Thermal Stability Of Polymers Research Articles

Synthesis, Characterization and Thermal Stability of Polymers Containing 2,2-Bisferrocenylpropane Group

Synthesis, Characterization and Thermal Stability of Polymers Containing 2,2-Bisferrocenylpropane Group

A solvent additive to enhance the efficiency and the thermal stability of polymer:fullerene solar cells

A novel bisazide molecule to be used in polymer–fullerene bulk heterojunction (BHJ) solar cells with two distinct functionalities is reported here.

Using thermogravimetric analysis to determine polymer thermal stability: Relevance of changes in onset temperature of mass loss

the field of polymer composites and nanocomposites, where composite samples were characterised, thermogravimetric analysis (TGA) data are almost always presented as part of a whole range of analysis methods. Most of the time the shifting of the TGA mass loss steps to higher temperatures is interpreted as being indicative of delays in the thermal degradation process and hence improvements in the thermal stability of the polymer(s) brought about by the presence of the filler (nano)particles. The question one should ask oneself: Is it possible to measure the onset of degradation of a polymer or composite by using TGA, or does one only measure the onset of mass loss? Of course one only measures the onset of mass loss, which means that anything that may delay the transport of volatile degradation products out of the composite will cause a delay in the evaporation of these products, and the onset of mass loss will only be seen after a longer time or at a higher temperature, depending on whether the analysis was performed as function of time or temperature. This means that the (nano) filler probably had no effect on the thermal stability of the polymer matrix, but that it either contributed to the formation of a carbonaceous char layer or strongly interacted with the volatile degradation products, both of which would retard the diffusion of these degradation products out of the polymer. This would give rise to the mass loss step starting at higher temperatures (after longer periods of time) giving the impression of an apparent increase in thermal stability. On the other hand, one cannot neglect the possibility that the (nano)filler can retard the actual degradation process though strong interaction with the polymer chains and/or free radical chains, which can restrict the chain mobility and slow down the degradation propagation reactions. Whatever the reason for the delayed onset of mass loss, one has to delve deeper to find the real reason and not just assume that it is the result of the (nano)filler improving the thermal stability of the polymer. It is also important to realise that, although the onset of degradation is not necessarily delayed in the presence of (nano)filler particles, any delay in the volatilization of the degradation products (which is measurable with TGA) is an important factor to keep in mind regarding the flammability of the polymer.

Atomic Force Microscope Manifestation of Heat-Resistant Polymer Thermal Stability

Aimed at BH heat-resistant polymer, 4500mg/L solution is compounded by oilfield sewage, and then diluted into 1500mg/L solution by oilfield sewage again under room temperature, aging in the constant temperature box of 95°C finally. Test slides are made of different aging time BH heat-resistance polymer solution, whose thermal stability is manifested by atomic force microscope. Results show the aggregation degree of BH heat-resistant polymer solution are different after aging for 30d, 60d, 90d under 95°C. They gather largely before aging, are into a loose branch distribution. After aging for 30d, their aggregation degree declines, branch length becomes shorter. After aging for 60d, their aggregation status change greatly, are into "╫╫" shape comb distribution. After aging for 90d, they gather into about 10μm in diameter short fat wafer, and are not easy to expand.

Structure and properties of ultra‐high molecular weight bisphenol a polycarbonate synthesized by solid‐state polymerization in amorphous microlayers

ABSTRACTThe structure and properties of ultrahigh molecular weight polycarbonate synthesized by solid‐state polymerization in micro‐layers (SSPm) are reported. A low molecular weight prepolymer derived from the melt transesterification of bisphenol A and diphenyl carbonate as a starting material was polymerized to highly amorphous and transparent polycarbonate of molecular weight larger than 300,000 g mol−1 in the micro‐layers of thickness from 50 nm to 20 µm. It was observed that when the polymerization time in micro‐layers was extended beyond conventional reaction time, insoluble polymer fraction increased up to 95%. Through the analysis of both soluble and insoluble polymer fractions of the high molecular weight polycarbonate by 1H NMR spectroscopy and pyrolysis‐gas chromatography mass spectrometry (Py‐GC/MS), branches and partially crosslinked structures have been identified. The thermal, mechanical and rheological properties of the ultra‐high molecular weight nonlinear polycarbonates synthesized in this study have been measured by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and rheometry. The nonlinear chain structures of the polymer have been found to affect the polymer's thermal stability, mechanical strength, shear thinning effect, and elastic properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41609.

Heterofunctional Condensation of α,ω - Bis (Aminodimethylsilil) Tetramethyl - Cyclodisilazanes With Dichloranhydride Tereftalic Acids and α,ω - Bis (β - Carboxyethyl) Dimethylsiloxanes

With a view to synthesizing heat-resistant polymers, we performed the heterofunctional condensation (HFC) of α,ω-bis (aminodimethylsilil) tetramethyl- cyclodisilazanes with terephthaloyl chloride. The synthesized polymers are elastic products in light color. Their elasticity increases with an increase in cyclodisilazane fragments in the polymer chain. At temperatures of 360 to 380 0 C, there starts slow polymer degradation, while fast degradation occurs at a temperature of 400 to 450 0 C. We also performed the HFC of α,ω-bis (aminodimethylsilil) tetramethyl- cyclodisilazanes with α,ω-bis ( -carboxyethyl) dimethylhexanes. The synthesized products are caoutchouc-like products, as they contain pliant siloxane and cyclodisiloxane fragments. They have quite high thermal stability. The stability is impacted on by an increase in the dimethylsiloxane block in the copolymer chain. Polymers are resistant at temperatures of 510 to 550 0 C. At these temperatures, there starts their slow degradation. The thermal stability of polymers is not impacted on by an increase in the share of silazane cycles in the chain.

Study of the stability of siloxane stone strengthening agents

The commercial organosilicone compounds Rhodorsil Consolidante RC90 and Rhodorsil Consolidante RC80, commonly used as stone strengthening agents for the conservation of artefacts, were tested to ascertain their chemical nature, the mechanisms involved in the polymerization reactions and their stability under oxidative stress. The resins were first chemically characterized by means of GC/MS, FTIR and EDXRF techniques, then applied to slides and subjected to controlled photo-oxidative and thermo-oxidative weathering. The film's morphology was observed by SEM determinations, while DTA-TG techniques were used to determine polymer thermal stability. The features examined prompted a number of considerations on the effects of the resins applied on stone materials and were the reference point for speculation on the chemical nature and the performance of Sogesil XR893, a silicon resin which is no longer available on the market.

Synthesis and fluorescence properties of N-substituted 1-cyanobenz[f]isoindole chitosan polymers and nanoparticles for live cell imaging.

Highly fluorescent N-substituted 1-cyanobenz[f]isoindole chitosans (CBI-CSs) with various degrees of N-substitution (DS) were synthesized by reacting chitosan (CS) with naphthalene-2,3-dicarboxaldehyde (NDA) in the presence of cyanide under mild acidic conditions. Introduction of 1-cyanobenz[f]isoindole moieties into the CS backbone resulted in lowering of polymer thermal stability and crystallinity. The fluorescence quantum yield (Φf) of CBI-CS was found to be DS- and molecular-weight-dependent, with Φf decreasing as DS and molecular weight were increased. At similar DS values, CBI-CS exhibited 26 times higher Φf in comparison with fluorescein isothiocyanate-substituted chitosan (FITC-CS). CBI-CS/TPP nanoparticles were fabricated using an ionotropic gelation method in which pentasodium triphosphate (TPP) acted as a cross-linking agent. CS and CBI-CS exhibited low cytotoxicity to normal skin fibroblast cells over a concentration range of 0.1-1000 μg/mL, while an increased cytotoxicity level was evident in CBI-CS/TPP nanoparticles at concentrations greater than 100 μg/mL. In contrast with CBI-CS polymers, the CBI-CS/TPP nanoparticles exhibited lower fluorescence; however, confocal microscopy results showed that living normal skin fibroblast cells became fluorescent on nanoparticle uptake. These results suggest that CBI-CS and fabricated nanoparticles thereof may be promising fluorescence probes for live cell imaging.

Poly(acrylate) with a tetraphenylethene pendant with aggregation-induced emission (AIE) characteristics: highly stable AIE-active polymer nanoparticles for effective detection of nitro compounds

Acrylate monomers with aggregation-induced emission (AIE) attributes were prepared by reacting 4-(1,2,2-triphenylvinyl)phenol with 1-bromoalkan-1-ol, followed by the treatment with acryloyl chloride in the presence of a base. The resulting acrylate monomers were polymerized by free radical polymerization to give very high molecular-weight AIE-active polymers (400 000–650 000) with low polydispersity indices (1.28–1.51). Thermal stabilities of the AIE polymers are comparable to that of poly(methyl methacrylate) (PMMA), while their glass transition temperatures are 50–70 °C lower than that of PMMA. The AIE polymers are soluble in common organic solvents and have outstanding film-forming ability. Most importantly, the polymers in the mixtures of THF–H2O can form extremely stable nanoparticles, with no tendency towards agglomeration at 4 °C for over nine months. The polymers exhibit much more significant AIE activity than their monomers and their precursor 4-(1,2,2-triphenylvinyl)phenol in THF–H2O mixtures. Fluorescence of the polymers in THF–H2O mixtures and in the film state can be dramatically quenched by a wide variety of nitro compounds, including picric acid, 2,4,6-trinitrotoluene, 2,4-dinitrotoluene, 4-nitrophenol, 4-nitrotoluene, nitromethane and nitrous sulfuric anhydride. The AIE polymers show no response to the reference compounds toluene and phenol. These AIE polymers are thus potential fluorescence sensors for nitroaromatic explosives.

Preparation and Thermal Stability Properties of Epoxy Matrix/Nano-SiO<sub>2</sub> Composites

The addition of nanoparticles has been proven to a high potential application for improving polymer thermal stability properties. In this paper, the nanocomposites based on epoxy matrix modified with different mass ratio of silica nanoparticles were investigated. In order to disperse and incorporate silica nanoparticles into epoxy matrix, silica nanoparticles were modified with coupling agent (Gamma-glycidoxy propyl trimethoxy silan, KH-560). FTIR spectra showed that KH-560 was absorbed on the surface of SiO2 nanoparticles. The thermo gravimetric traces indicated that the addition of silica nanoparticles has improved the thermal stability properties of epoxy matrix significantly. The decomposition temperature of nanocomposite increased with the addition of nanoSiO2, and the temperatures of the maximum rate of degradation of the unmodified nanocomposite with 0wt%, 1wt%, 3wt%, 5wt% nanoSiO2 were 401oC, 405oC, 411oC, 421oC, respectively. The temperatures for 50% weight loose of the modified nanocomposite with 1wt% and 3wt% nanoSiO2 were 389oC and 405oC, respectively.

Enzyme immobilization in a photosensitive conducting polymer bearing azobenzene in the main chain

A new photosensitive and thermosensitive monomer, namely bis(4-(3-thienyl ethylene)-oxycarbonyl)diazobenzene (TDAZO), was synthesized. The photochemical and thermal cis–trans isomerization of the monomer has been investigated. The rate constants of the photoisomerization of TDAZO in ACN and DCM were 0.195 and 0.308 min−1, respectively. For spectroelectrochemical investigation and enzyme immobilization application, TDAZO copolymerized with thiophene and pyrrole. Electrochemical and spectroelectrochemical properties of P(TDAZO-co-Th) were investigated and invertase was immobilized in P(TDAZO-co-Py) copolymer. Immobilization of enzymes was carried out by the entrapment of the enzyme in conducting polymer matrices during electrochemical polymerization of pyrrole through thiophene moieties of the TDAZO. Optimum conditions for this electrode, such as pH, temperature, kinetic parameters (K m and V max) and operational stability were investigated. Kinetic parameters invertase-immobilized in copolymer were smaller than free enzyme. The optimum operational temperature was 10 °C higher for immobilized enzyme than that of the free enzyme. Due to strong interaction between enzyme and diazo group in the polymer main chain, thermal, pH and operational stability of enzyme has been enhanced.

Polymer Stabilized Undoped and Copper Doped Cadmium Sulphide Nanoparticles: Polymer Crosslinked, Optical, and Thermal Stability

Cadmium sulfide (CdS) nanoparticles synthesized by utilization of wet chemical technique are grown in polyvinyl alcohol (PVA) matrix. X-ray diffraction (XRD) pattern shows the typical inter-planar spacing corresponding to the cubic phase of CdS. High-resolution transmission electron microscopy (HRTEM) studies show the nanoparticles formation with diameter around 11 nm. Particle size is further determined by dynamic light scattering (DLS) measurement. The polymerization of PVA is confirmed by fourier transform infrared (FTIR) spectroscopy of CdS nanoparticles. UV-visible optical spectroscopy study shows that sharp excitonic bands are largely blue shifted from the absorption onset of bulk CdS and inter band transition of copper doped samples. Thermal stability of the samples is measured by thermogravimetric (TG) analysis which is also studied in details.

Influence of clay organic modifier on the thermal-stability of PLA based nanocomposites

Poly(lactic acid) (PLA) is a biodegradable aliphatic thermoplastic polyester well known for being a promising alternative to petroleum-based materials since it can be produced from renewable resources. Although this polymer has good properties when compared to other biodegradable polymers, it presents some limitations like poor thermal, mechanical resistance and gas barrier. The incorporation of clay minerals has been used as a way to overcome this problem. The present work aims to investigate the influence of clay organic modifier (Cloisite 30B, Cloisite 15A and Dellite 43B) and amount (3 and 5%) on PLA thermal stability. PLA and PLA nanocomposites were submitted to thermo-oxidative degradation at 140°C during 120h. Samples removed along the time were characterized by gel permeation chromatography (GPC), scanning electron microscopy (SEM), X-ray diffraction (XRD), nuclear magnetic resonance (1H NMR), Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). After degradation, even though all samples exhibited a significant decrease of molecular weight, it was smaller for nanocomposites. As a consequence of chain scission an increase in the crystallinity degree was observed for all nanocomposites. Results showed that clay mineral incorporation, mainly D43B enhanced the polymer thermal stability.

Investigations on PEO/PVP/NaBr complexed polymer blend electrolytes for electrochemical cell applications

Experimental investigations on a sodium ion conducting polymer blend electrolyte system based on polyethylene oxide (PEO) and polyvinyl pyrrolidone (PVP), complexed with NaBr salt are presented in this paper. The complexed polymer blend electrolytes were obtained in the form of dimensionally stable and free-standing films by solution cast technique. Physical characterization by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were performed to study the structural properties, their change along with ion–polymer interactions and thermal stability of the samples. The transport numbers of different mobile species were determined by means of d.c. polarization and combined a.c./d.c. techniques. Cationic transportation was found to be dominant in the films of high degree of amorphicity. Electrical properties were measured as a function of composition and temperature using complex impedance spectroscopy. The temperature dependent electrical conductivity showed Arrhenius type behavior. Activation energies were found to decrease with increasing concentration of the salt. Electrochemical cells were prepared using PEO/PVP/NaBr polymer blend electrolyte system and their discharge characteristics were studied. These studies suggested the practical realization of electrochemical cells using the present sodium ion conducting polymer blend electrolyte system.

Thermal studies and chromium removal efficiency of thermoresponsive hyperbranched copolymers based on PEG-methacrylates

This study deals with the removal of chromium species from aqueous dilute solutions using thermoresponsive linear and hyperbranched copolymers based on PEG-methacrylates. The thermal stability of polymers was studied by thermogravimetric analysis and chemiluminescence emission, which evidenced a slightly enhanced stability for hyperbranched polymers respect to linear structures. Their LCST was successfully determined by TOPEM (temperature-modulated DSC), and similar values to those obtained by UV spectroscopy were obtained. The adsorption capacities for chromium hexavalent of the polymers have been investigated as function of LCST. The results showed highest retention capacity of Cr(VI) for all polymers above LCST. Hyperbranched polymers were more efficient than linear polymers, because of the structure of the polymers. Hyperbranched polymers when precipitate form a network with more nanocavities where the chromium can be adsorbed. The efficiency increased with ratio of OEGMA/DEGMA, reaching a maximum retention capacity value of 40 mg Cr(VI)/g polymer.

Electrochemical properties and characterisation of novel polyurethane/polyindene, poly(ethylene terephthalate)/polyindene and poly(vinyl chloride)/polyindene conducting composites

This study covers the synthesis of conducting polyindene (PIn) homopolymer, polyurethane/polyindene (PU/PIn), poly(ethylene terephthalate)/polyindene (PET/PIn) and poly(vinyl chloride)/polyindene (PVC/PIn) composites. Polyindene and composites were synthesised electrochemically by cationic mechanism using LiClO4 as an initiator. From Fourier transform infrared spectroscopy spectra of polymers, it was revealed that the polymerisation reaction occurred by one to two mechanisms. The conductivities of polymers were also measured by four-probe technique, and it was found that PIn had the highest conductivity with 7·86×10−4 S cm−1 among the homopolymer and composites;the conductivity values of PU/PIn, PET/PIn and PVC/PIn composites were 4·23×10−5, 4·34×10−5 and 3·87×10−5 S cm−1 respectively. Magnetic properties of the polymers were analysed by Gouy scale measurements, and it was found that their conducting mechanisms are of polaron and bipolaron natures. Thermal stability of polymers was investigated by thermogravimetric analysis, and the initial degradation temperatures were found to be 271, 420, 390 and 465°C for PIn, PU/PIn, PET/PIn and PVC/PIn respectively. Scanning electron microscopy was used for microstructural analysis, and when the morphologies of PET/PIn, PVC/PIn composites and PIn, PU/PIn were compared, it was observed that PET/PIn and PVC/PIn composites have smoother layers and are more compact than PIn and PU/PIn composite. X-ray diffraction spectra showed that the crystallisation degree of PET and PVC increased after polymerisation of PIn; degrees of crystallinity of PIn, PU/PIn, PET/PIn and PVC/PIn were obtained as 14·6, 18·8, 19·3 and 20·2% respectively.

Adsorption-controlled preparation of molecularly imprinted hybrid composites for selective extraction of tetracycline residues from honey and milk

Molecularly imprinted organic–inorganic hybrid composite materials (MIP-HCMs) with controlled swelling and adsorption properties were prepared through copolymerization and the sol–gel process by using doxycycline (DC) as the template molecule, methacrylic acid (MAA) as a functional monomer, methacryloxypropyltrimethoxysilane (KH-570) as a coupling agent and TEOS as an inorganic precursor. By means of changing polymerization conditions as well as the copolymerization ratio of the inorganic precursor and the organic functional monomer, the properties of sorbents can be adjusted for different needs. So the effect of preparation conditions on the structure of the material was studied. The polymer group, thermal stability, adsorption and selectivity characteristics, and the volume swelling degree of the MIP-HCMs were characterized by FTIR, TGA, and dynamic adsorption and swelling experiments, respectively. It was observed that the MIP-HCMs exhibited the highest selectivity (4.9), maximum adsorption capacity (58.2 mg g−1) and good thermal stability. The obtained MIP-HCM was used as an adsorbent for solid-phase extraction of tetracyclines from the milk and honey samples. The average recoveries of three tetracycline antibiotics (DC, tetracycline and chlortetracycline) were obtained in the range of 74.7–115.5% with the precision of 2.1–4.9%. The limits of detection and quantitation of the proposed method were in the range of 4.9–15.3 μg kg−1 and 16.6–51.0 μg kg−1 for the milk samples, and 8.3–15.1 μg kg−1 and 18.3–50.2 μg kg−1 for the honey samples, respectively.

Polystyrene- and poly (methyl methacrylate)-organoclay nanocomposites using a one-chain benzimidazolium surfactant

In this paper, the synthesis of a one-chain benzimidazolium surfactant is accomplished and polystyrene (PS) and poly(methyl methacrylate) (PMMA) nanocomposites with organoclay modified by the above surfactant are prepared by melt blending. XRD, TEM, TGA and cone calorimetry are employed to evaluate the dispersion of the clay in the polymer matrices, thermal stability and fire behavior. TEM results show that the clay disperses more uniformly in the PMMA matrix than in PS. Both polymer nanocomposites exhibit enhanced thermal stability. From cone calorimetry, substantial reduction of heat release rates is obtained at 3wt% and 5wt% of clay from polystyrene and a more remarkable reduction in PMMA.

Thermal properties of poly (methyl methacrylate)/organomodified montmorillonite nanocomposites obtained by in situ photopolymerization

The organoclay/poly(methyl methacrylate) (PMMA) nanocomposites were prepared by in situ photopolymerization method using two solvents, ethanol and acetonitrile. The influences of organoclay loading, solvent nature and length of attached surfactant (C8 or C16) on thermal and mechanical properties were studied by thermogravimetric analysis and dynamic mechanical analysis. Alkylammonium surfactants with C8 and C16 chain lengths were evaluated as clay modifiers. All the nanocomposites prepared in acetonitrile exhibited improvement in their thermal stability, mainly due to the interaction between the clay and the polymer which is maximized by the exfoliated clay structure. In the case of PMMA and nanocomposites synthesized in ethanol, the thermal stability of polymer and nanocomposites remained practically the same once the clay structure is predominantly of the intercalated type. In comparison with pure PMMA, glass transition temperature and storage modulus of polymer are notably increased by the presence of clay. It was found that the chain length of surfactant attached to the SWy-1 clay affects the Tg values. Glass transition temperatures of nanocomposites SWy-1-C16/PMMA were significantly higher than the values obtained for nanocomposites SWy-1-C8/PMMA. This can be attributed to the modifying agent C16, which has a greater hydrophobic chain length. The organic tail can provide a better dispersion of the MMA monomer in the organoclay, resulting in a nanocomposite with predominant exfoliated structure. Another significant factor to be considered was the effect of solvent used in the nanocomposite preparation. Considering nanocomposites with the same chain length (C8 or C16), Tg values obtained for nanocomposites prepared with ethanol is higher than those observed for those prepared in acetonitrile. This was attributed to the influence of the average molecular weight; once the nanocomposites prepared in ethanol exhibited higher polymeric chains.

Anhydrous Novel Acid-Base Binary and Ternary Systems for Fuel Cell Applications

A new series of anhydrous binary and ternary acid-base systems composed of trifluoroacetic acid (TFAA), imidazole (IM) and Poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP) has been developed. The acid and base was added to the polymer in various compositions to improve the properties of polymer electrolyte such proton conductivity and thermal stability. However, it was found that some of the acid and base combinations outperformed the ternary system in proton conductivity testing obtaining conductivity in the 10-2 S/cm range. Further testing was then carried out on the binary systems to determine their suitability for use as high temperature performance materials. Analysis of their thermal stabilities found that these materials were not only good proton conductors but also had high thermal stabilities, where some of them resulted in high thermal stability of up to 200oC.