Edwin Murillo

Characterization of hydroxylated hyperbranched polyesters of fourth and fifth generation

Abstract Hydroxylated hyperbranched polyester (HBPs) of fourth and fifth generation were obtained by three methods; one step (HBP4, HBP5), step by step (HBP4P, HBP5P) and combinations of one step and step by step (HBP1-4, HBP1- 5). The HBPs were synthesized in bulk from 2,2-bis(hydroxymethyl)propionic acid (DMPA) and pentaerythritol (PE) using acid catalysis (p-toluenesulfonic acid) and characterized by infrared analysis, 1H and 13C nuclear magnetic resonance, gel permeation chromatography, vapor pressure osmometry, electro spray ionizationmass spectrometry, dynamic light scattering, refractive index, thermogravimetric and differential scanning calorimetric analysis. The refractive index of HBPs were low, the infrared and nuclear magnetic resonance analysis showed evidence of the occurrence of reaction between from 2,2-bis(hydroxymethyl) propionic acid (DMPA) and pentaerythritol (PE). The molar mass values of the HBPs determined by gel permeation chromatography were different to vapor pressure osmometry measurements due to small hydrodynamic volume of the HBPs. The mass spectrometry analysis showed different acyclic and cyclic units in the HBPs. The distributions of HBPs studied by dynamic light scattering were monomodal in number and volume and bimodal in intensity. The thermal stability of the fifth generation HBPs was higher than that the fourth generation. All HBPs presented amorphous behavior

Synthesis and characterization of a pressure-sensitive adhesive based on an isobutyl acrylate / 2-ethylhexyl acrylate copolymer

Abstract A removable pressure-sensitive adhesive was obtained by free-radical emulsion polymerization. The product is a low-viscosity copolymer from different polar and apolar acrylic monomers consisting of microspheres of about 1 μm diameter. 2-Ethylhexyl acrylate and isobutyl acrylate were used as non-polar constituents while acrylic acid and acrylamide provided the more polar constituents to regulate the cohesive force of the adhesive. The amounts of initiator, water and emulsifier (nonylphenol) were varied to obtain the best adhesive properties at the given copolymer composition. The resulting adhesive showed the desired balance of low tack and good adhesive strength in combination with a wide variety of substrates, which made it useful as a removable adhesive for many applications. The product was characterised by viscometry, measurements of tack and peel strength, FTIR, DSC, and microscopy.

Hyperbranched polyester polyol plasticized tapioca starch/low density polyethylene blends

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.

Synthesis And Characterization Of Pressure Sensitive Adhesive Based On Isobutyl Acrylate And 2-Ethyl Hexyl Acrylate Copolymer

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Hyperbranched polyester polyol modified with polylactic acid as a compatibilizer for plasticized tapioca starch/polylactic acid blends

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.

Waterborne hyperbranched alkyd-acrylic resin obtained by miniemulsion polymerization

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.