Estudo sobre a formação de microporos em filmes de PLA e em blendas PLA/PBAT pelo método breath figure / Study on formation of microporous in PLA films and PLA/PBAT blends by breath figure method

Filmes microporosos de PLA puro e de blendas PLA/PBAT foram preparados pelo método de automontagem denominado breath figure. Diferentes fatores influenciam a formação dos poros, entre eles foram investigados o efeito do solvente, da concentração, da natureza dos polímeros PLA e PBAT e da adição de PBAT em blendas PLA/PBAT com composição 95/5 e 70/30. As imagens de microscopia óptica mostraram que o diclorometano é o melhor solvente para obter poros com tamanhos mais regulares nos filmes de PLA puro e nas blendas com composição 95/5. A estrutura linear dos polímeros PLA e PBAT não contribuíram para a estabilizar e evitar a coalescia das gotículas de água, resultando em poros com distribuição de tamanho aleatória. Blendas contendo 5 e 30% de PBAT apresentaram poros com tamanhos mais regulares para soluções preparadas com concentrações de 1 e 2% (m/v).

Estudo da miscibilidade de blendas de poli (ácido lático)/ poli (butileno adipato-co-tereftalato) preparadas pelo método de evaporação de solvente

A produção de blendas de PLA/ PBAT tem por objetivo superar as desvantagens que cada polímero possui individualmente, como fragilidade, limitações de processabilidade e custo. Neste estudo, investigamos a miscibilidade e as propriedades de filmes biodegradáveis de PLA - Poli (ácido lático), PBAT- Poli (butileno adipato-co-tereftalato) e de suas blendas com proporções de 95/5, 70/30, 30/70 e 5/95 de PLA/PBAT, respectivamente, produzidos pelo método de evaporação de solvente. As blendas produzidas foram caracterizadas pelas técnicas de espectroscopia Raman, calorimetria exploratória diferencial (DSC), termogravimetria (TGA), microscopia eletrônica de varredura (MEV), viscosimetria de soluções diluídas e ensaio mecânico de tração. A análise dos espectros Raman, temperatura de transição vítrea (Tg), e TGA indicaram imiscibilidade dos polímeros em todas as composições estudadas. As análises mecânicas apontaram para diminuição da rigidez das blendas com a adição do PBAT. Os valores dos parâmetros de interação obtido pela análise de viscosimetria de soluções diluídas, sugerem miscibilidade parcial da blenda contendo 5% de PBAT. O estudo da miscibilidade e das propriedades das blendas de PLA/PBAT obtidas por evaporação de solvente possibilitarão a produção de novos materiais por diferentes técnicas visando novas aplicação para este material.Palavras-chave: Poli (ácido lático). Poli (butileno adipato-co-tereftalato). Blendas. Misicibilidade. Viscosidade. Espectroscopia Raman.

Filmes de amido reticulado: estudo da incorporação e liberação de sulfato de condroitina / Crosslinked- starch films: study of the incorporation and release of chondroitin sulfate

Filmes de amido de mandioca e amido de mandioca/sulfato de condroitina reticulados com ácido cítrico (AC) foram preparados pela técnica de "casting" a partir de soluções de amido de SC utilizando glicerol como plastificante. O efeito da concentração do AC e da proporção do sulfato de condroitina (SC) nas propriedades térmicas (TGA), de permeabilidade ao vapor de água (PVA) e cinética de liberação de SC foram avaliadas. As análises de FTIR indicam a presença de formação de ligações ésteres entre as cadeias de amido e ácido cítrico, confirmando a reação de reticulação. A estabilidade térmica dos filmes aumentou com a adição de AC e reduziu com a adição de SC. Tanto o AC quanto o SC tiveram efeito de aumentar a PVA dos filmes. A liberação de SC apresentou mecanismo de transporte anômalo com 1 >n> 0,5 (Equação de Korsmeyer-Peppas) para todos os filmes e taxa de liberação (k) dependente das quantidades de AC e de SC

Physical and mechanical properties of starch films: the role of the cross-linking mechanism through iodine binding capacity

In this study, a better knowledge of the influence of cross-linking mechanism on the mechanical properties of starch films is presented. Thus, waxy starch and cassava starch films, cross-linked with trisodium trimetaphosphate (TMPT), were produced and characterized with respect to their morphology, transport, and mechanical properties. Starch cross-linking was verified by RAMAN spectroscopy and by iodine binding capacity (IBC) values, which were determined by color analysis of digital images. Although cross-linking affects the morphology and crystallinity of the films, it was not observed a relationship between the mechanism of the cross-linking reaction of the starch chain (amylose-amylopectin and amylopectin-amylopectin) and the transport properties. The lower Young Modulus and IBC value and the higher elongation at break observed for cross-linking cassava starch films relative to control and waxy films indicate that cross-linking mechanism influences the mechanical properties of starch films and should be considered to tailor the final properties of packaging and biobased products. </p

Physical and Mechanical Properties of Starch Films – The role of the crosslinking mechanism through iodine binding capacity

In this study, a better knowledge of the influence of cross-linking mechanism on the mechanical properties of starch films is presented. Thus, waxy starch and cassava starch films, cross-linked with trisodium trimetaphosphate (TMPT), were produced and characterized with respect to their morphology, transport, and mechanical properties. Starch cross-linking was verified by RAMAN spectroscopy and by iodine binding capacity (IBC) values, which were determined by color analysis of digital images. Although cross-linking affects the morphology and crystallinity of the films, it was not observed a relationship between the mechanism of the cross-linking reaction of the starch chain (amylose-amylopectin and amylopectin-amylopectin) and the transport properties. The lower Young Modulus and IBC value and the higher elongation at break observed for cross-linking cassava starch films relative to control and waxy films indicate that cross-linking mechanism influences the mechanical properties of starch films and should be considered to tailor the final properties of packaging and biobased products. In this study, a better knowledge of the influence of crosslinking mechanism on the mechanical properties of starch films is presented. Thus, waxy starch and cassava starch films, cross-linked with trisodium trimetaphosphate (TMPT), were produced and characterized with respect to their morphology, transport, and mechanical properties. Starch crosslinking was verified by RAMAN spectroscopy and by iodine binding capacity (IBC) values, which were determined by color analysis of digital images. Although crosslinking affects the morphology and crystallinity of the films, it was not observed relationship between the mechanism of the crosslinking reaction of starch chain (amylose-amylopectin and amylopectin-amylopectin) and the transport properties. The lower Young Modulus and IBC value and the higher elongation at break observed for crosslinking cassava starch films relative to control and waxy films indicate that crosslinking mechanism influences the mechanical properties of starch films and should be considered to tailor the final properties of packaging and biobased products

Synthesis of star poly(N-isopropylacrylamide) by β-cyclodextrin core initiator via ATRP approach in water

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Glycerol-derived polyurethane nanocomposites containing cellulose nanowhiskers - doi: 10.4025/actascitechnol.v35i4.20276

This work describes the synthesis of glycerol-derived polyurethane nanocomposite films containing unmodified cellulose nanowhiskers (CNW) or hexamethylene diisocyanate-modified cellulose nanowhiskers (HDICNW) as a mechanical support.  Cellulose was prepared from sugarcane bagasse using a delignification and whitening approach that is wholly free of chlorine. CNW’s were obtained by acid hydrolysis in hydrochloric acid. The formation of nanocomposites was demonstrated by NMR, TEM, FTIR and WAXD. The films with different concentrations of CNW and HDICNW were characterized by FTIR spectroscopy, and stress-strain measurements. The samples experienced plastic deformation as subjected to an increasing elongation load, and right after yield limit, they fractured without necking. In such a case, the limit tension, which is the maximum stress supported by the sample, matches with the rupture tension. Polyurethane nanocomposites with CNW (CNW-PU) showed values of modulus of elasticity and tensile strength higher than HDICNW-PU.