Thermostable Polymers Research Articles

Study of the thermal properties of miscible blends between poly(ether ketone ketone) (PEKK) and polyimide

This study deals with the enhancement of the thermal behavior of thermostable thermoplastic polymers dedicated to high performance composites. Semi-crystalline poly(ether ketone ketone) and amorphous poly(imide) have been blended at different ratios by using a high temperature co-rotative twin screw extruder and injected using an injection-molding machine with a “cold” mold. Injected samples have been characterized by different techniques and we especially discuss how crystallinity affects the composition of the amorphous phase and consequently the variation of the glass transition temperature value according to the composition that we propose to model by a modified Gordon–Taylor law.

Difference in Physicochemical Property of β-Glucan from Barley Flour and Bran

Two kinds of β-glucan were extracted from barley flour and bran, with the purity of 75.3% and 76.2% respectively. Molecular size characterization was caarried out with high performance size exclusion chromatograhy combined with a multi-angle laser light scattering and a refractive index detector (HPSEC-MALL) , the molecular weight (Mw) of β-glucan from barley flour and bran was 2.262×104,7.128×104. X-ray diffraction and thermodynamics tests indicated that all β-glucans were noncrystalline but thermostable polymers. Differential scanning of calorimetry (DSC) showed the presence of peak related with water loss, confirmed by thermogravimetric analysis (TGA), the β-glucan from barley bran had higher onset temperature (T0=49.89°C) and peak temperature (TP=197°C). In scanning electron microscope (SEM) observations, the β-glucan from barley bran showed more tight surface,which could be caused by higher molecular weight.

Advanced materials based on new structurally designed poly(naphthylimide-amide)s

This work reports the synthesis and characterization of novel six-membered poly(imide-amide)s based on a naphthalene-N,N′-bis(imido-amine) and various dicarboxylic acids containing flexible units such as ether, hexafluoroisopropylidene and diphenylsilane. A new design is proposed for aromatic poly(imide-amide)s, in which the imide and amide units are directly connected through a NN bond. These highly thermostable polymers were successfully synthesized using Yamazaki–Higashi reaction conditions. The poly(imide-amide)s were processed into thin hydrophobic films having self-assembled micellar structures. The presence of aggregates in solutions with concentrations below 1% was evidenced and is discussed in relation to the chemical structure. The photoluminescence properties of polymer solutions and films showed their ability to produce white and blue light emission. The lowest unoccupied molecular orbital energy level was calculated using cyclic voltammetry data, showing good electron injection and transport characteristics. The properties of these polymers make them attractive for applications in advanced optoelectronics and related fields. © 2014 Society of Chemical Industry

Thermo-sensitive luminescent materials composed of Tb(III) and Eu(III) complexes

Thermo-stable lanthanide coordination polymers [Tb,Eu(hfa)3(dpbp)]n composed of Tb(III) ion, Eu(III) ion, bidentate phosphine oxide (dpbp: 4,4’-bis(diphenylphosphoryl)biphenyl), and low-vibrational frequency hexafluoroacetylacetonate (hfa) ligand are reported. The lanthanide coordination polymers [Tb,Eu(hfa)3(dpbp)]n (Tb/Eu=1, 10, 250, 500, and 750) are characterized by XRD, emission spectra and emission lifetime measurements. The energy transfer efficiencies among lanthanide ions are estimated using the emission lifetimes of solid-state coordination polymers. Characteristic emission properties of lanthanide coordination polymers composed of Tb(III) ions and a small amount of Eu(III) ions (Tb/Eu=750) have been observed for the first time. The energy transfer between lanthanide ions in coordination polymers is described in terms of solid-state materials.

Integrated piezoelectric function in a high thermostable thermoplastic PZT/PEEK composite

A piezoelectric structural material has been developed. Lead Zirconate Titanate (PZT) submicronic nanoparticles have been dispersed in a thermostable high performance thermoplastic polymer Poly(Ether Ether Ketone) i.e. PEEK to ensure piezoelectric properties. The inorganic particles with a mean diameter of 900nm are polycrystalline as highlighted by HRTEM with a grain diameter estimated at 15nm. XRD patterns have shown that the crystalline structure is rhombohedral i.e. ferroelectric. The PZT/PEEK composites have been elaborated by extrusion which allows reaching a satisfactory dispersion of particles even at high volume fraction (30% in volume). One of the challenges was to find poling conditions compatible with the thermal stability of the matrix. Indeed, this composite must be poled above the polymer glass transition temperature to improve matching of dielectric permittivity between inorganic and organic phases. The influence of the poling electric field on the final piezoelectric activity of the composite has also been studied to better understand the role of the polymer matrix. Finally, after a poling step, the PZT/PEEK composite exhibits a piezoelectric strain coefficient which can be exploited over a wide temperature range.

Electrical application of polystyrene (PS) reinforced with old tire rubber (GTR): dielectric, thermal, and mechanical properties

AbstractMass production of tires and their subsequent storage after use are serious environmental problems that are being tried to be solved in various ways. One of these is the mixture of these old used tires [ground rubber tire (GTR)] with various thermoplastic and thermostable polymers. The present work aimed to obtain materials suitable for the electric industry from the mixture of polystyrene (PS) with old used tires (GTR), starting from the requirement of minimum recycling costs, i.e., by using vulcanized GTR without any prior treatment but acting on the particle sizes with a simple and inexpensive screening. In order to do so, dielectric, mechanical, thermal, and microstructure analyses were performed for a large number of compounds, which were obtained using three GTR particle sizes (p<200 μm, 200 μm<p<500 μm, and p>500 μm) and seven concentrations of GTR in the compound (0%, 5%, 10%, 20%, 40%, 50%, and 70%). All these data have allowed an accurate characterization of the properties of the new compounds, and according to these results, possible electrical applications have been explored.

Optical and electrochemical properties of thermostable polymers containing light-emitting units

Two series of polymers and copolymers containing oxadiazole units have been studied with respect to their photo-optical and electrochemical behavior. Fluorene units were introduced in the macromolecular chain together with oxadiazole rings in order to obtain a better balance between electrons and holes injection and transporting properties. Upon irradiation with UV light the polymers showed photoluminescence maxima in the blue spectral range. Cyclic voltammetry was performed in order to obtain information about the electrochemical stability and reversibility of the redox processes of these polyoxadiazoles. The highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels, and electrochemical and optical band gap values were calculated by using the results of cyclic voltammetry and UV/vis spectroscopy, respectively, showing very good electron injection and transport characteristics. POLYM. ENG. SCI., 54:1126–1133, 2014. © 2013 Society of Plastics Engineers

P-Hydroxycinnamic acid production directly from cellulose using endoglucanase- and tyrosine ammonia lyase-expressing Streptomyces lividans

Backgroundp-Hydroxycinnamic acid (pHCA) is an aromatic compound that serves as a starting material for the production of many commercially valuable chemicals, such as fragrances and pharmaceuticals, and is also used in the synthesis of thermostable polymers. However, chemical synthesis of pHCA is both costly and harmful to the environment. Although pHCA production using microbes has been widely studied, there remains a need for more cost-effective methods, such as the use of biomass as a carbon source. In this study, we produced pHCA using tyrosine ammonia lyase-expressing Streptomyces lividans. In order to improve pHCA productivity from cellulose, we constructed a tyrosine ammonia lyase- and endoglucanase (EG)-expressing S. lividans transformant and used it to produce pHCA from cellulose.ResultsA Streptomyces lividans transformant was constructed to express tyrosine ammonia lyase derived from Rhodobacter sphaeroides (RsTAL). The transformant produced 786 or 736 mg/L of pHCA after 7 days of cultivation in medium containing 1% glucose or cellobiose as the carbon source, respectively. To enhance pHCA production from phosphoric acid swollen cellulose (PASC), we introduced the gene encoding EG into RsTAL-expressing S. lividans. After 7 days of cultivation, this transformant produced 753, 743, or 500 mg/L of pHCA from 1% glucose, cellobiose, or PASC, respectively.ConclusionsRsTAL-expressing S. lividans can produce pHCA from glucose and cellobiose. Similarly, RsTAL- and EG-expressing S. lividans can produce pHCA from glucose and cellobiose with excess EG activity remaining in the supernatant. This transformant demonstrated improved pHCA production from cellulose. Further enhancements in the cellulose degradation capability of the transformant will be necessary in order to achieve further improvements in pHCA production from cellulose.

Electrical application of polyamide reinforced with old tire rubber (ground tire rubber)

Mass production of tires and their subsequent storage after use is a serious environmental problem that is tried to be solved in various ways. One of these ways is the mixture of these old used tires (ground tire rubber (GTR)) with various thermoplastic and thermostable polymers. These blends are made by modifying the pretreatment the GTR is subjected to, the degree of devulcanization, the mixing or pressing conditions, etc. Later the mixtures are analyzed structurally and mechanically, looking for possible industrial applications for them. The present work aims to obtain materials suitable for the electric industry from the mixture of polyamide with old used tires (GTR), starting from the requirement of minimum recycling costs, that is using vulcanized GTR without any prior treatment but acting on the particle sizes with a simple and inexpensive screening. A novelty of this study is the large number of compounds analyzed, and the deep analysis these have been submitted to dielectric, mechanical, thermal and microstructure analyses to get a large number of variables in each test. Compounds were categorized as the three GTR particle sizes ( p < 200 μm, 200 < p < 500 μm and p > 500 μm) and seven concentrations of GTR (0%, 5%, 10%, 20%, 40%, 50% and 70%), resulting in a total of 21 new compounds. In addition, in order to have the dielectric tests as much exhaustive as possible and to show the behavior of the compound under widely changing conditions, a wide range of temperatures (30–120°C) and frequencies (1 × 10−2 Hz to 3 × 106 Hz) were taken into consideration. All these data have provided an accurate characterization of the properties of the new compounds, and according to these results, possible electrical applications have been explored, with the requirement that they must comply with official regulations.

Study on Dielectric, Mechanical and Thermal Properties of Polypropylene (PP) Composites with Ground Tyre Rubber (GTR)

Mass production of tyres and their subsequent storage after use is a serious environmental problem whose solution has been attempted in various ways. One of these is the mixture of old, used tyres (GTR) with various thermoplastic and thermostable polymers. These blends are made by modifying the pre-treatment to which the GTR is subjected, the degree of devulcanization, the mixing or pressing conditions, etc. Later, the mixtures are analyzed structurally and mechanically, looking for possible industrial applications. The present work aims to obtain materials suitable for the electrical industry from the mixture of polypropylene (PP) with old used tyres (GTR), starting from the requirement of minimum recycling costs, i.e. by using vulcanized GTR without any prior treatment, but acting on the particle sizes with a simple and inexpensive screening. A large number of composites have been analyzed, and these have been submitted to dielectric, mechanical, thermal and microstructural examination. Composites were obtained using the three GTR particle sizes (p<200 μm, 200<p<500 μm and p>500 μm), and the seven concentrations of GTR in the composite (0%, 5%, 10%, 20%, 40%, 50% and 70%), meaning a total of 21 new composites. In addition, in order to have the dielectric tests as exhaustive as possible and show the behaviour of the composite under widely changing conditions, a wide range of temperatures (30 °C to 120 °C) and frequencies (1·10-2 Hz and 3·106 Hz) were used. All these data have allowed an accurate characterization of the properties of the new composites, and according to these results, possible electrical applications have been explored, with the requirement that they must comply with Official Regulations.

Characterizations and microsphere formulation of polysaccharide from the marine clam (Mactra veneriformis)

Powder like samples named MVPS, containing 95.8% of polysaccharide, were extracted from a well-known marine bivalve Mactra veneriformis. Some in vitro tests were carried out to characterize its physicochemical properties. X-ray diffraction and thermodynamics tests indicated that MVPS were noncrystalline but thermostable polymers. Solubility and rheology tests showed that MVPS could easily dissolve in aqueous media and its solution obviously belonged to non-Newtonian fluids even at relatively high concentration. Furthermore, via blending MVPS solution with other polymers and then spray drying the blends, several composite microparticles were prepared. The chitosan/MVPS particles are available not only with spherical morphology but also with higher production yield. As a model drug, metformin can be encapsulated into the composite microsphere and then achieve the sustained release. The chitosan/MVPS composite microspheres loaded with drug might be an appropriate for nasal formulation since its particle sizes are in the range of 1–10μm.

Poly(naphthoylenebenzimidazole)s with trifluoromethyl and phenyl substituents

129 Poly(naphthoylenebenzimidazole)s (PNBIs) is one of the most important classes of thermostable polymers with a combination of unique properties: thermal stability; heat, fire, and chemical resistance; high hydrolytic and radiation stability; etc. [1–3]. However, the application of these polymers is limited by their insolubility in organic solvents and, hence, poor processability. Therefore, attempts have been made in recent years to introduce flexible fragments or bulky substituents into polymeric chains to impart sol ubility to PNBIs [4, 5].

Sulfonic and Phosphonic Acid and Bifunctional Organic-Inorganic Hybrid Membranes and Their Proton Conduction Properties

Hybrid organic-inorganic approaches are used for the synthesis of bifunctional proton exchange membrane fuel cell (PEMFC) membranes owing to their ability to combine the properties of a functionalized inorganic network and an organic thermostable polymer. We report the synthesis of both sulfonic and phosphonic acid functionalized mesostructured silica networks into a poly(vinylidenefluoride-co-hexafluoropropylene) (poly(VDF-co-HFP) copolymer. These membranes, containing different amounts of phosphonic acid and sulfonic acid groups, have been characterized using FTIR and NMR spectroscopy, SA-XRD, SAXS, and electrochemical techniques. The proton conductivity of the bifunctional hybrid membranes depends strongly on hydration, increasing by two orders of magnitude over the relative humidity (RH) range of 20 to 100%, up to a maximum of 0.031 S cm(-1) at 60 °C and 100% RH. This value is interesting as only half of the membrane conducts protons. This approach allows the synthesis of a porous SiO(2) network with two different functions, having -SO(3)H and -PO(3)H(2) embedded in a thermostable polymer matrix.

Thermostable waterproof polymer materials based on latent self-curing oligomer 4,4′-bis(glycidylamino)-3,3′-dichlorodiphenylmethane

Latent epoxide oligomers of N-glycidyl-ortho-chloroaniline and 4,4′-diamino-3,3′-dichlorodiphenylmethane were synthesized that are capable of self-curing and forming films at elevated temperatures and their reactivity was studied. Thermostable polymer composition materials that are waterproof and characterized by high stability were designed and tested.

Single‐step technique allowing formation of microscaled thermally stable polymer honeycomb reliefs demonstrating reversible wettability

AbstractThe procedure allowing single‐step formation of microscaled thermostable polymer honeycomb patterns is reported. Polymer substrates soluble in chlorinated solvents were pulled from the solvents before their final dissolution and placed into a humid atmosphere. Honeycomb patterns were deposited by this method on polyetherimide, polysulfone (PSF), and polyethersulfone (PESF) substrates. PSF and PESF substrates demonstrated reversibly switchable wetting under UV irradiation/heating cycles strengthened by the Cassie–Baxter wetting regime. Copyright © 2010 John Wiley & Sons, Ltd.

Effect of an epoxy octasilsesquioxane on the thermodegradation of an epoxy/amine system

AbstractPolyhedral oligomeric silsesquioxanes (POSS®) can be added to thermoplastic and thermostable polymers to obtain hybrid materials with only a minor tendency to suffer ignition. The aim of the work reported was to analyse the influence of an octafunctional POSS® in the pyrolysis of an epoxy/amine system as well as during the combustion process. Thermal degradation of the modified materials, with respect to the unmodified ones, was analysed using thermogravimetric analysis. As the content of POSS® increased the stability improved and the char/ceramic yields were higher. The Kissinger–Akahira–Sunose method was applied to the modified blends and it showed a decrease in the activation energy with POSS® content. Empirical kinetic models, as well as generalized master plots, were applied to explain the degradation mechanism for ternary blends. The limiting oxygen index parameter was measured to analyse the fire retardancy effect of POSS®: it increased from 24.3 to 25.4% with the addition of 2.5 wt% of POSS®. The mechanism of thermal degradation of the hybrid materials based on an epoxy resin is affected by the presence of the octaepoxy POSS®. Only small amounts of POSS® are necessary to enhance the combustion resistance of the system. Copyright © 2009 Society of Chemical Industry

Reprint of “Polymer electrolyte fuel cell stack research and development”

The research activity in polymer electrolyte fuel cell (PEFC) is oriented to the evolution of components and devices for the temperature range from 20 to 130°C, and covers all the aspects of this matter: membranes and electrodes, fuel cell stack engineering (design and manufacturing) and characterization, computational modelling and small demonstration systems prototyping. Particular attention is devoted to portable and automotive application. Membranes research is focused on thermostable polymers (polyetheretherketone, polysulphone, etc.) and composite membranes able to operate at higher temperature (> 100 °C) and lower humidification than the commercial Nafion ® , while Pt load reduction and gas diffusion layer improvement are the main goals for the electrode development. PEFC stack engineering and characterization activity involve different aspects such as the investigation of new materials for stack components, fuel cell modelling and performance optimization by computational techniques, single cell and stack electrochemical characterization, development of investigation tools for stack monitoring and data acquisition. A lot of work has been focused to the fuel cell stack architecture, assembling, gas leakage and cross-over reduction (gasketing), flow field and manifold design. Computational fluid dynamics studies have been performed to investigate and improve reactants distribution inside the cell. A flow field design methodology, developed in this framework and related to serpentine like flow field, is actually under investigation. All of these aspects of PEFC stack research are realized in the framework of National and European research projects, or in collaboration with industries and other research centres. In the present work our stack research activity is reported and the most important results are also considered.

Heterocyclic polyimides containing siloxane groups in the main chain

AbstractBACKGROUND: Among the polymers widely studied for applications in advanced techniques, aromatic polyimides have received considerable attention due to their outstanding thermal stability associated with good electrical and mechanical properties. However, these polymers are usually difficult to process, being insoluble and without a glass transition. To improve the processing characteristics of polyimides, modification of their structure is often achieved by the introduction of flexible linkages in the macromolecular chain or various substituents on the aromatic rings.RESULTS: A series of polyimides and intermediate polyamidic acids were synthesized from aromatic oxadiazole‐diamines and a dianhydride containing a siloxane bridge (R2SiOSiR2). These polymers exhibit good solubility in certain organic solvents and can be cast into thin and very thin films from their solutions. They exhibit high thermal stability with decomposition being above 440 °C and relatively low glass transition temperatures in the range 160–190 °C. These polymers show strong photoluminescence in the blue spectral region.CONCLUSION: The introduction of oxadiazole rings together with siloxane groups into the chains of aromatic polyimides gives highly thermostable polymers with remarkable solubility and film‐forming ability and that emit blue light, being attractive for applications in micro‐ and nanoelectronics and other related advanced fields. Copyright © 2009 Society of Chemical Industry

Three-component granular mixtures on the basis of hexogen, aluminium and polystirene as a binder

The characteristics of three-component RDX/PS/Al mixtures have been described s well as the method for their preparation. Polystirene as a binder is a thermostable polymer with satisfactory characteristics for bonding explosives. The constant content of 5% m/m PS was applied for different contents of hexogen and aluminium. The content of Al in the mixtures was 10, 15, and 20% m/m. The composition of the bonded explosives was examined as well as the detonation velocity of these mixtures. .

Synthesis and properties of polythiophene derivatives containing triphenylamine moiety and their photovoltaic applications

AbstractA series of novel soluble polythiophene derivatives containing triphenylamine moiety were synthesized by Grignard metathesis (GRIM) method. The structures of the polymers were characterized and their physical properties were investigated. High molecular weight (Mn up to 25,800 g/mol) and thermostable polymers were obtained. The absorption spectra demonstrated that the absorption wavelength of the polymers could be tuned dramatically by introducing thiophene units in the main chain of the polymers. Photoluminescence spectra indicated that there was intramolecular energy transfer from the side chain to the main chain, and the maximum emission was red‐shifted gradually with the increase of thiophene units in the main chain. Cyclic voltammetry displayed that the polymers possessed relatively high oxidation potential, which promised good air stability and high open circuit voltage for photovoltaic cells application. Finally, bulk heterojunction photovoltaic devices were fabricated by using the polymers as donors and (6,6)‐phenyl C61‐butyric acid methyl ester (PCBM) as acceptor. The maximal open circuit voltage of the photovoltaic cells reached 0.71–0.87 V and the power conversion efficiencies of the devices were measured between 0.014% and 0.45% under white light at 100 mW/cm2. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3970–3984, 2008