by determination of the compressive elastic modulus. It was also found that exfoliated or highly expanded intercalated nanocomposite structure was obtained and clay incorporation into the AMPS-AAM hydrogel structure improved its swelling capacity. The highest swelling capacity (1030 g H2O/g) was observed for the nanocomposite sample prepared with the montmorillonite amount of 5% (w). Furthermore, mechanical strength of the hydrogels against compression forces was significantly improved by the clay addition. It was found that the type of clay, in other word filler geometry, affected the compressive elastic modulus (E) of the samples. It was concluded that halloysite, which is considered to be a one dimensional (1D) nanotubular filler was less effective to enhance the compressive elastic modulus (E) of such materials compared with the montmorillonite and mica having two dimensional (2D) platelet or disk-like shapes at a particular amount of clay.

Thermal decomposition behavior and mechanical properties of elastomeric composites based on polyolefinic thermoplastic elastomer and organomontmorillonite

The elastomeric composites based on organomontmorillonite (OMMT) and Santoprene thermoplastic elastomer were prepared by melt processing. Maleic anhydride grafted polypropylene (PP-g-MA) was used as a compatibilizer for the composite system. By adding optimum content of PP-g-MA, the fracture surface of the composites observed by SEM was smoothened as a result from compatibilizing effect. From XRD results, the measured d-spacing data proved a good dispersion of nanoclay along with compatibilizer. Thermal decomposition behavior of the neat components and its composites obtained from simultaneous TG and DSC profiles indicated that the incorporation of OMMT into the matrix polymer improved the thermal stability in air but not in nitrogen. No significant change in thermal stability of the composites with addition of PP-g-MA. The incorporation of clay significantly enhanced in dynamic mechanical and tensile properties of the composites. The dynamic storage modulus, tensile modulus and yield stress of the composites with the presence of PP-g-MA were remarkably improved.

Effect of clay loading on flammability of poly(methyl methacrylate)/clay nanocomposites

The present study is related to the investigation of flammability properties of poly(methyl methacrylate) (PMMA) after incorporation of clay. PMMA/layered silicate (nanoclay) nanocomposites with 5% loading of nanofiller were prepared using melt intercalation technique. Commercially modified nanoclays such as Cloisite 30B, Cloisite 93A and in-house modified nanoclay (Quaternary ammonium salt modified Na-MMT i.e. OTAB-Na-MMT have been used as organoclays for the preparation of nanocomposites. Thermal characterization of the above prepared nanocomposites was carried out by thermal conductivity, horizontal burning test (UL94HB) and cone calorimeter experiments. The morphological behavior of nanocomposites was characterized by wide angle x-ray diffraction technique. The morphology of charred material obtained after burning was investigated using scanning electron microscopic analysis.

Crystal structure and orientation of uniaxially and biaxially oriented PLA and PP nanoclay composite films

AbstractCast films of poly(lactic acid) (PLA) and polypropylene (PP) with 2.5 and 5 wt % organo modified nanoclay were prepared and then uniaxially and biaxially hot drawn at T = 90 and 155°C, respectively, using a biaxial stretcher. The orientation of PLA and PP crystal unit cells, alignment of clay platelets, as well as the extent of intercalation and exfoliation were studied using wide angle X‐ray diffraction (WAXD). The measurement of d‐spacing of the 001 plane (normal to platelets plane) of the clay tactoids indicated the intercalation of the silicate layers for the PLA nanocomposite films, whereas the PP nanofilled films showed only dispersion of the nanoparticles (i.e., neither intercalation nor exfoliation were observed). The intercalation level of the clay platelets in PLA was almost identical for the uniaxially and biaxially drawn films. Our finding showed that the crystallite unit cell alignments are appreciably dependent on uniaxial and biaxial stretching. Moreover, the incorporation of clay to some extent influenced the orientation of the crystal unit cell axes (a, b, and c) of the oriented films. The silicate layers revealed a much higher orientation into the flow direction in the uniaxially stretched films compared to the biaxially drawn samples. In addition, the orientation of the 001 plane of nanoclays was significantly greater in the PLA compared to the PP nanoclay composite films probably due to a better intercalation and stress transfer in the former. Morphological pictograms illustrating the effects of uniaxial and biaxial stretching on the clay orientation are proposed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Preparation and characterization of sodium alginate/poly(N-isopropylacrylamide)/clay semi-IPN magnetic hydrogels

pH- and temperature-responsive semi-interpenetrating magnetic nanocomposite hydrogels (NC hydrogels) were prepared by using linear sodium alginate (SA), poly(N-isopropylacrylamide) (PNIPAM) and Fe3O4 nanoparticles with inorganic clay as an effective multifunctional cross-linker. The effects of cross-linker and SA contents on various physical properties were investigated. The NC hydrogels exhibited a volume phase transition temperature (VPTT) around 32 °C with no significant deviation from the conventional chemically cross-linked PNIPAM hydrogels (OR hydrogels). The swelling ratios of NC hydrogels were much larger than those of OR hydrogels. Moreover, the swelling ratios of NC hydrogels gradually decreased with increasing the contents of clay and increased with increasing the contents of SA. The pH sensitivity of NC hydrogels was evident below their VPTT. The NC hydrogels had a much better mechanical property than the OR hydrogels. The results showed that the incorporation of clay did not affect the saturation magnetization of the hydrogels.

Hyperbranched polymers as clay surface modifiers for UV-cured nanocomposites with antimicrobial activity

In this work, the influence of organoclays modified with three different hyperbranched polymers (MMT-PEI800Q, MMT-PEI25000Q based on polyethylenimine, and Hybrane MMT-HA1690Q aliphatic polyestheramide), on the photopolymerization reaction of nanocomposites based on HEMA/PEGDMA has been investigated. In general, the clay incorporation increased the reaction rates, associated with the low diffusivity of the monomer into the polymer matrix. The XRD patterns and TEM images of nanocomposites indicated the formation of intercalated/exfoliated structure in the nanocomposites. An enhancement in the thermal stability of nanocomposites was observed by TGA and CL emission, which was related to the great barrier properties of the nanolayers dispersed in the nanocomposites. The antimicrobial activity of the nanocomposites against Bacillus subtilis and Pseudomonas aeruginosa was tested. For the nanocomposites the inhibition of the adhesion of the two bacteria was observed on comparison to the HEMA/PEGDMA surface, where the colonization by both microorganism was evidenced in SEM images, reflecting no antibacterial activity. The obtained results would indicate that nature of organomodifier in the clay play a more important role in B. subtilis and P. aeruginosa adhesion processes than stiffness, and the high efficiency against microorganism may be related to the presence of hyperbranched polymers with a high density of quaternary ammonium groups attached to the clay.

Melt Mixed Polypropylene/Metallocene Polyethylene Thermoplatic Elastomer Nanocomposites: Part I: Effect of Silane Modification

Polypropylene/metallocene polyethylene (PP/mPE) thermoplastic elastomer nanocomposites were prepared by a melt blending process. Metallocene polyethylenes grafted with vinyltriethoxy silane (mPE-g-silane) and neat mPE, both premixed with commercial organoclay (20A) to serve as the elastomer domains, were compared to investigate the silane curing effect on the prepared nanocomposites. According to X-ray diffraction and transmission electron microscopy analyses, the mPE-g-silane was of help in facilitating the intercalation and partial exfoliation of clay for PP/mPE-g-silane/clay system. A slight melting temperature depression of mPE and its nanocomposites was observed with the introduction of the silane curing due to the induced imperfect crystals. There was no silane curing effect found on the thermal stability, but the incorporation of clay increased the thermal stabilities. The PP/mPE-g-silane/clay system conferred higher tensile strength and tear strength than that of PP/mPE/clay system, mainly attributed to the better dispersion in the case of PP/mPE-g-silane. In general, the addition of clay gave more positive enhancement to the tensile and tear properties of the PP/mPE-g-silane/clay system in comparison with the PP/mPE/clay system.

Rheological properties and crystal morphology of poly(ethylene oxide)/clay nanocomposites

Poly(ethylene oxide) (PEO)/organoclay nanocomposites were prepared by a solution intercalation method. The crystallization behavior of the nanocomposites was investigated by a cross-polarized optical microscopy (CPOM) fitted with a hot-stage facility. A decrease in size and regularity were observed as a result of incorporation of clay into the PEO matrix. The dynamic viscoelastic behavior of PEO/organoclay nanocomposites was assessed using a strain-controlled parallel plate rheometer. The effects of clay concentration on the rheological properties of the nanocomposites were extensively studied. A significant increase in the viscosity and storage modulus of the nanocomposites was found with increasing clay content. The reinforcing effect of the organoclay was determined by using a dynamic mechanical analyzer (DMA) and compared with the theoretically calculated values. POLYM. COMPOS., © 2011 Society of Plastics Engineers.

Study on properties of nanocomposites based on HDPE, LDPE, PP, PVC, wood and clay

Wood polymer nanocomposite (WPC) was prepared by solution blending of high density polyethylene, low density polyethylene, polypropylene and polyvinyl chloride (1:1:1:0.5) with wood flour and nanoclay. Xylene and tetrahydrofuran were used as solvent and the ratio was optimized at 70:30. TEM study revealed better dispersion of silicate layers in WPC loaded with 3 wt% of clay. WPC loaded with 3 wt% nanoclay exhibited higher thermal stability compared to WPC loaded with 1 and 5 wt% clay. The storage and loss modulus were found to enhance on incorporation of clay to WPC. The damping peak was found to be lowered by the addition of clay to WPC. Limiting oxygen index value increased due to incorporation of nanoclay. WPCs were subjected to exposure to cellulase producing Bacillus sp. and it showed the growth of bacteria as revealed by SEM study. Mechanical properties of WPC decreased due to degradation by bacteria. Water vapour uptake of WPC decreased due to addition of nanoclay.

Effect of clay contents on mechanical and water vapor barrier properties of agar-based nanocomposite films

Agar/clay (Cloisite Na+) nanocomposite films with different amount of the nanoclay (0, 2.5, 5, 10, 15, and 20g clay/100g agar) were prepared using a solution intercalation method. Results on X-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed well developed intercalated nanocomposite films especially at low level of nanoclay addition, and their properties were greatly influenced with the clay content. Tensile strength (TS) increased with increase in the clay content up to 10%, and decreased with more than 10% of clay incorporation. Water vapor permeability (WVP), water vapor uptake ratio (WVUR5), and water solubility (WS) decreased with increase in the nanoclay content due to the tortuous path for water vapor diffusion and strong structure formed between the intercalated silicate layers and the polymer matrix. Hydrophilicity of the nanocomposite films increased with increase in the hydrophilic nanoclay, resulted in decreased water contact angle (CA) and increased swelling ratio (SR).

Rheological characterization of melt compounded polypropylene/clay nanocomposites

Polypropylene/clay nanocomposites were prepared by using a two step melt compounding process on twin screw extruders and then rheologically investigated. The melt rheological measurements were performed using an ARES-rheometer in the dynamic mode at 220°C over frequency varying from 100 to 0.017rad/s and in the parallel plate geometry with 25mm diameter.The results showed that the storage modulus and viscosity are found to be increased with the incorporation of clay into PP. A significant increase of these quantities is observed by the incorporation of modified clay that drastically changes the rheological behavior. The results with modified clay indicate an evidence of exfoliation which could be detected rheologically.

Micro-mechanisms of deformation in polyethylene/clay micro- and nanocomposites

Incorporation of clay in polymers is known to improve mechanical properties such as tensile modulus and tensile strength, but to generally decrease elongation at break and toughness. However, recent studies reported an increase in elongation at break for linear low density polyethylene based nanocomposites. In this work, the tensile properties of clay micro- and nanocomposites based on high density polyethylene (HDPE), low density polyethylene (LDPE) and linear low density polyethylene (LLDPE) of similar molecular weights were evaluated. LLDPE micro- and nanocomposites exhibited an extraordinary enhancement in toughness compared to LDPE or HDPE microcomposites. Based on electron microscopy and on acoustic emission and volume strain measurements during tensile testing, micro-mechanisms of deformation in polyethylene/clay micro- and nanocomposites were proposed.

Synthesis and characterization of 1, 1-bis (3-methyl-4-epoxyphenyl) cyclohexane-toughened DGEBA and TGDDM organo clay hybrid nanocomposites

1,1-bis (3-methyl-4-epoxyphenyl) cyclohexane (BMEPC) was synthesized from 1,1-bis (3-methyl-4-hydroxyphenyl) cyclohexane and 2-(chloromethyl) oxirane, and its structure was confirmed by Fourier transform infrared (FT-IR), 1H-, 13C-NMR and electron impact-mass spectrometry. Both diglycidyl ether of bisphenol-A (DGEBA) and tetraglycidyl diamine diphenyl methane (TGDDM) epoxy resins were toughened with BMEPC using 4,4′-diaminodiphenylmethane (DDM) as a curing agent. Epoxy and BMEPC-toughened epoxy systems were further modified with organophilic MMT (OMMT) clay. The chemical reactions involved between epoxy and DDM with OMMT was confirmed by FT-IR. OMMT clay-filled hybrid BMEPC-epoxy resin castings were characterized for their mechanical, thermal, thermo-mechanical and morphological properties. The values of Tg and heat distortion temperature of hybrid epoxy decreased with increasing incorporation of OMMT. The data obtained from thermal studies indicated that the incorporation of nano clay into BMEPC-modified hybrid systems possess improved thermal stability. The mechanical properties were studied as per ASTM standards. The TGDDM-based hybrid epoxy system exhibited higher values of tensile and flexural properties than that of the DGEBA hybrid epoxy system, whereas the impact strength of the DGEBA system was higher when compared with that of the TGDDM system. The values of dielectric constant (ϵ′) and dielectric loss (ϵ′′) were increased with increased incorporation of OMMT clay in both systems. From the X-ray diffraction analysis it was observed that the absence of d001 reflections in OMMT-filled BMEPC-modified epoxy systems indicated the formation of exfoliated nano hybrids. The homogenous morphologies were ascertained from scanning electron microscope and transmission electron microscope.

Spontaneous exfoliation and self-assembly phenomena in polyvinylpyrrolidone/synthetic layered silicate nanocomposites

Nanocomposites of polyvinylpyrrolidone (PVP) and unmodified synthetic montmorillonite (MMT) were prepared by solution-intercalation method using water as solvent. Structure of systems was investigated extensively by wide- and small angle X-ray diffraction techniques (WAXS and SAXS, respectively) including methods involving two-dimensional (2D) detection of scattered radiation. Results of this study, supplemented by transmission electron micrographs, clearly suggest that the nanocomposites are exfoliated up to 20 wt% of MMT in the polymer. Structural investigations revealed also that in 0.25 mm films, clay particles spontaneously orient parallel to the film's surface. Statistical analysis of TEM images showed that in nanocomposites containing 5 wt% of MMT, the average distance between montmorillonite platelets is equal to approximately 10 nm. In addition to structural investigations, thermal properties and optical transparency of the nanocomposites were investigated. DSC and TGA results indicate that incorporation of clay in PVP matrix causes no significant changes in glass transition temperatures ( T g) and thermal stability of the systems. UV–vis spectroscopy revealed lower UV-transmittance of nanocomposites in comparison to neat polyvinylpyrrolidone. However, PVP/MMT has similar transparency of the visible light.

Synthesis and characterization of organic-inorganic hybrid clay filled and bismaleimide—siloxane modified epoxy nanocomposites

Organic-inorganic hybrids involving organo-modified montmorillonite (OMMT) clay and tetraglycidyl diamino diphenyl methane epoxy (TGDDM) were prepared via in situ polymerization by the homogeneous dispersion of various percentages (1–5% w/w) of clay in epoxy matrix resin. The resulting homogeneous epoxy—clay hybrids were modified with 10 wt% of hydroxyl terminated polydiemthyl siloxane (HTPDMS) using γ—aminopropyltriethoxysilane (γ-APS) as coupling agent in the presence of tin catalyst. The siliconized epoxy-clay prepolymers were further modified separately with 15 wt% of bismaleimide (BMI) monomers and cured with diaminodiphenylmethane. The reactions involved during the curing process between epoxy resin, siloxane and BMI were confirmed by using FTIR and DSC curing analysis. The differential scanning calorimetry (DSC) show that the significant increase in glass transition temperatures in the clay filled hybrid epoxy systems than that of neat epoxy resin. The data obtained from thermal studies indicates that the appreciable improvement in hybrid systems was due to the incorporation of MMT clay, BMI and siloxane into epoxy systems. Scanning electron microscopy (SEM) of the hybrid systems show that the homogenous morphology. X-ray diffraction analysis of the clay hybrid systems shows that the amorphous diffraction patterns and the peaks are broadened and nearly disappeared after 24 h swelling, suggesting the formation of exfoliated structure.

Molecular-scale design of a high performance organic–inorganic hybrid with the help of gamma radiation

In the age of green chemistry, gamma-radiation-assisted grafting of polar groups onto polymers in aqueous solution is becoming attractive as it is a rapid, scalable, clean physical process with much less chance of contamination. In this case, a methacrylic acid (MAA) polar group was grafted onto LDPE (low density polyethylene) by gamma radiation to increase the compatibility of LDPE with organically modified clay by reducing the hydrophobicity of LDPE. The clay, cloisite 20A was melt-mixed with g-LDPE (grafted LDPE) to synthesize a nanohybrid and the mixes were subsequently compression-molded to make a sheet, which was used for characterization. Many of the drawbacks of polyolefin based nanohybrid synthesis were overcome by this technique. Wide angle X-ray diffraction (WAXS), transmission electron microscopy (TEM), thermogravemetric analysis (TGA), differential scanning calorimetry (DSC) and tensile testing were conducted to characterize the nanohybrids. The interlayer distance (d values) change in WAXS confirmed nanohybrid formation, which was later directly seen by TEM. TGA revealed that nanohybrids were more thermally stable than pure polymer and this went on increasing with clay loading. From DSC it was noticed that melting temperatures (Tms) remained unchanged, but the crystallinity of the polymer was increased by more than 5% at higher clay loading (8 wt%), which was useful for barrier properties as well as mechanical property improvement. Young's modulus of nanohybrid was increased considerably by a small mount of clay incorporation (by 50% and 85% for 2 and 8 wt% clay). Uniquely, with increase in modulus toughness was also found to increase by more than 20%, keeping the elongation-at-break unchanged. Thus by this rapid, clean, user friendly and well controlled technique, pure and high-performance nanohybrids were developed successfully.

Microstructure and mechanical properties of polypropylene/poly (ethylene-co-octene copolymer)/clay ternary nanocomposites prepared by melt blending using supercritical carbon dioxide as a processing aid

To improve the mechanical properties of polypropylene (PP), poly (ethylene-co-octene copolymer) (PEOc) and clay particles were incorporated by melt blending with the aid of supercritical carbon dioxide. Results from X-ray diffraction, electron microscopy, and rheology show that using sc-CO2 makes the clay layers mainly intercalated by polymer chains and well exfoliate in the nanocomposites relative to direct melt blending. This leads to a three-dimensional network structure formed in the nanocomposites as confirmed by rheology. Evidences from scanning electron microscope (SEM) indicate most of clay particles are mainly localized close to or inside the PEOc phase and others disperse separately in the PP phase. The incorporation of PEOc and clay significantly improve the impact strength of PP without the expense of lowering PP’s stiffness and strength. The use of sc-CO2 or PP-g-MA during melt-compounding can further improve the mechanical properties of the ternary nanocomposites. Compared to PP-g-MA, sc-CO2 is more favorable for dispersing clay in PP/PEOc blend and improving the mechanical properties of the nanocomposites.

POLYPROPYLENE/CLAY NANOCOMPOSITES: SYNTHESIS AND CHARACTERIZATION

abstract Polypropylene nanocomposites were synthesized by using the method of mixing in the molten state. Nanocomposites were obtained in twin-screw co-rotating extruders and the nanocomposites were prepared with percentage of nanoclay (C 2 ) from 5 wt-%, with and without compatibilizer agent (PP- g -MA).The thermal (DSC, TGA), morphology (XRD, TEM), and dynamical mechanical (DMA) properties of the nanocomposites were characterized.All nanocomposites prepared are in intercalated state as corroborated by XRD and TEM. The Tm and Xc were not affected by the presence of clay, PP-g-MA, or processing support. The incorporation of clay and compatibilizer agent increases the thermal stability and heat deflection temperature (HDT). Keywords : Nanocomposites, polypropylene, clays. compatiblizer agent 1. introdUction Polypropylene is a polymer widely used in many applications, and their thermal (1-2), rheological (3), mechanical (4-5), and gas permeation properties (6-7) need to be improved. A large number of studies have focused to improve a range of capabilities for these materials used in the automotive industries, and which show a great potential for use in the aeronautical field (7). The study of polymer nanocomposites has focused on enhancing the conventional properties of this polymeric material (8),

Effects of PBO fiber and clay on the mechanical, morphological, and dynamic mechanical properties of NR/HDPE blends

AbstractPoly(p‐phenylene‐2,6‐benzobisoksazole) (PBO) and natural rubber (NR)/high density polyethylene (HDPE) composites were melt‐blended in a Haake internal mixer. The tensile strength, tensile modulus, and impact strength increased with fiber loading and optimized at 20%. Incorporation of clay into the NR/HDPE/PBO composites resulted in an improvement of tensile strength for NR/HDPE/PBO composites compared to the systems without clay. However, addition of clay was only effective at low contents (5–7.5%). Additional improvement of tensile strength, tensile modulus, and impact strength of the hybrid composite was observed on addition of liquid natural rubber (LNR). Scanning electron micrographs of the samples had indicated that the presence of clay decreased the domain size of the dispersed phase. Results on dynamic response showed that incorporation of clay and LNR into the composites had increased the storage modulus and reduced the tan δ. The shift of glass transition temperature (Tg) to higher values for composites also indicated good interaction between the fiber and the matrix. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.