Miscible blends of nitro‐substituted polybenzimidazole and polyetherimide

A novel blend system was prepared by blending organosoluble nitro‐substituted polybenzimidazole (NO₂‐PBI) and polyetherimide (PEI) in a cosolvent at a moderate condition. It was shown that the NO₂‐PBI/PEI blends not only possess tractable processability owing to the enhanced solubility of NO₂‐PBI but also retain the desirable features of unmodified PBI/PEI blends. Apparent miscibility in the blends was observed and attributed to hydrogen‐bonding interactions between N? H groups in NO₂‐PBI and carbonyl groups in PEI. It was revealed that the NO₂‐PBI/PEI blends phase‐separate upon heating above the glass‐transition temperatures. The observed mixing of NO₂‐PBI and PEI in a molecular level, although sustainable only in the glassy region, was shown to lend synergy effects to the physical properties of the blends. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1778–1783, 2001     

Thermal behaviour of bisitaconimide and reactive diluent blends

Thermal behaviour of blends based on N,N'-bis(4-itaconimidophenyl) ether (IE) and 4,4'-bis(4-allyl-2-methoxyphenoxy) benzophenone (R₁) or 4,4'-bis(2-allylphenoxy) benzophenone (R₂) are described in this paper. The reactive diluent content was varied from 5-50% (mass/mass) in these blends. A decrease in the melting point and exothermic peak temperature was observed with increasing mass percent of reactive diluent. Thermal stability of blends was affected at high mass percentage of reactive diluents. This revised version was published online in August 2006 with corrections to the Cover Date.     

Dilatometric studies of physical aging of polyetherimide

Physical aging of polyetherimide (PEI) was studied using a bellows dilatometer based on Zoller's design. A linear variable differential transformer (LVDT) is used to measure the displacement of the bellows. The voltage output of the LVDT is interfaced to a computer for automated data collection. Isothermal aging experiments were carried out at temperatures near the glass temperature (206–209 C) using a constant temperature oil bath maintained at the desired aging temperature. The time required to reach equilibrium and the reduced curve produced by aging time-temperature superposition are given. The results compare well with data obtained by capillary dilatometry for the same material.     

Thermal and rheological properties of miscible polyethersulfone/polyimide blends

Blends of an aromatic polyethersulfone (commercial name Victrex) and a polyimide (commercial name Matrimid 5218), the condensation product of 3,3′,4,4′-benzophenone tetracarboxylic dianhydride and 5(6)-amino-1-(4′-aminophenyl)-1,3,3′-trimethylindane, were studied by differential scanning calorimetry, dynamic mechanical analysis, and rheological techniques. The blends appeared to be miscible over the whole range of compositions when cast as films or precipitated from solution in a number of solvents. After annealing above the apparent phase boundary, located above T_g, the blends were irreversibly phase separated indicating that the observed phase boundary does not represent a true state of equilibrium. Only a narrow “processing window” was found for blends containing up to 20 wt % polyimide. Rheological measurements in this range of compositions indicated that blending polyethersulfone with polyimide increases the complex viscosity and the elastic modulus of the blends. For blends containing more than 10 wt % polyimide, abrupt changes in the rheological properties were observed at temperatures above the phase boundary. These changes may be consistent with the formation of a network structure (due to phase separation and/or crosslinking). Blends containing less than 10 wt % polyimide exhibited stable rheological properties after heating at 320°C for 20 min, indicating the existence of thermodynamic equilibrium.     

Synthesis of aliphatic diamine and polyetherimide with long perfluoroalkyl side chain

The monomer, 2-(perfluorohexylmethyl)butan-1,4-diamine (TFD), was prepared from itaconic acid dimethyl ester via the addition of perfluorohexyl iodide followed by the gradual transformation of ester groups into amino groups. The polymerization of bisphenol-A diphthalic anhydride (BAPA) with TFD led to hydrophobic fluorinated polyetherimide (FPEI) with R_F=C₆F₁₃ side chain. This polymer makes it possible to cast films.     

Phase separation during synthesis of polyetherimide/epoxy semi-IPNs

The phase separation behavior and the morphology of polyetherimide (PEI)-modified diglycidyl ether of bisphenol A (DGEBA) epoxy resin were studied using scanning electron microscopy and light scattering. Reaction kinetics, cloud point and onset of gelation were determined by differential scanning calorimeter, optical microscope and physica rheometer, respectively. The mixture of partially cured epoxy and PEI showed bimodal upper critical solution temperature (UCST) behavior. For PEI content smaller than 10 wt%, the blends exhibited a sea-island morphology formed via nucleation and a growth mechanism. Above 25 wt% PEI content, the phase separation proceeded via a spinodal decomposition mechanism and a nodular structure was formed. With PEI content between 15 and 20 wt%, dual phase morphology was observed. This morphology was formed via primary spinodal decomposition and secondary phase separation within the dispersed phases and the matrix phases formed by the primary phase separation. This morphology was presumed to be formed in the reaction-induced phase separation mechanism with the mixture showing bimodal UCST behavior. The curing temperature had an effect on the final morphology, and the modulus of PEI-modified epoxy was influenced by the phase separation.     

Thermal properties of polyamide 6/polyurethane blends

Equilibrium melting temperatures and crystallization parameters of polyamide 6/polyurethane blends were investigated. Thermal properties of the crystalline phase of blends obtained from polyamide 6 and polyurethane containing 40 wt% of hard segments, are only limited influenced by the overall blend compositon. Because from separate measurements single glass transitions for all samples were estimated, so in the investigated case the blending process may occur mainly between amorphous fraction of polyamide 6 and the polyurethane or, what is more probable, the polyurethane phase is dispersed in the continuous polyamide matrix, although some interactions exist.     

Thermal and rheological behavior of diesel and methanol biodiesel blends

The most feasible alternative among fuels derived from biomass seems to be the biodiesel, having the required characteristics for a total or partial substitution of diesel oil. Therefore, the aim of this work is to evaluate the thermal and rheological behavior of the blends of diesel with the methanol biodiesel obtained from soybean oil, using B5, B15 and B25 blends. All thermogravimetric curves exhibited one overlapping mass loss step in the 35–280°C temperature range at air atmosphere and one step between 37–265°C in nitrogen. The rheological study showed a Newtonian behavior (n=1) for all blends.     

Thermal and Rheological Behavior of Collagen. Chitosan blends

Collagen:chitosan blends in 1:1 ratio were prepared and characterized by Fourier transform infrared spectroscopy, thermal (DSC, TG) and rheological studies. Apparently each material maintains its behavior and addition of chitosan does not denature collagen fibers. The rheological behavior showed that adding chitosan to collagen causes a decrease of storage modulus (G’),viscous loss modulus (G”) and apparent viscosity when measured as a function of frequency. Both anionic and native collagen presented more solid-like behavior than fluid-like viscoelastic behavior. Collagen:chitosan blends exhibits a more fluid-like viscoelastic behavior. This revised version was published online in July 2006 with corrections to the Cover Date.     

Photooxidative behaviour of polyethylene/polyamide-6 blends

The photochemical behaviour of several polyethylene/polyamide-6 blends was studied under conditions of artificial accelerated weathering. Particular attention was paid to five different compositions ranging from pure polyethylene to pure polyamide with blends of PE/PA-6 of various compositions: 75/25, 50/50 and 25/75 wt/wt%. Analysis by infrared spectroscopy of the chemical modifications caused by photooxidation showed that exposing the polyethylene/polyamide-6 blends to UV-light irradiation led to the formation of oxidation photoproducts in both polymer phases. In agreement with both the mechanical and spectroscopic analyses, the photooxidation rate of the blends was observed to be much higher than that of the homopolymers. The results given in this paper suggest that photooxidation of the PE/PA blends starts in the polyamide phase and that the subsequent photooxidation of the polyethylene phase may be initiated by the radicals coming from the oxidation of PA.     

Recent developments in polyetherimide membrane for gas separation

Polyetherimide (PEI) is an extraordinary type of polyimide with excellent thermal and mechanical properties. The polymer is also gas permeable and is considered one of the best membranes for gas separation. Despite the high selectivity, PEI suffers from low permeability due to the trade‐off between phenomena in polymers. To overcome this limitation, fillers are added during the membrane preparation to create voids for better gas transport. In this paper, permeability and selectivity data of PEI membranes for the separation of oxygen, carbon dioxide, and helium are discussed. The paper also summarizes the reported studies for adding fillers to improve the membrane performance.     

Thermal characterization of polycarbonate/polycaprolactone blends

In this work, we prepared blends of bisphenol A polycarbonate (PC) and poly(ϵ‐caprolactone) (PCL) in a wide composition range by melt mixing and solution mixing. Two different molecular weights of PCL were used (nominally, 10.000 g/mol, PCL10, and 80.000 g/mol, PCL80). The thermal behavior of both systems was studied via differential scanning calorimetry under dynamic and isothermal conditions. The blends were miscible in the entire composition range in the liquid and amorphous states, as indicated by the single glass‐transition temperature (T_g) exhibited by both the PC/PCL10 and PC/PCL80 blends. The compositional variation of the T_g was accurately described by the Fox equation for the PC/PCL80 blends, whereas slight deviations from this equation were exhibited by the PC/PCL10 blends. For blend compositions containing 40% or more PCL, either one or both blend components crystallized. Crystallization occurred during cooling from the melt or during subsequent heating in the form of cold crystallization. Although PCL crystallization was reduced and its crystallization rate decreased with the addition of PC, PCL was a very effective macromolecular plasticizer for PC, to the extent that crystallization during the scan was detected for some blend compositions. Isothermal crystallization experiments allowed the determination of equilibrium melting points (T) by the Hoffman–Weeks extrapolation method. A T depression was found for both PCL and PC components as the content of the other blend component was increased. The Avrami equation was closely obeyed by both blend components during the isothermal overall crystallization kinetics up to crystalline conversion degrees of 60–70% and with values of Avrami indices ranging from 3 to 4, depending on the crystallization temperature employed. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 771–785, 2001     

Physical aging of a polyetherimide: Creep and DSC measurements

Creep and differential scanning calorimetry (DSC) measurements have been used to study the physical aging behavior of a polyetherimide. Isothermal aging temperatures ranged from 160°C to T_g with aging times ranging from 10 min to 8 days. The only measurable effect of physical aging on the short-time creep curves is a shift of the creep compliance to longer times. Andrade plots of the compliance versus the cube root of time are linear at short times with the slope β decreasing with increasing aging time to a constant value once equilibrium is reached. Log β³ is related directly to the degree to which the creep curves shift to longer times with physical aging, and is used in this work as a measure of physical aging. A reduced curve of log β³ versus log aging time is obtained for the aging temperatures investigated by appropriate vertical and horizontal shifts. The enthalpy change during aging increases linearly with the logarithm of the aging time, t_a, leveling off at equilibrium at values which increase with decreasing aging temperature. Hence, both nonequilibrium and equilibrium temperature shift factors can be calculated from the DSC data. Good agreement is observed between the equilibrium temperature shift factors obtained from the creep and DSC data. The temperature dependence of the nonequilibrium temperature shift factors is found to be an order of magnitude smaller than that of the equilibrium shift factors. The time scales to reach equilibrium for enthalpy and for mechanical measurements are found to be the same within experimental error. © 1995 John Wiley & Sons, Inc.     

Preparation of polyaniline grafted multiwalled carbon nanotubes and conductive application in polyetherimide

A methodology for improving antistatic property of polyetherimide (PEI) composite using polyaniline (PANI) grafted multi‐walled carbon nanotubes (MWNTs) as conductive medium was proposed. First, the MWNTs grafted with PANI (PANI‐g‐MWNTs) were prepared by in‐situ polymerization in an emulsion system. Subsequently, PANI‐g‐MWNTs were blended with PEI using N‐methyl‐2‐pyrrolidone as solvent. After removing the solvent, the PEI/PANI‐g‐MWNT composite was prepared. As assisted conductive medium, the grafted PANI molecular chains on MWNT surface were dispersed in the PEI matrix to decrease the percolation value of the antistatic composites. The structure and morphology of PANI‐g‐MWNTs were characterized by Fourier transform infrared spectroscopy, transmission electron microscope, thermogravimetric analysis, and X‐ray powder diffraction, respectively. The dispersion of PANI‐g‐MWNTs in PEI matrix was studied by scanning electron microscope. The electrical performance was characterized by highly resistant meter. The volume resistivity of the conductivity percolation threshold was 1.781 × 10^?8 S/cm when the loading of PANI‐g‐MWNTs was 1.0 wt%. The conductivity of PANI‐g‐MWNTs/PEI composites was found to be higher than that of pristine MWNTs/PEI composite. Copyright © 2012 John Wiley & Sons, Ltd.     

The addition of functionalized graphene oxide to polyetherimide to improve its thermal conductivity and mechanical properties

The thermal and electrical conductivity and mechanical properties of polyetherimide (PEI) containing either alkyl‐aminated (enGO) or phenyl‐aminated graphene (pnGO) oxides were studied. A solution casting method was used to prepare functionalized graphene oxide/PEI composites with different filler contents. The introduction of functionalized graphene oxide to the PEI matrix improved the thermal conductivity, electrical conductivity, and mechanical properties. The thermal conductivities of the enGO 3 wt%/PEI and pnGO 3 wt%/PEI composites were 0.324 W/mK and 0.329 W/mK, respectively, due to the high thermal conductivity of the graphene‐based materials and the strong interface adhesion due to the filler surface treatment between the fillers and the matrix. The electrical conductivities of the functionalized graphene oxide/PEI composites were larger than that of PEI, but the electrical conductivity values were generally low, which is consistent with the magnitude of the insulator. The strong interfacial adhesion between the fillers and the matrix led to improved mechanical properties. Copyright © 2014 John Wiley & Sons, Ltd.     

Polymerized ionic liquid functionalized multi-walled carbon nanotubes/polyetherimide composites

Thin polyetherimide (PEI) films containing 0.1–3 wt.% multi-walled carbon nanotubes (MWCNTs), have been prepared from three types of MWCNTs, namely pristine, oxidized and polymerized ionic liquid (PIL) functionalized CNTs. Oxidized and PIL functionalized CNTs (CNT–PIL) showed better dispersion in the matrix compared to pristine CNTs. For CNT–PIL, alignment of CNTs has been observed in the matrix. Regardless of the type of CNTs, their incorporation led to an increased thermal stability of the polymer matrix. Dynamic mechanical analysis showed that storage modulus increased by up to 25% (3 wt.% CNT–PIL) and an increase in the height of the damping peaks (tan δ). The addition of CNTs did not have any significant influence on the tensile properties and T_g of the polymer, and the electrical conductivity did not decrease in the case of modified CNTs.     

Cellulose acetate and polyetherimide blend ultrafiltration membranes: II. Effect of additive

Ultrafiltration membranes are largely applied in the separation of heavy metal ion and macromolecular solutes from aqueous streams. Studies are presented on ultrafiltration blend membranes, based on cellulose acetate (CA) and polyetherimide (PEI) in various blend compositions. Polyethylene glycol (PEG 600) was employed as a non‐solvent additive in various concentrations to the casting solution to improve the ultrafiltration performance of the resulting membranes. The blend membranes prepared were characterized in terms of compaction time, pure water flux (PWF), water content, membrane resistance, and scanning electron microscopy (SEM). The molecular weight cut‐off (MWCO) obtained from the protein separation studies is also reported. Applications of these membranes for separating toxic metal ions from aqueous streams are discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

Thermal properties of poly(vinyl chloride)/polyurethane blends

Blends of poly(vinyl chloride) and a polyurethane elastomer were investigated by DSC and tensile testing. Up to 30 wt% single glass transition was found. It was concluded that the polyurethane forms partly a true blend and is partly disperged in the continuous blend phase.     

Radar transparent glass fabric reinforced polyetherimide/Cloisite 30B nanocomposites

High performance radar transparent materials (RTMs) are important materials for the fabrication of radomes, nosecones, etc. of high velocity aerospace vehicles. RTMs with good mechanical performance and temperature capability are required for such applications. Toward this, fabric reinforced nano‐reinforced matrix composites (FRNCs), using reinforcing E‐glass fabric in Cloisite 30B reinforced polyetherimide (PEI) nanocomposite matrix (GNRPEI), was prepared. The properties of GNRPEI were evaluated and compared with E‐glass fabric reinforced PEI composites (GRPEI) with special reference to their radar transparent character for aerospace applications. Tensile and flexural properties along with interlaminar shear strength of GRPEI were observed to be lower than those of GNRPEI. Thermal behavior of both the composites was similar in differential scanning calorimetry and thermal gravimetric analysis. But, in dynamic mechanical analysis, an increase in storage modulus and decrease in loss tangent were observed in GNRPEI compared to GRPEI. The values of dielectric constant and loss tangent of GNRPEI were lesser than those of GRPEI, but no significant difference was observed in the values of transmission and reflection losses for both the composites at 8–12 GHz frequency. FRNCs, based on organoclay reinforced PEI matrix, hold good promise as high performance RTMs. Copyright © 2010 John Wiley & Sons, Ltd.