Thermal Behavior (thermal + behavior)

Distribution by Scientific Domains
Distribution within Polymers and Materials Science


Selected Abstracts


EFFECT OF PRETREATMENTS AND ADDITIVES ON THE THERMAL BEHAVIOR AND HYGROSCOPICITY OF FREEZE-DRIED PINEAPPLE JUICE POWDER

JOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 5-6 2005
H.S. PHANINDRAKUMAR
ABSTRACT Pasteurization of pineapple juices at 80C for 5 min in the presence of added acids (citric, malic and fumaric) and cane sugar was found to increase its reducing sugar content from 3.5 to 6.5%, which in turn decreased the glass transition temperature (Tg) and increased the hygroscopicity of the juice powder. Inversion of sucrose could be avoided by adding sugar and acid to a pasteurized cooled juice. Among the acids, citric acid caused 30% more hygroscopicity than malic and fumaric. Incorporation of additives into the juice prior to freeze-drying helped in reducing the hygroscopic tendency of the juice powder. Among the additives tried, trehalose, beta-cyclodextrin and sorbitol were found to be beneficial as they increase the Tg and reduce the hygroscopic tendency of the juice powder. [source]


Thermal Behavior of Tetrahydropyran-Intercalated VOPO4: Structural and Dynamics Study

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 3 2007
Klra Melnov
Abstract The thermal behavior of tetrahydropyran-(THP-)intercalated VOPO4 was probed by an extensive combination of experimental methods (XRD, DSC, FTIR, solid-state NMR) and quantum chemical calculations. Two temperature-induced transitions were detected and all polymorphs exhibit a high degree of molecular order and tight packing of THP in VOPO4. The first reversible thermal transition at around 100 C was attributed to boat/chair conformation changes of the THP molecules. Most probably, a low-temperature boat conformation of the guest molecules present in the interlayer space of VOPO4 changes to a high-temperature chair conformation. This rearrangement of the THP molecules was confirmed by variable-temperature 13C CP/MAS NMR spectroscopy. Quantum chemical calculations using a B3LYP functional and 6-31G(d) basis set also support this idea. The second change at around 140 C is probably caused by a weakening of the donor,acceptor bond between the oxygen molecule of THP and the vanadium atom of the host and the formation of a disorder in packing of the THP molecules. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]


Thermal Behavior of Free-Base and Core-Modified Bicyclo[2.2.2]octadiene-Fused Porphyrins

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 1 2008
Hidemitsu Uno
Abstract Multistep thermal fragmentation of quadruply bicyclo[2.2.2]octadiene-fused porphyrins giving tetrabenzoporphyrins was examined in detail. After the first extrusion of an ethylene molecule from the porphyrin derivative, the opposite bicyclo[2.2.2]octadiene moiety preferentially underwent the second retro-Diels,Alder reaction to give an opp -dibenzoporphyrin derivative rather than an adj -dibenzoporphyrin derivative. These two benzoporphyrin derivatives then decomposed to give a tribenzoporphyrin derivative in similar rates. The temperature regions of these fragmentations could not be distinguished by thermogravimetric analysis. In contrast, the third and the fourth fragmentations obviously occurred stepwise. There was a temperature region where the tribenzoporphyrin derivative preferentially existed. In the case of the 21,23-dithiaporphyrin derivative, opp -21,23-dithiadibenzoporphyrin, possessing benzo moieties fused at the pyrrole parts of the core-modified porphyrin chromophore was predominantly formed during the fragmentation. In the case of the 21-thiaporphyrin derivative, an ethylene molecule was extruded selectively from the bicyclo[2.2.2]octadiene moiety adjacent to the thiophene part to give 21-thiabenzo[q]porphyrin and then 21-thiabenzo[g,q]porphyrin derivatives. In these cases, the last ethylene extrusion also occurred very slowly. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]


Effects of Arabinoxylans on Thermal Behavior of Frozen Wheat Doughs as Measured by DSC, DMA, and DEA

JOURNAL OF FOOD SCIENCE, Issue 1 2002
T. J. Laaksonen
ABSTRACT: The effects of water extractable arabinoxylans (WEA) on physical state of frozen wheat dough with added sucrose, NaCl, and their mixture were investigated using DSC, DMA, and DEA. DSC thermograms were obtained for annealed samples, and they showed only an endothermic peak of ice melting. Annealed samples were also analyzed using DMA and DEA with both dynamic heating and isothermal steps. Added sucrose and NaCl decreased the onset temperature of ice melting and it decreased with increasing WEA concentration. Isothermal measurements showed an a-relaxation peaks, taken as the Tg,. Added NaCl had a great depressing effect on the Tg, at low frequencies as measured by DEA. [source]


Modeling of Thermal Behavior of Ancient Metallurgical Ceramics

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2007
Anno Hein
The finite element method is used to examine the thermal properties of functional ceramics, which were used in metallurgical processes during antiquity. Based on the ceramics' microstructure a model is developed considering the impact of porosity and inclusions and the heat transfer from ceramics to environment. An example of a Bronze Age copper smelting furnace from Cyprus is presented. Particularly the influence of pore shape and pore orientation on the thermal conductivity is investigated. Temperature development in the entire furnace is simulated and compared with estimations of the firing temperature in particular areas of the furnace. [source]


Influence of the Composition on Crystal Phase and Thermal Behavior of trans -1,4-Butadiene/Isoprene Copolymers

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 23 2007
Fabio Bertini
Abstract Butadiene/isoprene copolymers were prepared using the catalyst system V(acac)3 -MAO. The structure of the comonomers is trans -1,4 and the butadiene and isoprene units are statistically distributed along the polymer chain. The attitude of the butadiene sequences to crystallize in the monoclinic form and to evolve in the hexagonal form is preserved in the copolymer for a certain range of composition. The temperature interval between the two endothermic events is progressively reduced by increasing the isoprene content. The monoclinic/hexagonal transition produces a considerable increase in the lamellar thickness of the polymers. Thermal degradation of the copolymers is influenced by the composition and takes place in two different stages: a series of cyclization and cross-linking reactions occur before the decomposition step. [source]


Immiscible Poly(L -lactide)/Poly(, -caprolactone) Blends: Influence of the Addition of a Poly(L -lactide)-Poly(oxyethylene) Block Copolymer on Thermal Behavior and Morphology

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 7 2004
Giovanni Maglio
Abstract Summary: A binary blend of poly (L -lactide) (PLLA) and poly(, -caprolactone) (PCL) of composition 70:30 by weight was prepared using a twin screw miniextruder and investigated by differential scanning calorimetry (DSC), optical microscopy and scanning electron microscopy (SEM). Ternary 70:30:2 blends were also obtained by adding either a diblock copolymer of PLLA and poly(oxyethylene) (PEO) or a triblock PLLA-PCL-PLLA copolymer as a third component. Optical microscopy revealed that the domain size of dispersed PCL domains is reduced by one order of magnitude in the presence of both copolymers. SEM confirmed the strong reduction in particle size upon the addition of the copolymers, with an indication of an enhanced emulsifying effect in the case of the PLLA-PEO copolymer. These results are analyzed on the basis of solubility parameters of the blend components. Optical micrograph of M3EG2 blend melt quenched at 125,C. [source]


Thermal Behavior of Isotactic Poly(propylene)/Maleated Poly(propylene) Blends

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 4 2007
Catalin Vlcu
Abstract This paper analyzes the thermal and thermo-oxidative degradation behavior, phase separation, melting, and crystallization of blends consisting of isotactic poly(propylene) (IPP) and poly(propylene) grafted with maleic anhydride (PP- g -MA). It has been established that, depending on the blend composition and crystallization/preparation procedure, the blends of IPP and PP- g -MA can either co-crystallize or evidence phase separation. This conclusion has been attained by comparing the DSC results of crystallization under dynamic and isothermal conditions with X-ray diffraction results. On the basis of the obtained results, the optimum mixing ratios have been established as 95,85 wt.-% IPP/5,15 wt.-% PP- g -MA. Thermo-oxidative behavior has been studied by thermogravimetry and differential thermal analysis. [source]


ChemInform Abstract: Thermal Behavior of Bicyclo[2.2.2]octadiene-Installed Precursors for 2H-Anthra[2,3-c]pyrroles and Anthra[2,3-c]thiophene.

CHEMINFORM, Issue 34 2010
Hiroki Uoyama
Abstract 4,11-Ethano-4,11-dihydro-2H-anthra[2,3-c]pyrroles (IV) and the corresponding thiophene (VI) are prepared, and their thermogravimetric behavior is studied. [source]


ChemInform Abstract: Crystal Chemistry and Thermal Behavior of Anhydrous Phosphates.

CHEMINFORM, Issue 9 2009
Part 42.
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


ChemInform Abstract: Synthesis, Crystal Structure and Thermal Behavior of Trihydrated Acid Holmium Diphosphate HHoP2O73H2O.

CHEMINFORM, Issue 48 2008
Sana Hraiech
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


ChemInform Abstract: From Molecular to Two-Dimensional Anderson Polyoxomolybdate: Synthesis, Crystal Structure, and Thermal Behavior of [{Ni(H2O)4}2{Ni (OH)6Mo6O18}]4H2O and [Ni(H2O)6] [Ag2{Ni(OH)6Mo6O18}] 8H2O.

CHEMINFORM, Issue 27 2008
Feng-Xian Liu
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


ChemInform Abstract: Two Ce(SO4)24H2O Polymorphs: Crystal Structure and Thermal Behavior.

CHEMINFORM, Issue 5 2008
Barbara M. Casari
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


Crystal Structure and Thermal Behavior of (Rb,Cs)BSi2O6 Solid Solutions.

CHEMINFORM, Issue 22 2006
M. G. Krzhizhanovskaya
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]


Multianvil High-Pressure/High-Temperature Synthesis, Crystal Structure, and Thermal Behavior of the Rare-Earth Borogermanate Ce6(BO4)2Ge9O22.

CHEMINFORM, Issue 16 2006
Gunter Heymann
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]


Crystal Structure and Thermal Behavior of the Mixed-Valent Basic Mercury Nitrate Hg2I(OH)(NO3)HgIIO.

CHEMINFORM, Issue 24 2005
Matthias Weil
Abstract For Abstract see ChemInform Abstract in Full Text. [source]


ChemInform Abstract: M(SCN)2 (M: Eu, Sr, Ba): Crystal Structure, Thermal Behavior, Vibrational Spectroscopy.

CHEMINFORM, Issue 42 2001
Claudia Wickleder
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


ChemInform Abstract: Synthesis of Novel Dendrimers Having a Thermally Reactive Fluorescent Core, and Their Thermal Behavior.

CHEMINFORM, Issue 27 2001
Hideo Tokuhisa
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


ChemInform Abstract: Contributions on Crystal Structures and Thermal Behavior of Anhydrous Phosphates.

CHEMINFORM, Issue 7 2001
Part 29.
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


Thermal Behavior and Non-isothermal Decomposition Reaction Kinetics of NEPE Propellant with Ammonium Dinitramide

CHINESE JOURNAL OF CHEMISTRY, Issue 5 2010
Weiqiang Pang
Abstract Thermal decomposition behavior and non-isothermal decomposition reaction kinetics of nitrate ester plasticized polyether NEPE propellant containing ammonium dinitramide (ADN), which is one of the most important high energetic materials, were investigated by DSC, TG and DTG at 0.1 MPa. The results show that there are four exothermic peaks on DTG curves and four mass loss stages on TG curves at a heating rate of 2.5 Kmin,1 under 0.1 MPa, and nitric ester evaporates and decomposes in the first stage, ADN decomposes in the second stage, nitrocellulose and cyclotrimethylenetrinitramine (RDX) decompose in the third stage, and ammonium perchlorate decomposes in the fourth stage. It was also found that the thermal decomposition processes of the NEPE propellant with ADN mainly have two mass loss stages with an increase in the heating rate, that is the result of the decomposition heats of the first two processes overlap each other and the mass content of ammonium perchlorate is very little which is not displayed in the fourth stage at the heating rate of 5, 10, and 20 Kmin,1 probably. It was to be found that the exothermal peak temperatures increased with an increase in the heating rate. The reaction mechanism was random nucleation and then growth, and the process can be classified as chemical reaction. The kinetic equations of the main exothermal decomposition reaction can be expressed as: d,/dt=1012.77(3/2)(1,,)[,ln(1,,)]1/3 e,1.723104/T. The critical temperatures of the thermal explosion (Tbe and Tbp) obtained from the onset temperature (Te) and the peak temperature (Tp) on the condition of ,,0 are 461.41 and 458.02 K, respectively. Activation entropy (,S,), activation enthalpy (,H,), and Gibbs free energy (,G,) of the decomposition reaction are ,7.02 Jmol,1K,1, 126.19 kJmol,1, and 129.31 kJmol,1, respectively. [source]


Hydrothermal Syntheses, Crystal Structure and Thermal Behavior of [(CH3)2NH2]2[B5O6(OH)4]2[HCON(CH3)2] and [NH3CH2CH2NH3]2[B14O20(OH)6]

CHINESE JOURNAL OF CHEMISTRY, Issue 11 2009
Ping Li
Abstract Two novel organic base templated nonmetal borates [(CH3)2NH2]2[B5O6(OH)4]2[HCON(CH3)2] (?) and [NH3CH2CH2NH3]2[B14O20(OH)6] (II) have been synthesized under hydrothermal conditions, and characterized by elemental analyses, FT-IR spectroscopy, X-ray diffraction, and TG-DTA. Their crystal structures were determined from single crystal X-ray diffraction. The crystal structure of compound I is characterized by forming a 3D supramolecular structure with large channels along axes b and c through OHO hydrogen-bonding among the [B5O6(OH)4], anions. The crystal structure of compound II is characterized by forming a 3D supramolecular structure with large channels along axis a and direction [111] through OHO hydrogen-bonding among the [B14O20(OH)6]4, anions. The templating organic amine cations in I and II are both obtained through in situ hydrothermal reactions, and are both located in the channels of the 3D supramolecular structure, respectively. Their thermal behavior has been also investigated. [source]


Synthesis and Characterization of Dendrimeric Bridged Salen/Saloph Complexes and Investigation of Their Magnetic and Thermal Behaviors

HELVETICA CHIMICA ACTA, Issue 5 2010
Ziya Erdem
Abstract Eight new multinuclear FeIII and CrIII complexes involving the tetradentate Schiff bases N,N, -bis(salicylidene)ethylenediamine (salenH2) or N,N, -bis(salicylidene)benzene-1,2-diamine (salophH2) and the two new ligands 4,4,,4,,4,,,,4,,,,,4,,,,-[1,3,5-triazine-2,4,6-triyltris(nitrilomethylidyne-4,1-phenyleneoxy-1,3,5-triazine-6,2,4-triyldiimino)]hexakis[benzoic acid] (4) or 5,5,,5,,5,,,,5,,,,,5,,,,-[1,3,5-triazine-2,4,6-triyltris(nitrilomethylidyne-4,1-phenyleneoxy-1,3,5-triazine-6,2,4-triyldiimino)]hexakis[benzene-1,3-dicarboxylic acid] (5) were synthesized (Schemes,1 and 2) and characterized by means of 1H-NMR and FT-IR spectroscopy, elemental analysis, LC/MS analysis, AAS (atomic-absorption spectrum) analysis, thermal analyses, and magnetic-susceptibility measurements. The complexes can also be characterized as low-spin distorted-octahedral FeIII and CrIII complexes bridged by carboxylato moieties. [source]


ChemInform Abstract: Synthesis, Characterization and Thermal Behaviors of 4-Amino-5-nitro-1,2,3-triazole (ANTZ) and Its Derivatives.

CHEMINFORM, Issue 41 2010
Bozhou Wang
Abstract The synthesis of 4-amino-5-nitro-1,2,3-triazole (II), a high performance insensitive explosive, via Hofmann rearrangement and its transformation into a high nitrogen containing derivative (IV) or salt (VI) are reported. [source]


Morphology of poly(ethylene terephthalate) blends: An analysis under real processing conditions by rheology and microscopy

ADVANCES IN POLYMER TECHNOLOGY, Issue 3 2009
lhan zen
Abstract The present work describes the formation of co-continuous phase morphologies in uncompatibilized and compatibilized poly(ethylene terephthalate) (PET),poly(m -xylene adipamide) (MXD6) and PET, poly(ethylene- co -vinyl alcohol) (EVOH) melt-extruded blends. Phase continuity has been determined by using the Jordhamo relationship. Viscosity values, which are essential for the calculation of the phase continuity, have been obtained by capillary rheometry. Thermal behavior of the blends has been analyzed by employing differential scanning calorimetry and phase continuity has been investigated for the noncompatibilized and the compatibilized blends by scanning electron microscopy. PET,MXD6 blends [92.35:7.65 (v/v) and 84.5:15.5 (v/v)] and PET,EVOH blends [73.63:26.37 (v/v)] exhibit droplet-in-matrix phase morphology, whereas uncompatibilized PET,MXD6 [75.8:24.2 (v/v)] blend has a combination of rod-like, droplet,matrix structure, and quasi-interpenetrating network structure. 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:173,184, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20156 [source]


From Chelating Precursor to Perovskite Oxides and Hollow Fiber Membranes

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2007
S. Liu
Perovskite Ba0.5Sr0.5Co0.8Fe0.2O3-, (BSCF) is a promising mixed-conducting ceramic membrane material in addition to being a good electrode catalyst for solid oxide fuel cells. In this study, BSCF powder was synthesized via a chelated water-soluble complex method at relatively low temperatures. The combined ethylenediaminetetraacetic acid and citric acid was used for the synthesis of a complex-based precursor, followed by thermal decomposition of the precursor at high temperatures. Thermal behavior, crystal phases, and structures of the prepared powders were characterized by thermogravimetric analysis/differential scanning calorimetry, XRD, and scanning electron microscopic (SEM) techniques, respectively. Pure and single-phase perovskite could be obtained after sintering at a temperature higher than 800C for 5 h. The soft precursor powder synthesized at lower temperatures, i.e., 600C, is water insoluble and more appropriate for use as a membrane material to prepare gas-tight tubular or hollow fiber ceramic membranes. By contrast, the hollow fibers prepared via the traditional techniques where the perovskite powder is used as the starting membrane materials display gas leakage. The fibers were characterized by SEM, XRD, and tested for air separation at ambient pressure and temperatures between 700 and 950C. The oxygen flux measured in this work reached 3.90 mL(mincm2),1 and compares favorably with any experimental values reported in the open literature. [source]


Thermal behavior and flame retardancy of flexible poly(vinyl chloride) treated with zinc hydroxystannate and zinc stannate

JOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 1 2008
Weihong Wu
The flame-retardant and smoke-suppressant properties of inorganic tin compounds such as zinc hydroxystannate (ZHS) and zinc stannate (ZS) were studied in comparison with those of alumina trihydrate and magnesium hydroxide through the limiting oxygen index test and a smoke density test. The thermal degradation in air of flexible poly(vinyl chloride) (PVC) treated with the above compounds was studied by thermal analysis from ambient temperature to 800C. The activation energy was calculated by using the Vyazovkin model-free kinetic method and the Kissinger method. The results showed that tin compounds such as ZHS and ZS could be used as highly effective flame retardants for flexible PVC; these flame retardants enhanced the stability and the activation energy of the oxidation of the char. J. VINYL ADDIT. TECHNOL, 2008. 2008 Society of Plastics Engineers [source]


Structural Study on Water-induced Phase Transitions of Poly(ethylene imine) as Viewed from the Simultaneous Measurements of Wide-Angle X-ray Diffractions and DSC Thermograms

MACROMOLECULAR SYMPOSIA, Issue 1 2006
Tomoko Hashida
Abstract Thermal behavior of poly(ethylene imine) [PEI] has been studied using simultaneous WAXD/DSC measurement system. PEI exhibits water-induced and thermally-induced phase transitions among four kinds of crystalline hydrates: anhydrate (EI/water,=,1/0), hemihydrate (1/0.5), sesquihydrate (1/1.5), and dihydrate (1/2). The chain conformation changes from a double helix in the anhydrate to a planar zigzag form in the three hydrates. The anhydrate melts at 60,C while the hydrates melt differently in the temperature region of 70,110,C. By means of the simultaneous WAXD/DSC measurements, complex DSC thermograms of PEI hydrates were characterized on the basis of X-ray diffractions obtained concurrently. [source]


Mechanical properties of natural fibers/polyamides composites

POLYMER COMPOSITES, Issue 3 2009
Patricia Alvarez de Arcaya
The aim of this investigation has been to use high performance thermoplastic matrices such as polyamides instead of the commonly used polyolefins to develop natural fiber composites for substituting glass fibers without renouncing to their mechanical properties. For this purpose, different natural fibers such as flax, jute, pure cellulose, and wood pulps have been melt compounded with different polyamides to analyze the effect of fiber content on mechanical properties. Fibers have not been treated as polyamides are less hydrophobic than polyolefins. Thermal behavior of the different fibers was determined by thermogravimetry to know the boundary for processing at high temperatures, since the melting points of the polyamides are much higher than those of polyolefins and this could lead to a higher degradation of the natural fibers. Rheological parameters were deduced by measuring torque values during the mixing process. Flexural and tensile modulus and strength of composites were analyzed, finding an increase in the mechanical properties compared with the unreinforced matrix that turns natural fibers into a considerable reinforcement offering a wealth of possibilities for industrial applications. POLYM. COMPOS., 2009. 2008 Society of Plastics Engineers [source]


Synthesis of biodegradable polyhydroxyalcanoate copolymer from a renewable source by alternate feeding

POLYMER ENGINEERING & SCIENCE, Issue 10 2008
Silvia M.F. Pereira
Polyhydroxyalcanoates copolymers with 3-hydroxybutirate (3HB) and 3-hydroxyvalerate (3HV) co-monomers, P3(HB-co-x%HV), were produced in fed-batch culture by Ralstonia eutropha DSM428 using fructose as a single carbon source in the first step and adding propionic acid in the second step by alternating feeding. Polymer yield was 0.18 g/L with a content of 24 mol% of the 3HV fraction determined by 1H NMR. NMR measurements indicated that the polymer obtained is isotactic. The copolymer attained 35% of crystallinity according to X-ray diffraction measurements, and two (020) planes were observed. Thermal behavior presented melting temperature at 154C and the crystallization temperature was 65C. A glass transition temperature was observed at ,10C. Average molecular weight measured by GPC was 4.9 105 Dalton. Isothermal radial growth rates of spherulites of P3(HB-co-24%HV) were studied. All experimental facts and the analysis of the sequence distribution of diads and triads of 3HB and 3HV units led to the conclusion that it is not a completely statistical random copolymer once it contains different types of segments. POLYM. ENG. SCI., 2008. 2008 Society of Plastics Engineers. [source]


Thermal behavior and flame retardancy of flexible poly(vinyl chloride) treated with Al(OH)3 and ZnO

POLYMER INTERNATIONAL, Issue 11 2005
Hongqiang Qu
Abstract Al(OH)3 as flame retardant and smoke suppressant for flexible poly(vinyl chloride) was evaluated alone and with ZnO, using thermal analytical techniques, limiting oxygen index and smoke density rating tests. The thermal behavior and flammability of the samples treated with Al(OH)3 and ZnO were studied by differential thermal analysis and thermogravimetric analysis. The activation energy was calculated by using the Vyazovkin model-free kinetic and Kissinger methods. The results showed that the flame-retardant and smoke-suppressant properties of the samples treated with Al(OH)3 and ZnO were related to the content of ZnO and the thermal effect during the process of thermal degradation of the samples. Copyright 2005 Society of Chemical Industry [source]