Abstract The vinyl ester resins and natural composites have emerged as a suitable alternative in tribological application due to mechanical behavior, which relates to the conversion of the double bonds. During tribological test the permanent contact between polymeric sample and counterpart can increase the temperature affecting the crosslinking of the samples. These variations have direct implications in the curing rate and the global conversion. In this work, the FTIR evaluation is used to evaluate possible changes on the global conversion of vinyl ester and their composites reinforced with Musaceae fiber bundles and cured using two hardeners, after a specific tribological test. Increments around 15% on global conversion of styrene double bonds were observed for neat matrix and composites using both hardeners, suggesting that during tribology test some alterations on resin structure takes place. These results open alternatives to manipulate the curing conditions in order to control the tribological behavior.

Neste trabalho são apresentados os resultados da síntese de nanocompósitos baseados em amido termoplástico (TPS) reforçado com nanofitas de celulose bacteriana (BC). A síntese foi feita por fermentação in situ e formação de ligações cruzadas. A fermentação para a obtenção das nanofitas foi conduzida por sete dias empregando a bactéria colombiana nativa Gluconacetobacter medellinenses; os nanocompósitos foram plasticizados com glicerol e as ligações cruzadas foram formadas com ácido cítrico. Os nanocompósitos obtidos depois destes sete dias de fermentação foram caracterizados por análise termogravimétrica (TGA), espectroscopia na região do infravermelho com transformada de Fourier com refletância total atenuada (FTIR-ATR) e microscopia electrônica de varredura (SEM). Observou-se que, ao longo da fermentação, a porcentagem de reforço nos nanocompósitos permaneceu constante. Os novos nanocompósitos TPS/BC apresentaram uma forte adesão interfacial e uma maior estabilidade térmica e aquosa, assim como propriedades mecânicas melhoradas. Os resultados obtidos aumentam consideravelmente as possibilidades de aplicação do amido na indústria de embalagens.

In this paper, a nanocomposite based on thermoplastic starch (TPS) reinforced with bacterial cellulose (BC) nanoribbons was synthesized by in situ fermentation and chemical crosslinking. BC nanoribbons were produced by a Colombian native strain of Gluconacetobacter medellinensis; the nanocomposite was plasticized with glycerol and crosslinked with citric acid. The reinforcement percentage in the nanocomposites remained constant throughout the fermentation time because of the TPS absorption capability of the BC network. Nanocomposites produced after fermentation for seven days were characterized using thermogravimetric analysis (TGA); Fourier transformed infrared spectroscopy with attenuated total reflectance (FTIR-ATR), mechanical testing and scanning electron microscopy (SEM). The new TPS/BC nanocomposites exhibit strong interfacial adhesion, improved thermal behavior, water stability and enhanced mechanical properties. These findings support the applications of starch in the packaging industry.

No presente trabalho, biofilmes condutores foram sintetizados através de soluções de 100 mL de água com 3 g de amido de mandioca (Manihot esculenta Crantz) e quantidades diferentes de glicerina, glutaraldeído, polietilenoglicol e perclorato de lítio. Estes filmes foram caracterizados por espectroscopia de impedância eletroquímica (EIS), microscopia eletrônica de varredura (SEM), espectrometria de reflexão total atenuada no infravermelho com transforma de Fourier (ATR-FTIR), termogravimetria (TG). Os resultados mostraram que os biofilmes com quantidades mais elevadas de perclorato de lítio possuem valores maiores de condutividade e as diferenças morfológica e molecular foram observadas como sendo um resultado das proporções adicionadas dos compostos em cada uma das rotas de preparação

In the current work, conductor biofilms were synthesized by means of solutions of 100 mL of water with 3 g of starch from cassava (Manihot esculenta Crantz) and different amounts of glycerin, glutaraldehyde, polyethyleneglycol and lithium perchlorate. These biofilms were characterized through electrochemical impedance spectroscopy (EIS), scanning electronic microscopy (SEM), attenuated total reflectance Fourier transform infrared spectroscopy (ATR‑FTIR) and thermogravimetry (TG). Results showed that biofilms with higher amount of lithium perchlorate portray higher values of conductivity and morphological and molecular differences could be observed as a result of the added proportions of the compounds in each one of the trials.

Polyolefins as polypropylene are used in agricultural applications for plant assistance and protection. However, their massive consumption is causing environmental problems. In this study, polypropylene and polypropylene blends with starch and biodegradable polymers such as Mater-Bi that could be used in this agricultural endeavor, were exposed to several thermoxidation conditions. Using the standard test method ASTMD 5510, different temperature and exposure time conditions were analyzed. According to the viscosimetric results, temperature has a stronger effect on chain scission than exposure time. Groups that contain oxygen were detected on degraded samples by FTIR spectroscopy. They could improve the biodegradation process. Slight variations on the melting and crystallization temperature of degraded samples were found by differential scanning calorimetry. Degraded zones where the matrix/additive adhesion was improved where observed in the SEM micrographs of exposed blends.

Poliolefinas como el polipropileno son ampliamente utilizadas en el campo agrícola, en particular para la protección y sostenimiento de plantas. Sin embargo, su masivo consumo viene generando importantes problemas ambientales. En este estudio muestras de polipropileno y sus mezclas con almidón y un biopolìmero como el Mater-Bi, los cuales se pueden emplear en este tipo de aplicaciones, han sido sometidas a un proceso de degradación térmica o termoxidación. Diferentes condiciones de temperatura y tiempos de exposición han sido analizadas tomando como base la norma técnica ASTMD 5510. De acuerdo con los resultados obtenidos a través de viscosimetría se aprecia que la temperatura tiene un mayor efecto sobre la escisión de cadena de la matriz que el tiempo de exposición. Los espectros infrarrojos indican la presencia de grupos funcionales que contienen oxígeno asociados con la degradación, los cuales pueden ser útiles en una posterior etapa de biodegradación. En ensayos realizados mediante calorimetría diferencial de barrido se observan pequeñas variaciones sobre la temperatura de fusión y cristalización de los diferentes materiales. En tanto que las micrografías de SEM de la mezclas muestran regiones en donde la interfase matriz/aditivo ha sido mejorada por efecto de la degradación.

Banana fruit production is a dynamic economical sector in Colombia. However during the agricultural labor, banana plants need to be tied to each other using strings. This practice helps to support the fruit weight before the harvesting. Polypropylene strings are used in this application. This practice is becoming an environmental issue in cultivation areas, and it is necessary to identify biodegradable alternative materials. In this study, samples of polypropylene, polypropylene/starch blend and a commercial biopolymer, referred to as Mater-Bi and PP/ Mater-Bi, were analyzed. The stability of these materials in tropical regions such as Uraba (Colombia) was evaluated. The changes in the material structure and properties were analyzed by differential scanning calorimetry (DSC) and FTIR spectroscopy. Slight variations of mechanical and physical behavior of exposed samples were observed. Even though starch and biopolymer reduced the tensile behavior of polypropylene blends, these blends can be used for this application.

La producción de banano es una dinámica actividad económica en Colombia, sin embargo durante las labores agrícolas, las plantas deben ser unidas unas a otras a través de cuerdas. Esta prácticas contribuye a solventar el peso de los frutos antes de la cosecha. Cuerdas de polipropileno son utilizadas para este fin. Sin embargo, esta práctica genera problemas ambientales en las regiones de cultivo, haciendo necesario identificar materiales biodegradables alternativos. En este estudio, muestras de polipropileno, mezclas de polipropileno con almidón, así como un biopolímero conocido como Mater-Bi y éste combinado con PP fueron analizados. Su estabilidad fue evaluada al ser expuestas a las condiciones medioambientales de la región tropical de Urabá (Colombia). Los cambios en la estructura de los materiales expuestos fueron analizados utilizando calorimetría diferencial de barrido (DSC) y espectroscopía infrarroja FTIR. Pequeñas diferencias en el comportamiento mecánico y físico de las muestras expuestas fueron observadas, y pese a que la adición tanto del almidón como del biopolímero reducen el comportamiento a tracción del polipropileno, estas mezclas pueden ser útiles para esta aplicación.

Desde hace un par de décadas, las fibras naturales son en una importante alternativa como refuerzo de materiales compuestos reciclables e incluso biodegradagables. Pese a combinar ventajas técnicas, económicas y ambientales, su carácter hidrofílico es su principal barrera al incorporarlas en matrices poliméricas hidrofóbicas como las poliolefinas. Algunas modificaciones superficiales de carácter físico y químico, se han empleando en las fibras. Estos tratamientos a la par que reducen la tendencia hidrofílica, mejoran el desempeño de la interfase fibra/matriz. El tratamiento alcalino o mercerización se considera uno de los más importantes. Pese a los estudios que se han realizado sobre este proceso, persiste la necesidad de definir condiciones de aplicación para este tratamiento que brinden una adecuada combinación de desempeño mecánico con un reducido impacto sobre el medio ambiente a costos razonables. En el presente trabajo, se reporta una apropiada condición de tratamiento alcalino que equilibra bajas concentraciones de hidróxido de sodio con un buen comportamiento mecánico. Los parámetros considerados son: concentración de la solución, tiempo de exposición y tipo de secado. La espectroscopia infrarroja FTIR, la microscopía óptica (OM) y de fuerza atómica (AFM) indican que aún en estas condiciones de tratamiento la fibra experimenta cambios sobre su estructura y comportamiento

For the last decades, natural fibers have been used as reinforcement of friendly environmental polymeric composites, due to their technical, economical and environmental advantages that include: moderate mechanical and thermal properties. However, the OH groups in some of their chemical structures like cellulose, reduce the compatibility with hydrophobic polymeric matrices such as polyolefines. Natural fiber, usually are exposed to chemical and physical treatment to reduce their hydrophilic tendency and to enhance fiber/matrix adhesion. Alkalinization, alkali treatment or mercerization, is one of the most common procedures applied on natural fibers. This process introduces important changes on its mechanical properties, physical and morphological characteristics, and chemical composition. In spite of other studies, it is necessary define surface treatment conditions in accordance with industrial processing and environmental considerations. In this study, the influence of different alkali treatment conditions on the fique fiber tensile behavior has been evaluated. Treatment parameters as solution concentration, exposure time and dry conditions have been analyzed. Fourier transformation infrared spectrophotometry (FTIR) analysis, atomic force (AFM) and optical microscopies have been used to evaluate alteration on chemical and morphological characteristics. Treatment conditions that include low solution concentration bring a good enough quality in the mechanical behavior required by fique fiber bundles as polymeric reinforcement