Authors:Jianxi Zhu, Wei Shen, Yuehong Ma, Lingya Ma, Qing Zhou, Peng Yuan, Dong Liu, and Hongping He
], we have discussed in detail about the influences of montmorillonite's CEC and surfactant configuration on the basal spacing. Therein, we reported that the basal spacing of the organo-montmorillonites increased with surfactant loading, while the
Poly(lactic acid)/organo-montmorillonite nanocomposites were prepared by melt intercalation technique. Maleic anhydride-grafted
ethylene propylene rubber (EPMgMA) was added into the PLA/OMMT in order to improve the compatibility and toughness of the
nanocomposites. The samples were prepared by single screw extrusion followed by compression molding. The effect of OMMT and
EPMgMA on the thermal properties of PLA was studied. The thermal properties of the PLA/OMMT nanocomposites have been investigated
by using differential scanning calorimeter (DSC) and thermo-gravimetry analyzer (TG). The melting temperature (Tm), glass transition temperature (Tg), crystallization temperature (Tc), degree of crystallinity (χc), and thermal stability of the PLA/OMMT nanocomposites have been studied. It was found that the thermal properties of PLA
were greatly influenced by the addition of OMMT and EPMgMA.
Authors:Roberta Peila, S. Lengvinaite, G. Malucelli, A. Priola, and S. Ronchetti
In this work a commercially available organophilic Montmorillonite (Cloisite 30B) was modified by interaction with different
surfactants, namely dodecylsuccinic anhydride (DSA), octadecylamine (ODA), octadecanoic alcohol (ODOH) and octadecanoic acid
(ODAc), in order to increase its basal spacing and to achieve a better dispersibility in LDPE. The morphology of the dispersions
was investigated through XRD and TEM analyses. Intercalation phenomena were found for all the systems investigated. The thermal
properties of the obtained nanocomposites were studied by means of DSC and TGA measurements. No variation of Tm and crystallinity of LDPE was found after the addition of the nanoclays (5 mass/mass%). A significant increase of the air
thermal stability of LDPE was achieved in the presence of the modified nanoclays.
Authors:Roberta Peila, J. Seferis, T. Karaki, and G. Parker
Three types of commercially available organophilic Montmorillonite (Cloisite 30B, 25A and 15A) were used to prepare VARTM
epoxy resin nanocomposites in order to study the effect of the nanoclay organophilic modification on the epoxy matrix. The
morphology of the dispersions was investigated through XRD and TEM analyses. The thermal stability of the nanocomposites was
studied by means of HI-RES TG measurements and the influence of the nanoclay on the viscosity of the resin was investigated
through rheological measurements. It was found that the nanoclay modification had no significant influence on the dispersion
and on the thermal properties of the nanocomposites. Areas of exfoliated and intercalated morphology were observed. The viscosity
of the resin furthermore did not exceed the critical value of the infusion process.
The Flory's gelation theory, non-equilibrium thermodynamic fluctuation theory and Avrami equation have been used to predict
the gel time tg and the cure behavior of epoxy resin/organo-montmorillonite/diethylenetriamine intercalated nanocomposites at various temperatures
and organo-montmorillonite loadings. The theoretical prediction is in good agreement with the experimental results obtained
by dynamic torsional vibration method, and the results show that the addition of organo-montmorillonite reduces the gelation
time tgand increases the rate of curing reaction, the value of k, and half-time of cure after gelation point t1/2 decreases with the increasing of cure temperature, and the value of n is ~2 at the lower temperatures (<60C) and decreases to ~1.5 as the temperature increases, and the addition of organo-montmorillonite
decreases the apparent activation energy of the cure reaction before gelation point, but has no apparent effect on the apparent
activation energy of the cure reaction after gelation point. There is no special curing process required for the formation
of epoxy resin/organo-montmorillonite/diethylenetriamine intercalated nanocomposite.
Sodium montmorillonite has been modified via cation exchange reaction using gemini surfactants. Montmorillonite modified by
cetyltrimethyl ammonium bromide (CTAB) is used for comparation. Basal spacings and thermal stability of these organo-montmorillonite
clays have been characterized using X-ray diffraction analysis and thermogravimetric analysis. The d(001) spacings of montmorillonite-Gemini14,
montmorillonite-Gemini16, montmorillonite-Gemini18 can reach above 35 Å compared with the 23.66 Å of the montmorillonite-CTAB
at 2.2CEC. The thermogravimetric analysis show four-step degradation which corresponds to residual water desorption, dehydration,
followed by decomposition of the organic modifier and the dehydroxylation of the organo-montmorillonite. In addition, DTG
enables two different structural arrangements of gemini surfactant molecules intercalating the montmorillonite to be proposed
that is different from montmorillonite-CTAB.
Authors:F. Burstein, M. Borisover, I. Lapides, and S. Yariv
In the present research we studied the effect of the solvent used, whether it was polar water or a non-polar organic solvent
(n-hexane or n-hexadecane), on the basal-spacing and bulk structure of the sorbate-sorbent complexes obtained by the secondary adsorption
of nitrobenzene and m-nitrophenol by two types of organo-montmorillonites. X-ray measured basal spacings before and after thermal treatments up
to 360°C. The organo-clays were synthesized, with 41 and 90% replacement of the exchangeable Na+ by hexadecyltrimethylammonium (HDTMA), with mono-and bilayers of HDTMA cations in the interlayer space, labelled OC-41 and
OC-90, respectively. After heating at 360°C both organo-clays showed spacing at 1.25–1.28 nm, due to the presence of interlayer-charcoal,
indicating that in the preheated organo-clays the HDTMA was located in the interlayer.
The thermo-XRD-analysis of Na-clay complexes showed that from organic solvents both sorbates were adsorbed on the external
surface but from water they were intercalated. m-Nitrophenol complexes of both organo-clays obtained in aqueous suspensions contain water molecules. Spacings of nitrobenzene
complexes of OC-41 and OC-90 and those of nitrophenol complexes of OC-41 showed that the adsorbed molecules were imbedded
in cavities in the HDTMA layers. Adsorption of m-nitrophenol by OC-90 from water and n-hexane resulted in an increase of basal spacing (0.21 and 0.29 nm, respectively) suggesting the existence of a layer of nitrophenol
molecules sandwiched between two parallel HDTMA layers.