ВЫСОКОМОЛЕКУЛЯРНЫЕ СОЕДИНЕНИЯ, Серия Б, 2012, том 54, № 2, с. 358-368
КОМПОЗИТЫ
УДК 541(64+518):547.1'128
STRUCTURAL, THERMAL AND MORPHOLOGICAL PROPERTIES OF AQUEOUS HYBRID EMULSION OF SILYLATED POLY (URETHANE)/ORGANIC MODIFIED MONTMORILLONITE NANOCOMPOSITES BASED ON A NEW SILICONE AND IMIDE RING CONTAINING VINYLIC MACROMONOMER1
© 2012 г. Hamid Javaheriannaghash and Maryam Arianfar
Department of Chemistry, Shahreza Branch, Islamic Azad University, 311- 86145, Shahreza, Isfahan, Iran
e-mail: javaherian@iaush.ac.ir Received May 25, 2011 Revised Manuscript Received August 29, 2011
Abstract — A new silicone and imide ring containing vinylic macromonomer, N-trimethylsiloxyethyltrimel-litilimidomethacrylate (TMSETMIM), has been synthesized for the formulation of waterborne polyurethane (PU). A vinyl group containing silicone, the (3-methacryloyloxypropyl) trimethoxysilane (MPTMS) was used for comparison of the effects of silicone type with TMSETMIM on the PU. Then, a series of new sili-conized PU hybrid nanocomposites, were successfully synthesized by the emulsion polymerization in the presence of organic modied montmorillonite (OMMT) and an aqueous PU dispersion using ammonium per-oxodisulfate (APS) as an initiator. The PU dispersion was synthesized by a polyaddition reaction of hexame-thylene diisocyanate (HMDI), on polypropylene glycol (PPG-1000) and dimethylol propionic acid (DMPA) as a chain extender. The obtained NCO chain ends reacted with water (which acts as a further chain extender producing some urea bonds). The structural elucidation of monomer was carried out by FTIR, 1H-NMR, and 13C-NMR spectroscopic techniques. The copolymers were also characterized by using FTIR. Thermal properties of the copolymers were studied by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The morphologies of the copolymers were characterized with scanning electron microscopy (SEM) and transition electron microscopy (TEM) and then the effects of silicone concentrations on the water absorption ratio was examined. The formed film from the hybrid emulsion containing TMSETMIM could provide obviously higher water-resistance property in comparison with MPTMS. Also, the heat stability increases while the Tg decreased.
INTRODUCTION
The idea of reinforcing polymers with other materials is not new and materials such as cellulose, calcium carbonate, carbon, metal oxides, montmorillonite and various forms of silica have been used in this role for quite some time. Just as in other fields of nanotech-nology, however, the novelty of these new materials is to what scale by which they occur. In order to meet the rising demands of applications, hybrids of inorganic "functional fillers" and polymeric materials are being constantly developed so as to combine their beneficial properties or to induce new ones [1, 2]. Particulate-filled polymers are often classified as either micro or nanocomposites depending upon the dimensions of the phases involved. Nanoparticles often strongly influence the properties of composites at very low-volume fractions. This is mainly due to the small distances between particles and the conversion of large fractions of the polymer matrix near their surfaces into an interphase of different properties, as well as to the con-
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sequent change in morphology. As a result, the desired properties are usually achieved at low-filler volume fractions, which allow the nanocomposites to retain their macroscopic homogeneity. Also, the geometrical shape of the particles plays an important role in determining the properties of the composites [3]. Depending upon the organization of the silicate layers in a polymer matrix, two types of morphology can be achieved in the nanocomposites: intercalated or exfoliated. Exfoliated polymer/silicate nanocomposites were considered to have better mechanical properties than the intercalated polymer/silicate nanocomposites. This is due to the uniform dispersion of the silicate layers in the polymer matrix. In general, there are four methods that can be used to prepare poly-mer/montmorillonite (MMT), i.e., exfoliation—adsorption, in situ intercalative polymerization, melt intercalation and template synthesis [4]. In order to prepare exfoliated polymer/silicate nanocomposites, various methods were developed: melt intercalation [5—7], in situ polymerization [8], curing systems [9], and sol—gel methods [10].
Polyurethanes (PU) represent extraordinarily versatile polymeric materials, which can be tailored to meet the highly diversified demands of modern technology such as coatings, adhesives, and composites [11]. As waterborne polymer systems are environmentally-friendly, they have been widely used in coatings and adhesives. Properties of polyurethane are modified either by varying polyurethane microstructures or by dispersing inorganic and organic fillers within the polyurethane continuous matrix. A wide variety of fillers, including clay and wollastonites or montmorillo-nite, are being applied to polyurethane formulations in order to reduce costs and to reinforce the polyurethane matrix. Many papers have described the use of special intercalated organophilic clays in PU matrix and a few researchers have reported on morphological studies and improvements in the properties of aqueous aliphatic PU nanocomposites have been determined [12—15]. In the present study, the aim is to further improve the properties of new silylated aqueous PU by reinforcing organic modified montmorillonite via exfoliated method.
EXPERIMENTAL
Materials
Methacryloyl chloride (MC), trimellitic anhydride (TMA), ethanolamine (EA) and chlorotri-methyl silane (CTMS) (Fluka) were used as received. Polypropylene glycol 1000 (PPG-1000, Korea Polyol Ltd., Korea) was dried and degassed at 65°C under vacuum. Hexamethylene diisocyanate (HMDI), dimethylol propionic acid (DMPA), (3-methacryloy-loxypropyl) trimethoxysilane (MPTMS), hydroxyeth-yl cellulose (HEC), triethylamine (TEA), cetyltrime-thylammonium bromide (CTAB), sodium silicate (Na2SiO3) and N,N dimethyl formamide (DMF) were supplied by Merck, Hohenbrunn, Germany, and were used without further purification. Sodium montmorillonite (MMT) is supplied by Zhejiang Geologic Institute. Double-distilled and deionized (DDI) water was used throughout.
Synthesis
of N-Trimethylsiloxyethyltrimellitilimidomethacrylate (TMSETMIM)
In a three-neck flask equipped with a teflon-stirrer and a thermometer and purged with nitrogen gas at a constant flow rate, 1.83 g (0.03 mol) of ethanolamine was added gradually into the solution of trimellitic anhydride 5.76 g (0.03 mol) in 50 ml of DMF and the mixture was stirred two h in a water bath to obtain a clear amic acid solution. A mixture of 5.5 g phosphorus pentaoxide, 2.5 g sulfuric acid and 50 ml DMF was then added drop-wise to the amic acid solution, al-
ready raised temperature to 70°C, over a period of one h. After stirring for 4 h, the mixture was cooled and poured into 500 ml ice water to obtain the precipitate by filtering. The precipitate was washed several times with double-distilled water and recrystallized several times with isopropanol to obtain the 2-(2-hy-droxyethyl) -1,3- dioxoisoindoline- 5 -carboxylic acid (HEDOIC) monomer dried under reduced pressure to obtained a viscous yellow oil (step 1). A flask as above with ice bath was charged with 25 ml DMF and added to a mixture of 2.35 g (0.01 mol) HEDOIC and 3 ml TEA. Then, 1.2 g (0.01 mol) chlorotrimethyl silane (CTMS) was added gradually to the mixture and stirring during 24 h to obtained viscous white oil (step 2). Finally, 1.045 g (0.01 mol) methacryloyl chloride was added to 3.07 g (0.01 mol) of HEDOIC and the reaction was kept first at ice bath for one h and then at re-fluxed temperature for 12 h, respectively (step 3). The mixture was distilled under reduced pressure to remove solvents to obtain the macromonomer. The reaction path is given in Scheme 1. The final product was viscous brown oil. Yield = 3.40, 82%. FTIR (KBr, cm-1): 3208, 3150 and 3200 (aliphatic -OH), 1718 and 1720 (C=O), 3361(aliphatic N-H), 2931, 2866 and 2942 (aliphatic C-H), 1261 (Si-CH3), 1023 (Si-O), 1450 (C=C), 1H-NMR (CDCl3, ppm): 1(Si-CH3), 3 (C-CH3), 3.7 and 4 (CH2-CH), 6.4-6.5 (CH2=CH), 6.8 and 7.6 (Ar-H), 13 C-NMR (CDCl3, ppm): 10(Si-CH3), 35 (C-CH3), 47 and 65 (aliphatic carbons),123 and 124 (aromatic carbons), 125 (CH2-CH),135, 136 and 138 (CH=CH), 167 and 168 (aliphatic C=O), 170 (aromatic C=O).
Preparation of Organic Modified Montmorillonite (OMMT)
Organic modified montmorillonite are produced by the exchange of organic cations for inorganic ions (e.g., K+, Na+, and Ca+2) on the layer surfaces of montmorillonite. The sorption properties of organic modied montmorillonite surfaces may be signicantly altered by this exchange reaction. The mineral surfaces of the resulting organic modified montmorillonite may become organophilic because the organic functional groups of the quaternary ammonium cations are not strongly hydrated. As a result, quaternary ammonium cations derived from cetyltrimethylammonium bromide were inoculated to the surface of montmoril-lonite and organic modied montmorillonite is powerful sorbent for TMSETMIM /PU relative to montmo-rillonite.
The organic modified montmorillonite (OMMT) was prepared using the following procedure [16]. 5g of MMT and 50 ml distilled water were put into a three-necked flask. 1.4 ml sodium silicate was added to ad-
Step 1: O
HO
O
O + H,N-CH2CH2—OH
O
DMF HO
2 h
O
TMA
EA
n-ch2ch2oh
O
O
H2SO4, P2O^ HO' 70°C reflux, 4 h*
Step 2:
(A)
CH3
I
O
(A) + Cl-Si-CH3
TEA
| 3 140°C reflux, 24 h
CH3
CTMS
HO
n-ch2ch2-oh
0 CH3
N-CH2CH2—O—Si—CH3
(B)
O
I
CH
3
Step 3:
OO
O CH
3
12 h
(B) + Cl"C"C=CH2 influx
I
CH3
O
CH3
N-CH2CH2-0-Si-CH3
O
MC (C)
Scheme 1. Preparation of TMSETMIM.
CH3
just pH to 11. The mixture was allowed to stand for 1 d
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