Melt intercalation and exfoliation of maleated polypropylene modified polypropylene nanocomposites

Melt blending of maleic anhydride-grafted polypropylene (PPgMA) and organically modified clay nanocomposites were first prepared in a plasticorder. PPgMAs, including PB3150, PB3200, PB3000, and E43, with a wide range of MA content and molecular weight were used. The structure was investigated with X-Ray diffraction (XRD) and transmission electron microscopy (TEM). PPgMA compatiblizers gave rise to similar degree of dispersion beyond the weight ratio of 3 to 1 with the exception of E43, which had the highest MA content and the lowest molecular weight. It was found that thermal instability and high melt index were responsible for ineffective modification by E43. Furthermore, PPgMA with lower molecular weight and higher melt index had to be compounded at lower mixing temperature in order to achieve a reasonable level of torque for clay dispersion. We then modified polypropylene/organoclay nanocomposites with different levels of PPgMA compatibilizers on a twin-screw extruder. The PP/E43/clay system, as shown through XRD patterns and TEM observation, yielded the poorest clay dispersion among the compatibilizers under investigation. The relative complex viscosity curves also revealed a systematic trend with the extent of exfoliation and showed promise for quantifying the hybrid structure of the nanocomposites. Mechanical properties and thermal stability were determined by dynamical mechanical analysis (DMA) and thermogravimeric analysis (TGA), respectively. Though PPgMA with lower molecular weight would lead to better clay dispersion in the polypropylene nanocomposites, it caused deterioration in both mechanical and thermal properties of the hybrid systems.     

Preparation and Properties of Epoxy‐Clay Nanocomposites

Epoxy‐clay nanocomposites were synthesized to examine the effects of adding different contents of nanoclays on the physical, mechanical, and thermal properties of the epoxy resin system used in composite pipes manufacturing. Diglycidyl ether of bisphenol‐A (epoxy) with a cycloaliphatic amine heat curing hardner was reinforced by 1–7 wt.% of an organically modified type of montmorillonite. SEM results showed the change in failure of epoxy from brittle to tough mode by addition of nanoclays. X‐ray results indicated some degree of exfoliation by 1 wt.% clay and a decrease in d‐spacing in higher clay loadings after that. The heat‐distortion temperature of epoxy-clay nanocomposites increased from 125.5 to 138.7°C with 3 wt.% organoclay loading. Tensile and flexural modulus increased with increasing clay loading in this type of nanocomposite, but addition of organically modified clay decreased the tensile and flexural strengths and tensile elongation at break. Addition of 7 wt.% nanoclay improved the impact strength by 25.6%.     

Parametric Studies on the Grafting of Poly(Methyl Methacrylate) onto Organophilic Montmorillonite Using Silylated Clay Platelets

Poly(methyl methacrylate) (PMMA)/organophilic montmorillonite (Cloisite 30B) nanocomposites were synthesized by the chemical grafting of PMMA onto Cloisite 30B via solution polymerization of methyl methacrylate (MMA) with vinyl-modified organoclay. The effects of different parameters such as clay weight percent (CWP), solvent per monomer volume ratio, and dispersion time on the properties of the PMMA grafted Cloisite 30B were investigated using the Taguchi experimental design method. This method gives a much-reduced variance for the experiments with optimum setting of control parameters and provides a set of minimum experiments compared to the conventional methods. Qualitative evidence for the chemical grafting of the PMMA onto Cloisite 30B was confirmed by Fourier transform infrared spectroscopy (FT-IR). X-ray diffraction (XRD) was used to investigate interlayer changes of the clay in the grafted nanoplatelets. The exfoliated/intercalated morphology of the nanocomposites was confirmed by XRD. Furthermore, thermal properties were measured by thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA). Statistical analysis of results revealed that clay weight percent and solvent per monomer ratio had significant effects on the properties of final products. The percent of grafted PMMA and storage modulus of PMMA/30B nanocomposites decreased with increasing clay content due to better dispersion of the clay at lower loadings. On the other hand, because of a tendency to formation of homopolymer and oligomers at higher solvent loadings; the percent of grafted PMMA, storage modulus and glass transition temperature of PMMA/30B nanocomposites decreased with an increase in solvent per monomer volume ratio. However, the obtained PMMA/30B nanocomposites at the optimum conditions, was exhibited a higher glass transition temperature, higher storage modulus and better thermal stability than the pure PMMA.     

Preparation and Properties of Polypropylene/Organo-Vermiculite Nanocomposites

Polypropylene/organo-vermiculite (OVMT) nanocomposites with different clay loadings were prepared via melt-mixing using a twin-screw extruder. The vermiculite was premodified with maleic anhydride by ball milling. The resultant polypropylene/OVMT nanocomposites possess an intercalated structure as confirmed by both wide-angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM). The mechanical property tests show that the tensile and flexural strength of these nanocomposites increase dramatically with the OVMT loading; the fracture toughness remains almost unchanged and the Charpy impact strength decreases slightly. Finally, differential scanning calorimetry (DSC) and WAXD results show that the addition of vermiculite can induce the β crystal structure of polypropylene.     

Synthesis and characterization of PMMA/silylated MMTs

Commercially available Sodium clay (Dellite HPS) and organo-clay (Dellite 72T) are modified via a silylation reaction. These silylated clays are characterized by IR, XRD, thermogravimetric analyses, and their equilibrium contact angles are measured. They are used to prepare nanocomposites at different loading percentage (1, 3, 5% wt) by in situ intercalative polymerization of Methyl methacrylate and morphology and thermal properties of nanocomposites are examined. SEM images of nanocomposites fractured surface show the absence of clays aggregates, confirming a good dispersion and distribution of montmorillonites in the polymer matrix. The effects of modified clays on the thermal properties of nanocomposites are analyzed by differential scanning calorimetry and thermogravimetric analyses showing an increase of glass and decomposition temperatures of all nanocomposites respect to homopolymer ones. The best results are obtained in the presence of silylated montmorillonites, clearly the organosilane improves the compatibility between polymer matrix and clay and as effect the properties of nanocomposites.     

Enhancement of thermal and mechanical properties of poly(MMA-co-BA)/Cloisite 30B nanocomposites by ultrasound-assisted in-situ emulsion polymerization

This study reports synthesis and characterization of poly(MMA-co-BA)/Cloisite 30B (organo-modified montmorillonite clay) nanocomposites by ultrasound-assisted in-situ emulsion polymerization. Copolymers have been synthesized with MMA:BA monomer ratio of 4:1, and varying clay loading (1–5 wt% monomer). The poly(MMA-co-BA)/Cloisite 30B nanocomposites have been characterized for their thermal and mechanical properties. Ultrasonically synthesized nanocomposites have been revealed to possess higher thermal degradation resistance and mechanical strength than the nanocomposites synthesized using conventional techniques. These properties, however, show an optimum (or maxima) with clay loading. The maximum values of thermal and mechanical properties of the nanocomposites with optimum clay loading are as follows. Thermal degradation temperatures: T_10% = 320 °C (4 wt%), T₅₀ = 373 °C (4 wt%), maximum degradation temperature = 384 °C (4 wt%); glass transition temperature = 64.8 °C (4 wt%); tensile strength = 20 MPa (2 wt%), Young’s modulus = 1.31 GPa (2 wt%), Percentage elongation = 17.5% (1 wt%). Enhanced properties of poly(MMA-co-BA)/Cloisite 30B nanocomposites are attributed to effective exfoliation and dispersion of clay nanoparticles in copolymer matrix due to intense micro-convection induced by ultrasound and cavitation. Clay platelets help in effective heat absorption with maximum surface interaction/adhesion that results in increased thermal resistivity of nanocomposites. Hindered motion of the copolymer chains due to clay platelets results in enhancement of tensile strength and Young’s modulus of nanocomposite. Rheological (liquid) study of the nanocomposites reveals that nanocomposites have higher yield stress and infinite shear viscosity than neat copolymer. Nonetheless, nanocomposites still display shear thinning behavior – which is typical of the neat copolymer.     

Study on Preparation and Properties of Acrylonitrile‐Butadiene‐Styrene/Montmorillonite Nanocomposites

Acrylonitrile‐butadiene‐styrene (ABS)/organically modified montmorillonite nanocomposites were prepared by melt blending in an internal mixer, and their morphology, rheological behaviors and mechanical properties were characterized using X‐ray diffraction (XRD), capillary rheometer and tensile, flexural and impact tests. X‐ray diffraction studies revealed the presence of intercalated structure for the prepared nanocomposites and good dispersion of clay layers at low levels of its loading. From the rheological investigations it was observed that the prepared nanocomposites and their pristine counterpart have shear‐thinning behavior, obeying the power law equation. At low shear rates, the steady shear viscosity and shear stress of the nanocomposites increase with increasing of nanoclay content. However, at high shear rates they behave similar to pure ABS. It was shown that the flow activation energy (E) values increase with increasing of nanoclay content. Mechanical tests showed that the flexural moduli of the nanocomposites increase with increase of nanoclay loading, but the flexural strength and the tensile and impact properties decrease with increase of nanoclay content.     

The effects of ultrasound on organoclay dispersion in the PP matrix

PP/MMT nanocomposites were prepared by solution intercalation using sonication and quiescent conditions, and the effects on the morphological, thermal and mechanical properties were evaluated by WAXD, TEM, DMA, TGA and DSC analyses. The present study aims to clarify the effects of ultrasound use on the organoclay surface with different amounts of organic modifiers and on the exfoliation processes. The sonication process decreased around of 200 nm the aspect ratio of C15A organoclay. Besides, the effectiveness of the ultrasound process was only achieved with the C15A system because there is a small energetic barrier between their layers (clay with larger d 001). The sonication process increased the exfoliation and distribution of the C15A platelets in the PP matrix, increasing by 5% its reinforcement capacity. However, for I44P system, the use of ultrasound did not show any significant effect on the morphology and consequently on the final properties of the PP matrix. The T(c) temperature and the thermal stability of the PP nanocomposites were increased, independent of the clay type or of the ultrasound use.     

Synthesis of poly(butylene succinate) nanocomposites via in-situ interlayer polymerization: thermo-mechanical properties and morphology of the hybrid fibers

A series of poly(butylene succinate) (PBS) nanocomposites with the organoclay C₁₂PPh-Mica were synthesized by using the in-situ interlayer polycondensation of 1,4-butanediol with succinic acid. The PBS nanocomposites were melt-spun to produce monofilaments with various organoclay contents and draw ratios (DRs). The thermo-mechanical properties and morphologies of the PBS nanocomposites were determined using differential scanning calorimetry, thermogravimetric analysis, wide angle X-ray diffraction, transmission electron microscopy, and a universal tensile machine. Some of the clay particles were found to be well dispersed in the PBS matrix, with some agglomerated at a size level greater than approximately 20 nm. The thermal degradation properties of undrawn PBS hybrid fibers were found to improve with increasing clay content. The ultimate tensile strengths and initial moduli of the hybrid fibers increased with increasing clay content at DR = 1. However, the ultimate strengths were found to decrease markedly with increases in DR from 1 to 6. In contrast to the trend for the tensile strengths, the initial moduli of the hybrid fibers increased only slightly with increases in DR up to 6.     

Influence of Compatibilizer-Type and Processing Approach on the Dispersion of OMMT in High-Density Polyethylene Matrix

High-density polyethylene/organoclay nanocomposites were prepared via melt intercalation in an internal mixer using both a direct mixing and master batching method. Two types of maleic anhydride grafted polyethylene, high-density polyethylene grafted maleic anhydride, and linear low-density polyethylene grafted maleic anhydride, (HDPE-g-MA, LLDPE-g-MA) were used as compatibilizers to enhance the dispersibility of nanoclay in HDPE. Dispersion of organoclay in the nanocomposites was characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), and rheological mechanical spectroscopy (RMS). Effects of clay content and degree of clay dispersion on the rheological and tensile properties were also investigated. Furthermore, the effect of order of mixing on the dispersion and distribution of the clay layers was studied. The obtained results showed that organoclay in the nanocomposites were dispersed homogeneously and exfoliated better when HDPE-g-MA and the direct mixing route were used. Although in the master batching method clay intercalated better, clay layers chiefly remain in compatibilizer rich areas. On the other hand, direct mixing was observed to lead to clay particles being dispersed in the HDPE matrix or at the interface of the matrix and compatibilizer and, consequently, better improvement in the tensile modulus was achieved. It was determined that the compatibilizer with the higher miscibility with the matrix was the key factor for achieving better exfoliation of clay sheets.     

Effect of interfacial interaction on the structure and rheological properties of polyamide-6/clay nanocomposites

A series of polyamide-6 (PA6)/layered silicate (clay) nanocomposites were prepared via direct melt compounding using a conventional single screw extruder, and then the effect of interfacial interaction on the characteristic internal structure and rheological properties of PA6/clay nanocomposites was investigated. XRD diffractograms indicated a large extent of exfoliation of the layered silicate entering into a strong interaction with PA6. The formation of such morphology was further supported by TEM images. In addition, various rheological properties were interpreted in conjunction with morphological characteristics depending on interfacial interaction between PA6 and the layered silicate.     

Polymer–Clay Nanocomposites Based on Blends of Various Types of Polyethylenes and PE-g-MA: Morphology,Thermal Properties,Microhardness, and Transparency

Polymer–clay nanocomposites have been prepared by melt blending of commercial organoclay Cloisite 15A with blends of polyethylenes (PE) and maleic-anhydride-grafted PE (PE/PE-g-MA) with wide range of composition. Three types of PE/PE-g-MA blends with different molecular structure, namely blends of high-density PE (HD) with HD-g-MA (HDMA), blends of low-density PE (LD) with LD-g-MA (LDMA), and blends of linear low-density PE (LL) with LL-g-MA (LLMA) were used. The influence of the molecular structure of the PE matrixes and the compatibility between the blend components on the morphology of the nanocomposites was studied. The thermal properties, microhardness, and transparency of the nanocomposites were investigated. The influence of the degree of exfoliation/intercalation on the materials characteristics is discussed.     

Effects of Modifier Concentration on Structure and Viscoelastic Properties of Copolyester/Clay Nanocomposites

Abstract

Poly(ethylene glycol‐co‐cyclohexane‐1,4‐dimethanol terephthalate)(PETG)/clay nanocomposites were prepared via melt intercalation technique. The effects of concentration of the organic modifier in the clay on the properties of the nanocomposites were studied. Three clays modified using the same alkyl ammonium modifier, but differing in modifier concentration, are used for this purpose. The nanocomposites are characterized using wide‐angle x‐ray diffraction for their structure. Dynamic mechanical analysis of these nanocomposites is also studied to investigate their viscoelastic behaviors. The x‐ray diffraction study shows an increase in the interlayer spacing of organically modified clays as compared to that of Na⁺ clay. The extent of increase in the interlayer spacing is dependent on the concentration of organic modifier used to modify the montmorillonite. The presence of well‐defined diffraction peaks and the observed increase in the interlayer spacing in the nanocomposites imply the formation of an intercalated hybrid. Dynamic mechanical properties show an increase in the storage modulus of the nanocomposite over the entire temperature range studied, as compared to the pristine polymer. Investigation of the rubbery plateau modulus confirms the reinforcing effect of organically modified clay. The observed enhancement in the modulus was greater for the clay with the lowest content of the organic modifier. These results indicate that in nanocomposites, apart from the compatibility of the organic modifier with the polymer, its concentration in the interlayer also plays a critical role in the structure development and thus in the enhancement of the properties. The nanocomposites showed reduced damping, which was governed by the modifier concentration in the clay.     

Characterization of HDPE/MMT-Based Nanocomposites

A series of HDPE/MMT nanocomposites with different proportions of compatibilizers, PE-g-MAH (AC573A and 5TP409/E) were prepared in a counter rotating twin screw extruder. The effect of nanoclay loading, compatibilizer type and amount was examined. The work was carried out using a specific grade of HDPE recommended for blow-moulding applications and modification of the same by blending with selected polymer and nanofiller to achieve the desired properties. The composition containing higher percentage of nanoclay showed improvement in mechanical properties. About 17% in tensile modulus and about 20% increase in flexural modulus were observed with high-viscous compatibilizer. The dispersion behaviour of nanoclay in PE matrix was studied using X-ray diffraction and transmission electron microscopy. It was clear from WXRD that in all nanocomposite samples, the peaks were shifted to lower 2 values implying that the d-spacing increases and that intercalation occurred. Low molecular weight compatibilizer PE-g-MA resulted in better intercalation than high molecular weight compatibilizer. It was observed that in the case of 5% AC573A loading, there was slight decrease in d-spacing value which indicated that some exfoliation also occurred in nanocomposite. Nanocomposite containing PE-g-MAH is higher concentration gives better dispersion than at low concentration. TEM results show that PE-g-MAH (AC573A) at 5% loading is more efficient as compatibilizer (not many aggregates seen) than other compositions.     

Intercalative polymerization of cyclic esters in layered silicates: thermal vs. catalytic activation

Poly(ε-caprolactone) layered silicate nanocomposites were synthesized by in situ intercalative ring-opening polymerization (ROP) of ε-caprolactone. The polymerization was promoted by thermal or catalytic initiation starting from either non-modified natural sodium-montmorillonite (MMT-Na) or montmorillonite modified by different ammonium cations bearing either non-functional alkyl chains or chains terminated by carboxylic acid or hydroxyl functions. The resulting compositions were analyzed by small-angle X-ray diffraction and transmission electron microscopy. The clay dispersion depended on the structure of the alkyl ammonium. Exfoliated nanocomposites were formed when hydroxyl-containing alkyl ammonium was used; otherwise, partially intercalated/partially exfoliated structures were observed. Moreover, owing to the inherent catalytic properties of the montmorillonite surface, it was also possible to prepare intercalated nanocomposites by in situ polymerization of ε-caprolactone in presence of non-modified montmorillonite-Na (MMT-Na) without any added catalyst.     

Polypropylene/clay nanocomposites prepared with masterbatches of polypropylene ionomer and organoclay

Polypropylene (PP) ionomers were obtained by the neutralization of maleic anhydride groups in a maleated PP of which maleic anhydride content was 1 wt%; these were studied as vehicle resins for the masterbatches of an organoclay for PP nanocomposites. PP/clay nanocomposites were prepared by melt mixing of PP with the masterbatches employing a twin screw extruder. Intercalation and/or exfoliation of the organoclay in the PP nanocomposites were observed. It was found that the PP nanocomposite prepared with the masterbatch of an organoclay and the PP ionomer obtained by 75% neutralization of maleic anhydride groups in the maleated PP showed the largest improvement in dispersion of organoclay. Very large increase of Young's modulus was observed in the nanocomposites with the PP ionomer obtained by 75% neutralization of maleic anhydride groups in the maleated PP. The improvements in the dispersion and mechanical properties were attributed to strong interactions between ionic groups of the PP ionomer and ionic surfactants of the organoclay.     

Thermal,Mechanical, and Rheological Characterization of Polylactic Acid/Halloysite Nanotube Nanocomposites

Halloysite nanotube (HNT) clay and biodegradable polylactic acid (PLA) nanocomposites were fabricated by a melt-blending method with five different clay levels (1, 3, 5, 7, and 9 wt%). The effect of HNT loading on the thermal and mechanical properties of the PLA/HNT nanocomposites was examined by thermogravimetric analysis and universal tensile testing, respectively. Morphological characteristics were investigated by transmission electron microscopy. The composites' melt rheological characteristic analyses were conducted using a rotational rheometer in both steady-shear and oscillatory dynamic testing modes. The data were found to be well-analyzed using the Carreau model, Cox–Merz rule, modified Cole–Cole plot, and van Gurp–Palmen plot.     

Carboxylated acrylo nitrile butadiene rubber latex/kaolin nanocomposites: preparation and properties

Carboxylated nitrile butadiene rubber (XNBR)–based nanocomposites with varying amounts of nanokaolin were produced by latex stage mixing. Sonication of the unmodified kaolin and the technique adopted for the preparation of the composite have helped to get a uniform dispersion of clay in XNBR matrix. Nanokaolin caused enhancement in the mechanical properties of the composites. Proper dispersion of the clay particles, partial exfoliation/intercalation of clay, and interaction of clay with the polar rubber latex made nanokaolin good reinforcing filler in XNBR latex. Swelling studies conducted in methyl ethyl ketone showed a decrease in the swelling index and solvent uptake confirming the hindrance exerted by clay and the possible clay–rubber interaction. Increase in complex modulus obtained from the strain sweep analysis is a further evidence for better rubber filler interaction. The composites were characterized by the scanning electron microscopy, X-ray diffraction analysis, and atomic force microscopy.     

Epoxy-organoclay nanocomposites: morphology,moisture absorption behavior and thermo-mechanical properties

The morphology and moisture barrier characteristics are studied of epoxy-based nanocomposites reinforced with layered silicates. Two different types of organoclay, including the quaternary alkylamine modified montmorillonite (KH-MT) and the octadecylamine modified montmorillonite (I30P), were studied. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicate that the I30P system exhibited a large increase in interlayer d -spacing from 3.39 mm to over 8 nm during the curing process, whereas the KH-MT system showed negligible changes in reflection angle and d -spacing, with the final interlayer distance of 3.39 nm after cure. The moisture absorption behaviour was different for different organoclays: the moisture absorption rate was similar for the neat polymer and the KH-MT system, which could be fitted to Fick's second law. The moisture absorption rate of the I30P system was much lower than the two systems, which was predicted using a non-Fickian model based on the ID Langmuirian solution. The deviation from the Fickian diffusion for the latter system is associated with exfoliated morphology and more uniform dispersion of clay particles, which altered the diffusion path of water molecules in the nanocomposite. The moisture diffusivity of nanocomposites in general decreased with increasing clay content, the reduction being more pronounced for the I30P system. The normalized permeability also showed a systematic degradation with increasing clay content, which agrees well with the prediction based on the tortuous path model.     

Continuous extrusion of long-chain-branched polypropylene/clay nanocomposites with high-intensity ultrasonic waves

A continuous extrusion processing method with high-intensity ultrasonic waves was developed to make a long-chain-branched polypropylene/clay nanocomposite. A multifunctional agent was used to enhance and control the recombination reaction during sonification. The ultrasonic waves induced chain scission and created reactive macromolecules of polypropylene successfully in the continuous extrusion process without any peroxide. The rheological property measurements confirmed that the modified polypropylene had a nonlinear branched structure. Another purpose of dosing high-intensity ultrasonic waves was to enhance nano-scale dispersion during melt mixing of polypropylene and clay. The sonication during processing led to enhanced breakup of the clay agglomerates and reduction in size of the dispersed phase. The observed clay was in the intercalated state without any compatibilizer. The fine dispersion of clay was also quite effective in reducing the end pressure losses in capillary dies and, as a result, significantly improved the extrudate appearance during processing.