7 research outputs found
Microrheology of poly(butylene terephthalate) / poly(styrene-co-acrylonitrile) blends.
This work was motivated by the need of a better understanding of the
microrheological characteristics of polybutylene terephthalate, PBT, polymer
blends, such as the matrix phase PBT and the styrene-acrylonitrile, SAN
copolymer as dispersed phase. The main purpose of the microrheological
studies carried out was to analyze the rheological behavior and the morphology,
as well as their correlation, in the preparation of the PBT/SAN immiscible blend,
with and without the use of an interfacial compatibilizer. The rheological
behavior was analyzed by torque rheometry, rotational rheometry with parallelplates
geometry, and capillary rheometry. The interfacial tensions were
measured by the modified ellipsoidal drop retraction method, using an optical
polarized light microscope coupled to a hot stage. Two complementary
techniques were used in the morphological analyses: scanning electron
microscopy (SEM) with tetrahydrofuran (THF) extraction of the dispersed
phase, and transmission electron microscopy (TEM) with rutene tetroxide
(RuO4) deposition in the dispersed phase. The interfacial tension between the
PBT polymer and the SAN copolymer was found to increase as the molar mass
of the PBT increased. The use of rotational rheometry with parallel plates at low
shear rates allowed the increase in viscosity to be quantified as a function of the
reaction of the polymeric macromolecules in the PBT/SAN blend compatibilized
or not with the interfacial compatibilizer, the MMA-GMA-EA copolymer. Based
on the morphological characterizations, an analysis was made of the fibril
formation mechanisms, break up and coalescence of the particles of dispersed
phase and their interactions with the addition of interfacial compatibilizers. The
rotational rheometry at low shear rates proved to be extremely efficient in the
analysis of blend compatibilization, which is usually analyzed by torque
rheometry. It was checked that, at high shear rates, the viscosity ratio
influenced the formation of more finely dispersed phases.Financiadora de Estudos e ProjetosO motivo que levou à realização deste trabalho de doutorado consistiu
na necessidade de um melhor entendimento das características
microrreológicas de blendas poliméricas constituídas de poli(tereftalato de
butileno), PBT, como fase matriz, e do copolímero estireno-acrilonitrila, SAN,
como fase dispersa. Os estudos microrreológicos realizados tiveram como
enfoque principal analisar o comportamento reológico e a morfologia, bem
como suas correlações na preparação da blenda imiscível PBT/SAN, com e
sem a utilização de um compatibilizante interfacial. Nas análises do
comportamento reológico, foram utilizadas reometria de torque, reometria
rotacional na geometria de placas paralelas e reometria capilar. As medidas de
tensões interfaciais foram realizadas através do método de retração de gotas
elipsoidais modificado, utilizando-se de um microscópio óptico com luz
polarizada acoplado a um estágio a quente. Nas análises morfológicas, foram
utilizadas duas técnicas complementares, através de microscopia eletrônica de
varredura (MEV) com extração da fase dispersa com tetrahidrofurano (THF) e
por microscopia eletrônica de transmissão (MET) com a deposição de tetróxido
de rutênio (RuO4) sobre a fase dispersa. Utilizando-se do método de retração
de gota modificado, verificou-se que a tensão interfacial entre o polímero PBT e
o copolímero SAN aumenta com o aumento da massa molar do PBT.
Utilizando-se da reometria de placas paralelas a baixas taxas de cisalhamento,
foi possível quantificar o aumento de viscosidade em função da reação das
macromoléculas poliméricas na blenda PBT/SAN, compatibilizada ou não com
o agente de compatibilização interfacial (o terpolímero metacrilato de metilametacrilato
de glicidila-acrilato de etila, MMA-GMA-EA). Por meio das
caracterizações morfológicas, foi possível analisar os mecanismos de formação
de fibrilas, cominuição e coalescência das partículas de fase dispersa e de
suas interações com a adição de agentes de compatibilização interfacial. A
técnica de reometria rotacional de placas paralelas em baixas taxas de
cisalhamento mostrou-se extremamente eficiente na análise de
compatibilização de blendas, que, na maioria das vezes, é feita através de reometria de torque. Verificou-se que, a altas taxas de cisalhamento, a razão
de viscosidade influencia a formação de fases mais finamente dispersas em
função da taxa de cisalhamento aplicada à blenda PBT/SAN
Interfacial tension of PBT/SAN blends by the drop retraction method
The aim of this work was to evaluate the interfacial tension from the poly(butylene terephtalate) and poly(styrene-co-acrylonitrile) (PBT/SAN) interface region using the drop retraction method. SAN filaments were sandwiched between two PBT films; the whole system was heated up to 240 °C, in a hot stage coupled to an optical microscope. The rheological parameters of the PBT/SAN system were obtained by parallel plates rheometry. An increase of the interfacial tension with the PBT molecular weight was observed with values between 0.57 and 1.06 mN/m, depending on the molecular weight. Theoretical values were calculated using the geometric-mean and harmonic-mean equations and were found to be similar to the experimental results. Viscosity measurements showed that the higher the SAN/PBT viscosity ratio, the lower the interfacial tension of these blends
Rheological, mechanical and morphological properties of poly(methyl methacrylate)/poly(ethylene terephthalate) blend with dual reactive interfacial compatibilization
Abstract In this work, the rheological, mechanical and morphological behavior of immiscible blend poly (methyl methacrylate) with elastomeric particles (PMMAelast) and post-consumer poly (ethylene terephthalate) (PET) with and without the use of the interfacial compatibilizer poly (methyl methacrylate-co-glycidyl methacrylate-co-ethyl acrylate) (MGE) was studied. The significant increase in torque presented in rheological analyses has shown a indication of chemical reactions between the epoxy group of MGE with end groups of PET chains and also with the elastomeric phase of PMMAelast. The increased concentration of PET yielded an increase in maximum strength and elasticity modulus and a decrease in elongation at break. The PMMAelast/PET binary blend (50/50 wt%) and PMMAelast/PET/MGE compatibilized blend (65/30/5 wt%) showed pronounced results in elongation at break compared to PMMAelast, whereas, in the first results were due to the evidence of a co-continuous morphological structure and in the second, due to the efficiency of the dual reactive interfacial compatibilization of PMMAelast/PET blends. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses showed that PMMAelast/PET/MGE blends exhibit complex phase morphology due to the presence of elastomeric particles in the PMMAelast copolymer and in the use of MGE terpolymer
A Microrheological Study of Poly(Methyl Methacrylate) Elastomer/Poly(Ethylene Terephthalate) (PMMAelast/PET) Blends
<div><p>This study involved an evaluation of the influence of phase inversion in poly(methyl methacrylate) elastomer/poly(ethylene terephthalate) binary blends (PMMAelast/PET) and the effect of the addition of poly(methyl methacrylate-glycidyl methacrylate-ethyl acrylate) (MGE) interfacial compatibilizer on the microrheological properties of this polymer blend. Thermal, dynamic mechanical thermal, rheological and morphological analyses were performed using sensitive techniques such as differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), parallel plates rheometry in the linear viscoelastic region, and atomic force microscopy (AFM), respectively. In this study, it was found that variations in the percentage of the PET phase influenced the correlation between the rheological properties at low shear rates and the morphology of the PMMAelast/PET binary blend and of the PMMAelast/PET/MGE compatibilized blend.</p></div
Structure and mechanical properties of polyamide 6/Brazilian clay nanocomposites
Recent interest in polymer/organoclays nanocomposites systems is motivated by the possibility of achieving enhanced properties and added functionality at lower clay loading as compared to conventional micron size fillers. By adding montmorillonite clay to polyamide 6 increases the Young modulus, yield strength and also improves barrier properties. In this work, nanocomposites of polyamide 6 with montmorillonite clay were obtained. The clay was chemically modified with three different quaternary ammonium salts such as: Dodigen, Genamin and Cetremide. In this case, a dispersion of Na-MMT was stirred and a salt equivalent to 1:1 of cation exchange capacity (CEC) of Na-MMT was added to the dispersion. The montmorillonite clay (untreated and treated by ammonium salts) and nanocomposites were characterized by X ray diffractions. Also the nanocomposites were characterized by transmission electron microscopy and mechanical properties. The results indicated that all the quaternary ammonium salts were intercalated between the layers of clay, leading to an expansion of the interlayer spacing. The obtained nanocomposites showed better mechanical properties when compared to polyamide 6. The clay acted as reinforcing filler, increasing the rigidity of nanocomposites and decreasing its ductility