Obtenção e caracterização físico-química de blendas poliméricas, baseadas em POE e PMMA, dopadas com dióxido de titânio

The study of polymer blends has been an alternative method in the search field of new materials for obtaining materials with improved properties. In this work blends of poly(methyl methacrylate) (PMMA) and poly(ethylene oxide) (PEO) doped with titanium dioxide (TiO2) were studied. The PEO is a polymer semicrystalline structure varying between, 70 and 84% crystallinity, while the PMMA exhibits behavior amorphous in their structure. The use of TiO2 is related to corrosion-resistant of titanium as well as good heat transfer and other characteristics. The study of these polymer blends doped TiO2 gives the properties junction organic (polymer) and inorganic (oxide) which leads to modification of the properties of the resultant material. The blends were doped TiO2 (POE/PMMA/TiO2) in different proportions of the PMMA with the PEO and TiO2 fixed. The ratios were: 90/10/0,1; 85/15/0, 1; 80/20/0,1, 75/25/0,1 and 70/30/0,1. The resulting material was obtained in powder form and being characterized by Fourier Transformed Infrared (FTIR) Spectroscopy, Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA) and Electrochemical Impedance Spectroscopy (EIS). The infrared spectra (IR) for the blends in different ratios showed a band at 1744 cm-1, characteristic of the C=O stretching, which increases in intensity with increasing PMMA composition, while in the spectrum of pure PEO this band is absent. This may suggest that the interaction is occurring between the polymers. In the micrographs of the blends also observed change in their surfaces with variation of the composition of PMMA, contributing to the change of the electrical properties of the material. The EIS data showed that the material exhibited conductivity of the order of 10-6 S.cm-1. The blend in the ratio B2(85/15/0, 1) showed better conductivity, σ = 1.56 x 10-6 S.cm-1. It was observed that the diffusion coefficient for the blends, B5(70/30/0, 1) was the largest, 1.07 x 10-6 m2.s-1. The XRD data showing that, with the variation in the composition of the PMMA blend crystallinity of the material is decreased reaching a minimum B3(80/20/0,1), and then increases again. Thermal analysis suggests that blends made from the material obtained can be applied at room temperature

Role of polyethylene-graft-glycidyl methacrylate compatibilizer on the biodegradation of poly(epsilon-calprolactone)/cellulose acetate blends

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Thermal analysis of conductive blends of PVDF and poly(o-methoxyaniline)

The thermal behavior of blends of poly(vinylidene fluoride), or PVDF, and poly(o-methoxyaniline) doped with toluene sulfonic acid was studied by thermogravimetic analysis, electrical conductivity measurements, differential scanning calorimetry, X-ray diffraction and scanning electron microscopy. Blends with thermal and electrical conductivity stabler than the conductive polymer alone were obtained. Nevertheless, degradation occurs after a long period of time (500 h) at high temperatures. The possible association of the conductivity decay with dopant loss, degradation and structural and morphological changes of the blend is discussed. (C) 2000 Elsevier Science Ltd.

Morphological, mechanical and rheological properties of nylon 6/acrylonitrile-butadiene-styrene blends compatibilized with MMA/MA copolymers

The morphological, mechanical and rheological properties of nylon 6/acrylonitrile-butadiene-styrene blends compatibilized with MMA-MA [poly(methyl methacrylate-comaleic anhydride)] copolymers were studied. A twin screw extruder was used for melt-blended the polymers and the injection moulding process was used to mold the samples. The main focus was on nylon 6/ ABS blends compatibilized with one MMA-MA copolymer. This copolymer has PMMA segments that appear to be miscible with the styrene-acrylonitrile (SAN) phase of ABS and the anhydride groups can react with amine end groups of the nylon 6 (Ny6) to form graft copolymers at the interface between Ny6 and ABS rich phases. Tensile and impact and morphological properties were enhanced by the incorporation of this copolymer. Transmission electron microscopy (TEM) observations revealed that the ABS domains are finely dispersed in nylon 6 matrix and led to the lowest ductile-brittle transition temperatures and highest impact properties. It can be concluded that the MMA-MA copolymer is an efficient alternative for the reactive compatibilization and can be used as a compatibilizer for nylon 6/ABS blends.© 2003 Kluwer Academic Publishers.

Morphology of Nylon 6/Acrylonitrile-Butadiene-Styrene Blends Compatibilized by a Methyl Methacrylate/Maleic Anhydride Copolymer

The morphologies of nylon 6/acrylonitrile-butadiene-styrene blends compatibilized with a methyl methacrylate/maleic anhydride copolymer, with 3-20 wt % maleic anhydride, were examined by transmission electron microscopy. Some staining techniques were employed for identifying the various phases. The binary blends were immiscible and exhibited poor mechanical properties that stemmed from the unfavorable interactions among their molecular segments. This produced an unstable and coarse phase morphology and weak interfaces among the phases in the solid state. The presence of the copolymer in the blends clearly led to a more efficient dispersion of the acrylonitrile-butadiene-styrene phase and consequently optimized Izod impact properties. © 2003 Wiley Periodicals, Inc.

Effect of compatibilizer in acrylonitrile-butadiene-styrene toughened nylon 6 blends: Ductile-brittle transition temperature

The ductile-brittle transition temperatures were determined for compatibilized nylon 6/acrylonitrile-butadiene-styrene (PA6/ABS) copolymer blends. The compatibilizers used for those blends were methyl methacrylate-co-maleic anhydride (MMA-MAH) and MMA-co-glycidyl methacrylate (MMA-GMA). The ductile-brittle transition temperatures were found to be lower for blends compatibilized through maleate modified acrylic polymers. At room temperature, the PA6/ABS binary blend was essentially brittle whereas the ternary blends with MMA-MAH compatibilizer were supertough and showed a ductile-brittle transition temperature at -10°C. The blends compatibilized with maleated copolymer exhibited impact strengths of up to 800 J/m. However, the blends compatibilized with MMA-GMA showed poor toughness at room temperature and failed in a brittle manner at subambient temperatures.

Morphological, mechanical and thermal properties of nylon 6/ABS blends using glycidyl methacrylate-methyl methacrylate copolymers

Nylon6 is an attractive polymer for engineering applications because it has reactive functionality through amine and carboxyl end groups that are capable of reacting. For this reason, it has been used a lot in polymeric blends. Blends of nylon6/ABS (acrylonitrile-butadiene-styrene) were produced using glycidyl methacrylate-methyl methacrylate (GMA-MMA) copolymers as compatibilizer. The binary blends were immiscible and exhibited poor mechanical properties that stemmed from the unfavorable interactions among their molecular segments. This produced an unstable coarse phase morphology and weak interfaces between the phases in the solid state. The presence of the copolymer in the blends clearly led to a more efficient dispersion of the ABS phase and consequently optimized Izod impact properties. However, the compatibilized blend showed poor toughness at room temperature and failed in a brittle manner at subambient temperatures. © 2005 Springer Science + Business Media, Inc.

Ferroelectric switching and dielectric response of P(VDF-TrFE)/PMMA blends

The ferroelectric and the dielectric behaviors of binary blends formed by an equi-molar Poly(vinylidene fluoride trifluoroethylene) copolymer [P(VDF-TrFE)] and Poly(methyl methacrylate) [PMMA] were investigated, for several PMMA compositions. For 40 wt.% or more PMMA contents, the blends are completely amorphous. Below this value, they crystallize in the usual Cm2m polar structure of P(VDF-TrFE). The ferroelectric switching characteristics and the dielectric response of the blends demonstrate the formation of dynamically stable ferroelectric domains. Moreover, the blended films are highly transparent in the optical region. Therefore, thin films of these binary blends are good candidates as host materials for nonlinear optical applications.

Electrical behavior of PU/POMA blends

The incorporation of conducting polymer into a conventional polymer matrix has received attention because of the possibility of combining the good processability and mechanical performance of the conventional polymer with the electrical and optical properties of conducting polymer. In this work, flexible films of polyurethane (PU) and Poli(o-metoxyaniline)(POMA) blends were obtained by casting and investigated using thermally stimulated depolarisation current (TSDC) measurements. Two relaxation peaks were found in the range of-20°C to 90°C. The first one at T=24°C was attributed as α relaxation associated to the glass transition of PU/POMA blend and the second one located at T=60°C can be attributed to space charge.

Blends of cross-linked high amylose starch/pectin loaded with diclofenac

Polymers blends represent an important approach to obtain materials with modulated properties to reach different and desired properties in designing drug delivery systems in order to fulfill therapeutic needs. The aim of this work was to evaluate the influence of drug loading and polymer ratio on the physicochemical properties of microparticles of cross-linked high amylose starch-pectin blends loaded with diclofenac for further application in controlled drug delivery systems. Thermal analysis and X-ray diffractograms evidenced the occurrence of drug-polymer interactions and the former pointed also to an increase in thermal stability due to drug loading. The rheological properties demonstrated that drug loading resulted in formation of weaker gels while the increase of pectin ratio contributes to origin stronger structures. © 2012 Elsevier Ltd.

Linear viscoelasticity of immiscible blends: The application of creep

A new method to characterize the long-time linear relaxation mechanisms of immiscible blends based on creep experiment was developed. Small-amplitude oscillatory shear and incomplete creep/recovery experiments were combined to characterize immiscible blends of polypropylene with dispersed droplets of polystyrene. An experimental protocol was defined such that the full creep compliance function could be obtained while minimizing morphological changes. Dynamic experiments were performed to characterize the shorter time relaxation processes, and creep and recovery measurements were used to detect the longer time portions of the relaxation spectra. Extended retardation and relaxation spectra were constructed by combining these data. It was found that using this technique, very long-time relaxation peaks which were inaccessible with dynamic experiments alone could be detected. (C) 2012 The Society of Rheology. [http://dx.doi.org/10.1122/1.4720081]

Understanding the mechanical and biodegradation behaviour of poly(hydroxybutyrate)/rubber blends in relation to their morphology

In this work poly(hydroxybutyrate/poly(vinyl butyral)- co-(vinyl alcohol)-co(vinyl acetate) (or ethylene propylene diene monomer rubber) blends were prepared by conventional processing techniques (extrusion and injection moulding). A droplet type morphology was obtained for P(3HB)/PVB blends whereas P(3HB)/EPDM blends presented some extent of co-continuous morphology. In addition, rubbery domains were much smaller in the case of PVB. These differences in morphology are discussed taking into account solubility parameters and rheological behaviours of each component. For both blends, the increase of elastomer ratio led to a decrease of Young's modulus but an increase in elongation at break and impact strength. The latter increased more in the case of P(3HB)/EPDM blends although the rubbery domains were larger. These results are explained in the light of the glass transition of the rubber and the presence of plasticizer in the case of PVB. The addition of elastomer also resulted in an increase of P(3HB) biodegradation rate, especially in the case of EPDM. It is assumed that, in this case, the size and morphology of the rubbery domains induce a geometrical modification of the erosion front which leads to an increase of the interface between P(3HB) phase and the degradation medium and consequently to an apparently faster biodegradation kinetics of PHB/rubber blends. Copyright (C) 2011 Society of Chemical Industry

Compatibilization of polypropylene/poly(3-hydroxybutyrate) blends

Blending polypropylene (PP) with biodegradable poly(3-hydroxybutyrate) (PHB) can be a nice alternative to minimize the disposal problem of PP and the intrinsic brittleness that restricts PHB applications. However, to achieve acceptable engineering properties, the blend needs to be compatibilized because of the immiscibility between PP and PHB. In this work, PP/PHB blends were prepared with different types of copolymers as possible compatibilizers: poly(propylene-g-maleic anhydride) (PPMAH), poly (ethylene-co-methyl acrylate) [P(EMA)], poly(ethylene-co-glycidyl methacrylate) [P(EGMA)], and poly(ethylene-co-methyl acrylate-co-glycidyl methacrylate) [P(EMAGMA)]. The effect of each copolymer on the morphology and mechanical properties of the blends was investigated. The results show that the compatibilizers efficiency decreased in this order: P(EMAGMA) > P(EMA) > P(EGMA) > PP-MAH; we explained this by taking into consideration the affinity degree of the compatibilizers with the PP matrix, the compatibilizers properties, and their ability to provide physical and/or reactive compatibilization with PHB. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 3511-3519, 2012

Proton-conducting copolymers, blends and composites with phosphonic acid as protogenic group

ABSTRACT: In this work, proton conducting copolymers, polymer blends and composites containing phosphonic acid groups have been prepared. Proton conduction mechanisms in these materials are discussed respectively in both, the anhydrous and humidified state. Atom transfer radical copolymerization (ATRCP) of diisopropyl-p-vinylbenzyl phosphonate (DIPVBP) and 4-vinyl pyridine (4VP) is studied for the first time in this work. The kinetic parameters are obtained by using the 1H-NMR online technique. Proton conduction in poly(vinylbenzyl phosphonic acid) (PVBPA) homopolymer and its statistical copolymers with 4-vinyl pyridine (poly(VBPA-stat-4VP)s) are comprehensively studied in both, the “dry” and “wet” state. Effects of temperature, water content and polymer composition on proton conductivities are studied and proton transport mechanisms under various conditions are discussed. The proton conductivity of the polymers is in the range of 10-6-10-8 S/cm in nominally dry state at 150 oC. However, proton conductivity of the polymers increases rapidly with water content in the polymers which can reach 10-2 S/cm at the water uptake of 25% in the polymers. The highest proton conductivity obtained from the polymers can even reach 0.3 S/cm which was measured at 85oC with 80% relative humidity in the measuring atmosphere. Poly(4-vinyl pyridine) was grafted from the surface of SiO2 nanoparticles using ATRP in this work for the first time. Following this approach, silica nanoparticles with a shell of polymeric layer are used as basic particles in a polymeric acidic matrix. The proton conductivities of the composites are studied under both, humidified and dry conditions. In dry state, the conductivity of the composites is in the range of 10-10~10-4 S/cm at 150 oC. While in humid state, the composites show much higher proton conductivity. The highest proton conductivity obtained with the composites is 0.5 S/cm measured at 85oC with 80% relative humidity in the measuring atmosphere. The miscibility of poly (vinyl phosphonic acid) and PEO is studied for the first time in this work and a phase diagram is plotted based on a DSC study and optical microscopy. With this knowledge, homogeneous PVPA/PEO mixtures are prepared as proton-conducting polymer blends. The mobility of phosphonic acid groups and PEO in the blends is determined by 1H-MAS-NMR in temperature dependent measurements. The effect of composition and the role of PEO on proton conduction are discussed.

Processing and characterization of plasticized PLA/PHB blends for biodegradable multiphase systems

Blends of poly(lactic acid) (PLA) and poly(3-hydroxybutyrate) (PHB) plasticized with a lactic acid oligomer (OLA) added at three different concentrations (15, 20 and 30 wt% by weight), were prepared by an optimized extrusion process to improve the processability and mechanical properties of these biopolymers for flexible film manufacturing. Morphological, chemical, thermal, mechanical, barrier and migration properties were investigated and formulations with desired performance in eco-friendly films were selected. The efficiency of OLA as plasticizer for PLA_PHB blends was demonstrated by the significant decrease of their glass transition temperatures and a considerable improvement of their ductile properties. The measured improvements in the barrier properties are related to the higher crystallinity of the plasticized PLA_PHB blends, while the overall migration test underlined that all the proposed formulations maintained migration levels below admitted levels. The PLA_PHB blend with 30 wt% OLA was selected as the optimum formulation for food packaging, since it offered the best compromise between ductility and oxygen and water vapor barrier properties with practically no migration.