Thermal Stability Of Polymers Research Articles

Synthesis, thermal and optical properties of new nanosized polyamides containing N-phenyl- and O-naphthyl-s-triazine rings; part 2

ABSTRACTWe report the chemistry and properties of two new series of well-defined nano sized spheres aramides-containing N- and O-naphthyl-s-triazines. The polymers were carefully characterized by different techniques including infrared, ultraviolet, fluorescent emission, elemental, thermal analyses and scanning electron microscopy (SEM). The polymers were readily soluble in polar aprotic solvents while insoluble neither in water nor halogenated solvents. Thermal analyses data up to 900°C showed high thermal behavior and the polymers were classified either as “slow burning polymers” or “self-extinguishing polymers” based on their calculated the limiting oxygen index. Interestingly, the naphthyl / phenyl interchange has dramatic improvement on the thermal properties. Obviously, the pyridine / phenylene interchange has no influence on the thermal properties of the addressed polymers. Thermal stability of the aniline-containing polymers proved to be comparable to their naphthylamine analogues. Polymers containing p-phenylene moieties exhibited better thermal results compared to their analogues containing m-phenylene moieties. Benzidine containing polymers and sulfone containing polymers exhibited better thermal stabilities than their analogues containing either ether or methylene flexible linkages. The kinetic data obtained from the nonisothermal decomposition of the prepared polyamides series were also studied. The polymers exhibited emissions ranging from blue to orange wavelength depending on the nature of the signaling unit. The naphthyl / phenyl interchange led to either appreciable red-shifted absorptions in some cases or blue-shifted absorptions in other cases and this behavior may be attributed to the contorted, twisted structural nature of the naphthalene ring. Such attracting properties make these polymers good candidates for applications such as processable high-temperature materials and also as heat-resistant polymeric materials.

Ammonium salt catalyzed ring-opening polymerization of 1,3-benzoxazines

The effect of amine HCl salts as catalysts on the ring-opening polymerization (ROP) of simple 1,3-benzoxazines was investigated. The catalyst effects on the structure of the final polymer was examined and compared. The curing process for each salt-benzoxazine mixture was monitored by using Differential Scanning Calorimetry (DSC) and it was found that amine salts cause clear reduction in ROP temperature. As followed by 1H NMR investigations, the ring-opening of oxazine can take place even at r.t. when suitable solvent is used. Moreover, the analysis gave evidences that amine HCl salts act as nucleophilic catalyst and their efficiency is dependent on ionization ability and solubility of the salts. Thermal stability of the final polymers was also analyzed using Thermal Gravimetric Analysis (TGA).

Surface Energy and Thermal Stability Studies of Poly(dimethyl siloxane)–Poly(alkyl(meth)acrylate) Copolymers

ABSTRACTThe correlation between the surface energy and thermal stability of polymers plays an important role in engineering of plastic materials. In this work, microstructural characteristics of copolymers of poly(dimethyl siloxane) with benzyl methacrylate, ethyl methacrylate, and methyl acrylate are correlated with their surface energy and thermal stability. The poly(dimethyl siloxane) segments in the copolymer chains affected the hydrophobic behavior. The surface energy of the synthesized copolymers decreased by increasing segments of alkyl methacrylates. The thermal stability of copolymers suggesting that heat resistance of poly(dimethyl siloxane) copolymers used in this correlation can be improved by adjusting the units of alkyl methacrylates in copolymers.

Thermal degradation and flammability of polyamide 11 filled with nanoboehmite

The flame-retardant effect of rod-like nanoboehmite was evaluated in biobased polyamide 11. Thermal analysis reveals that hydrated nanofillers modify the degradation pathway of polyamide 11 turning from a two-step to a single-step mechanism. The polymer thermal stability is increased due to interactions between polar groups and filler surface hydroxyl groups. Despite this improved thermal stability, polyamide 11/nanoboehmite composites exhibit shorter times to ignition in cone calorimeter. The phenomenon was attributed to changes in thermoradiative properties leading to a faster heating of the polymer surface. The most significant flame-retardant action is a reduction in heat release rate that was related to a barrier effect while endothermic water release seems to play a minor role.

Synthesis and properties of a novel bio-based polymer from modified soybean oil

Maleated acrylated epoxidized soybean oil (MAESO) was prepared by acrylated epoxidized soybean oil (AESO) and maleic anhydride. AESO were obtained by the reaction of epoxidized soybean oil (ESO) with acrylic acid as the ring-opening reagent. The polymer was prepared by MAESO react with styrene. The structures of the products were studied by Fourier transformation infrared spectrometer (FT-IR), and were consistent with the theoretical structures. Swelling experiment indicated that the crosslinking degree increased with increasing epoxy value of ESO. Thermal properties was tested by thermo-gravimetric analysis (TG) and differential scanning calorimetry analysis (DSC), indicating that glass transition temperature (Tg) of the polymer increased with increasing epoxy value of ESO, and thermal stability of polymer have a good correlation with the crosslinking degree. Mechanical properties analysis presented that tensile strength and impact strength affected by epoxy value of ESO. With the increase of epoxy value, the tensile strength increase, while the impact strength decrease. The property of the polymer ranged from elastomer to plastic character depended on the functionality of the ESO.

Feasibility study into the deposition of an organic planarization layer using sequential polymerization initiated chemical vapor deposition

In this work, we investigated the film growth and planarization properties of sequential polymerization initiated chemical vapor deposition method (SP-iCVD). Supersaturated concentration of monomer and small amount of initiator were introduced sequentially into chamber. The obtained film properties such as uniformity, polymer molecular weight and thermal stability were same or better than iCVD processed film. Additionally, good planarization of high aspect ratio (7:1) patterned wafer was demonstrated in SP-iCVD. The overburden from top of feature was within 20nm and film thickness between isolated and dense feature areas was very uniform in this single-step process.

THE EFFECT OF CHLORO ACETIC ACID CONCENTRATION AND TEMPERATURE REACTION OF CARBOXYMETHYL CHITOSAN FORMATION ON CATION EXCHANGE CAPACITY AND THERMAL STABILITY

<p>The research on the effect of chloro acetic concentration and temperature reaction of carboxymethyl chitosan formation on cation exchange capacity and thermal stability of polymer have been done. Carboxymethyl chitosan was synthesized by reaction of chitosan and chloro acetic acid with NaOH as catalyst. Polymer was characterized by Fourier Transform Infrared Spectrofotometer, cation exchange capacity test, and thermal analysis with thermogravimetric method. Carboxymethyl chitosan has strong FTIR adsorption of carboxyl group (-COO-) in 1606,70 cm<sup>-1</sup> and 1444,68 cm<sup>-1</sup>. The increasing of chloro acetic acid concentration and reaction temperature decreased cation exchage capacity and changed thermal stability of polymer.</p>

Development and evaluation of a calcium alginate based oral ceftriaxone sodium formulation.

The purpose of this work was to develop a multiparticulate system exploiting the pH-sensitive property and biodegradability of calcium alginate beads for intestinal delivery of ceftriaxone sodium (CS). CS was entrapped in beads made of sodium alginate and sodium carboxymethylcellulose (CMC), acacia, HPMC K4M and HPMC K15M as drug release modifiers. Beads were prepared using calcium chloride as a cross-linking agent, followed by enteric coating with cellulose acetate phthalate (CAP). The beads were then evaluated for entrapment efficiency using HPLC, in vitro drug release examined in simulated gastric fluid (pH 1.2) and simulated intestinal fluid (pH 6.8), swellability, particle size and surface characterization using optical microscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM). Thermal gravimetric analysis (TGA) was utilized to check the polymer matrix strength and thermal stability. The drug entrapment efficiency of the optimized formulation was determined to be 75 ± 5 %. Swelling properties of drug-loaded beads were found to be in a range of 0.9–3.4. Alginate beads coated with CAP and containing CMC as a second polymer exhibited sustained release. The drug release followed first-order kinetics via non-Fickian diffusion and erosion mechanism. The particle size of the beads was between 1.04 ± 0.20 and 2.15 ± 0.36 mm. TGA, AFM, and SEM data showed composition and polymer-dependent variations in cross-linking, thermal stability, surface structure, morphology, and roughness. The physico-chemical properties of the developed formulation indicate suitability of the formulation to deliver CS orally.

Synthesis and Characterization of Polyurea Resin for Dielectric Coating Applications

ABSTRACTIn this article, polyurea coatings were synthesized by reaction between toluene diisocyanate, and polyether difunctional and trifunctional amines PO-1 and PO-2 by incorporating urea linkage. The isocyanate-terminated prepolymers formed were further reacted with short-chain amines as chain extender as well as curing agents. These resins were synthesized by varying the molar ratio of amines and isocyanate and keeping the molar ratio of other monomers constant. The presence of functional groups were determined using Fourier transform infrared spectroscopy. The thermal stability of polymers was determined using the thermogravimetric analysis and differential scanning calorimetry. The polymers were further tested for mechanical and electrical properties. It was observed that on increasing the hard segments in the polymer the electrical properties increase whereas elongation decrease. As isocyanate content increases, crosslinking increases resulting in improvement in dielectric properties. The maximum dielectric strength observed was 45 kV mm−1 and dissipation factor was 0.068.

Sulfonated poly(ether ether ketone)-based hybrid membranes containing graphene oxide with acid-base pairs for direct methanol fuel cells

The graphene oxide (GO) sheets are functionalized by histidine molecules and incorporated into sulfonated poly (ether ether ketone) (SPEEK) matrix to fabricate hybrid polymer electrolyte membranes for direct methanol fuel cells (DMFCs). The loading of functionalized GO is varied to investigate its influence on cross-sectional morphology, crystalline structure, polymer chain stiffness, thermal stability and fractional free volume of membrane, etc. The acidic −SO3H groups (proton donors) in SPEEK and basic imidazole groups (proton acceptors) in histidine molecules form acid-base pairs and transport protons synergistically, thus yielding efficient proton channels inside the hybrid membranes. The maximum proton conductivity (at 100% RH) of hybrid membranes is elevated by 30.2% compared with the plain SPEEK membrane at room temperature. The functionalized GO flakes also confer the hybrid membranes low methanol permeability in the range of 1.32–3.91×10−7cm2s−1. At the filler content of 4wt%, the hybrid membrane shows a superior selectivity of 5.14×105Sscm−3 and its maximum power density of single DMFC cell (43.0mWcm−2) is 80.7% higher than that of plain SPEEK membrane.

Poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)] active bilayer films obtained by compression moulding and applying essential oils at the interface

AbstractFour active components, oregano essential oil (OR) and its respective main compound carvacrol (CA) and clove essential oil (CLO) and its respective main compound eugenol (EU), were used separately to obtain, using compression moulding, poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)] (PHBV) bilayer films with antimicrobial activity. The active compounds were sprayed (15% w/w, polymer to active compound ratio) at the interface between two layers of PHBV, which were joined using thermo‐compression. Tensile, barrier and optical properties, as well as thermal behaviour, of the films were characterized after one week at 25 °C and 53% relative humidity. Likewise, the antimicrobial activity of the films was evaluated against Escherichia coli and Listeria innocua. Although the tensile properties of the films were not improved with respect to pure PHBV films by the addition of the active compounds, more transparent materials with better water vapour barrier capacity were obtained. Thermogravimetric analyses showed that CA and EU slightly decreased the polymer thermal stability, while OR and CLO led to more thermally resistant material. Miscibility of actives with the polymer was assessed through the promoted decrease in melting temperature and degree of crystallinity. PHBV films allowed the release of the active compounds in adequate amounts and at adequate rates into culture media to control the microbial growth of the two tested bacteria. The films were significantly more effective against E. coli than against L. innocua. Both bacteria were more sensitive to OR and to its main compound, CA, due to the greater antimicrobial effectiveness of these components. © 2016 Society of Chemical Industry

Synthesis and characterisation of certain biodegradable xylitol based polyesters

Bioresorbable polymeric materials are emerging biomaterials to meet the demands in the biomedical field such as tissue engineering, drug delivery and wound healing applications. In this work, we focused on the biodegradable polymers with tunable properties for biomedical application. A polyol based crosslinked polyesters were synthesized by melt polycondensation. Xylitol, Maleic acid and the dicarboxylic acid such as succinic acid/sebacic acid were used for the synthesis of polymers by catalyst free melt polycondensation method. The synthesized polymers were characterized by fourier transform infrared spectroscopy (FTIR), 1H nuclear magnetic resonance (1H NMR) and 13C nuclear magnetic resonance (13C NMR). The thermal stability of polymers was studied by Differential scanning calorimetry (DSC).

Development of PVC membranes with clove oil as plasticizer for blood bag applications

In the present study, Antimicrobial PVC films containing different amounts of clove oil as a plasticizer were prepared using traditional casting method. The physical and mechanical properties of the plasticized PVC membranes e.g. surface wettability were investigated. The increase of clove oil content demonstrated an increase in surface hydrophilicity and elongation to break the film. The thermogravemetric analysis revealed a decrease of polymer thermal stability by increasing clove oil concentration. The antibacterial activities against four different bacterial strains (two-gram positive: Staphylococcus aureus and Bacillus cereus & two-gram negative: Pseudomonas aeruginosa and Escherichia coli were promoted by addition of clove oil. Although the natural source of clove oil, the bio-evaluation of plasticized membranes showed an increase in hemolysis percent (%) and thrombus weight. It can be concluded that the addition of clove to PVC need to further studies for applying in blood bags.

Semiconducting Carbon Nanotubes for Improved Efficiency and Thermal Stability of Polymer–Fullerene Solar Cells

The effects of the incorporation of semiconducting single‐walled nanotubes (sc‐SWNTs) with high purity on the bulk heterojunction (BHJ) organic solar cell (OSC) based on regioregular poly(3‐hexylthiophene‐2,5‐diyl):[6,6]‐phenyl‐C61‐butyric acid methyl ester (rr‐P3HT:PCBM) are reported for the first time. The sc‐SWNTs induce the organization of the polymer phase, which is evident from the increase in crystallite size, the red‐shifted absorption characteristics and the enhanced hole mobility. By incorporating sc‐SWNTs, OSC with a power conversion efficiency (PCE) as high as 4% can be achieved, which is ≈8% higher than our best control device. A novel application of sc‐SWNTs in improving the thermal stability of BHJ OSCs is also demonstrated. After heating at 150 °C for 9 h, it is observed that the thermal stability of rr‐P3HT:PCBM devices improves by more than fivefold with inclusion of sc‐SWNTs. The thermal stability enhancement is attributed to a more suppressed phase separation, as shown by the remarkable decrease in the formation of sizeable crystals, which in turn can be the outcome of a more controlled crystallization of the blend materials on the nanotubes.

Effect of Sr2TiMnO6 fillers on mechanical, dielectric and thermal behaviour of PMMA polymer

Composites of poly(methyl methacrylate) (PMMA) and [Formula: see text] (STMO) were fabricated via melt mixing followed by hot pressing technique. These were characterized using X-ray diffraction (XRD), thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC), thermo mechanical analysis (TMA) and impedance analyser for their structural, thermal and dielectric properties. The coefficient of thermal expansion (CTE) was measured between 40°C and 100°C for pure PMMA is 115.2 ppm/°C, which was decreased to 78.58 ppm/°C when the STMO content was increased to 50 wt.% in PMMA. There was no difference in the glass transition ([Formula: see text]) temperature of the PMMA polymer and their composites. However, the FTIR analysis indicated possible interaction between the PMMA and STMO. The density and the hardness were increased as the STMO content increased in the PMMA matrix. Permittivity was found to be as high as 30.9 at 100 Hz for the PMMA+STMO-50 wt.% composites, indicating the possibility of using these materials for capacitor applications. The thermal stability of polymer was enhanced by incorporation of STMO fillers.

Effect of hydrothermally synthesized titanium nanotubes on the behaviour of polypropylene for antimicrobial applications

AbstractTiO2 nanotubes (TiO2‐Ntbs) synthesized by a hydrothermal method were used as filler to prepare polypropylene (PP) composites by melt blending. Their structural properties as well as their biocidal potential were studied. Nanotubes were used either as‐synthesized or organically modified with hexadecyltrimethoxysilane (Mod‐TiO2). These nanoparticles form secondary structures with sizes around 100 nm that are well dispersed in the polymer matrix, but not homogeneously because agglomerates larger than 1 µm are also seen by transmission electron microscopy. Regarding the properties of the composites, the incorporation of the nanoparticles increased the polymer's crystallinity and thermal stability. The maximum decomposition temperature of the matrix increased by ca 13 °C compared to virgin PP. The nanotubes further increase the spherulite nucleation density, and therefore a reduction in the diameter of spherulites and an increase in their number were observed. Despite the above, the addition of TiO2 nanoparticles did not modify the mechanical properties of PP. The PP/TiO2‐Ntb nanocomposites exposed to UVA radiation showed a biocidal behaviour, reducing a colony of Escherichia coli by 81%. © 2015 Society of Chemical Industry

Hydrothermal synthesis of novel cobalt–organic framework, involving in-situ ligand transformation, DFT calculation, spectroscopic and thermal studies

The novel 1-D polymeric compound, namely {[(H2O)3(2,2′-bpy)Co(μ2-oxo-bpdc)Co(H2O)3](NO3)2·2H2O}n, where bpdc is 2,2′-bipyridine-3,3′-dicarboxylate, bpy is bipyridine ligand has been hydrothermally synthesized. X-ray single crystal structural analysis revealed that in-situ transformation of 1,10-phenanthroline-5,6-dione (phendione) into bpdc2− occurs under hydrothermal treatment. This coordination polymer exhibited one-dimensional chains with side branches. Thermal stability of coordination polymer was investigated by thermo gravimetric analysis (TGA). A feasible mechanism for in-situ generation of bpdc2− ligand will also be provided. Density functional theory (DFT) calculations were also performed to understand the electronic structure of the compound from theoretical point of view. The electronic spectrum of title compound was analyzed and the absorption bands were assigned through the DFT/TDDFT procedures.

Poly(ether‐imide) and related sepiolite nanocomposites: investigation of physical, thermal, and mechanical properties

Novel poly(ether‐imide) and sepiolite nanocomposites were synthesized based on a unique diamine monomer with the aim of improving physical and mechanical properties of final polyimide films. The diamine was polycondensed with 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride to produce related poly(ether amic acid) prepolymer. Pure poly(ether‐imide) and nanocomposite films were prepared via thermal imidization process of poly(ether amic acid). Coexistence of ether, pyridine, and phenylene functional groups in the diamine chemical structure resulted in flexible polyimide films with significant thermal, physical, and mechanical properties. Thermal stability, glass‐transition temperature, dimensional stability, and tensile properties of polymer and nanocomposites were studied and compared. Morphology of nanocomposites was also investigated using scanning and transmission electron microscopic methods to study the distribution and dispersion behavior of sepiolite nanofibers in the polyimide matrix. By introduction of sepiolite nanoparticles, overall improvement of properties was observed in respect to pure polyimides. Copyright © 2015 John Wiley & Sons, Ltd.

Studies on Hydrophilicity and Thermal Stability of Poly(isoalkyl lactate methacrylate)s

Isopropyl and isobutyl lactates were reacted with methacrylic acid to obtain corresponding methacrylates through the azeotropic distillation method and their formation was confirmed by mass spectroscopy. Homopolymers were prepared by the solution polymerization method. Both monomers and homopolymers were characterized by FT-IR and NMR spectroscopic techniques. Hydrophilicity of polymers followed the Fickian process and moisture absorption was in the range of 10–24% (w/w). Glass transition temperature decreased with an increase in isoalkyl chain length of polymers. Thermal stability of polymers was explained on the basis of average molecular interchain spacing value, which was calculated using 2θ value of amorphous halo of polymers.

Preparation and characterization of zeolite polymer composite proton exchange membrane

Sulfonated polystyrene (SPS) and sulfonated polystyrene zeolite composite (SPS-Z) membranes were prepared by solution casting technique. SPS was synthesized using acetyl sulfate as a sulfonating agent in a reflux condenser under nitrogen atmosphere. The membrane casting was done without isolating the SPS. The SPS-Z membrane was fabricated by adding the zeolite to the SPS solution by the same technique. The synthesized SPS and SPS-Z membranes were characterized with Fourier transform infrared spectroscopy, thermogravimetric analysis, field emission scanning electron microscopy, and atomic force microscopy to identify the −SO3H functional group attached onto the polymer membrane, thermal stability, and surface morphology. The membranes were further examined for their water uptake capacity, swelling behavior, and degree of sulfonation. In addition, the performance of the fabricated membranes was examined based on their ion exchange capacity (IEC) and proton conductivity. The results revealed that both the membranes have good thermal and surface properties. The SPS-Z membrane has less swelling tendency than the SPS membrane due to lower water uptake capacity of SPS-Z membrane (2.5%) than the SPS membrane (3.5%). The proton conductivity of the SPS-Z membrane (1.11 × 10−5S/cm) is higher than the SPS membrane (1.68 × 10−6S/cm). The IEC capacity of SPS and SPS-Z membranes is found to be 0.03 and 0.17 meq/g, respectively. The proton conductivity of SPS and SPS-Z membranes is comparable with the Nafion 117® membrane (5.32 × 10−6S/cm) under the same experimental conditions indicates that the fabricated membranes have the good potential for membrane applications, especially for fuel cell applications.