The Enhanced Melt Intercalation of Polyethylene Using Exothermal Montmorillonite

Exothermal montmorillonite (EMMT) was prepared and used in the preparation of HDPE composites in which the EMMT was intercalated. Compared with the ODA modified montmorillonite (OMMT), EMMT exhibited better intercalation behavior during melt compounding, resulting in similar tensile modulus and better tensile strength and elongation at break of the corresponding composites. The crystallization of the polymeric matrix and the dispersion of MMT were systemically investigated; their relationship with the mechanical properties of the composites are discussed as well.     

Morphology and Properties of Poly(vinyl alcohol)/MMT Nanocomposite Prepared by Solid-state Shear Milling (S3M)

Poly(vinyl alcohol) (PVA)/montmorillonite (MMT) nanocomposites were prepared by combining solid-state shear milling (S³M) technology with melt intercalation. Compared with the composite obtained by simple melt intercalation, more MMT layers were exfoliated and apparently oriented along the injection molding direction in the nanocomposite prepared by combining S³M technology and melt intercalation, which greatly increased the orientation degree of MMT, resulting in the greater interactions between PVA and MMT layers. Simultaneously, this also promoted the orientation of PVA molecules and produced effective nucleation of the crystallization of PVA. Consequently, the thermal stability and mechanical properties of PVA were obviously improved. For instance, when the MMT content was 3 wt%, the tensile strength and modulus of the nanocomposite with MMT prepared by S³M were 98.9 MPa and 3.1 GPa, respectively, increasing by 52% and 63.2% compared with PVA.     

Effect of Surfactant Concentration on Thermal and Mechanical Properties of Poly(Butylene Succinate)/Organoclay Composites

Composite materials consisting of poly(butylene succinate) (PBS) and montmorillonite (MMT), modified to various extents using trihexyltetradecylphosphonium chloride (THTDP) cations, were prepared using a simple melt intercalation technique. The surfactant contents were varied, i.e. 0.4, 0.6, 0.8, 1.0, and 1.2 times the cation exchange capacity (CEC) of the MMT. The intercalation of the surfactant molecules into MMT layers, confirmed by the increase in interlayer spacing and significant changes in the morphology of the modified MMT, facilitated the dispersion of the clay in the PBS matrix. The properties of the PBS-based composites were changed with increasing surfactant content. The melting and crystallization temperatures increased and the degree of crystallinity (χ_c) decreased. The storage modulus was significantly enhanced below the glass transition temperature (Tg), and Tg shifted to a higher temperature, with a maximum at a surfactant loading of 0.6 CEC. The mechanical properties, including tensile strength, flexural strength, flexural modulus and impact strength, increased and then decreased with surfactant loading, with the maximum observed also at a surfactant loading of 0.6 CEC. In conclusion, an ideal balance between thermal and mechanical properties can be obtained at a surfactant quantity equivalent to 0.6 times the clay CEC. Moreover, all the composites exhibited obvious improvement in thermal and mechanical properties as compared to those of neat PBS.     

Preparation and Properties of Organically Modified Montmorillonite/Nitrile Rubber Nanocomposites

A series of organically modified montmorillonite (OMMT)/nitrile rubber (NBR) nanocomposites were prepared by a simple mechanical-mixing method. The structures of OMMT and the dispersion of OMMT in the rubber matrix were detected by X-ray diffraction (XRD). The mechanical properties of the NBR/OMMT nanocomposites were characterized, and the tribological behaviors of the nanocomposites were evaluated on a ring-block (MRH-3) wear tester. The results showed that the OMMT was homogeneously dispersed in the NBR matrix. The tensile strength of the OMMT/NBR nanocomposites increased with increasing OMMT contents. Both the coefficient of friction (COF) and wear of the nanocomposites decreased remarkably with increasing OMMT content. In addition, the influence of the applied load on the tribological properties of the nanocomposites is discussed. It is expected that the research may be of aid in the rational design and use of solid, self-lubricating nanocomposites under different loading states.     

A Novel Potential Ecomaterial Based on Poly(p-Dioxanone)/Montmorillonite Nanocomposite With Improved Crystalline,Processing, and Mechanical Properties

Poly(p-dioxanone) (PPDO) is a useful biomaterial and potential ecomaterial due to its biodegradability and good mechanical properties. Like other aliphatic polyesters, however, it has a low crystallization rate and low melt strength; it is difficult to produce thin films from it by blown film processing. In this work, poly(p-dioxanone)/montmorillonite (MMT) nanocomposites have been prepared successfully by in situ ring-opening polymerization of p-dioxanone and MMTs. The novel, biodegradable nanocomposites have a remarkably increased crystallization rate and melt strength; moreover, they can be blown into thin films, which have excellent mechanical properties. A typical sample showed a tensile strength of 59.2 MPa and elongation at break 605%.     

High-Performance Poly(vinyl alcohol) Nanocomposites Filled with Individual Montmorillonite Nanolayers

Filling poly(vinyl alcohol) (PVA) with clay, typically montmorillonite (MMT), has been proven to be an attractive option to meet the high-performance requirements of PVA-based materials. In previous reports MMT or organophilic MMT (OMMT) were directly used as fillers. As a result, both exfoliated and intercalated MMT structures coexisted in the resultant nanocomposites. However, there is still a large gap between these nanocomposites and ideally designed ones where individual clay nanolayers (CNLs) are expected to be uniformly dispersed in the PVA. With this in mind, an ameliorative solution casting process is proposed here to prepare PVA nanocomposites. For this purpose the CNLs were prepared ahead of time by exfoliation of MMT in water and then used as fillers. Assessment of the dispersion state of the CNLs in PVA revealed that they (≤5.0 wt%) were randomly and uniformly dispersed (down to the level of individual silicate layers) in and formed strong interfacial interactions with the PVA. This resulted in significantly enhanced physical properties of the resultant nanocomposites relative to neat PVA. In particular, a 104.7% increment in the yield stress was achieved with 5.0 wt% CNLs, much larger than the 15–70% increments of previous PVA nanocomposites using MMT or OMMT as fillers. Additionally, excellent optical clarity of the PVA was obtained for the nanocomposites.     

Effect of clay silylation on curing and mechanical and thermal properties of unsaturated polyester/montmorillonite nanocomposites

This work focuses on the chemical modification of montmorillonite (MMT) (Cloisite® Na) with compatible silanes, vinyltriethoxysilane (CVTES) and γ-methacryloxypropyltrimethoxysilane (CMPS) in order to prevent agglomeration and to improve montmorillonite interaction with an unsaturated polyester resin matrix seeking to achieve a multifunctional composite. Clays were dispersed in the resin by mechanical stirring and sonication and the nanocomposites were prepared by resin transfer into a mold. The mechanical, morphological, thermal and flammability properties of the obtained composites were compared with those prepared using commercial Cloisite® 30B (C30B) and Cloisite® 15A (C15A) clays. Advantages of using silane-modified clays (CVTES and CMPS) as compared with organic-modified clays (C30B and C15A) can be summarized as similar flexural strength and linear burning rate but higher storage modulus and improved adhesion to the polyester resin with consequent higher thermal deflection temperature and reinforcement effectiveness at higher temperatures. However, organic modified clays showed better dispersion (tendency to exfoliate) and consequently delayed thermal volatilization due to the clay barrier effect.     

Polymer Dynamics in Polyurethane/clay Nanocomposites Studied by Dielectric and Thermal Techniques

Differential scanning calorimetry (DSC), broadband dielectric relaxation spectroscopy (DRS), and thermally stimulated depolarization current (TSDC) techniques were employed to investigate glass transition and polymer dynamics in nanocomposites of polyurethane (PU) and organically modified montmorillonite (MMT) (weight fraction 0%–15%) prepared by solution casting. The PU matrix was obtained from oligo(oxytetramethylene glycol) of molar mass 1000 g/mol, 4,4′-diphenylmethane diisocyanate and 1,1-dimethylhydrazine as chain extender. Wide-angle X-ray scattering confirmed the formation of partly exfoliated structures at low MMT content. DSC, DRS, and TSDC show, in agreement with each other, that a fraction of polymer makes no contribution to the glass transition and to the corresponding α relaxation, whereas the rest exhibits similar glass transition dynamics as the pure matrix. This fraction of immobilized polymer reaches a maximum at about 5 wt% MMT. Effects of MMT on the microphase-separated structure of PU are negligible, as indicated by the study of glass transition and interfacial dielectric polarization/relaxation. No effects of MMT on the local, secondary γ and β relaxations were observed. Mechanical properties show a maximum improvement at about 5 wt% MMT, in good correlation with morphology and dynamics.     

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.     

Characteristics of Rubber/Sodium Montmorillonite Nanocomposites Prepared by a Novel Method

In order to enhance the fine dispersion of hydrophilic sodium montmorillonite (Na‐MMT) in the matrix of hydrophobic rubber, the hydrophobic modification of Na‐MMT was carried out via an in situ method in the melt compounding process using the modifiers poly(ethylene glycol) monooleate or poly(ethylene glycol) diacrylate, both of which have a hydrophilic poly(ethylene glycol) (PEG) segment and a hydrophobic hydrocarbon segment. The X‐ray diffraction patterns showed that the interlayer distance of Na‐MMT was expanded by the intercalation of these modifiers. The morphology observed by scanning electron microscopy as well as the cure characteristics and tensile modulus showed that this organic modification effectively enhanced the fine dispersion of Na‐MMT in the rubber matrix.     

Synthesis and Characterization of Novel Poly(1‐Naphthylamine)‐Montmorillonite Nanocomposites Intercalated by Emulsion Polymerization

Nanocomposites of montmorillonite (MMT) with poly(1‐naphthylamine) (PNA) is investigated for the first time by emulsion polymerization using three different oxidants. Polymerization of PNA was confirmed by Fourier transformation infrared (FT‐IR) as well as UV‐visible spectra. The in situ intercalative polymerization of PNA within MMT layers was confirmed by FT‐IR, X‐ray diffraction, conductivity; scanning electron microscopy (SEM) as well as transmission electron microscopy studies. X‐ray diffraction revealed intercalated as well as exfoliated structures of PNA/MMT nanocomposites, which were compared with the reported polyaniline‐MMT nanocomposites. It was found that the increase in the concentration of PNA in the interlayer galleries of MMT led to destruction of the layered clay structure resulting in exfoliation of the nanocomposite. Conductivity of the nanocomposites was found to be in the range of 10^?3 to 10^?2 S cm^?1 which was found to be higher than the ones reported for polyaniline‐clay nanocomposites as well as PEOA‐OMMT nanocomposites at similar concentrations of intercalated species. The morphology of PNA/MMT nanocomposites was found to be governed by the nature of the oxidant used.     

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%.     

Polycyanurate–Organically Modified Montmorillonite Nanocomposites: Structure–Dynamics–Properties Relationships

Polycyanurate‐modified montmorrilonite (PCN‐MMT) nanocomposites were synthesized by polymerization of dicyanate ester of bisphenol A in the presence of MMT dispersed by ultrasound. Techniques of IR spectroscopy, WAXD, and TEM were applied to study polymerization kinetics and structure of the nanocomposites prepared, whereas their dynamics and thermal/mechanical properties over the ?30 to 420°C range were studied by using DSC, laser‐interferometric creep rate spectroscopy (CRS), and dielectric relaxation spectroscopy (DRS) techniques. It was shown that a small amount of MMT additive acts as a catalyst of polymerization and results in the formation of complicated intercalated/exfoliated structures, as well as strongly modifies the dynamics in the PCN network. Pronounced dynamic heterogeneity was observed for PCN/MMT nanocomposites. Along with the main PCN glass transition, two new glass transitions, at much higher and much lower temperatures, were revealed as a consequence of constrained dynamics in matrix interfacial nanolayers and due to incomplete local cross‐linking in the PCN matrix, respectively. In addition, increased sub‐T _g mobility was observed in these nanocomposites. A two‐fold rise of modulus of elasticity as well as increasing thermal stability and arising microplasticity at low temperatures, promoting, obviously, improved crack resistance in a brittle PCN network, were found for the PCN‐MMT nanocomposites.     

Comparative Study of the Effect of Addition of Silica and Silicate Nanofillers on the Properties of Epoxy Coatings

The effect of adding different amounts (0.5–3 wt%) of nanosilica (NS) and organomodified montmorillonite (MMT) to diglycidyl ether bisphenol A (DGEBA) cured with isophorone diamine at different temperature on the viscoelastic, topographical and gelation properties of epoxy resin was studied. Gel time measurements revealed that both NS and MMT accelerated the curing reaction of DGEBA with IPDA. Both nanofillers were adequately dispersed in DGEBA. The particle size distribution depended on the amount of nanofiller. A broader distribution for NS than for MMT filled epoxy was obtained. On the other hand, an increase in the curing temperature was required to obtain the intercalation of the epoxy into the MMT tactoids. At room temperature, the addition of NS increased both the stiffness (high storage modulus) and the toughness (an increase in the area and height of the tan δ curve) of epoxy, but no significant differences were found by curing at higher temperature. Epoxy/MMT composites showed higher storage modulus in the rubbery region. The improved properties imparted by NS can be ascribed to the interactions between the silanol moieties on the nanosilica surface and the polar groups in the epoxy, whereas the improvement imparted by MMT organoclay was related to tactoid intercalation within the epoxy matrix.     

Preparation,Characterization, and Properties of Polyamide 66/Maleic Anhydride -grafted-polypropylene/Clay Ternary Nanocomposites

Polyamide (PA) 66/PP-g-MA/Organic-modified MMT (OMMT) ternary composites were prepared by direct melt compounding. The FESEM results showed that the PP-g-MA phase dispersed homogeneously in the PA matrix due to the interfacial chemical reactions between the two phases. The mechanical properties of the composites were evaluated. The tensile and bending properties decreased and the notched impact strength increased with the increase of PP-g-MA. The tribological behaviors of the ternary composites were studied by means of a ball-on-disk apparatus. The ternary composites exhibited better tribological properties compared with the PA/OMMT system. This was probably due to the fact that the PP has good flexibility and a transferring film could be formed easily on the counterpart. Combining the results of the mechanical and tribological properties, the optimal mass fraction of PP-g-MA was 10 wt. %.     

Nonisothermal Crystallization Kinetics of Nylon 66/Montmorillonite Nanocomposites

Polyamide 66(PA66)/montmorillonite nanocomposites were prepared via direct melt compounding. The nonisothermal crystallization of PA66 and PA66/MMT nanocomposites were investigated by differential scanning calorimetry. The results show that MMT platelets play a competing role in the crystallization process of nylon 66. On the one hand, they can act as a nucleator for the PA66 matrix, accelerating the crystallization rate; on the other hand, they retard the crystal/spherulite growth, especially for nanocomposites with higher MMT content. The analysis results using Jeziorny and Mo equations verify the dual actions of the nucleation and the obstruction of crystallization of MMT in the PA66 matrix. Kissinger's method was used to obtain the activation energy of the crystallization process; the results confirm that the incorporation of MMT causes the above actions.     

Effects of Montmorillonite on the Nonisothermal Crystallization Behavior of the Poly(trimethylene terephthalate)/Polypropylene/Montmorillonite Nanocomposites

Organic montmorillonite (MMT) reinforced poly(trimethylene terephthalate) (PTT)/ polypropylene (PP) nanocomposites were prepared by melt blending. The effects of MMT on the nonisothermal crystallization of the matrix polymers were investigated using differential scanning colorimetry (DSC) and analyzed by the Avrami equation. The DSC results indicated that the effects of MMT on the crystallization processes of the two polymers exhibited great disparity. The PTT's crystallization was accelerated significantly by MMT no matter whether PTT was the continuous phase or not, but the thermal nucleation mode and three-dimensional growth mechanism remained unchanged. However, in the presence of MMT, the PP's crystallization was slightly retarded with PP as the dispersed phase, and was influenced little with PTT as the dispersed phase. When the MMT content was increased from 2_wt% to 7_wt%, the crystallization of the PTT phase was slightly accelerated, whereas the crystallization of the PP phase was severely retarded, especially at lower temperatures. Moreover, the nucleation mechanism for the PP's crystallization changed from a thermal mode to an athermal one. In the polypropylene-graft-maleic anhydride (PP-g-MAH) compatibilized PTT/PP blends, with the addition of 2_wt% MMT during melt blending, the T _c (PTT) shifted 7.8°C to lower temperature and had a broadened exotherm, whereas the T _c (PP) shifted 17.1°C to higher temperature, with a narrowed exotherm. TEM analysis confirmed that part of the PP-g-MAH was combined with MMT during blending.     

Structure and Properties of Poly(Oxypropylene) Diamine Intercalated Montmorillonite/Epoxy Composites

Abstract

A type of micro-multilayer particles with a structure similar to that of nacre was prepared by poly(oxypropylene) diamine (POPD) intercalating organic montmorillonite (OMMT). The prepared particles were then blended with epoxy resin (EP) to obtain high performance EP composites. The Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and contact angle analysis of the OMMT showed that the (POPD) had been successfully intercalated into the OMMT and the micro-multilayer particles were obtained as expected. Transmission electron microscope observation of the cured composites further confirmed that the micro-multilayer particles were well maintained in the EP network. The tensile and bending strength and glass transition temperature of the OMMT/EP composites were all increased compared with those of the EP. All these showed that the addition of the OMMT was an effective way to obtain high performance EP composites.     

Structure and Properties of a cis-1,4-Polybutadiene/Organic Montmorillonite Nanocomposite Prepared via In Situ Polymerization

Cis-1,4-polybutadiene (cis-1,4-PB) is one of the most important synthetic rubbers, having superior performances such as wear resistance, cold resistance and high elasticity. However, its mechanical properties, including low tensile strength, tear resistance and thermal stability, limit its application in comparison to natural rubber and butadiene-styrene rubber that have excellent overall performances. Thus, the reinforcing of cis-1,4-PB is a necessity. The dispersion of clay in rubbers on the nanoscale can improve the mechanical, gas permeability and thermal properties of the resulting composites. In this paper, organic montmorillonite (OMMT) clay was dispersed into the cis-1,4-PB matrix via an in-situ polymerization method and the chemical structure, phase morphology, mechanical properties and thermal stability of the composite were investigated. The properties of the composite were analyzed by such techniques as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and thermal gravimetric analysis (TGA). In the in-situ polymerization, a Ni-based catalyst system with the presence of OMMT showed high efficiency and 1,4-selectivity for the polymerization of butadiene. The OMMT could be dispersed in the polymeric matrix on the nanoscale during the polymerization. The interfusion of OMMT had little influence on the thermal stability and the chemical micro-structure of the cis-1,4-PB when the content of cis-1,4 units was more than 95%. The loss tangent of the composite was higher than that of cis-1,4-PB from ?110 to ?55°C, the temperature range examined, and the mechanical properties of the cis-1,4-PB/OMMT nanocomposite (NC) were improved upon the addition of OMMT.     

Effect of Morphology and Composition of Organic Montmorillonite on the Structure and Properties of Poly(Butylene Terephthalate) Nanocomposites

The morphology and composition of organic montmorillonites are critical for their dispersion in polymer matrixes. In the current study, the pristine montmorillonite (MMT) was first surface modified with silane and then intercalated using two kinds of intercalating agents in supercritical carbon dioxide (scCO₂). The obtained OMMTs with tunable morphology and composition, together with pristine MMT and commercial MMT, were introduced into poly(butylene terephthalate) (PBT) to investigate the MMTs dispersion in the PBT matrix and the final properties of the PBT/MMT nanocomposites. The structure of the different MMTs and their dispersion in the PBT matrix were characterized by SEM and TEM, respectively. The crystallization behavior, storage moduli and loss factors of the PBT/MMT nanocomposites were also investigated.