Increasing OMMT Content Research Articles

Localization of different types of organoclay montmorillonite in the compatibilized polyamide 6/carboxylated acrylonitrile butadiene rubber nanocomposites: Morphology and rheological properties

AbstractIn this study, nanocomposites based on polyamide 6/carboxylated acrylonitrile butadiene rubber (PA6/XNBR) reinforced by the clay montmorillonite (OMMT) (Cloisite 20A and Cloisite 30B) were prepared by melt mixing. Glycidyl methacrylate‐grafted XNBR (XNBR‐g‐GMA) compatibilizer was used for immiscible blends of PA6/XNBR. The results illustrated that OMMT wanted to be selectively present in the more hydrophilic PA6 phase. Also, by adding the XNBR‐g‐GMA compatibilizer and increasing OMMT content, tensile strength, rheological and dynamic mechanical properties of the nanocomposites improved. According to transmission electron microscopy (TEM) images, a few layers of OMMT (Cloisite 20A) in the XNBR‐g‐GMA compatibilizer phase was observed. The results of X‐ray diffractometry and TEM analyses demonstrated that the formation of intercalated or exfoliated structures for both types of OMMT nanocomposites. In end of all analysis was found PA6/XNBR reinforced by the Cloisite 30B could be substantially improved by adding XNBR‐g‐GMA as a compatibilizer when compared to those reinforced by Cloisite 20A.

Development of Flexible Polyurethane Nanostructured Biocomposite Foams Derived from Palm Olein-Based Polyol

This study examined the effect of organoclay montmorillonite (OMMT) on the mechanical properties and morphology of flexible polyurethane/OMMT nanocomposite (PU/OMMT) foams prepared from petroleum- and palm olein-based polyols. Palm-based PU foams exhibited inferior mechanical strength as compared to neat petroleum PU foams. However, addition of OMMT significantly improved the foams strength of flexible polyurethane/OMMT nanocomposite foams prepared from palm olein-based polyol (PU bionanocomposite foam). The morphology analysed by scanning electron microscopy (SEM) showed that the cell size of the foam decreased with increasing OMMT content. PU bionanocomposite foam with 5 wt% of OMMT had the most improved tensile (63%) and tear (48%) strengths compared to its neat counterpart. Transmission electron microscopy (TEM) revealed the exfoliated structure of the respective foam. It was concluded that OMMT improved mechanical properties and morphology of PU foams.

Preparation and Properties of Poly(L-Lactid Acid)/Organo-Montmorillonite Composites by Solution Casting Method

PLLA / OMMT composite films were prepared through solution casting method, in which chloroform was used as solvent. Mechanical, thermal and crystallization properties of neat PLLA and PLLA / OMMT composites films were investigated as well as morphology through scanning electron microscope. It was shown that tensile strength of PLLA / OMMT composite films gradually increased with increasing OMMT content, but reduced when more filler were added. Loading of 2wt% of OMMT seemed to benifit PLLA in tensile strength most. With the increase of montmorillonite content, the elongation at break of PLLA decreased first and then reached to a steady level. When compared with pure PLLA, the composite system showed decreased spherulite size, lower degree of order and an increase in the number of grains. Thermal analysis has proved that the addition of OMMT greatly enhanced crystability and thermal stability of PLLA.

Effect of OMMT on Morphology and Property of PTT/ASA Blends

Nanocomposites of poly(trimethylene-terephthalate)/poly(acrylonitrile-styrene-acrylate)/organic montmorillonite(PTT/ASA/OMMT) were prepared by means of melt-blending intercalation. The effect of OMMT contents on the phase morphology, crystallization behavior, rheological- and mechanicalproperties were investigated. The results show that the size of dispersed phases decreases with increasing OMMT content. The crystallization peak shifts to high temperature and melting peak moves to low temperature owing to the heterogeneous nucleation of OMMT. The exfoliated OMMT is located in the PTT matrix and at interface of PTT/ASA phases The rheological measurements show that the elastic modulus and complex viscosity increase with increasing OMMT content. The interfacial modulus and interfacial layer thickness predicted by Palierne and Gramspacher-Meissner models are enhanced by introduction of OMMT. The tensile strength and notched impact strength of blends increase with increasing OMMT content.

Phase Morphology and Rheology Behaviors of PTT/POE/OMMT Nanocomposites

The phase morphology and dynamic rheology of poly (trimethylene terephthalate)/maleinized poly (octene-ethylene)/organo-montmorillonite nanocomposites were investigated by using transmission electron microscopy (TEM) and rotational rheometer. The results suggest that some of the OMMT are peeled off and the nanosheets are dispersed evenly in the polymer matrix. When the OMMT content is more than 4%, they are tended to form the aggregates in nanocomposites. The nanocomposites’ melt are pseudo-plastic fluid, and both complex viscosity and shear storage modulus increase with increasing OMMT content due to the interaction between the OMMT and polymers. The nanocomposites’ melt show more elasticity behavior with more OMMT content especially at low shear frequencies.

Dynamic Mechanical Properties and Thermal Stability of PTT/POE/OMMT Nanocomposites

The dynamic mechanical properties, phase morphology and thermal stability of the poly(trimethylene terephthalate)/maleinized poly(octene-ethylene)/organo-montmorillonite nanocomposites (PTT/POE/OMMT) were investigated by using the thermodynamic mechanical analyzer (DMA), transmission electron microscopy (TEM) and thermal gravimetric analyzer (TGA), respectively. The results suggest that the modulus of elasticity of the PTT/POE/OMMT nanocomposite increases, and the glass transition temperature first slightly decreases and then increases with increasing OMMT content because that the TPP plays the role of plasticizer and OMMT plays the role of reinforcing agent. OMMT disperse evenly in the polymer matrix with most of the strip-like sheet morphology. The addition of the OMMT does not apparently affect the thermal stability of the PTT/POE/OMMT nanocomposite.

Rheological Properties of PTT/POE/OMMT Composites

Poly(ethylene-octene)(POE) and organic montmorillonite(OMMT) acting respectively as the toughening agents and reinforcing agents, were used to prepare nanocomposites with Poly(trimethylene terephthalate)(PTT) in order to modify PTT, and the rheological properties of these composites were investigated by using capillary rheometer instrument. The OMMT used in composite was prepared by intercalating triphenyl phosphate (TPP) into MMT by mixed solution method. PTT/POE/OMMT nanocomposites were prepared by melt blending in twin-screw corotating extruder. Rheological results show that PTT/POE/OMMT composite melt was pseudo-plastic liquid and the pseudo-plasticity of the melt was decreased with increasing OMMT content for the strong interface interactions between OMMT and polymer molecular chains. The melt apparent viscosity was increased with increasing OMMT content. The flow activation energy results suggested that the composite melt having more OMMT components is more sensitive to the change of temperature.

Supercritical CO 2 intercalation of polycaprolactone in layered silicates

Supercritical carbon dioxide (scCO 2) intercalation of polycaprolactone (PCL) in layered silicates (clay) is studied. Wide angle X-ray diffraction patterns find that PCL is slightly intercalated in unmodified montmorillonite clay (NaMMT) but considerably intercalated in organic-modified montmorillonite clay (OMMT). The interlayer spacing in OMMT increases considerably from 1.94 nm in OMMT to 3.58 nm in the OMMT/PCL 10/90 sample. PCL8 having molecular weight of 80,000 is harder to intercalate into OMMT than PCL1 having molecular weight of 10,000. Higher scCO 2 pressures at a temperature allow larger intercalations of PCL in OMMT to exhibit larger interlayer spacings in OMMT. The interlayer spacings in OMMT, however, are not clearly found to relate with the CO 2 temperature at a given pressure. TGA data show that OMMT enhances the thermal stability of PCL1, with a higher content of OMMT giving a higher amount of PCL1 residue. DSC data find that the PCL1-intercalated OMMT expedites the melt-crystallization rate of PCL1 from the melt but suppresses the crystallinity of PCL1. Study of Avrami's rate constants k and exponent n finds that the PCL1-intercalated OMMT enhances the isothermal crystallization rate of PCL1 and that the crystal growth dimension is 3 for pure PCL1 but decreases with increasing OMMT content in the blends. Modulus data find that the PCL1-intercalated OMMT is an effective reinforcement for PCL8.

Isothermal Curing Kinetics and Thermal Degradation of o-CFER/MeTHPA/O-MMT Nanocomposite

The isothermal curing kinetics of nanocomposite of o-cresol-formaldehyde epoxy resin (o-CFER), 3-methyl-tetrahydrophthalic anhydride (MeTHPA) with organic montmorillonite (O-MMT) were investigated by means of X-ray diffraction (XRD) and differential scanning calorimetry (DSC) using N,N-dimethyl-benzylamine as a curing accelerant. The XRD result indicates that an exfoliated O-MMT nanocomposite was obtained. The analysis of DSC data indicated that an autocatalytic behavior appeared in the first stages of the cure for the system, which could be well described by the Kamal model. In the later stages, the reaction is mainly controlled by diffusion and a diffusion factor, f(α), was introduced into Kamal's equation. In this way, the curing kinetics were predicted well over the entire range of conversion. The thermal degradation kinetics of this composite were investigated by thermogravimetric analysis (TGA), which revealed that with increasing O-MMT content, TG curves shift to higher temperature.

Study on the microstructure and mechanical properties for epoxy resin/montmorillonite nanocomposites by positron

Positron annihilation lifetimes have been measured for epoxy resin/organic montmorillonite (OMMT) nanocomposites. Effects of different dispersion states of nano-layered OMMT on the positron annihilation parameters and the mechanical properties were studied. We found that the ortho-positronium ( o-Ps) intensity decreased with increasing OMMT content, which indicated that the interaction between the host and nanofillers restrained the segmental motion, resulting in a decrease of the free volume. On the other hand, it is very interesting to observe a good correlation between the interfacial interaction and mechanical properties, suggesting that the dispersion states of OMMT and interfacial property between clay layers and matrix played an important role in determining the mechanical properties.

The glass transition temperature and microstructure of polyurethane/epoxy resin interpenetrating polymer networks nanocomposites

Nanocomposites with various contents of organophilic montmorillonite (oMMT) have been prepared by adding oMMT to interpenetrating polymer networks (IPNs) of polyurethane and epoxy resin (PU/EP) which had been prepared by a sequential polymeric technique. DSC experiment indicates a novel phenomenon that the glass transition temperature (Tg) of the nanocomposites increases with the oMMT content up to 3 %, then decreases with further increasing oMMT content. In order to explain this phenomenon, crosslink density, hydrogen bonding in the hard segments, crystallization of the nanocomposites and the exfoliation degree of oMMT in the nanocomposites have been investigated by swelling method, FT-IR, XRD, SEM and TEM, respectively. The results indicate that the crosslink density and the hydrogen bonding index of the nanocomposites increase, but the crystallization degree of the nanocomposites decreases with increasing oMMT content. In addition, oMMT improves the network structure of PU/EP.

High performance epoxy resin nanocomposites containing both organic montmorillonite and castor oil-polyurethane

Epoxy resin/polyurethane interpenetrating polymer network nanocomposites with various contents of organophilic montmorillonite (oM-EP/PU nanocomposites) were prepared by a sequential polymeric technique and an in situ intercalation method. X-ray diffraction(XRD), and transmission electronic microscopy(TEM) analysis showed that organophilic montmorillonite (oMMT) disperses uniformly in epoxy resin/polyurethane interpenetrating networks(IPNs), and the intercalated or exfoliated microstructures of oMMT are formed. Differential scanning calorimetry(DSC) test proved that oMMT promotes the compatibility of EP phase and PU phase, and glass transition temperature(Tg) of oM-EP/PU nanocomposites improves with increasing oMMT content. Mechanical properties tests and thermal gravity analysis (TGA) indicated that oMMT and the IPNs of EP and PU exhibit synergistic effect on improving mechanical and thermal properties of pure EP. The mechanism of toughing and reinforcing of oM-EP/PU nanocomposites was further discussed by scanning electronic microscope(SEM).

Synthesis, characterization and properties of organoclay‐modified polyurethane/epoxy interpenetrating polymer network nanocomposites

Abstractorganoclay‐modified polyurethane/epoxy interpenetrating network nanocomposites (oM‐PU/EP nanocomposites) were prepared by adding organophilic montmorillonite (oMMT) to interpenetrating polymer networks (IPNs) of polyurethane and epoxy resin (PU/EP) which had been prepared by a sequential polymerization technique. Wide‐angle X‐ray diffraction (WAXD) and transmission electronic microscopy (TEM) analysis showed that the interpenetrating process of PU and EP improved the exfoliation and dispersion degree of oMMT. The effects of the NCO/OH ratio (isocyanate index), the weight ratio of PU/EP and oMMT content on the phase structure and the mechanical properties of the oM‐PU/EP nanocomposites were studied by tensile testing and scanning electronic microscopy (SEM). Water absorption tests showed that the PU/EP interpenetrating networks and oMMT had synergistic effects on improvement in the water resistance of the oM‐PU/EP nanocomposites. Differential scanning calorimetry (DSC) analysis showed that PU was compatible with EP and that the glass transition temperature (Tg) of the oM‐PU/EP nanocomposites increased with the oMMT content up to 3 wt%, and then decreased with further increasing oMMT content. The thermal stability of these nanocomposites with various oMMT contents was studied by thermogravimetric analysis (TGA), and the mechanism of thermal stability improvement was discussed according to the experimental results. Copyright © 2005 Society of Chemical Industry

Preparation and Properties of Semi-Transparent EPDM/Montmorillonite Nanocomposites

Ethylene-propylene-diene rubber (EPDM)/organic montmorillonite (OMMT) nanocomposites were prepared through a melt-mixing process in an internal mixer. The nanoscale dispersion of OMMT in the EPDM matrix was verified by X-ray diffraction (XRD) and transmission electron microscopy (TEM), relating to an exfoliated morphology. The effects of OMMT content on the mechanical properties, curing behaviour, optical properties and thermal properties of the EPDM/OMMT nanocomposites were studied. The experimental results showed that OMMT had good reinforcement on the EPDM vulcanizates. The tensile strength and tear stress of the EPDM/OMMT nanocomposites significantly increased with increasing OMMT content. When the OMMT content was 15 phr, the tensile strength and elongation at break reached 19.8 MPa and 540%, respectively. The EPDM/OMMT nanocomposite cured by 2,5-dimethyl-2, 5-bis (tert-butyl peroxy) hexane was semi-transparent and the OMMT content had little influence on the curing behaviour of the nanocomposites. The increases in the glass transition temperature and thermal decomposition temperature were observed in the nanocomposites and were supposed to be related with the nanoscale dispersion of the OMMT and the strong interaction between EPDM and OMMT. Moreover, the permeability of oxygen for the EPDM/OMMT nanocomposites was reduced remarkably.

Effect of alkyl quaternary ammonium on processing discoloration of melt-intercalated PVC-montmorillonite composites

The effects of alkyl quaternary ammonium on the processing thermal stability of poly (vinyl chloride)/alkyl quaternary ammonium modified montmorillonite (PVC/OMMT) composites were investigated. PVC/sodium montmorillonite (MMT) composites were prepared for comparison. The intercalated PVC/OMMT composites exhibited a non-terminal rheological behavior, and showed better mechanical properties and higher thermal degradation stability than the PVC/MMT composites. However, under identical melt processing conditions, the PVC/OMMT composites were observed to discolor from light yellow to pink with increasing OMMT content, while the PVC and PVC/MMT composites kept good processing stability. It is suggested that the decomposition of alkyl quaternary ammonium modifier and the following catalytic effects on the dehydrochlorination of PVC were the main reasons for the discoloration of the PVC/OMMT composites. Discoloration of all the composites was investigated by UV–visible spectroscopy, yellowness index and haze measurement. All the composites were characterized and tested using wide angle X-ray diffraction, transmission electron microscopy, infrared spectroscopy, solution 1H nuclear magnetic resonance spectroscopy, tensile testing, notched Izod impact testing and thermogravimetric analysis as well as ARES rheometrics.