Resumen En este trabajo, se evaluó el efecto de la proporción de un poliéster poliol altamente ramificado (HBP) de cuarta generación en las propiedades estructurales, térmicas, reológicas, morfológicas y mecánicas de mezclas de almidón de yuca/HBP (TPS). Para este propósito las relaciones de almidón:HBP empleadas para preparar los TPS fueron: 30:70 (TPS30), 40:60 (TPS40) and 50:50 (TPS50). Por análisis infrarrojo (IR) se observó que la presencia de HBP produjo un desplazamiento en las absorciones de los enlaces C-OH, C-O and C-O-C del TPS. El análisis de difracción de rayos X mostró que la cristalinidad del almidón es tipo A y B, las cuales incrementaron con la cantidad de HBP. La temperatura de transición vítrea (Tg) de los TPS, incrementó con el contenido de HBP, pero la estabilidad térmica y la viscosidad (a una frecuencia angular de 1 Hz) presentaron un comportamiento opuesto. El análisis de microscopia de barrido electrónica (SEM), reveló que la estructura granular del almidón no fue completamente desestructurada.

Abstract In this work, the effect of the proportion of a hyperbranched polyester polyol (HBP) of fourth generation on the structural, thermal, rheological, morphological and mechanical properties of tapioca starch/HBP blends (TPS) was evaluated. For this purpose, the ratios of starch:HBP employed to prepare the TPS were: 30:70 (TPS30), 40:60 (TPS40) and 50:50 (TPS50). Using infrared (IR) analysis, it was observed that the presence of HBP produced a displacement at the absorptions of the C-OH, C-O and C-O-C bonds of the TPS. The X-ray diffraction (DRX) analysis showed that the starch crystallinity is A and B type, which increased with the HBP amount. The glass transition temperature (Tg) of the TPS, increased with the HBP content, but the thermal stability and viscosity (at an angular frequency of 1 Hz) presented an opposite behavior. The scanning electronic microscopy analysis (SEM) revealed that the granular structure of the starch was not completely destructured.

Abstract A hyperbranched polyester polyol of the second generation (HBP2) was modified with polylactic acid (HBP2-g-PLA) and employed as a compatibilizer for plasticized tapioca starch (TPS)/polylactic acid (PLA) blends. The effect of the compatibilizer HBP2- g-PLA was evaluated in comparison to the control sample (TPS/PLA blend without HBP2-g-PLA). The torque value of the TPS/PLA blends with HBP2- g-PLA was lower than that of the control sample, while thermal stability and crystallinity followed opposite behavior. The glass transition temperature (Tg) and degree of crystallinity of the TPS/PLA blends with HBP2-g-PLA decreased with increasing mass fraction of HBP2-g-PLA. By scanning electron microscopy (SEM), it was observed that the morphology of the TPS/PLA blends with HBP2-g -PLA was more homogeneous than that of the control sample, confirming that HBP2- g-PLA acted as a compatibilizer and plasticizing agent to the TPS/PLA blends. Rheological analysis of the compatibilized TPS/PLA blends indicated the presence of microstructure.

Abstract In this work, low density polyethylene (LDPE)/plasticized starch (TPS) blends were prepared. The TPS employed in this study was obtained by plasticization of tapioca starch with a hyperbranched polyester polyol. Differential scanning calorimetry analysis showed that the melting temperature increased with the TPS content. The opposite effect was exhibited in the crystallization temperature and additional changes were not observed during the heating. X-ray diffraction analysis showed a reduction in intensity of the peak at Bragg’s angle 17.5°, proving a diminution on A type crystallinity with the increasing amount of LDPE. Micrographs obtained by scanning electron microscopy exhibited starch granules without destructure. TPS acted as a filler to LDPE, since the mechanical properties (Young’s modulus and tensile strength) improved ostensibly. The Young’ modulus and tensile strength decreased with the amount of LDPE, however, the elongation at break exhibited an opposite behavior.

Abstract Four waterborne hyperbranched alkyd-acrylic resins (HBRAA) were synthesized by miniemulsion polymerization from a hyperbranched alkyd resin (HBR), methyl methacrylate (MMA), butyl acrylate (BA) and acrylic acid (AA), by using benzoyl peroxide (BPO) and ammonium persulfate (AP) as initiators. The reaction between HBR and acrylic monomers was evidenced by differential scanning calorimetric (DSC), nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). The conversion percentage, glass transition temperature (Tg), content of acrylic polymer (determined by soxhlet extraction) and molecular weight increased with the content of acrylic monomers used in the synthesis. The main structure formed during the synthesis was the HBRAA. The analysis by dynamic light scattering (DLS) showed that the particle size distribution of HBRAA2, HBRAA3 and HBRAA4 resins were mainly monomodal. The film properties (gloss, flexibility, adhesion and drying time) of the HBRAA were good.

Abstract New functional polymers will be prepared using alkyd resins having high solid content (environmentally friendly) and comb-type structural morphology. Different copolymers of hydroxyethyl acrylate and methyl methacrylate (HEMMA) were synthesized by solution polymerization using azo-bis-(isobutyronitrile) (AIBN) as initiator and dimethylformamide as a solvent. The proportions utilized of AIBN were 0.5 (HEMMA1), 1.0 (HEMMA2), 1.5 (HEMMA3) and 2.0 wt. % (HEMMA4). The conversion percentage of the reaction was higher than 90%. The formation of the copolymers was evidenced by infrared analysis, hydroxyl value, and nuclear magnetic resonance. The intensity of OH group adsorption increased with the molecular weight and hydroxyl value. The polydispersity index was lower than 1.5. All copolymers exhibited a stable region on viscosity at a shear rate between 0.1 and 10 s–1. The copolymers exhibited good thermal stability, flexibility, and adherence.

Resumen En este trabajo, polietileno de baja densidad (PEBD) fue modificado en estado fundido con un poliester poliol altamente ramificado maleinizado (HBPAM), usando varias proporciones de peróxido de dicumilo (0.5, 1.0, 1.5 y 2.0%). El análisis infrarrojo mostró las señales de grupos OH, C=O, -COOR y -C=C- del HBPAM en el espectro de las muestras funcionalizadas (PEBD-g-HBPAM). El grado de injerto (GI) fue entre 9.14 y 9.82%. El índice de fluidez de las muestras PEBD-g-HBPAM fue más bajo que el del PEBD, y no exhibió una dependencia con el contenido de peróxido de dicumilo y GI. Excepto para la muestra obtenida con un 2.0% de peróxido de dicumilo, todas las temperaturas de fusión de las muestras de PEBD-g-HBPAM fueron similares a la del PEBD. La entalpia de fusión de las muestras de PEBD-g-HBPAM disminuyó con la concentración de peróxido de dicumilo y GI. El módulo ténsil de estas muestras fue más alto que el del PEBD, pero la elongación a la ruptura fue más baja

Abstract In this work, low density polyethylene (LDPE) was modified in the melt state with a maleinized hyperbranched polyester polyol (HBPAM), using several proportions of dicumyl peroxide (0.5, 1.0, 1.5 and 2.0 %). Infrared analysis showed the signals of OH, C=O, -COOR and -C=C- groups of the HBPAM in the spectra of the functionalized samples (LDPE-g-HBPAM). Grafting degree (GD) was between 9.14 and 9.82 %. Melt flow index of the samples LDPE-g-HBPAM was lower than that of the LDPE, and it did not exhibit dependency on the dicumyl peroxide content and GI. Except for the sample obtained with a 2.0 % of dicumyl peroxide, all melting temperatures of the samples of LDPE-g-HBPAM were similar to that of the LDPE. The melting enthalpy of the samples LDPE-g-HBPAM decreased with the concentration of dicumyl peroxide and GD. The tensile modulus of these samples was higher than that of LDPE, but the elongation at break was lower

Este estudio evalúa la influencia de caucho reciclado (RR) con un tamaño de partícula específico en las propiedades de mezclas, mezclas de polipropileno reciclado/polietileno (RPP) y RR (RPP/RR). Las proporciones de RPP/RR para obtener los compósitos fueron como sigue: 90/10 (PP90), 75/25 (PP75), 60/40 (PP60) and 45/55 (PP45). El tamaño de partícula empleado del RR fue 850 μm. Las propiedades de las mezclas, fueron evaluadas por análisis reométrico, termogravimétrico (TGA), calorimetría diferencial de barrido (DSC), microscopia de barrido electrónica (SEM), densidad, índice de fluidez y ténsil. El torque máximo incrementó con el contenido de RPP. Por análisis DSC se observó que el RPP exhibió dos temperaturas de fusión, la primera correspondió al polietileno de baja densidad (LDPE) y la segunda al polipropileno (PP). Además, el RR afectó la cristalinidad del RPP. Por análisis de SEM y TGA, se determinó que el RR y el RPP contenían rellenos. Las densidades de las mezclas fueron más altas que la del RPP. El índice de fluidez exhibió una tendencia con la cantidad de RR

This study evaluates the influence of recycled rubber (RR) with a specific particle size in the properties of blends, blended recycled polypropylene/polyethylene (RPP) and RR (RPP/RR). The proportions of RPP/RR employed to obtain the blends were as follows: 90/10 (PP90), 75/25 (PP75), 60/40 (PP60) and 45/55 (PP45). The particle size of the RR employed was 850 μm . The properties of the blends were evaluated by rheometric, thermogravimetric (TGA), differential scanning calorimetric (DSC), scanning electronic microscopy (SEM), density, melt flow index and tensile analysis. The maximum torque increased with the RPP content. By DSC analysis, it was observed that the RPP exhibited two melting temperatures, the first corresponded to low density polyethylene (LDPE) and the second to polypropylene (PP). Furthermore, the RR affected the crystallinity of the RPP. By using SEM and TGA analyses, it was determined that the RPP as well as RR contained fillers. The blend densities were higher than those of RPP. The melt flow index exhibited a trend with the amount of RR

In this study, low density polyethylene (LDPE) was modified with maleic anhydride (AM) in the molten state by using different concentrations of dycumil peroxide (DCP) (0.25, 0.50, 0.75 and 1.0 %). The materials obtained were characterized by gel content, acid-base titrations, infrared spectroscopy (IR), differential scanning calorimetry (DSC), thermogravimetry (TGA), rheological analysis, mechanical properties, hardness and oxygen permeability. Rheometric analysis indicated that the optimum time to obtain the mixtures is ca.7.5 minutes. IR analyses showed that the AM was grafted into the LDPE backbone. The grafting degree increased with the content of DCP and the highest grafting degree (1.12 ± 0.015 %), was exhibited by the sample obtained employing the highest amount of DCP. Thermal stability of the functionalized samples was slightly higher than LDPE. The crystallinity of the functionalized samples was different, when compared to LDPE. The rheological behavior presented by the samples was pseudoplastic. The mechanical properties, hardness and the oxygen permeability were dependent of the amount of DCP and AM grafted into LDPE.

En este estudio, polietileno de baja densidad (PEBD) fue modificado con anhídrido maleico (AM) en estado fundido usando concentraciones diferentes de peróxido de dicumilo (DCP) (0.25, 0.50, 0.75 y 1.0 %). Los materiales obtenidos fueron caracterizados por contenido de gel, titulaciones ácido-base, análisis infrarrojo (IR), calorimetría de barrido diferencial (DSC), análisis termogravimétrico (TGA), análisis reológico, propiedades mecánicas, dureza y permeabilidad al oxígeno. El análisis reométrico indicó que el tiempo óptimo para obtener las mezclas es alrededor de 7.5 minutos. El análisis IR mostró que el AM fue injertado en el esqueleto del PEBD, el grado de injerto incrementó con el contenido de DCP y el más alto grado de injerto (1.12 ± 0.015 %), fue exhibido por la muestra obtenida empleando la mayor cantidad de DCP (1 %). La estabilidad térmica de las muestras funcionalizadas fue ligeramente mayor que la del PEBD. La cristalinidad de las muestras funcionalizadas fue diferente a la exhibida por el PEBD. El comportamiento reológico presentado por las muestras fue seudoplástico. Las propiedades mecánicas, dureza y la permeabilidad al oxigeno fueron dependientes de la cantidad de DCP y AM injertado en el PEBD.