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Previous issue date: 2014-05-28 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Sustainable development is a major challenge in the oil industry and has aroused
growing interest in research to obtain materials from renewable sources.
Carboxymethylcellulose (CMC) is a polysaccharide derived from cellulose and becomes
attractive because it is water-soluble, renewable, biodegradable and inexpensive, as well as
may be chemically modified to gain new properties. Among the derivatives of
carboxymethylcellulose, systems have been developed to induce stimuli-responsive properties
and extend the applicability of multiple-responsive materials. Although these new materials
have been the subject of study, understanding of their physicochemical properties, such as
viscosity, solubility and particle size as a function of pH and temperature, is still very limited.
This study describes systems of physical blends and copolymers based on
carboxymethylcellulose and poly (N-isopropylacrylamide) (PNIPAM), with different feed
percentage compositions of the reaction (25CMC, 50CMC e 75CMC), in aqueous solution.
The chemical structure of the polymers was investigated by infrared and CHN elementary
analysis. The physical blends were analyzed by rheology and the copolymers by UV-visible
spectroscopy, small-angle X-ray scattering (SAXS), dynamic light scattering (DLS) and zeta
potential. CMC and copolymer were assessed as scale inhibitors of calcium carbonate
(CaCO3) using dynamic tube blocking tests and chemical compatibility tests, as well as
scanning electron microscopy (SEM). Thermothickening behavior was observed for the 50 %
CMC_50 % PNIPAM and 25 % CMC_75 % PNIPAM physical blends in aqueous solution at
concentrations of 6 and 2 g/L, respectively, depending on polymer concentration and
composition. For the copolymers, the increase in temperature and amount of PNIPAM
favored polymer-polymer interactions through hydrophobic groups, resulting in increased
turbidity of polymer solutions. Particle size decreased with the rise in copolymer PNIPAM
content as a function of pH (3-12), at 25 ?C. Larger amounts of CMC result in a stronger
effect of pH on particle size, indicating pH-responsive behavior. Thus, 25CMC was not
affected by the change in pH, exhibiting similar behavior to PNIPAM. In addition, the
presence of acidic or basic additives influenced particle size, which was smaller in the
presence of the additives than in distilled water. The results of zeta potential also showed
greater variation for polymers in distilled water than in the presence of acids and bases. The
lower critical solution temperature (LCST) of PNIPAM determined by DLS corroborated the
value obtained by UV-visible spectroscopy. SAXS data for PNIPAM and 50CMC indicated
phase transition when the temperature increased from 32 to 34 ?C. A reduction in or absence
of electrostatic properties was observed as a function of increased PNIPAM in copolymer
composition. Assessment of samples as scale inhibitors showed that CMC performed better
than the copolymers. This was attributed to the higher charge density present in CMC. The
SEM micrographs confirmed morphological changes in the CaCO3 crystals, demonstrating the
scale inhibiting potential of these polymers / O desenvolvimento sustent?vel ? um dos principais desafios da ind?stria do petr?leo,
que tem despertado crescente interesse por pesquisas para obten??o de novos materiais
provenientes de fontes renov?veis. A carboximetilcelulose (CMC) ? um polissacar?deo
derivado da celulose, que se destaca por ser sol?vel em ?gua, renov?vel, biodegrad?vel, de
baixo custo e por apresentar possibilidades de modifica??es em sua estrutura qu?mica. Dentre
os derivados de carboximetilcelulose, alguns sistemas t?m sido desenvolvidos para induzir
propriedades est?mulos-responsivos e ampliar a aplicabilidade desses materiais
multirresponsivos. Embora esses novos materiais sejam atualmente objeto de estudo, a
compreens?o de suas propriedades f?sico-qu?micas, tais como viscosidade, solubilidade e
tamanho de part?culas em fun??o do pH e temperatura ainda ? muito limitada. Esta tese
descreve sistemas de misturas f?sicas e copol?meros ? base de carboximetilcelulose e poli (Nisopropilacrilamida)
(PNIPAM) com diferentes composi??es percentuais de alimenta??o
reacional (25CMC, 50CMC e 75CMC), em solu??o aquosa. A estrutura qu?mica dos
pol?meros foi investigada por infravermelho e an?lise elementar CHN. As misturas f?sicas
foram analisadas por reologia e os copol?meros foram analisados por UV-vis?vel,
espalhamento de raios-X a baixos ?ngulos (SAXS), espalhamento de luz din?mico (DLS) e
potencial zeta. CMC e copol?mero foram avaliados como inibidores de incrusta??o de
carbonato de c?lcio (CaCO3) usando os testes de compatibilidade qu?mica e precipita??o
din?mica em capilar, assim como a microscopia eletr?nica de varredura (MEV). As misturas
f?sicas 50% CMC_50% PNIPAM e 25% CMC_75% PNIPAM em solu??o aquosa, nas
concentra??es de 6 e 2 g/L, respectivamente, apresentaram comportamento
termoviscosificante dependente da concentra??o de pol?mero e da composi??o. Para os
copol?meros, o aumento da quantidade de PNIPAM e da temperatura favoreceu as intera??es
pol?mero-pol?mero atrav?s dos grupos hidrof?bicos, resultando no aumento da turbidez das
solu??es polim?ricas. O tamanho das part?culas diminuiu com o aumento do teor de PNIPAM
na composi??o dos copol?meros em fun??o do pH (3-12), a 25 ?C. Maiores quantidades de
CMC resultaram em um efeito mais forte do pH nos tamanhos das part?culas, exibindo um
comportamento pH-responsivo. Assim, 25CMC n?o foi afetada pela mudan?a de pH,
apresentando comportamento similar a PNIPAM. Al?m disso, a presen?a de aditivos de
car?ter ?cido ou b?sico influenciou no tamanho das part?culas, que foram menores na
presen?a desses aditivos do que em ?gua destilada. Os resultados de potencial zeta tamb?m
sofreram maior varia??o para os pol?meros em ?gua destilada do que na presen?a de ?cidos e
bases. A temperatura consoluta inferior (LCST) da PNIPAM determinada por DLS foi
concordante com o valor obtido por UV-visible. Os dados de SAXS mostraram para PNIPAM
e 50CMC uma transi??o de fase quando a temperatura aumentou de 32 para 34 ?C. Um
aumento do car?ter polieletrol?tico foi observado em fun??o do aumento da CMC na
composi??o dos copol?meros. A avalia??o das amostras como inibidores de incrusta??o
mostrou que a CMC apresenta um melhor desempenho do que o copol?mero. Isto foi atribu?do
a maior densidade de cargas presente na CMC. As micrografias do MEV confirmaram
mudan?as morfol?gicas dos cristais de CaCO3, indicando o potencial desses pol?meros para
inibi??o de incrusta??o
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/17797 |
| Date | 28 May 2014 |
| Creators | Lima, Bruna Vital de |
| Contributors | CPF:65946499734, http://lattes.cnpq.br/7711521318854102, Maia, Ana Maria da Silva, CPF:00750317442, http://lattes.cnpq.br/1894812921636224, Villetti, Marcos Antonio, CPF:49242172049, http://lattes.cnpq.br/8504489050993642, Borges, Maur?cio Rodrigues, CPF:56928807768, http://lattes.cnpq.br/7409076038495589, Bicudo, Tatiana de Campos, CPF:25935096862, http://lattes.cnpq.br/2712586287719863, Balaban, Ros?ngela de Carvalho |
| Publisher | Universidade Federal do Rio Grande do Norte, Programa de P?s-Gradua??o em Qu?mica, UFRN, BR, F?sico-Qu?mica; Qu?mica |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Format | application/pdf |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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