Evaluation of thermal behavior of latex membranes from genetically improved rubber tree (Hevea brasiliensis)

Thermal stability, thermal decomposition process, residual mass, temperature of glass transition (T_g) and temperature dependence of storage modulus (E’), were determined for latex membranes prepared from six clones of Hevea brasiliensis: IAC 331, IAC 332, IAC 333 and IAC 334 grown at experimental plantations of Instituto Agronômico de Campinas (IAC) in Votuporanga, São Paulo State, Brazil. Latex membranes from GT1 and RRIM 600 Asian matrix clones were used as references. The thermal behavior of latex membranes from genetically improved rubber trees was characterized using thermogravimetry/derivative thermogravimetry (TG/DTG), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The thermal behavior of latex from clones studied in the present work showed similar features of the clones previously reported (IAC 40, IAC 300, IAC 301, IAC 328, IAC 329 and IAC 330), with mass loss in four consecutive steps, except IAC 333, which showed an additional mass loss step.     

Oxidation of Metal Sulphides and Determination of Characteristic Temperatures by DTA and TG

The oxidation of metal sulphides and sulphide concentrates was studied by means of DTA, TG and DTG curves. The behaviour of ZnS, CdS, GaS, Tl₂S, Sb₂S₃ and Sb₂S₅ during thermal treatment in an oxidizing medium was investigated. The properties of these sulphides were compared and conclusions were drawn about their probable oxidation reactions and the kind of end-products obtained. The characteristic temperatures of the studied sulphides were determined on the basis of curves (DTA). The values obtained were used to compare the behaviour of the sulphides during the oxidation process in a fluid bed. The results can be used to improve the technological and economic indices in the industrial production of zinc. This revised version was published online in July 2006 with corrections to the Cover Date.     

Forest fire retardancy evaluation of carbonate minerals using DTG and LOI

Two methods were employed for measuring fire retardancy of minerals hydromagnesite, huntite and natural hydromagnesite/huntite mixtures, on forest species. The first was based on DTG under N₂ atmosphere, to isolate pyrolysis of forest species and the second on LOI for combustion measurements. The selected forest species: Pinus halepensis Mill. and Cistus incanus L., were collected from a WUI zone and were treated with 5, 10, 15 and 20 mass/mass% of minerals. Regarding DTG analysis, the minerals decrease pyrolysis rate and increase mass residue of forest species. Regarding LOI tests, minerals increase pilot ignitability of forest fuels. Hydromagnesite exhibits the best overall performance.     

高岭石/聚丙烯酰胺插层复合物的制备与表征

The kaolinite-polyacrylamide intercalation compound was prepared first by the displacement reaction of the kaolinite-formamide intercalation precursor with 30% acrylamide ethanol solution, and then the polymerization under 140℃ for 15h with the catalysis of dibenzoyl peroxide. The XRD analyses showed that the basal spacings of kaolinite-acrylamide intercalation compound and kaolinite-polyacrylamide compound were 1.135nm and 1.144nm respectively. The kaolinite-polyacrylamide compound was able to resist to 30-min washing with water, but the kaolinite-acrylamide compound was unstable during washing. FT-IR proved that the hydrogen bonds were formed between kaolinite Si-O group and polyacrylamide NH group and between kaolinite inner surface hydroxyl and polyacrylamide C=O group, and that parts of NH group keyed into the kaolinite ditrigonal hole. TG and DTG analysis proved that kaolinite-polyacrylamide was stable under 350℃. A net weight loss of 16.63% between 370℃～500℃ is due to the removal of intercalated polyacrylamide from the interlamellar space of kaolinite. These results clearly indicate that acrylamide has been intercalated into the layers of kaolinite and was polymerized in-situ.Based on the TG data, the formula of the kaolinite-polyacrylamide intercalation compound, Al₂Si₂O₅(OH)₄?CH₂CHCONH₂?_0.736, can be calculated.     

Thermal behavior of polystyrene synthesized in the presence of carboxymethyl cellulose

Summary Study of the decomposition kinetics is an important tool for the development of polymer recycling in industrial scale. In this work, parameters such as activation energy, frequency factor and reaction order, were measured under dynamic conditions. Flynn-Wall-Ozawa, Van Krevelen, Horowitz-Metzger, Coats-Redfern, Madhusudanan and Vyazovkin methods were used to determine the kinetic parameters. The analysis of the results obtained by the Coats-Redfern method shows that the thermal degradation process of LDPE and HDPE corresponds to a phase boundary controlled reaction (mechanism R2). This method shows that the reaction order values of LDPE and HDPE are about 0.7 and 0.6, respectively.     

The applicability of DTG to polymerisation studies

The application of derivativ thermogravimetry (DTG) to investigate polymerisation mechanisms is illustrated using the radical polymerisation of di-n-alkyl itaconates as well as the photoinitiated polymerisation of methyl methacrylate by colloidal CdS. The thermal properties of the resulting polymers are described. The advantages and disadvantages of DTG are discussed.

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Zusammenfassung Die Anwendung von DTGA zur Untersuchung von Polymerisationsmechanismen wird anhand der radikalischen Polymerisation von Di-n-alkyl-itakonaten und der fotoinitiierten. Polymerisation von Methylmetacrylat mittels kolloidalem CdS dargestellt. Die thermischen Eigenschaften der erhaltenen Polymere werden beschrieben. Es werden Vor-und Nachteile von DTGA diskutiert.

     

Preparation and thermal reactivity of some rare earth and uranyl hydrazinesulfinates and sulfite hydrazinates

Hydrazinesulfinate and sulfite hydrazinate derivatives of rare earth elements of composition Ln(N₂H₃SOO)₃(H₂O) and Ln₂(SO₃)₃(N₂H₄)_x(H₂O)_y, respectively, where Ln=La, Ce, Pr, Nd and Sm, have been prepared and characterized by chemical analysis and infrared spectra. The uranyl complexes of the composition UO₂(N₂H₃SOO)₂, UO₂(N₂H₃SOO)₂(N₂H₄) and UO₂SO₃(N₂H₄)(H₂O) have also been prepared under different reaction conditions and studied by different physicochemical techniques. Thermal properties of all these complexes have been studied by thermogravimetry, and differential scanning calorimetry. The hydrazinesulfinate derivatives of rare earth elements undergo thermal decomposition in multisteps to give the respective metal sulfate as the residue. The other series of complexes, viz., rare earth sulfite hydrazinates gave a mixture of metal sulfate and metal oxide as the end products. However, all the uranyl complexes undergo decomposition in air to give UO₂SO₃ as the final product.     

Thermal properties,induction period,interfacial energy and nucleation parameters of solution grown benzophenone

The kinetic parameters (reaction order, n, activation energy, E, pre-exponential factor, A, constant rate, k) for the dehydration step due to elimination of osmotic water and hydrogen-bounded water with the carboxylic groups, and for the anhydrifying step owing to the dehydration of two neighboring (-COOH) groups, were determined under non-isothermal conditions for some carboxylic resins with acrylic-divinylbenzene (DVB) matrix. The kinetic parameters were evaluated by means of isoconversional methods from (TG/DTG) thermal analysis data. The results show a dependence of the apparent kinetic parameters on the cross-linking degree, granulation, gel/macroporous matrix nature, exchange capacity and heating rate.     

Crystal Structures and Characterizations of Bis（1-benzoyl-methyl-benzotriazole-N^3）dichoro Metal（Ⅱ） Complex： [MCl2（C6H4N3CH2COPh）2] [M=Zn（Ⅱ），Co（Ⅱ）]

The structures of [MCl₂(C₆H₄B₃CH₂COPh)₂] [M=Zn(II) (1), Co(II) (2)] have been determined by X‐ray crystallography. They were characterized by elemental analysis, IR spectrum, electronic spectrum and thermogravimetric‐differential thermal analysis. They all crystallize in the triclinic system, space pup Pi, with lattice parameters a=0.9449(2) nm, b=1.1291(2) nm, c=1.3637(3) nm, α=111.70(3)°, β= 94.33(3)°, y=90.97(3), Z=2 for compound 1; a=0.9437(2) nm, b= 1.1277(2) nm, c= 1.3650(3) nm, a=111.76(3)°, β=94.50(3)°, y=90.80(3)°, Z=2 for compound 2. The metal ions are all coordinated by two C1^?‐ anions and two nitrogen atoms of 1‐benzoylmethyl‐bentriazole ligands. forming the distorted tetrahedral geometry. The Zn—Cl and Zn—N bond lengths are 0.2209(2), 0.2210(2) nm and 0.2059(4), 0.2067(4) nm. respectively. The CO‐Cl 3 and Co–N bond lengths are 0.2215(2). 0.2222(2) nm and 0.2028(5), 0.2045(5) nm. respectively. The thermogravimetric (TG) data indicate that they are nearly similar in TG curve, and there are not structural transitions in the two compounds. They all have a high thd stability. But, there is little difference in DTG (differential thermogravimetric) curves of those two compounds. Elemental analysis, electronic and IR spectra are in agreement with the structural data.     

Thermal degradation of wood treated with flame retardants

Wood, one of the most flammable materials, was treated with various compounds containing nitrogen, phosphorus, halogens, and boron. For a study of flame retardance from the standpoint of thermal degradation, the samples were subjected to thermogravimetry (TG), differential thermal analysis (DTA) and differential thermogravimetry (DTG) in nitrogen to determine if there were any characteristic correlations between thermal degradation behaviors and the level of flame retardance. From the resulting data, kinetic parameters for different stages of thermal degradation are obtained using the method of Broido. The energies of activation for the decomposition of samples are found to be from 72 to 109 kJ mol^–1. For wood and modified wood, the char yields are found to increase from 10.2 to 30.2%, LOI from 18 to 36.5, which indicates that the flame retardance of wood treated with compounds is improved. The flame retardant mechanism of different compounds has also been proposed.