Nonpolluting systems based on anionic polyurethane aqueous dispersions were obtained. The prepolymer based on hydroxyl-terminated polybutadiene (HTPB), isophorone diisocyanate (IPDI), poly(propylene glycol) (PPG), and dimethylolpropionic acid (DMPA) were synthesized in bulk. After neutralization with triethylamine (TEA), the anionomer prepolymer was dispersed in water, followed by a chain-extension reaction with ethylenediamine (EDA). The prepolymers were characterized by Fourier transform infrared spectrometry (FTIR) and the average particle size of the aqueous dispersions was determined by laser light scattering (LLS). The mechanical behavior of polyurethane-cast films and the adhesive properties of the aqueous dispersions as coatings for wood were evaluated. It was observed that an increase in the HTPB content provoked an increase in the viscosity and in the particle size of the dispersions. The tensile strength and the modulus values of the films and the adhesiveness of the coatings in wood were also increased by increasing the HTPB content. On the other hand, the elongation of the polyurethane-cast films and the tackness of the surface coatings decreased as the HTPB was increased.
Resumo:Foram sintetizados sob a forma de dispersões aquosas estáveis, com viscosidade aparente na faixa de 30 a 220 cP, poliuretanos à base de polibutadieno líquido hidroxilado (HTPB) de massa molecular numéri-ca média 3500, poli(glicol propilênico) (PPG) de massa molecular viscosimétrica média 2490, diisocianato de isoforona (IPDI) e ácido dimetilolpropiônico (DMPA). O tamanho médio de partícula das dispersões foi determinado e as propriedades mecânicas dos filmes vazados avaliadas. As dispersões foram aplicadas em madeira formando revestimentos homogêneos cuja adesividade foi determinada. A inserção de HTPB na cadeia poliuretânica provocou um aumento no tamanho de partícula das dispersões aquosas, proporcionou uma maior resistência mecânica aos filmes e aumentou a adesividade dos revestimentos ao substrato.
Palavras-chave: HTPB, PPG, IPDI, DMPA, poliuretanos, dispersões aquosas.Synthesis and characterization of waterborne anionic polyurethanes based on hydroxy terminated polybutadiene, poly(propylene glycol) and isophorone diisocyanate Abstract: Non-polluting systems based on waterborne polyurethanes were obtained from hydroxy-terminated polybutadiene (HTPB) ('Mn = 3500), poly(propylene glycol) (PPG) ('Mv = 2490), isophorone diisocyanate (IPDI) and dimethylolpropionic acid (DMPA). The aqueous dispersions, with 35 % of solid content, were stable for nearly a month and their apparent viscosity ranged from 30 to 220 cP. An increase in HTPB content in the formulations led to an increase in the average particle size of the dispersions. This increase also promoted an improvement in the mechanical resistance of cast films from the aqueous dispersions. The adhesive properties of dispersions as wood coatings were determined and it was observed that the presence of HTPB improved the adhesion between coating and substrate.
Keywords: HTPB, PPG, IPDI, DMPA, polyurethanes, aqueous dispersions
IntroduçãoRevestimentos obtidos a partir de dispersões aquosas têm tido uma intensa participação no mercado nos últimos anos [1] . A crescente preocupação com questões ambientais deixou patente a necessidade da substituição de solventes orgânicos, cujas emissões para a atmosfera são tóxicas e causam danos ao meio ambiente, por água na obtenção e/ou aplicação de revestimentos [2][3][4] .A crescente aplicação das dispersões aquosas de poliuretanos como revestimentos está baseada em Autor para correspondência: Fernanda M. B. Coutinho,
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