Elsevier

European Polymer Journal

Volume 44, Issue 8, August 2008, Pages 2439-2447
European Polymer Journal

Macromolecular Nanotechnology
Comparative studies for the effect of intercalating agent on the physical properties of epoxy resin-clay based nanocomposite materials

https://doi.org/10.1016/j.eurpolymj.2008.06.015Get rights and content

Abstract

In this study, a series of comparative studies for the effect of intercalating agent on the physical properties of the epoxy resin-clay based nanocomposite materials were performed. First, the quaternary alkylphosphonium and alkylammonium salt were both used as the intercalating agents separately for the preparation of organophilic clay through the cationic exchange reactions with Na+-montmorillonite clay. Subsequently, the organophilic clay was blent into the epoxy resin through in-situ thermal ring-opening polymerizations to prepare a series of polymer-clay nanocomposite (PCN) materials. The as-synthesized PCN materials were subsequently characterized by Fourier-Transformation infrared (FTIR) spectroscopy, wide-angle powder X-ray diffraction (WXRD), and transmission electron microscopy (TEM).

It should be noted that the quaternary alkylphosphonium salt (Φ3P+-C12)-modified clay was found to show better dispersion capability than that of quaternary alkylammonium salt (Me3N+-C16)-modified clay existed in the polymer matrix based on the studies of WXRD and TEM. The better dispersion of (Φ3P+-C12)-modified clay in epoxy resin was found to lead more effectively enhanced physical property such as corrosion protection, gas barrier, mechanical strength, thermal stability, and flame retardant properties of polymers than that of (Me3N+-C16)-modified clay, in the form of coating and membrane, based on the measurements of a series of electrochemical corrosion parameters, gas permeability analysis (GPA), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and limiting oxygen index (LOI), respectively. Effect of material composition on the physical properties of as-prepared materials was also investigated.

Introduction

Nanocomposite materials consisted of organic polymeric matrix and inorganic nano-layered clay platelets have lately evoked a great deal of academic and industrial research activities due to their uniqueness of combining the organic and inorganic characteristics at the molecular level, leading to the formation of nanocomposite materials with effectively enhanced physical properties such as thermal properties (e.g., thermal stability [1], flame retardant [2], thermal conductivity [3]), mechanical properties (e.g., mechanical strength [4], hardness [5], abrasion resistance [6]), electro-rheological properties [7], permeability properties (e.g., gas barrier [8], pervaporation [9]) and corrosion protection properties [10] of polymers.

Currently, Na+-montmorillonite (Na+-MMT) clay is widely used in the preparation of polymer nanocomposite materials because its lamellar elements exhibit high in-plane strength, stiffness, and high aspect ratio. Typically, the chemical structures of MMT consist of two fused silica tetrahedral sheets sandwiching an edge-shared octahedral sheet of either magnesium or aluminum hydroxide. The Na+ and Ca2+ residing in the interlayer regions usually can be replaced by organic cations such as alkylammonium ions by a cationic-exchange reaction to render the hydrophilic-layered silicate organophilic. The organophilically charged clay layers exchanged by cationic surfactants playing an important role for the intercalation.

In the past decades, thermosetting polymers such as epoxy resin, polyimide or phenolic resins attracted many chemists, physicists, and material scientists devoting efforts to study their nanocomposites. Among these thermosets, epoxy resins evoked intensive studies much in the preparation of nanocomposite materials lately due to their high tensile strength, and modulus, good adhesive properties, good chemical, and corrosion resistance, low shrinkage in cure, and excellent dimensional stability. Up to date, many published literatures in terms of the investigations focused on the investigations of epoxy resin-clay nanocomposite materials have been reported and concentrated mainly on the exploration of mechanical and thermal properties based on the comparative studies between nanocomposites containing raw Na+-MMT and organophilic clay [11]. However, effect of different intercalation agent on physical properties of nanocomposite materials has seldom been mentioned.

Therefore, in this study, we present a series of comparative studies for the effect of intercalating agent on physical properties of epoxy resin-clay based nanocomposite materials. The as-synthesized nanopcomposite materials were subsequently characterized by FTIR spectroscopy, WXRD, and TEM.

Effect of intercalation agent used on the physical properties of nanocomposite materials (e.g., corrosion protection, gas barrier, mechanical strength, thermal stability, and flame retardant properties) in the form of coating and membrane, was evaluated a series of based on the measurements of electrochemical corrosion parameters, GPA, DMA, DSC, TGA, and LOI, respectively. Furthermore, effect of material composition on the physical properties was also investigated.

Section snippets

Materials and instrumentations

Triphenylolmethane triglycidyl ether (TGTPM) (Aldrich), N,N-dimethylacetamide (DMAc)(99%; Riedel-deHaën). Hydrochloric acid (37%; Riedel-deHaën) is applied to prepare the 1.0 M HCl aqueous solution, and potassium bromide (KBr) (Riedel-deHaën) is used as received without further purification. The used Na+-montmorillonite clay (PK 802) consisted of a unit cell formula Ca0.084Na0.143(Al1.69Mg0.31)Si4O10(OH)2·2H2O, which CEC (cation exchange capacity) value of 115 mEq/100 g is purchased from Pai-Kong

Results and discussion

In this work, one tri-functional epoxy as well as one tri-functional amine monomers for the formation of epoxy resin matrix and two different types of intercalation agents for the modification of Na+-MMT clay was used and their chemical structures were shown in Fig. 1. The two cationic surfactants were used for performing a series of comparative studies for the effect of intercalation agent on the physical properties of as-prepared materials. To prepare the polymer-clay nanocomposite materials,

Conclusion

In this article, a series of comparative studies for the effect of intercalating agent on the physical properties of the epoxy resin-clay based nanocomposite materials were performed. The quaternary alkylphosphonium and alkyl ammonium salt were both used as the intercalating agents separately for the preparation of organophilic clay through the cationic exchange reactions with Na+-MMT clay, followed by blending the organophilic clay into the epoxy monomer and hardener through the thermal

Acknowledgements

The financial support of this research by the Center-of-Excellence Program on Membrane Technology, the Ministry of Education, Taiwan, ROC, and NSC 94-2115-M-033-008 is gratefully acknowledged.

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