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Doctoral Thesis
DOI
https://doi.org/10.11606/T.75.2021.tde-03092021-090848
Document
Author
Full name
Deyvid de Souza Porto
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2021
Supervisor
Committee
Frollini, Elisabete (President)
Rosa, Derval dos Santos
Andrade, Cristina Tristão de
Fardim, Pedro Edson
Rodrigues Filho, Ubirajara Pereira
Title in Portuguese
Filmes formados simultaneamente às sínteses de poliuretanos: celulose microcristalina e óleo de mamona como polióis
Keywords in Portuguese
bio-baseado
celulose microcristalina
compósitos
filmes
poliuretanos
Abstract in Portuguese
Este estudo teve como objetivo a formação de filmes simultaneamente às sínteses de poliuretanos (PU), utilizando polióis de origem renovável, óleo de mamona (Castor oil, CO) e celulose microcristalina (MCC), na ausência de solventes e de catalisadores. Como isocianatos, foram usados o difenilmetano diisocianato polimérico, pMDI, e o trímero do hexametileno diisocianato, tHDI, com razão molar NCO/OH 1:1. Inicialmente, PUs foram sintetizados a partir de MCC (20 a 60%), CO e pMDI, temperatura ambiente, e parte das reações a 70, 90 e 100 oC. Resumidamente, foram observados valores para a temperatura do pico tan δ (relacionado à transição vítrea, Tg) na sequência PU20CELpMDI (16 oC)<PU25CELpMDI<PU30CELpMDI<PU35CELpMDI<PU40CELpMDI<PU45CELpMDI<PU50CELpMDI<PU55CELpMDI<PU60CELpMDI (78 oC). A complexidade estrutural das macromoléculas geradas aumentou com a maior proporção de anéis glicosídicos (três grupos hidroxila reativos cada um), restringindo a mobilidade de segmentos, e aumentando Tg. A resistência à tração na ruptura seguiu a mesma tendência de Tg, destacando-se PU20CELpMDI = 0,6 MPa e PU60CELpMDI = 14 MPa. PU60CEL100pMDI (60% MCC, 100oC) apresentou a maior resistência a tração (20 MPa) dentre os filmes PUs-pMDI, provavelmente devido a maior complexidade estrutural gerada a temperatura mais alta, incluindo possibilidades de entrecruzamentos (físico e químico). PUs-pMDI, e os demais filmes aqui citados, foram também caracterizados quanto à espectroscopia na região do infravermelho, análise termogravimétrica, difração de raios X, microscopia eletrônica de varredura, módulo de armazenamento, ângulo de contato-água, intumescimento por N,N- Dimetilformamida. O impacto da substituição de pMDI por tHDI nas propriedades dos filmes foi considerado, sendo realizadas sínteses usando de 30 a 80% de MCC (100 oC, devido propriedades de filmes PUs-pMDI formados nesta temperatura; para PUs30CELtHDI a temperatura foi alternada entre a ambiente e 60 oC, visando avaliar possível influência deste parâmetro). Os resultados de TgtHDI (Tg = 72 oC, resistência a tração = 18 MPa), viabilizada pela menor viscosidade de tHDI comparada a de pMDI. Filmes compósitos também foram formados a partir de sínteses PUs-tHDI (30 e 50% MCC) e celulose nanocristalina (CNC,10,0% e 12,5%-PU30CELtHDI; 5,0% e 7,5%-PU50CELtHDI), destacando-se o aumento nos módulos de Young, de 6,2 MPa (PU30CELtHDI) para 18,8 MPa (PU30CEL12,5CNCtHDI) e de 12,6 MPa (PU50CELtHDI) para 23,5 MPa (PU50CEL7,5CNCtHDI). Todos os filmes apresentaram transparência, com transmitância de luz visível diminuindo com o aumento da porcentagem de MCC, usada como poliól. Filmes PUs-pMDI, PUs-tHDI e PUs-tHDI/CNC se mostraram não-citotóxicos via análise de viabilidade celular com células de fibroblastos. Potenciais aplicações dos filmes formados incluem revestimento de superfícies, embalagens, área médica (curativos, dentre outros), dispositivos óticos. A partir do conhecimento que se tem, a ampla investigação realizada neste estudo sobre uso de celulose como poliol não tem precedentes, e permite modelar as propriedades dos filmes gerados. Também, adiciona importante contribuição à bioeconomia circular, considerando a imensa disponibilidade mundial deste polímero renovável.
Title in English
Films formed simultaneously to the polyurethane syntheses: microcrystalline cellulose and castor oil as polyols
Keywords in English
biobased
composites
films
microcrystalline cellulose
polyurethane
Abstract in English
This study aimed to form films simultaneously with the synthesis of polyurethanes (PU), using polyols of renewable origin, castor oil (CO), and microcrystalline cellulose (MCC), in the absence of solvents and catalysts. The polymeric diphenylmethane diisocyanate, pMDI, and the hexamethylene diisocyanate trimer, tHDI, were used as isocyanates, NCO/OH 1:1 as the molar ratio. Initially, PUs were synthesized from MCC (20 to 60%), CO, and pMDI, at room temperature, and part of the reactions at 70, 90, and 100 oC. Briefly, values for the tan δ peak temperature (related to the glass transition, Tg) were observed in the sequence PU20CELpMDI (16oC)<PU25CELpMDI<PU30CELpMDI<PU35CELpMDI<PU40CELpMDI<PU45CELpMDI<PU50CELpMDI<PU55CELpMDI<PU60CELpMDI (78 oC). The structural complexity of the generated macromolecules increased with the proportion of glycosidic rings (three reactive hydroxyl groups each), restricting the mobility of segments and increasing Tg. The tensile strength at rupture followed the same trend as Tg, with PU20CELpMDI = 0.6 MPa and PU60CELpMDI = 14 MPa standing out. PU60CEL100pMDI (60% MCC, 100 oC) showed the highest tensile strength (20 MPa) among PUs-pMDI films, probably due to the greater structural complexity generated at a higher temperature, including possibilities of crosslinking (physical and chemical). PUs-pMDI, and the others films mentioned here, were also characterized in terms of infrared spectroscopy, thermogravimetric analysis, X ray diffraction, scanning electron microscopy, storage modulus, water contact angle, swelling by N,N-Dimethylformamide. The impact of replacing pMDI by tHDI on the properties of the films was considered, with syntheses being performed using 30 to 80% MCC (100 oC, due to the properties of PUs-pMDI films formed at this temperature; for PUs30CELtHDI, the temperature was alternated using room temperature and 60 oC to evaluate the possible influence of this parameter). The results of Tg and tensile strength for PUs-tHDI films followed the same trends as PUs-pMDI films. It is noteworthy the high percentage of MCC used in the synthesis of PU80CELtHDI (Tg = 72 oC, tensile strength = 18 MPa), made possible by the lower viscosity of tHDI compared to that of pMDI. Composites films were also formed from PUs-tHDI syntheses (30 and 50% MCC) and nanocrystalline cellulose (CNC, 10.0% and 12.5% - PU30CELtHDI; 5.0% and 7.5% -PU50CELtHDI), highlighting there was an increase in Young's moduli, from 6.2 MPa (PU30CELtHDI) to 18.8 MPa (PU30CEL12.5CNCtHDI) and from 12.6 MPa (PU50CELtHDI) to 23.5 MPa (PU50CEL7.5CNCtHDI). All films showed transparency, with visible light transmittance decreasing with the increasing percentage of MCC used as a polyol. PUs-pMDI, PUs-tHDI, and PUs-tHDI/CNC films were shown to be non-cytotoxic via cell viability analysis with fibroblast cells. Potential applications of the formed films include surface coating, packaging, medical area (dressings, among others), optical devices. As far as it is known, the extensive research carried out in this study on the use of cellulose as a polyol is unprecedented, allows to tune the properties of the films generated. Also, it adds an important contribution to the circular bioeconomy, considering the immense worldwide availability of this renewable polymer.
 
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Publishing Date
2021-09-16
 
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