Marcia C. Delpech

Viscometric study of high-cis polybutadiene in toluene solution

Viscometric measurements, in toluene solution at 30 oC, were performed with high-cis polybutadiene synthesized by neodymium based catalyst. Six different equations were used to calculate intrinsic viscosities and viscosimetric constant values: Huggins, Kraemer, Martin and Schulz-Blaschke by graphic extrapolation, and Solomon-Ciuta, Deb-Chanterjee and again Schulz-Blaschke, through a single point determination. The molecular weight of the polymers was also determined applying Mark-Houwink-Sakurada equation using the values of intrinsic viscosity obtained by the six equations. The values of intrinsic viscosity and viscosity-average molecular weight obtained by the two methods were compared in order to verify the validity of the single point determination for high-cis polybutadiene.

Viscometric study of chitosan solutions in acetic acid/sodium acetate and acetic acid/sodium chloride.

A viscometric study was carried out at 25°C to assess the physical-chemical behavior in solution and the mean viscometric molar mass (M¯v) of chitosan solutions with different deacetylation degrees, in two solvent mixtures: medium 1-acetic acid 0.3mol/L and sodium acetate 0.2mol/L; and medium 2-acetic acid 0.1mol/L and sodium chloride 0.2mol/L. Different equations were employed, by graphical extrapolation, to calculate the intrinsic viscosities [η] and the viscometric constants, to reveal the solvents quality: Huggins (H), Kraemer (K) and Schulz-Blaschke (SB). For single-point determination, the equations used were SB, Solomon-Ciuta (SC) and Deb-Chanterjee (DC), resulting in a faster form of analysis. The values of ̄M¯v were calculated by applying the equation of Mark-Houwink-Sakurada. The SB and SC equations were most suitable for single-point determination of [η] and ̄M¯v and the Schulz-Blachke constant (kSB), equal to 0.28, already utilized for various systems, can also be employed to analyze chitosan solutions under the conditions studied.

Waterborne polyurethanes: influence of chain extender in ftir spectra profiles

Non-polluting systems based on waterborne polyurethanes (wPU) and poly(urethane-urea)s (wPUU) were synthesized employing poly(propylene glycol) (PPG), dimethylolpropionic acid (DMPA) and 4,4′-dicyclohexylmethane diisocyanate (HMDI) as monomers. In the formulations, the length and the proportion of the soft segments were varied. Three types of chain extenders were employed: ethylene glycol (EG), producing urethane linkages; and ethylenediamine (EDA) and hydrazine (HYD), forming urea linkages. Cast films obtained from wPU and wPUU, monomers and prepolymers were analyzed by Fourier transform infrared spectrometry (FTIR). The profile of carbonyl absorption bands obtained for the films showed some remarkable differences depending on the formulation. The bands were split into two parts, which were directly related to the tendency of hydrogen bond formation. The length of soft segment, the amount of rigid portions and the presence of urea linkages showed a marked influence in both intensity and frequency absorption of the bands.

Estudo viscosimétrico de prepolímeros uretânicos

In this study the behavior of urethane prepolymers based on poly(propylene glycol) (PPG) and isophorone diisocyanate (IPDI), in diluted solutions, were studied by viscosimetric measurements, at 30 °C, in two types of solvents with different polarities: isopropyl alcohol and toluene. Five different equations were used to determine intrinsic viscosities values: Huggins; Kraemer and Schulz-Blaschke, by graphic extrapolation; and Solomon-Ciuta; Deb-Chanterjee and; again, Schulz-Blaschke, by a single point determination. The intrinsic viscosities were obtained with two methods (graphic extrapolations and through a single point determination). Viscometric constants from Huggins; Kraemer and Schulz-Blaschke equations were also determined to verify the solvent quality. Regardless of the formulation, isopropyl alcohol was the best solvent for the samples and Solomon-Ciuta equation was the most suitable for the single point determination.

Dispersões aquosas à base de nanocompósitos de poliuretanos e argilas hidrofílicas brasileiras: síntese e caracterização

In this work nanocomposites based on polyurethane aqueous dispersion (NWPUs) were synthesized employing montmorillonite (MMT) hydrophilic brazilian clays (Brasgel PA and Brasgel NT), containing sodium and calcium, respectively, being the former more hydrophilic. The monomers used in the synthesis of the dispersions were: poly (propylene glycol) (PPG); dimethylolpropionic acid (DMPA), isophorone diisocyanate (IPDI) and hydrazine, as chain extender. It was varied the proportion between hard and soft segments and clay content (added in the range from 0.5 to 2.5% per mass). The clays were previously delaminated in water and incorporated in the moment of prepolymer dispersion. The clays were characterized by infrared spectrometry (FTIR) and X ray diffraction (XRD) and their degree of swelling were determined. Solid content of the formulations were calculated. The films, cast from aqueous dispersions, were characterized by FTIR, XRD and their mechanical properties were evaluated. The formation of nanocomposites was confirmed by XRD, by observing the absence of peaks indicating cristallinity, characteristic of the pure clays. Mechanical resistance was improved for the nanocomposite films when compared to materials with no clay addition.

Síntese e caracterização de dispersões aquosas de poliuretanos à base de copolímeros em bloco de poli(glicol etilênico) e poli(glicol propilênico)

SYNTHESIS AND CHARACTERIZATION OF POLYURETHANE AQUEOUS DISPERSIONS BASED ON POLY(ETHYLENE GLYCOL) AND POLY(PROPYLENE GLYCOL) BLOCK COPOLYMERS. Non-polluting polyurethane aqueous dispersions, with 40% of solids content, were synthesized based on block copolymers of poly(ethylene glycol) and poly(propylene glycol) (PEG-bPPG), with PEG hydrophilic segments content of 7 and 25%, poly(propylene glycol) (PPG), dimethylolpropionic acid (DMPA), isophorone diisocyanate (IPDI), and hydrazine. Different formulations were synthesized by varying the equivalent-grams ratios between isocyanate and hydroxyl groups (NCO/OH) and PPG and (PEG-b-PPG). The presence of high amounts of PEG in the formulations provoked the formation of gels. Average particle size and viscosity of the dispersions were determined. Mechanical properties and water absorption resistance of cast films were evaluated.

Evaluation of chemical and mechanical resistance of virgin and recycled poly (ethylene terephthalate) and poly(methylene oxide) when applied as gravel pack in petroleum wells

Nowadays more and more unexpected uses for common materials have been observed, especially when recycled polymers are concerned. In this work, the viability for application of virgin and recycled poly(ethylene terephthalate) (PETvir and PETrec, respectively) and also poly(methylene oxide) (PMO) as granular materials (gravel) for gravel packing in sand control systems for unconsolidated sandstone reservoirs was studied. Polymer samples were tested in conditions similar to those observed in Campos Basin sandstone formations, in Brazilian Southwest (70 °C and 24.1 MPa). Samples were individually confined in roller cells with chemicals used in formation treatment: hydrochloric acid, pentapotassic DTPA salt (chelant Trilon CK) and in a mixture of diesel, xylene and butyl glycol. Mass loss was measured and the changes in molecular mass verified by size exclusion chromatography (SEC). Physical shape and grain size distribution were verified by scanning electron microscopy (SEM) and sieving tests. The effects over the polymeric gravel pack confinement resistance and permeability were evaluated using an API permeability cell. PMO proved to have a limited use, whereas PETrec and PETvir samples were not significantly affected, suggesting the viability of applying that recycled polymer in gravel packing for sand control in petroleum wells.

Dispersões aquosas poliuretânicas à base de polibutadieno hidroxilado: influência das variáveis reacionais

In this work, polyurethane aqueous dispersions with different formulations were produced in the absence of organic solvents. In the synthesis, isophorone diisocyanate (IPDI), poly(propylene glycol) (PPG) and different types of hydroxy-terminated polybutadiene (HTPB) were employed. In order to make possible the dispersion of the polyurethane chains in water, dimethylolpropionic acid (DMPA), was used. Afterwards the acid groups were neutralized with triethylamine (TEA) to provide the ionic groups responsible for the particles stability in water. The solids content, viscosity and particle size of the formulations produced in this work were evaluated. These parameters were found to vary within a narrow range, regardless of the formulation. The films were transparent, flexible and showed a good adherence on aluminum surfaces. Their mechanical properties were satisfactory, particularly those obtained with higher contents of DMPA and at low values of NCO/OH ratio.