Dispersões aquosas à base de nanocompósitos de poliuretanos e argilas hidrofílicas brasileiras: síntese e caracterização

Abstract

Resumo: Neste trabalho foram sintetizados nanocompósitos à base de poliuretanos em dispersão aquosa (NWPUs) e argilas brasileiras hidrofílicas (Brasgel PA e Brasgel NT) do tipo montmorilonita (MMT), de natureza sódica e cálcica, respectivamente, tendo a primeira maior hidrofilicidade. Os monômeros empregados na síntese das dispersões foram: poli(glicol propilênico) (PPG); ácido dimetilolpropiônico (DMPA), diisocianato de isoforona (IPDI) e hidrazina, como extensor de cadeia. Foram variados a proporção de segmentos rígidos e flexíveis e o teor das argilas adicionadas (na faixa de 0,5 a 2,5% em massa). As argilas foram caracterizadas por espectrometria na região do infravermelho (FTIR) e difração de raio X (XRD) e tiveram seu grau de inchamento determinado. Os NWPUs foram avaliados em termos de teor de sólidos totais, FTIR, XRD e propriedades mecânicas. A ausência dos picos de cristalinidade, característicos das argilas puras, e resistência mecânica superior frente às dispersões sem argila, confirmaram a formação de nanocompósitos. Palavras-chave: Poliuretanos, dispersões aquosas, nanocompósitos, argilas, montmorilonita, formulações não-poluentes. Aqueous Dispersions Based on Nanocomposites of Polyurethanes and Hydrophilic Brasilian Clays: Synthesis and CharacterizationAbstract: In this work nanocomposites based on polyurethane aqueous dispersion (NWPUs) were synthesized employing montmorillonite (MMT) hydrophilic brazilian clays (Brasgel PA and Brasgel NT), containing sodium and calcium, respectively, being the former more hydrophilic. The monomers used in the synthesis of the dispersions were: poly (propylene glycol) (PPG); dimethylolpropionic acid (DMPA), isophorone diisocyanate (IPDI) and hydrazine, as chain extender. It was varied the proportion between hard and soft segments and clay content (added in the range from 0.5 to 2.5% per mass). The clays were previously delaminated in water and incorporated in the moment of prepolymer dispersion. The clays were characterized by infrared spectrometry (FTIR) and X ray diffraction (XRD) and their degree of swelling were determined. Solid content of the formulations were calculated. The films, cast from aqueous dispersions, were characterized by FTIR, XRD and their mechanical properties were evaluated. The formation of nanocomposites was confirmed by XRD, by observing the absence of peaks indicating cristallinity, characteristic of the pure clays. Mechanical resistance was improved for the nanocomposite films when compared to materials with no clay addition. Keywords: Polyurethanes, aqueous dispersions, nanocomposites, clays, montmorillonite, non-polluting systems. IntroduçãoNa atualidade, as exigências mundiais de aplicação industrial de tecnologias mais limpas e ambientalmente sustentáveis estão incrementando o desenvolvimento de sistemas poliméricos. Dentre esses, destacam-se as dispersões aquosas de poliuretanos (WPUs) que, além de muito versáteis em termos de aplicações industriais, têm permitido a gradativa substituição de compostos orgânicos voláteis (VOC's) po...

Waterborne poly(urethane‐urea) gas permeation membranes for CO2/CH4 separation

“…In poly(urethane‐urea) formulations, the equivalent‐number ratio of NCO groups of the diisocyanate and OH groups (NCO/OH) was fixed at 1.5. This ratio provided cast films with a little more elastomeric characteristic and a higher proportion of soft segments . The equivalent number of hydroxyl groups denoted the number of OH groups present in the hydroxylated compounds, DMPA and polyols (PPG + EG‐ b ‐PG).…”

“…The wide range of physical properties that PU chains can adopt results from a morphological combination of hard and soft segments. The former are derived from diisocyanate and have highly polar urethane groups, and the latter are composed of polyol, which may impart elastomeric characteristics to the polymer . In polyurethane synthesis, the use of a chain extender is common, aiming for an increase in the molecular mass of the chains.…”

Nanocomposites films obtained from protein isolates of mechanically deboned chicken meat added with montmorillonite

“…Figure 4b shows bands in the 3600-3400 cm -1 region, corresponding to stretching vibration (axial) of the hydroxyl groups related to the water adsorbed between the MMT plates. The characteristic bands of Si-O-Si bonds were observed in the region between 1150-1020 cm -1 and in the range of 945-810 cm -1 , corresponding to octahedral layers of the alumino silicate Si-O-Al [20] .…”