Carlos R. Wolf

Transformação de triglicerídeos em combustíveis, materiais poliméricos e insumos químicos: algumas aplicações da catálise na oleoquímica

The use of biomass as raw-material for obtaining chemicals, polymers and fuels is emerging as a clever alternative solution for the increasing energy demand, environmental awareness and petroleum shortage. In this work, some attempts in order to develop catalytic systems suitable for triglyceride transformation into fuels, polymers and intermediates are reviewed.

Linear Low Density Polyethylene Thermal Fractionation by DSC Technique

Abstract Crystallization of linear low density polyethylene was studied through DSC analyses. Melting peak resolution was determined in order to establish the effect of crystallization conditions on polymer thermal fractionation. The isothermal number, fractionation window, and annealing time were varied, and suitable crystallization conditions were evaluated based on the sharpness of the DSC endothermic curve. The results confirmed that the selection of the thermal fractionation conditions is very important to control the multiple melting peaks number. The polyethylene endothermic curve profile changed significantly according to the crystallization conditions.

Linear Low-Density Polyethylene Softening Point and Endothermic Curve Profile Correlation: DSC Technique

Two different linear low-density polyethylenes (LLDPE) were investigated by successive self-nucleation and annealing (SSA) thermal fractionation via differential scanning calorimetry (DSC). Samples with the same density and melt flow rate, very close comonomer content, and different softening points were investigated according to the endothermic curve profile, heat of fusion, and lamellar thicknesses of the multiple peaks. Changes in these parameters due to the LLDPE molecular chain heterogeneity could be used to characterize and identify the differences between the polyethylenes. The sample with the lower softening point presented multiple peaks or crystalline fractions with lower lamellar thickness, lower content of polyethylene homopolymer with high lamellar thickness, and relatively wider peak area related to very small lamellar crystallites. Thus, in this study, using the SSA technique it was possible to identify the LLDPE with the most suitable thermal fingerprint profile for hot-melt film application.

Determination of Alkyl Esters Content by Gas Chromatography: Validation of Method Based on Short Column and Response Factor

In this study an analytical method, based on gas chromatography with flame ionization detection, using a short column and response factor (GCSCRF), was validated for the quantification of fatty acid alkyl esters (methylic or ethylic). During the validation process, the proposed method was employed to analyze twenty samples of fatty acid methyl esters and fatty acid ethyl esters. Biodiesel samples were produced from soybean oil and the validated method was found to be selective, being able to separate and identify every ester species present in the samples according to its carbon number. When the method was submitted to some variations in the sample preparation procedure, it remained robust. Limits of detection and quantification were 6.76 and 20.4 mg mL, respectively. The suggested method also showed great precision when successive analyses were carried out for different analysts, with standard deviation (SD) 0.6 for repeatibility and relative standard deviation (RSD) percentage 7.3% for intermediate precision, excellent accuracy when compared to other reference methods (EN 14103 and high-performance liquid chromatography with ultraviolet dection (HPLC-UV)) and recovery studies.

Hybrid silicas/waterborne polyurethane composite properties: In situ formation vs. grafting methods

A series of composites of commercial waterborne polyurethane and hybrid silica were prepared by the sol–gel process through in situ synthesis. Mechanical properties, small angle X-ray scattering and differential scanning calorimetry measurements were performed to evaluate the effects that hybrid silica has on the properties of the resulting polyurethane composites. A series of 13 different organosilanes differing in polarity and alkyl chain length was studied. Under the present evaluated conditions, composites bearing hybrid silica were more likely to exhibit a reduction in mechanical resistance when compared to bare polyurethane. Samples also exhibited a negligible variation in glass transition temperature and a reduction in ΔCp. The enthalpy of the crystallization process exhibited an increase. Based on the small angle X-ray scattering measurements, the composites exhibited a small reduction in the interdomain spacing and an increase in the degree of phase separation.Graphical Abstract