Preparation of Exfoliated Low-density Polyethylene/Montmorillonite Nanocomposites Through Melt Extrusion

The effects of ethylene vinyl acetate copelymer （EVA） as a compatibilizer on the dispersion of organically modified montmorillonite（org-MMT） into low-density polyethylene（LDPE） during melt extrusion compounding were studied. The X-ray diffraction patterns reveal that as compared with LDPE, EVA can intercalate more easily into the interlay gallery of org-MMT when the composites contain a low org-MMT content. Exfoliated LDPE/org-MMT nanocompesites in the presence of an EVA compatibilizer could be prepared by using a two-step melt compounding technique with a twin-screw extruder.

The Dynamic Viscoelasticity of Polyethylene Based Montmorillonite Intercalated Nanocomposites

The viscoelastic behavior of melts for two systems composed of intercalated nanocomposites based on low density polyethylene and 3 wt% loading of cetyltrimethyl- ammonium bromide modified montmorillonite was studied. The results obtained through examining the dynamic storage module G' and dynamic loss module G' values of the composite revealed that the dynamic viscoelastic properties of composite strongly depended on intercalation of polymer, and exhibited dramatically change with altering intercalation conditions. Only when modified montmorillonite content was about 3 wt%, the composite showed a trend of pseudo-solidlike at lower frequencies.

Rheological Behavior of the Melts for Polyethylene-based Montmorillonite Nanocomposites

The viscoelastic properties of melts of nanocomposites with partially exfoliated structures, which were composed of low-density polyethylene （LDPE）, ethylene vinyl acetate copolymer （EVA）, and montmofillonite and modified by cetyltrimethyl ammonium bromide and octadecyltrimethyl ammonium bromide, were studied. The results obtained through measurements of the dynamic storage modulus G′, the dynamic loss modulus G″, and the transiem stress relaxation modulus G（t） of the composites, reveal that the viscoelastic properties of the composites strongly depend on the amount of montmorillonite that is exfoliated into the composites. With the increase in montmoriUonite content, the composites show an obvious property of pseudo solid-like materials within the region of lower frequencies （ω）. The montmorillonite layers are aligned along the stress direction, and the dependence of dynamic modulus on ω, appears quite different for the composites before and after being exposed to a large amplitude oscillatory shears.

Vertically aligned montmorillonite aerogel-encapsulated polyethylene glycol with directional heat transfer paths for efficient solar thermal energy harvesting and storage

The conversion and storage of photothermal energy using phase change materials(PCMs)represent an optimal approach for harnessing clean and sustainable solar energy.Herein,we encapsulated polyethylene glycol(PEG)in montmorillonite aerogels(3D-Mt)through vacuum impregnation to prepare 3D-Mt/PEG composite PCMs.When used as a support matrix,3D-Mt can effectively prevent PEG leakage and act as a flame-retardant barrier to reduce the flammability of PEG.Simultaneously,3D-Mt/PEG demonstrates outstanding shape retention,increased thermal energy storage density,and commendable thermal and chemical stability.The phase transition enthalpy of 3D-Mt/PEG can reach 167.53 J/g and remains stable even after 50 heating-cooling cycles.Furthermore,the vertical sheet-like structure of 3D-Mt establishes directional heat transport channels,facilitating efficient phonon transfer.This configuration results in highly anisotropic thermal conductivities that ensure swift thermal responses and efficient heat conduction.This study addresses the shortcomings of PCMs,including the issues of leakage and inadequate flame retardancy.It achieves the development and design of 3D-Mt/PEG with ultrahigh strength,superior flame retardancy,and directional heat transfer.Therefore,this work offers a design strategy for the preparation of high-performance composite PCMs.The 3D-Mt/PEG with vertically aligned and well-ordered array structure developed in this research shows great potential for thermal management and photothermal conversion applications.

Structure and Properties of Self-reinforced Material Made from Ultra-high Molecular Weight Polyethylene-montmorillonite Nanocomposite

High-strength and high-modulus ultra-high molecular weight polyethylene(UHMWPE), named self-reinforced material, was obtained by the elongation of UHMWPE-montmorillonite nanocomposite at melting temperature. According to the scanning electron microscope(SEM) analysis, a great deal of fibrillar texture formed in the direction of elongation, and the tensile fractured surface was similar to that of highly oriented fiber. The transmission electron microscope(TEM) and selective area electron diffraction(SAED) analyses reveal that the reinforced phase of the self-reinforced material is an extended chain crystal and its size is about 50_200 nm wide and several microns long, and the montmorillonite layers are broken up to pieces in the size from 100 to 10 nm. The broken layers which have a huge surface area interacting strongly with macromolecules reduces the entanglement density of UHMWPE and induces the chain orientation in flow field. It is supposed that the astriction of montmorillonite layers to polyethylene chains is not only end-tethered but also side-tethered. The differential scan calorimetry(DSC) analysis shows that there are two endothermal peaks for the self-reinforced material, of which the peak at a higher temperature(136.4 ℃) is ascribed to the melting of the reinforced phase.

Preparation and Properties of Phenolic Resin/Montmorillonite Intercalation Nanocomposites

Phenolic resin/montmorillonite intercalation composites were prepared by using the methods of pressing intercalation and melt intercalation.Properties and structure of the composites were investigated by using XRD,TG and test of softening point.It is indicated that both the pressing intercalation and melt intercalation can be used to prepare the phenolic resin/organo-montmorillonite intercalation nanocomposites.Compared with phenolic resin,the intercalation nanocomposites have better heat-resistance,higher decomposition temperatures and less thermal weight-loss.However,these two intercalation methods have different effects on the softening point of the intercalation nanocomposites.Pressing intercalation almost does not affect the softening point of the intercalation nanocomposites,while melt intercalation significantly increases the softening point of the intercalation nanocomposites, probably due to the chemical actions happening in the process of melt intercalation.

DISPERSION AND TENSILE BEHAVIOR OF POLYPROPYLENE/MONTMORILLONITE NANOCOMPOSITES PRODUCED VIA MELT INTERCALATION

Most of the articles on polymer nanocomposites focus on the importance of chemistry used to modify the surface of the clay, usually montmorillonite (MMT), and characterization of the nano-scale structure obtained. The role and importance of processing were also discussed recently. However, few papers concerning the correlation between morphology of MMT and mechanical properties were published. In order to understand. the tensile behavior of PP/Montmorillonite (MMT) nanocomposites better, and to further improve the reinforcement efficiency, we first prepared the PP nanocomposites via direct melt intercalation using conventional twin-screw extrusion. The dispersion and tensile property of the composites were then investigated by SEM, XRD, TEM and a video-controlled tensile set-up. The macroscopic and microscopic dispersion of MMT in PP matrix was verified by XRD and TEM, combined with SEM. The tensile properties were obtained by video-controlled tensile set-up, which gives true stress-strain curve. It was found that a partly intercalated and partly exfoliated structure (also called incomplete exfoliation) existed in the system. Though the tensile strength of PP nanocomposites is not much improved in engineering stress-strain curves, more than 20% increase of true stress was found in a true stress-strain experiment at high true strain, which indicates that only oriented silicate layers can have a big effect on tensile properties: Not only orientation of silicate platelets but also the degree of exfoliation is a key factor to determine the reinforcement efficiency. The reinforcement efficiency of MMT has been discussed based on the 'continuum' Halpin-Tsai equations. A good agreement was found between experimental data and theoretical prediction by changing N value (number of platelets per stack) which corresponding to different state of the dispersion of MMT in PP matrix.

PROPERTIES AND MORPHOLOGY OF UNSATURATED POLYESTER/ACRYLATE-TERMINATED POLYURETHANE/ORGANO-MONTMORILLONITE NANOCOMPOSITES

Unsaturated polyester resin （UPR）/acrylate-terminated polyurethane （ATPU）/organo-modified montmorillonite （OMMT） nanocomposites were prepared by the in situ intercalative polymerization method. Samples were prepared by the sequential mixing, i.e. mixture of the ATPU and styrene （S） and OMMT were prepared in the first step; UPR was then added to the pre-intercalates of ATPU/S/OMMT. Results indicate that the mechanical properties and thermal properties of UPR/ATPU/OMMT nanocomposites greatly depend on the amount of ATPU and OMMT. Results show that the addition of ATPU could increase the impact strength of UPR/ATPU composites, but the tensile strength, flexural strength and heat resistance of the materials are obviously decreased. When the weight ratio between UPR, ATPU and OMMT were 82：15：3, the impact strength and heat distortion-temperature of nanocomposite were greatly improved, meanwhile there was little change for other properties of the nanocomposites. The synergistic enhancement effects of ATPU and OMMT on the composites were observed. The structures and morphology of the composites were investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy.

Preparation and Characterization of Polylactide/Montmorillonite Nanocomposites

The montmorillonite, a form of layered silicate, was successfully intercalated into polylactide （PLA） matrix through solvent-casting technique. In addition, PLA/MMT nanocomposite films were produced, in which homogenous distribution of the silicate lamellae plays a key role in the mechanical properties of the films. A small amount（5wt%） of OMMT intercalated into the PLA matrix resulted in their flexibility enhancement, from 3.68%（pure PLA film） to 352.65%. The results of wide-angle X-ray diffraction （WAXD） patterns confirmed that the silicate interlayer distance increased from 3.044 nm （for OMMT） to 3.56nm （for 5wt%, maximum） with increasing OMMT contents, but decreased to 3.319 nm when OMMT content was over 8wt%. FT-IR also verified the molecular-level associations between PLA chains and OMMT lamellae by vibration variances of hydrogen bonding. DSC thermograms demonstrated that thermal stabilities of the nanocomposite films enhanced, due to the silicate lamellae dispersed into PLA matrix.

Structure Characterization and Thermal Properties of PMMA/Montmorillonite Nanocomposites via Emulsion Polymerization

Montmorillonite(MMT) modified with sodium silicate can change the arrangement of its layers from edge-face and edge-edge to face-face. With the fine dispersion of the modified MMT in water,the cation-exchange reaction was carried out with cetyltrimethyl ammonium bromide(CTAB) to obtain organo-montmorillonite(OMMT). As OMMT was uniformly dispersed in methyl methacrylate(MMA) monomer,PMMA/OMMT nanocomposites were formed via a common emulsion polymerization. The products were extracted with hot acetone and characterized by FTIR,molecular weight,X-ray diffraction(XRD),transmission electron microscopy(TEM),DSC and TGA. These results show that most of the OMMT layers have been exfoliated,while the thermal stability is increased obviously. By means of FTIR spectral analysis,the ratios of the macromolecular radicals′ termination of disproportionation patterns to combination are increased with the addition of OMMT. This result further confirms the increase of the thermal degradation temperatures and glass transition temperatures of the PMMA/OMMT nanocomposites.

Polynaphthoxazines-Montmorillonite Nanocomposites: Synthesis and Characterization

Polynaphthoxazines-clay nanocomposites were prepared from 1, 5-dihydroxynaphthalene, aniline, formaldehyde and different proportion montmorillonite(MMT) by in-situ reaction in ethanol. Dynamic TGA showed that nanocomposites have delayed decomposition temperatures when compared with pristine polynaphthoxazine indicating the enhancement in the thermal stability.

Synthesis and characterization of carboxymethyl cellulose/organic montmorillonite nanocomposites and its adsorption behavior for Congo Red dye

A series of carboxymethyl cellulose/organic montmorillonite （CMC/OMMT） nanocomposites with different weight ratios of carboxymethyl cellulose （CMC） to organic montmorillonite （OMMT） were synthesized under different conditions. The nanocomposites were characterized by the Fourier transform infrared （FT-IR） spectrophotometer, X-ray diffraction （XRD） method, transmission electron microscope （TEM）, scanning electron microscope （SEM）, and thermal gravimetric （TG） analysis. The results showed that the introduction of CMC may have different influences on the physico-chemical properties of OMMT and intercalated-exfoliated nanostructures were formed in the nanocomposites. The effects of different reaction conditions on the adsorption capacity of samples for Congo Red （CR） dye were investigated by controlling the amount ofhexadecyl trimethyl ammonium bromide （CTAB）, the weight ratio of CMC to OMMT, the reaction time, and the reaction temperature. Results from the adsorption experiment showed that the adsorption capacity of the nanocomposites can reach 171.37 rag/g, with the amount of CTAB being 1.0 cation exchange capacity （CEC） of MMT, the weight ratio of CMC to OMMT being l：l, the reaction time being 6 h, and the reaction temperature being 60~C. The CMC/OMMT nanocomposite can be used as a potential adsorbent to remove CR dye from an aqueous solution.

Characteristics of LDPE and Oriented Montmorillonite Nanocomposites Produced by Electric Field-inducement

In order to make montmorillonite (MMT) nanosheets disperse in low-density polyethylene (LDPE) with highly homogeneous orientation, alternating voltage is applied to molten LDPE with MMT nanosheets. The effect of electric field on the dispersion of MMT in the solidified LDPE is studied. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses suggest that the MMT nano- sheets are aligned with high anisotropy to the electric field direction, which is perpendicular to the LDPE film plane. Differential scanning calorimetry (DSC) results reveal that the crystallization degree of the oriented LDPE/MMT composite increases. Moreover, through a broadband dielectric spectroscopy analyzer, it is found that MMT manifests a significantly influence in the dielectric property of the oriented composite: the dielectric constant and loss tangent of the composite both become larger. Analysis shows that the electric field-induced torque caused by the polarization of MMT flakes is the main force inducing the orientation of the MMT flakes.

Effect of different montmorillonites on rheological properties of bitumen/clay nanocomposites

Different composites of organomodified montmorillonite(OMMT)/bitumen were prepared by melt blending with hexadecyl dimethyl benzyl ammonium modified montmorillonite(HBM) and double octadecyl dimethyl ammonium modified montmorillonite(DOM).The structures of two kinds of montmorillonite modified bitumen were characterized by X-ray diffraction(XRD).The effects of different montmorillonites on the dynamic rheological properties of the modified bitumens were investigated by dynamic shear rheometer(DSR).The XRD results show that DOM modified bitumen forms an intercalated structure,whereas the HBM modified bitumen forms an exfoliated structure.DSR results indicate that OMMT modified bitumens exhibit higher complex modulus,lower phase angle than pristine bitumen,which means that the resistance to rutting at high temperatures of pristine bitumen is improved due to the introduction of OMMT.Compared with DOM modified bitumen,HBM modified bitumen shows better rutting resistance,which is contributed to the formation of exfoliated structure in HBM modified bitumen.

LOW DENSITY POLYETHYLENE/CLAY NANOCOMPOSITES MODIFIED BY ETHYLENE COPOLYMERS: EFFECTS OF FUNCTIONALIZED SEGMENTS ON MORPHOLOGY

Melt extrusion was used to prepare binary nanocomposites of ethylene copolymers and organoclay and trinary nanocomposites of low-density polyethylene （LDPE）, ethylene copolymer and organoclay. X-ray diffraction （XRD） and transmission electron microscopy （TEM） were used to analyze the structure of the clay phase and the morphology of the nanocomposites. Influences of the comonomer in the copolymer and the content of the copolymer on the morphology of the resulting nanocomposites were discussed. The binary and the trinary composites may form intercalated or exfoliated structures depending on the interaction between the copolymer and the clay layers and the content of the copolymer.

Preparation of the Thermoplastic Starch/Montmorillonite Nanocomposites by Melt-intercalation

In this paper, the conception of melt-intercalation was introduced into the natural polymer field, and the thermoplastic starch/ethanolamine-activated montmorillonite (TPS/EMMT) nanocomposites were prepared by extruding the composites of EMMT and TPS, plasticized with ethanolamine/formamide. Wide angle X-ray diffraction (WAXD) and transmission electron microscope (TEM) revealed that TPS was intercalated into the layers of EMMT successfully and formed the intercalation nanocomposites with EMMT. When EMMT content was wt.10%, the mechanical testing indicated that the tensile stress of the nanocomposites reached 9.69 MPa, and the tensile strain reached 74.07%, Youngs modulus increased from the 47.23 MPa of TPS to 184.11 MPa of TPS/EMMT nanocomposites, and breaking energy increased from 1.34 N·m to 2.15 N·m after they had been stored at RH25% for 14 days.

Modification of Nanocomposites by Melting Intercalation of Polypropylene in Montmorillonite

The polypropylene wax modified by ultraviolet irradiation. The polypropylene-montmorillonite nanocomposiles were prepared by direct melting intercalation oj polypropylene powders. The structure of polypropylene , the polyproprlene irradiated, montmorillinote and polypropylene-montmorillonite composites were studied by XRD, 1R and DSC. The results show that the PP molecules can are oxidized during ultraviolet irradiation , melt polypropylene can intercalate into montmorillonite layer. As a result, the layered distance ( d0.01) of montmorillonite increases, and the melt absorption peak of polypropylene in layer is eliminated.

SYNTHESIS AND CHARACTERIZATION OF ORGANOMONTMORILLONITE AND POLYAMIDE 66/MONTMORILLONITE NANOCOMPOSITES

The montmorillonites (MMTs), layered, smectite-type silicates, were premodified by two different methods prior to the polymer melt intercalation. In one case MMTs were modified with cetyltrimethylammonium bromide (CTAB), and termed as organomontmorillonites (OMMTs); in the other case MMTs were modified by nylon, and the products were called modified montmorillonites (MMMTs). The effects of CTAB and nylon on the MMTs were investigated by using TG and WAXD. The results show that interlayer spacings of CTAB and nylon modified MMTs are larger than that of sodium MMTs. Then, polyamide 66 (PA 66)/MMT nanocomposites were obtained through the method of melt intercalation of polymers. The nanocomposites were characterized by WAXD, TEM and Molau experiments. The results indicate that the MMTs disperse homogeneously in the PA 66 matrix. The mechanical properties of nanocomposites, such as tensile properties and flexural properties, were also measured and show a tendency to increase with increase of MMT content and reach the maximum values at 5phr MMT content. The heat distortion temperature (HDT) of the nanocomposites (7 phr) is about 32 K higher than that of pure PA 66.

Structures and Mechanical Properties of PVC/Na^+- Montmorillonite Nanocomposites

Poly (vinyl chloride)/Na+-montmorillonite (PVC/MMT) nanocomposites with different MMT contents were prepared via melt blending. Wide-angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM) were used to characterize the structures. Effects of MMT content on the mechanical properties were also studied. It is found that PVC molecular chains can intercalate into the gallery of MMT layers during melt blending process, the stiffness and toughness of the composites are improved simultaneously within 0.5~7wt% MMT content, and the transparency and mechanical properties decrease as MMT content further increases.

Preparation and Structure of Poly(ethylene-co-vinylacetate)/Montmorillonite Nanocomposites

Poly(ethylene-co-vinylacetate)/sodium montmorillonite(EVA/MMT)and Poly(ethylene-co-vinylacetate)/organophilic montmorillonite(EVA/o-MMT)nanocomposite were prepared by solid-state mixing.The morphology and structure of the composites were explored by scanning electron microscopy(SEM),wide-angle X-ray diffraction(WAXD),differential scanning calorimetry(DSC),and dynamic mechanical analysis(DMA).The results showed that the intercalated nanocomposite was successfully synthesized for EVA/o-MMT system,while in the EVA/MMT nanocomposite,MMT were poorly dispersed in the order of μm.An unexpected rubbery plateau modulus of EVA/o-MMT nanocomposite above melting point of EVA was explored by DMA.The possible origins of this high-temperature modulus were analyzed.