A. Ruvolo-Filho

Transport properties of water in glassy polycarbonate films. Effects of the processing and thickness

Abstract In this work, using water as an inert penetrant, it was possible to obtain transport parameters without changing die original polymer structure, making possible a comparative analysis of how the methodologies of preparation and film thickness can influence the structural organization of the original polymer. A simultaneous analysis of transport and physical properties is very useful for this purpose. The water transport properties are of polycarbonate films, obtained via compression molding or solvent casting, controlling the cooling and the evaporation rates. From simultaneous analysis using wide-angle x-ray diffraction (WAXD), differential scanning calorimetry (DSC), and apparent density measurements, an analogy between the influence of the solvent evaporation rate and the cooling rate on the polymer crystallization phenomena is proposed. The presence of ordered domains, dependent on the film thickness, in the case of samples prepared by casting with low splvent evaporation rates, was detected ...

Correlation between crystallinity, sorption properties, and some infrared bands in the spectra of poly(ethylene terephthalate) films

Abstract Poly(ethylene terephthalate) (PET) films were obtained by cold crystallization. Samples with different crystallinities were produced by annealing amorphous samples at different temperatures and for different times. The structural organization was analyzed by x-ray, density, transport properties, and Fourier-transform infrared measurements. The presence of trans conformer is associated with the appearance in the infrared spectrum of a band at about 973 cm−1. A correlation between the intensity of this band and the structural order of different semicrystalline PET films was proposed. Assuming that the fraction of the amorphous component (αa) can be determined from the sorption measurements, at low dichlorometh-ane activity, the fraction of the ordered phase (1-αa) could be correlated with the intensity of the infrared band at 973 cm−1. The result was consistently found to be higher than the fraction of crystalline phase derived from x rays and density measurements. This led to the suggestion that i...

Preparação e Caracterização de Biocompósitos Baseados em Fibra de Curauá, Biopolietileno de Alta Densidade (BPEAD) e Polibutadieno Líquido Hidroxilado (PBHL)

In this work, curaua fibers were used in the reinforcement of a high-density (HDPE) thermoplastic matrix. The polyethylene used was obtained by polymerization of ethene produced from sugarcane ethanol. This polymer, also called high-density biopolyethylene (HDBPE), was prepared from a natural source material. The aim was to contribute to developing materials which could lead to smaller release of CO2 into the atmosphere in comparison to other materials. Additionally, liquid hydroxylatedpolybutadiene (LHPB) was added to the composite formulation, aiming at improving resistance to crack spreading during impact. The fibers and their composites were characterized by several techniques, such as scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermal gravimetry (TG). The composites were also characterized by dynamic mechanical thermal analysis (DMTA), mechanical properties (flexural and impact strength), and water absorption. The presence of curaua fibers reduced some of the properties of HDBPE, such as flexural and impact strength. DMTA indicated a more rigid material with the fibers incorporated. The addition of LHPB to the formulation was efficient, leading to greater impact strength for the HDBPE/LHPB/Fiber composite, as compared to the HDBPE/Fiber composite.

Transport of dichloromethane in poly(ether imide) films. Effect of the solvent activity and temperature

Abstract The sorption and diffusion of dichloromethane liquid in a wide range of activities and at different temperatures in poly(ether imide) (PEI) films was studied. They were prepared by solution casting at slow solvent evaporation conditions. The sorption behavior is characterized by two zones depending on temperature and penetrant activity. In zone I, at low activity, the isotherms follow Henrys law. The range of activity between 0.25 and 0.30 is characterized by a negative deviation from Henrys law and shows an accentuated dependence on previous thermal history of the films. In zone II, with a range of activity higher than 0.35, the isotherms follow Flory-Huggins behavior. In both zones, the diffusional behavior, based on sorption measurements, shows a linear relationship between the diffusion coefficient and the equilibrium sorption concentration of dichloromethane. In the activity range between 0.25 and 0.35, an accentuated discontinuity indicates a possible conformational structural change in ...

The mesomorphic phase structure in PET films: A conformational analysis

Abstract The conformational analysis of the mesomorphic phase structure in poly(ethylene terephthalate) (PET) films based on the determination of the amount of Ta (trans in the amorphous phase), Tc (trans in the crystalline phase), and G (gauche) isomers present in samples of PET films heat treated between 110°C and 230°C is presented. The change in the amount of isomers was related to the mesomorphic phase determined from a correlation among wide-angle X-ray diffraction (WAXD), Fourier transform infrared (FTIR), density, and sorption properties. The reduction in sorption in semicrystalline samples, with respect to completely amorphous samples, at low penetrant activity allowed determination of the fraction of impermeable phase. This fraction, when compared with crystallinity determined from WAXD and density techniques, is higher, indicating the presence of mesomorphic fractions that probably have a bidimensional order. Separation of the contribution of isomers Ta and Tc and its relation with the mesomorp...

Influence of Molecular Structure and Packing on Sorption and Transport Properties of Dichloromethane in Polyetherimides

The effects of thermal history on dichloromethane vapor sorption and transport properties of polyetherimides were studied. Films were prepared by solution casting at room temperature and heat treated for 24 h at different temperatures below the corresponding glass transition temperature of each material. Changes of the transport properties due to heat treatment were observed and are correlated to changes in density, free volume, and thermal transitions. Deviation from Ficks and Henrys laws was observed for all the samples studied. Without heat treatment and at low activities of the penetrant, the materials studied show sorption kinetics similar to the Fickian behavior. On the other hand, sorption measurements tests for the heat‐treated films at high activities of dichloromethane show kinetics similar to Case II diffusion. Equilibrium sorption data obtained at different penetrant concentrations show deviation from Henrys law behavior depending on the thermal history of the sample.

Effect of Blending Protocol on the Rheological Properties and Morphology of HDPE/LLDPE Blend-based Nanocomposites

Abstract Nanocomposites based on high density polyethylene (HDPE)/linear low density polyethylene (LLDPE) blend were prepared by melt compounding in a torque rheometer using an organoclay (montmorillonite) as nano-filler and maleic anhydride-grafted linear low density polyethylene (LLDPE-g-MA) as compatibilizer. The effects of five blending protocols on microstructure, crystallinity and rheological properties of the prepared samples were examined. The steady state rheological properties showed that the addition of nanoclay to the HDPE/LLDPE blend increased its shear viscosity at low shear rates changing the behavior of the HDPE/LLDPE matrix to a more pronounced shear thinning behavior. The blending sequence (LLDPE/LLDPE-g-MA/20A)/HDPE (where LLDPE and LLDPE-g-MA were first mixed with organoclay and then this system was later blended with HDPE) showed a lower slope of the log versus log curve and these results can be an indicative that the interactions between the matrix and the organoclay are stronger. The organoclay interlayer spacing and the crystallinity of the polymer domains were also influenced by the blending sequence. The crystallinity was calculated through the mathematical deconvolution of the peaks observed in the WAXD profiles. Overall, the crystallization of HDPE in the blends was hardly influenced by the presence of LLDPE. The blending sequence (LLDPE/LLDPE-g-MA/20A)/HDPE showed lower cristallinity when compared to others blending sequences. On the other hand, it was observed an increase in the organoclay interlayer spacing of this nanocomposite because the intercalation and/or exfoliation process occurs preferentially in the amorphous phase.

Correlation between thermal properties and conformational changes in poly(ethylene terephthalate)/poly(ether imide) blends

Abstract Miscibility, crystallisation and melting behaviour in blends of virgin and recycled poly(ethylene terephthalate) (PET) with poly(ether imide) (PEI) have been examined using DSC. The blends exhibit single, composition-dependent T g s over the entire composition range and a negative value of the Flory interaction parameter, indicating miscibility of the amorphous polymers. The crystallisation of the PET/PEI blends was dramatically slowed by PEI contents higher than 20%. A linear correlation between a structure-dependent parameter R T (from FTIR measurements) and the enthalpy of fusion (from DSC measurements) for both types of PET samples used in the blends, make the determination of the degree of crystallinity of the PET in any PET/PEI blend possible. In agreement with the melting behaviour of the PET/PEI blends, the average values of the activation energy for trans- conformer formation confirm the negative effect of the PEI on the crystallisation of the PET.

Selection Criteria for Recycled Polyolefins from Urban Wastes by Using TG Analysis

The thermal behavior of a mixture of recycled polyolefins (PE/PP mix), variously colored recycled polyolefins, recycled polyolefin blends and recycled polyolefin/PET blends was analyzed by thermogravimetry. Atmospheres of nitrogen and synthetic air were used to compare the effects of inert and oxidative medium. Four characteristic temperatures, T1, T2, T3 and T4, related to oxidative processes and atmospheric conditions, were defined. Relationships between T1, T2, T3 and T4 and comparing pigmented and transparent material allow assessing the effect of different pigments on volatilization, oxidation and onset temperatures of decomposition processes. These analyses provide preliminary parameters for selecting acceptable processing temperature conditions of recycled household and engineering plastics, and provide a few criteria to select colored recycled polyolefins.

Effect of Dichloromethane on Transport, Thermal, and Thermal‐Mechanic Properties of Amorphous Glass Poly(Ether Imide) Films

Abstract In this work the interaction effect of dichloromethane on amorphous glassy poly(ether imide) (PEI) films was analyzed from the correlation between transport, thermal, and mechanical properties. The resulting sorption curves were anomalous two‐stage in the solvent activity range 0–0.34 and pseudo‐Fickian for the solvent activity range 0.40–0.50. From a generalized diffusion equation to describe the combination of Fickian and Case II mechanisms we found that the velocity of solvent penetration (v) was higher than the diffusion coefficient (D) for all solvent activities studied. It was observed from the cluster function and the mean size cluster that solvent–solvent interactions may occur at higher solvent activities. Thermal differential scanning calorimetry (DSC) and thermal gravimetric analysis [(TGA) and thermal mechanical (DMTA)] characterization showed that the solvent clusters may act as an antiplasticizer, increasing the elastic modulus of the PEI matrix by 1.9 times. Therefore, a shifting of the β transition was observed at higher temperatures around the glass transition.