Now showing items 1-20 of 33

Synthesis and characterization of the oxide nanoparticles obtained by the polymeric precursor method

Murillo, Edwin A.; Raba, Angela; Bautista-Ruiz, Jorge (Journal of Physics: Conference SeriesBerlin , Alemania, 2016-02-12)

Niobium pentoxide (Nb2O5) nanoparticles were prepared by the polymeric precursor method using citric acid as a chelating agent and ethylene glycol as a polymerizing agent. The powders obtained were characterized by X-ray ...
Quicklime as an alternative in the photodegradation of contaminants

Raba, Angela; Bautista-Ruiz, Jorge; Rincón Joya, Miryam (Journal of Physics: Conference SeriesBogota ,Colombia, 2016-02-12)

Chemical oxidation is one of the many different methods of removing contaminants that has emerged recently, is an alternative method to traditional techniques. According to this research calcium peroxide is suitable choice ...
Polietileno de baja densidad funcionalizado con un poliéster poliol altamente ramificado maleinizado

Murillo, Edwin A.; Ararat, Carlos A. (Ingeniería Y CienciaBogota , Colombia, 2016-02-22)

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 ...
Styrene–hydroxyethyl acrylate copolymer based alkyd resins with a comb-type structural morphology obtained with a high solid content

Murillo, Edwin A.; Maria Cristina, Mejia (Journal of Applied Polymer ScienceWashintong D.C , Estados Unidos, 2016-06-22)

Nowadays, so many studies are being carried out with the goal of obtaining environmentally friendly materials. In this study, styrene–hydroxyethyl acrylate copolymer (St-co-HEA) based alkyd resins with high solid contents ...
Study of the structural, thermal, rheological and film properties of functional copolymers of hydroxyethyl acrylate and methyl methacrylate

Murillo, Edwin A.; Mejia, Maria Cristina (PolimerosBrasilia, Brasil, 2016-08-04)

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 ...
Synthesis and Structural Properties of Niobium Pentoxide Powders: A Comparative Study of the Growth Process

Raba, Angela; Rincón Joya, Miryam; Bautista-Ruiz, Jorge (Materials ResearchBrasilia , Brasil, 2016-10-10)

Powders Nb2 O5 were prepared by two different synthesis method, Sol-Gel and polymeric precursors (Pechini). In the Pechini method before adding the citric acid in the process, four different solutions were used to get the ...
Waterborne hyperbranched alkyd-acrylic resin obtained by miniemulsion polymerization

Lopez, Betty; Murillo, Edwin A. (PolimerosBrasilia , Brasil, 2016-12-08)

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 ...
Hyperbranched polyester polyol plasticized tapioca starch/low density polyethylene blends

Guzman, Manuel; Giraldo, Diego; Murillo, Edwin A. (PolimerosBrasilia , Brasil, 2017)

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 ...
Comb-shaped silicone-alkyd resins with high solid content

Mejía, María C.; Palacio, Juliana; Murillo, Edwin A. (Progress in Organic CoatingsWashintong D.C , Estados Unidos, 2017-04)

An unique com-shaped silicone-alkyd resins (SiAR) were synthesized with high solid content (65 wt%) prepared from an alkyd resin (AR) and a varying weight% (5, 10, 15, 20) of silicone moiety (Z-6018) by etherification ...
Mn-modification effects on Nb2O5 structural, optical and vibrational properties

Raba, Angela; Murillo, Edwin A.; Rincón Joya, Miryam (Journal of Physics: Conference SeriesWashintong D.C , Estados Unidos, 2017-12-29)

In this study Mn-modification (at 1%, 2.5%, 5% and 10%) on Nb2O5 was carried out through the Pechini method; the annealing temperatures: 400°C, 500°C, 600°C and 700°C, were used to study the thermal stability of the system ...
Hyperbranched polyester polyol modified with polylactic acid as a compatibilizer for plasticized tapioca starch/polylactic acid blends

Murillo Ruiz, Edwin Alberto; Mesias Alvarez, Ricardo Esteban (PolimerosBrasilia, Brasil, 2018-03-15)

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 ...
Effects of metal doping agent on the properties of Nb2−xMxO5 (M = Mn, Fe, and Ni) system

Raba, Angela; Barba, Jose; Rincón Joya, Miryam (International Journal Of Applied Ceramic TechnologyBogota , Colombia, 2018-05-21)

In order to improve the behavior Niobium pentoxide on oxidation-reductionreactions to degrade organic compounds in aqueous solutions, we developed the synthesis of Niobium pentoxide with the metal doping agents: manganese,iron, ...
Structural, thermal, rheological, morphological and mechanical properties of thermoplastic starch obtained by using hyperbranched polyester polyol as plasticizing agent

Murillo, Edwin A.; Guzman, Manuel (Revista DYNABogota ,Colombia, 2018-07-01)

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) ...
Functionalization in solution of polypropylene with a maleinized hyperbranched polyol polyester: Structural, thermal, rheological, and mechanical properties

Nova, María; Arévalo, Yaritza; Murillo, Edwin A. (Journal of Applied Polymer ScienceWashintong D.C , Estados Unidos, 2018-07-18)

The functionalization of polypropylene (PP) with a maleinized hyperbranched polyester polyol (MHBP) was performed in solution to obtain PP-g-MHBPs. The degree of functionalization (FD) increased with MHBP and dicumyl ...
Influence of the H2O content and the time on the formation of nanostructures in a chemical solution of H2O/HF/NH4F/EG

Raba, Angela; Bautista-Ruiz, Jorge; Rincón Joya, Miryam (Journal of Physics: Conference Series, 2018-12-07)

The influence of anodizing time on the length, morphology and photoelectrochem-ical properties of TiO2 Nanotubes has been investigated. An optimum anodizing time of 20 min at 20V leads to 220nm long of the nanotubes. By ...
Vibrational Raman modes and particle size analysis of cupric oxide with calcination temperature

Raba, Angela; Rincón Joya, Miryam; Barba, Jose (Indian Journal Of Pure '&' Applied PhysicsNueva Delhi , India, 2019)

In this work a study of the effect of the synthesis conditions on the vibratory and particle size properties in the cupric oxide (CuO) has been presented. The synthesis has been carried out by the polymeric precursor method ...
Maleinized Hyperbranched Polyol Polyester: Effect of the Content of Maleic Anhydride in the Structural, Thermal and Rheological Properties

Ararat, Carlos A.; Quiñonez, Winston; Murillo, Edwin A. (Macromolecular Research, 2019-03-29)

The aim of this work is to obtain the material that, in the future, may become a better alternative, as a functionalizing agent, to maleic anhydride (MA), or a crosslinking agent with the least amount of functional groups. ...
Colloidal, morphological, thermal, rheological, and film properties of waterborne hyperbranched alkyd¿acrylic resins

Murillo, Edwin A.; Lopez, Betty; Percino, M. Judith (Journal of Coatings Technology Research, 2019-04-23)

Waterborne hyperbranched alkyd–acrylic resins (HAAR) are interesting materials that provide excellent properties yet require only low levels of solvent in formulations using them. However, they have been scarcely studied. ...
Waterborne star-shaped styrene-alkyd resins

Murillo, Edwin A. (Journal of Applied Polymer Science, 2019-08-13)

Waterborne star-shaped styrene-alkyd resins (SSARs) were synthesized from a branched alkyd resin (AR) and styrene (St) by miniemulsion polymerization. SSARs are an environmentally friendly material. The ratio of AR to St ...
Structural, thermal, rheological, morphological and mechanical properties of polypropylene functionalized in molten state with maleinized hyperbranched polyol polyester

Murillo, Edwin A.; Caicedo, Carolina (European Polymer Journal, 2019-09)

In a previous study, we realized the functionalization of polypropylene (PP) with maleinized hyperbranched polyol polyester (MHBP) by using dicumyl peroxide (DCP) as an initiator for obtaining the PP-g-MHBPs. This process ...

Envíos recientes

Synthesis and characterization of the oxide nanoparticles obtained by the polymeric precursor method
...
Murillo, Edwin A. | 2016-02-12

Niobium pentoxide (Nb2O5) nanoparticles were prepared by the polymeric precursor method using citric acid as a chelating agent and ethylene glycol as a polymerizing agent. The powders obtained were characterized by X-ray diffraction and scanning electron microscopy. The results showed that the presence of HNO3, HCl or NH4OH in the employed aqueous solution favour the solubility of the used precursor salt, as well as also inside the oxide phase formation. The initial Nb2O5 powders were amorphous. The amorphous powders heated at 500°C contained Nb2O5 TT-phase, whereas at 650°C the Nb2O5 T-phase was obtained. In this way an increase in the synthesis temperature is related to the increase of the crystallinity, according to the values of the crystallite sizes that were estimated using the Scherrer method.

LEER
Quicklime as an alternative in the photodegradation of contaminants
...
Raba, Angela | 2016-02-12

Chemical oxidation is one of the many different methods of removing contaminants that has emerged recently, is an alternative method to traditional techniques. According to this research calcium peroxide is suitable choice for contaminant biodegradation in soil and ground water, but it happens at a very low speed. We hope that the method of synthesis of calcium peroxide in nano size by increased ratio of surface to volume can increase the speed of reaction and solve the problem. In the first synthesis of the material we obtained CaO instead of CaO2. Calcium oxide (CaO), commonly known as quicklime or burnt lime, is a widely used chemical compound in obtaining hypochlorite and to neutralize acidic soils. In this study we characterize the material by X-ray scanning electron microscopy, and ultraviolet-visible spectroscopy.

LEER
Polietileno de baja densidad funcionalizado con un poliéster poliol altamente ramificado maleinizado
...
Murillo, Edwin A. | 2016-02-22

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

LEER
Styrene–hydroxyethyl acrylate copolymer based alkyd resins with a comb-type structural morphology obtained with a high solid content
...
Murillo, Edwin A. | 2016-06-22

Nowadays, so many studies are being carried out with the goal of obtaining environmentally friendly materials. In this study, styrene–hydroxyethyl acrylate copolymer (St-co-HEA) based alkyd resins with high solid contents and comb-type structural morphologies were synthesized from St-co-HEA and macromonomers [MMs; dimethylol propionic acid modified with different proportions of tall oil fatty acids (TOFAs)]. The molar mass and gloss values of St-co-HEA were lower than those of the alkyd resins, but the thermal stability, viscosity, and glass-transition temperature exhibited the opposite behavior. In all cases, the conversion percentage was higher than 80 %. The hydroxyl value and viscosity of the alkyd resins decreased with the TOFA content present in the MMrs, but the molar mass and the thermal stability increased. The rheological behavior of these resins was mainly pseudoplastic. Furthermore, the viscosity values were lower than 10 Pa s. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43996.

LEER
Study of the structural, thermal, rheological and film properties of functional copolymers of hydroxyethyl acrylate and methyl methacrylate
...
Murillo, Edwin A. | 2016-08-04

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.

LEER
Synthesis and Structural Properties of Niobium Pentoxide Powders: A Comparative Study of the Growth Process
...
Raba, Angela | 2016-10-10

Powders Nb2 O5 were prepared by two different synthesis method, Sol-Gel and polymeric precursors (Pechini). In the Pechini method before adding the citric acid in the process, four different solutions were used to get the samples. For Sol-gel method, two different processes were also used in obtaining powders. The precursor was completely solubilized in ethanol and then hydrolyzed with ammonia and water. The calcination of the samples was between 500 and 750°C. The resulting powders were characterized by Scanning Electron Microscopy (SEM), Brunauer, Emmett and Teller (BET) surface area measurements, UV-visible and Raman spectroscopy. The formation of T−Nb2 O5 orthorhombic took place upon calcination at 7500C. Crystallite sizes were determined using the Scherrer method which resulted in an uniformed size of about 25 − 65nm. Ultraviolet-Visible diffuse reflectance spectroscopy indicated a variation in the optical band gap values (3.32-3.40 eV) in crystal growth process. The Raman vibrational modes indicate the presence of the orthorhombic phase of the material.

LEER
Waterborne hyperbranched alkyd-acrylic resin obtained by miniemulsion polymerization
...
Lopez, Betty | 2016-12-08

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.

LEER
Hyperbranched polyester polyol plasticized tapioca starch/low density polyethylene blends
...
Guzman, Manuel | 2017

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.

LEER
Comb-shaped silicone-alkyd resins with high solid content
...
Mejía, María C. | 2017-04

An unique com-shaped silicone-alkyd resins (SiAR) were synthesized with high solid content (65 wt%) prepared from an alkyd resin (AR) and a varying weight% (5, 10, 15, 20) of silicone moiety (Z-6018) by etherification reaction. The viscosity and the hydroxyl value (OHV) of the SiAR were found to be higher than those of the AR. The formation of the SiAR was confirmed by infrared spectroscopy and mass spectrometry analysis. The glass transition temperature (Tg), thermal stability, and molecular weight of the SiAR, increased with increasing the silicone content and compared with those of the AR. The results of chemical resistance showed that the SiAR exhibited a better resistance than AR against 0.1 M sodium hydroxide (NaOH) solution.

LEER
Mn-modification effects on Nb2O5 structural, optical and vibrational properties
...
Raba, Angela | 2017-12-29

In this study Mn-modification (at 1%, 2.5%, 5% and 10%) on Nb2O5 was carried out through the Pechini method; the annealing temperatures: 400°C, 500°C, 600°C and 700°C, were used to study the thermal stability of the system and the crystalline growth. The crystallization at high temperatures has been investigated because low annealing temperature cannot improve the crystallization and the effect of Mn-modification concentration is worthy of a further investigation. Before annealing the samples were analysed by TGA. The structural analysis through XRD is carried out to study a possible increase of the crystallite size (L) by increasing the Mn concentration; for the samples at 700°C and 1% and 2.5% concentrations, L is increased from 39.81 to 46.45nm while L changes from 32.67 to 35.63 with 5% and 10%, respectively. After Mn-modification the evolution of (100) and (180) peaks Nb2O5 was observed suggesting that they were well defined only until 2.5%. IR and Raman spectroscopies allowed to analyse vibrational modes present in the samples: the IR spectrums for the samples at 400°C, 500°C and 600°C showed a band around 1100cm-1 which can be associated to C-C(νC-C) and C-O(νC-O) vibrations; at 700°C the shoulder was distinguished around 750cm-1 characteristics of the Nb2O5 orthorhombic structure. Vibration modes associated with Nb2O5 were found with the Raman spectroscopy; these become less intense after Mn-modification. The band gap energy was obtained through UV-Vis spectrophotometry which revealed a slight increase at 700°C.

LEER
Hyperbranched polyester polyol modified with polylactic acid as a compatibilizer for plasticized tapioca starch/polylactic acid blends
...
Murillo Ruiz, Edwin Alberto | 2018-03-15

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.

LEER
Effects of metal doping agent on the properties of Nb2−xMxO5 (M = Mn, Fe, and Ni) system
...
Raba, Angela | 2018-05-21

In order to improve the behavior Niobium pentoxide on oxidation-reductionreactions to degrade organic compounds in aqueous solutions, we developed the synthesis of Niobium pentoxide with the metal doping agents: manganese,iron, and nickel (Nb2−xMxO5), respectively, and analyzing its effects on the structural and vibrational properties. The synthesis of the Nb2−xMxO5 (M = Mn, Fe, and Ni; x = 0.02 and 0.05) was performed according the Pechini method, but before the annealing, the samples were submitted to Thermogravimetric analysis study showing better pre-calcination annealing temperatures at 500 and 700°C for the materials. Then, we performed the crystal structural analysis by X-ray Diffraction, obtaining crystallite sizes between 15 and 47 nm, the accurate size analysis was calculated by Scherrer equation. Structural analysis was also performed by IR spectroscopy to evaluate the vibrational modes of synthetized samples. The dopping effects were evaluated by UV-Vis spectrophotometry through the energy band gap values, showing that doped samples with manganese and iron had lower values than undoped, except the sample doped with nickel. However, samples doped with iron at 2.5% showed better photocatalytic performance.

LEER
Structural, thermal, rheological, morphological and mechanical properties of thermoplastic starch obtained by using hyperbranched polyester polyol as plasticizing agent
...
Murillo, Edwin A. | 2018-07-01

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.

LEER
Functionalization in solution of polypropylene with a maleinized hyperbranched polyol polyester: Structural, thermal, rheological, and mechanical properties
...
Nova, María | 2018-07-18

The functionalization of polypropylene (PP) with a maleinized hyperbranched polyester polyol (MHBP) was performed in solution to obtain PP-g-MHBPs. The degree of functionalization (FD) increased with MHBP and dicumyl peroxide (DCP) contents, but the contact angle followed an opposite behavior. The sample obtained with the proportion of 9.0 wt % MHBP and 2.0 wt % DCP and presented the highest FD value. An FD value of 2.4 wt %, produced a reduction of 19° on the contact angle. It was observed by differential scanning calorimetry (DSC) that the PP-g-MHBPs obtained by employing 3.0 wt % of MHBP, exhibited a slight reduction of the melting temperature (Tm) with the increase in the amounts of FD and DCP. Some FD values obtained in this study are higher than those obtained both commercial and noncommercial grades of PP functionalized with maleic anhydride. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 46932.

LEER
Influence of the H2O content and the time on the formation of nanostructures in a chemical solution of H2O/HF/NH4F/EG
...
Raba, Angela | 2018-12-07

The influence of anodizing time on the length, morphology and photoelectrochem-ical properties of TiO2 Nanotubes has been investigated. An optimum anodizing time of 20 min at 20V leads to 220nm long of the nanotubes. By having a detailed control of the electric current one can know exactly the time in which the nanotubes grew and the time in which the process stopped. The FEG-SEM measures show the morphology of the nanotubes and how they come to separate and fall after a certain time. However, the growth of these, is uniform with little remaining material on the surface. For the solution of the anodizing process it is very important to control the amount of water, ethylene glycol and hydrofluoric acid. Small modifications in the solution change the growth time and size of the nanotubes.

LEER
Vibrational Raman modes and particle size analysis of cupric oxide with calcination temperature
...
Raba, Angela | 2019

In this work a study of the effect of the synthesis conditions on the vibratory and particle size properties in the cupric oxide (CuO) has been presented. The synthesis has been carried out by the polymeric precursor method without modifying the PH in the process, this being a low cost method. The samples obtained have been subjected to several calcination temperatures, 450 °C, 550 °C, 650 °C and 800 °C. In particle analysis by X-ray, scanning electron microscopy (SEM) and statistical it has been observed that for very low or very high calcination temperatures the particle size increases, finding 650 °C as the best calcination temperature. In the Raman spectra, the Ag and Bg vibration have been presented in the samples, with the peaks being narrower for the temperature of 450 °C.

LEER
Maleinized Hyperbranched Polyol Polyester: Effect of the Content of Maleic Anhydride in the Structural, Thermal and Rheological Properties
...
Ararat, Carlos A. | 2019-03-29

The aim of this work is to obtain the material that, in the future, may become a better alternative, as a functionalizing agent, to maleic anhydride (MA), or a crosslinking agent with the least amount of functional groups. To achieve that goal, a hyperbranched polyester polyol (HBP) of the second generation (HBP2G) was modified with MA to obtain HBP2GMA. The effects of the proportion of MA in the structural, thermal, and rheological properties of the HBP2GMAs were evaluated. Furthermore, these properties were compared with those of the HBP2G. A reduction in the intensity of peak corresponding to the OH stretching of HBP2G was observed with the increase in the extent of HBP2G modification by the analysis of the infrared (IR). HBP2GMAs showed a peak at 3030 cm-1 in their IR spectra, which was due to the -CH=CH- stretching of MA. This was further assessed by 1H NMR analysis. The number of MA units grafted into HBP2G was between 4 and 9, indicating a high degree of functionality. All materials possessed viscosity values below 34.94 Pa·s at 110 °C, which were dependent on the grade of the modification percentage (MP) and the molar content of MA grafted into HBP2G. Mass spectrometry analysis demonstrated the formation of products by the esterification reaction between the HBP2G and MA. The thermal stability of the HBP2GMAs determined as the decomposition temperature (Td) was between 258 and 281 °C which was better than that of the HBP2G.

LEER
Colloidal, morphological, thermal, rheological, and film properties of waterborne hyperbranched alkyd¿acrylic resins
...
Murillo, Edwin A. | 2019-04-23

Waterborne hyperbranched alkyd–acrylic resins (HAAR) are interesting materials that provide excellent properties yet require only low levels of solvent in formulations using them. However, they have been scarcely studied. Therefore, the goal of this work was to prepare and evaluate various properties of HAAR. These materials were obtained by miniemulsion polymerization from a hyperbranched alkyd resin (HAR), methyl methacrylate (MMA), butyl acrylate (BA), and acrylic acid (AA). The proportions of HAR:acrylic monomers were as follow: 50:50 (HAAR1), 40:60 (HAAR2), 30:70 (HAAR3), and 20:80 (HAAR4). The particle size increased with the content of HAR, but the colloidal stability, critical deformation, zeta potential, thermal stability, and hardness followed an opposite behavior. The order of colloidal stability of the HAAR miniemulsions was HAAR4 > HAAR3 > HAAR2 > HAAR1. The particle morphology of the HAAR was mainly core–shell, but acrylic and alkyd particles were also observed. In addition, all HAAR initially exhibited a reduction in complex viscosity (η*) with the increase in angular frequency. The thermal stability of the HAR was lower than that of the HAAR. The HAAR showed better resistance against a 0.10 M sodium hydroxide (NaOH) solution than HAR.

LEER
Waterborne star-shaped styrene-alkyd resins
...
Murillo, Edwin A. | 2019-08-13

Waterborne star-shaped styrene-alkyd resins (SSARs) were synthesized from a branched alkyd resin (AR) and styrene (St) by miniemulsion polymerization. SSARs are an environmentally friendly material. The ratio of AR to St for obtaining SSARs was as follows: 50:50 (SSAR1), 60:40 (SSAR2), 70:30 (SSAR3), and 80:20 (SSAR4). The conversion percentage was directly proportional to St used, and was higher than 94.0 %. Infrared analysis and protonic nuclear magnetic resonance revealed the reaction between AR and St. The synthesis process also leads to the formation of polystyrene and its concentration increases with the concentration of St. The values of the reacted double-bond fractions were higher than 17.80%. The SSARs drop size was bigger than the particle size. The miniemulsion colloidal stability was good at room temperature. The SSARs zeta potential was between −55 and −90 mV. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48386.

LEER
Structural, thermal, rheological, morphological and mechanical properties of polypropylene functionalized in molten state with maleinized hyperbranched polyol polyester
...
Murillo, Edwin A. | 2019-09

In a previous study, we realized the functionalization of polypropylene (PP) with maleinized hyperbranched polyol polyester (MHBP) by using dicumyl peroxide (DCP) as an initiator for obtaining the PP-g-MHBPs. This process was carried out in solution (it is not environmentally friendly). Therefore, in the present work was realized the synthesis in a molten state (free of organic solvent). The acid value (AV) of the PP-g-MHBP was lower than that of the MHBP and this increased with the proportions of DCP and MHBP employed. The presence of the characteristic signals of the MHBP in the infrared (IR) spectra of the PP-g-MHBPs allowed evidencing the functionalization of PP with MHBP. The higher functionalization degree (FD) presented by the samples was 9.10 wt%. Furthermore, all contact angles of the PP-g-MHBP were lower than that of the PP and inferior to 90°. The viscosity (η) values of the PP-g-MHBPs was lower than that of the PP. The Young’s modulus, the ultimate tensile strength and, the elongation at break of the PP-g-MHBPs were independent of the FD and DCP content.

LEER