Otimização do processo de dispersão de nanotubos de carbono em poliuretano termorrígido

Abstract

ResumoNeste trabalho foi desenvolvido um processo empregando misturador de alto cisalhamento e moinho de rolos para dispersar MWCNTs (multiwalled carbon nanotubes) puros e modificados em poliol visando a preparação de concentrados de 3% em massa. Condições otimizadas no trabalho permitiram a obtenção de suspensões com menor número e tamanho de agregados de MWCNTs. Compósitos contendo 0,5% em massa de MWCNTs foram preparados por diluição dos concentrados em poliol usando mistura mecânica seguida de cura. Resultados de microscopia indicaram que as melhores dispersões foram obtidas com os MWCNTs modificados, os quais permitiram um aumento na tensão na ruptura, no alongamento e uma melhor preservação da estabilidade térmica. Além disso, valores de condutividade elétrica sugerem que o compósito possa ser empregado para dissipação eletrostática. Dessa forma, os resultados obtidos demonstram que a modificação covalente da superfície dos MWCNTs e a utilização de estratégias eficientes de dispersão são essenciais para melhorar as propriedades finais dos nanocompósitos. Palavras-chave: dispersão de nanotubos de carbono, nanotubos de carbono modificados, propriedades mecânicas, poliuretano termorrígido elastomérico. AbstractA process employing high shear mixer and roll mill to disperse pristine and modified MWCNTs (multiwalled carbon nanotubes) in polyol was developed in order to prepare 3 wt% masterbatches. The optimum process conditions resulted in suspensions with smaller number and size of nanotube aggregates. Composites containing 0.5 wt% of MWCNTs were prepared by dilution of polyol masterbatches by simple mechanical mixing followed by cure. Microscopy data revealed better dispersion of modified carbon nanotubes in the polymer matrix, which promoted an increase in the tensile strength, elongation and a better preservation of thermal stability. Furthermore, electric conductivity values indicated that the composites can be used for electrostatic dissipation. These results demonstrate that the covalent modification of MWCNTs surface and the use of efficient dispersion strategies are essential to improve nanocomposites' final properties.

Evaluation of the dispersion of carbon nanotubes in an elastomeric polyurethane and fatigue test

“…The success, however, is being limited by the difficulties to disperse the nanomaterial and promote a good interaction with polymer chains at the interfaces. Various strategies using different processing equipment/methods, have been tested to improve dispersion: high shear mixers, three roll-mill, or planetary mixers in the case of resin to thermosets [6][7][8][9][10] ; and extrusion and injection in the case of thermoplastics [11,12] . Companies commercialize masterbatches with high concentrations of CNT up to 50 mass%.…”

Investigating the influence of conduit residues on polyurethane plates

“…Another indication of this interaction is that the images were obtained from the fracture surface, and there were no signs that the conduit was pulled out of the matrix at the time of the fracture. In fact, this homogeneity between conduit and matrix is essential for mechanical reinforcement [51] .…”

“…At 325.00 °C, the mass loss was 45.43%, and complete degradation occurred at 770 °C. The first and second PU decomposition steps correspond to urethane bond-breaking and polyol decomposition, respectively [8,39,50,51] .…”

“…Therefore, to meet the requirements of the NBR 9178:2015 [48] , a flame-retardant additive should be included in the formulation [11,51] .…”

Layer-by-Layer technique employed to construct multitask interfaces in polymer composites

“…It was also tested the hypothesis that the LbL technique would allow the incorporation of nanocomponents (such as carbon nanotubes) within the LbL layers. These nanocomponents are useful for introducing new functionalities on composites, such as to increase the stiffness, thermal and electrical properties [5,12,13] . Mechanical properties will be assessed in this work aiming structural applications.…”