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Abstract  

The influence of chemical modification of unsaturated polyesters on viscoelastic properties and thermal behavior of styrene copolymers has been investigated by DMA and TG analyses. Chemical modification of unsaturated polyesters obtained in polycondensation of cyclohex-4-ene-1,2-dicarboxylic anhydride (THPA), maleic anhydride (MA) and suitable glycol: diethylene glycol (DEG) or triethylene glycol (TEG) was performed using 38–40% peracetic acid. It allowed to selective and successful oxidation of carbon-carbon double bonds in unsaturated polyesters giving modified unsaturated polyesters/unsaturated epoxypolyesters/containing both carbon-carbon double bonds in polyester chain and new functional groups-epoxy groups in cycloaliphatic rings. Both unsaturated polyesters and unsaturated epoxypolyesters were used as a component of styrene copolymers cured with different hardeners. It has been demonstrated that the use of modified unsaturated polyesters as a component of styrene copolymers allowed obtaining more stiffness and more cross-linked network structure compared to styrene copolymers based on unmodified polyesters. The higher values of storage modulus, glass transition temperatures and better thermal stability for styrene copolymers based on unsaturated epoxypolyesters were obtained.

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Abstract  

A new type of toughened epoxy polymer based on epoxy cresol novolac resin (ECN) and carboxy terminated polybutadiene (CTPB) liquid functional rubber has been studied. ECN has been synthesized in the laboratory and CTPB used was also of indigenised origin. Rubber modified epoxies were characterized with the help of differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM) techniques.

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Journal of Thermal Analysis and Calorimetry
Authors: Gy. Marosi, P. Anna, Gy. Bertalan, A. Tohl, R. Lágner, I. Balogh, and I. Papp

Different levels of fibre technologies and application, from synthesis to degradation has been studied using the methods of thermal analysis. Recent results of these studies on synthetic and natural fibres are summarized. The effect of chemical and physical modification of polyolefin fibres as well as the synthesis of polymer emulsion used as additive in fibre technologies could be followed by DSC, DMA, TG methods.

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Abstract  

In order to expand the industrial usefulness of an isothermal time-temperature-transformation (TTT) cure diagram, a method to make it applicable to a solid-state sample involving only resins and a catalyst was studied by using dynamic DSC (DDSC) and cone plate dynamic mechanical analysis (DMA). To estimate how much curing occurred for an industrially used epoxy resin molding compound manufactured in a production process was also studied, together with its position in the TTT cure diagram. The TTT cure diagram proved to be useful for determining the differences between compounds without their dissolution in a solvent, and for estimating their heat history during the production process.

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Abstract  

Fibers drawn form poly[2,2'-(m-phenylene)-5,5'-bibenzimidazole] (PBI) were studied by DSC and DMA. PBI is a high temperature polymer T g is between 387 and450C depending on the measurement technique used. The as-spun fiber is free of orientation. The oriented fiber exhibits considerable dependence on whether the DSC measurements were carried out in free-to-shrink or fixed-length modes. The β-relaxation is at 290C, and was associated with loss of water. The γ-transition at 20C was not identified, while theδ-transition at –90C seems to correspond to rotation of the m-phenylene ring.

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Abstract  

Differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and dynamic mechanical analysis (DMA) of the blends ofepoxy cresol novolac (ECN) resin toughened with liquid carboxy terminated butadiene-co-acrylonitrile (CTBN) rubber have been carried out. Exothermal heat of reaction (ΔH) due to crosslinking of the resin in presence of diaminodiphenyl methane(DDM, as amine hardener) showed a decreasing trend with increasing rubber concentration. Enhancements of thermal stability as well as lower percentage mass loss of the epoxy-rubber blends with increasing rubber concentration have been observed in TG. Dynamic mechanical properties reflected a monotonic decrease in the storage modulus (E′) with increasing rubber content in the blends. The loss modulus (E″) and the loss tangent(tanδ) values, however, showed an increasing trend with rise of the temperature up to a maximum (peak) followed by a gradual fall in both cases. Addition of 10 mass% of CTBN resulted maximum E″ and tanδ.

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Abstract  

The power–time curves of micellar formation of two anionic surfactants, sodium laurate (SLA) and sodium dodecyl sulfate (SDS), in N,N-dimethyl acetamide (DMA) in the presence of various long-chain alcohols (1-heptanol, 1-octanol, 1-nonanol and 1-decanol) were measured by titration microcalorimetry at 298 K. The critical micelle concentrations (CMCs) of SLA and SDS under various conditions at 298 K were obtained based on the power–time curves. Thermodynamic parameters (
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,
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and
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) for micellar systems at 298 K were evaluated according to the power–time curves and the mass action model. The influences of the number of carbon-atom and the concentration of alcohol were investigated. Moreover, combined the thermodynamic parameters at 303, 308 and 313 K in our previous work and those of 298 K in the present work for SLA and SDS in DMA in the presence of long-chain alcohols, an enthalpy–entropy compensation effect was observed. The values of the enthalpy of micellization calculated by direct and indirect methods were made a comparison.
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Journal of Thermal Analysis and Calorimetry
Authors: G. Vázquez, F. López-Suevos, J. González-Alvarez, and G. Antorrena

Summary  

Phenol-urea-formaldehyde-tannin (PUFT) adhesives have been prepared by copolymerization at room temperature of pine bark tannins with phenol-urea-formaldehyde (PUF) prepolymers prepared under varying operating conditions. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) have been used to analyse the curing of prepolymers and adhesives. DSC curves were obtained at three different heating rates and, by means of the Model Free Kinetics isoconversional method, chemical conversion vs. time at a given temperature was obtained. Mechanical conversion was calculated from DMA storage modulus data for those adhesives which gave the best results for plywood and MDF boards.

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Poly(2-methylpentamethylene terephthalamide) (Nylon M5T) is a new high temperature aromatic polyamide developed by Hoechst Celanese. In this paper thermal properties of Nylon M5T chips, as well as as-spun and drawn fibers were studied by DSC, DMA, hot stage microscopy and WAXS.T g of the fully amorphous Nylon M5T is 143°C when measured by DSC;T g increases with crystallinity to 151°C. The temperature dependence of the solid and melt specific heat capacities has also been determined. The heat capacity increase at the glass transition of the amorphous polymer is 103.9 J °C−1 mol−1.T g by DMA for the as-spun fiber is 155°C, for a drawn fiber is 180°C. Three secondary transitions were observed by DMA in addition to the glass transition. These correspond to a local mode relaxation of the methylene groups at −120°C, onset of rotation of the amide-groups at −65°C and the onset of the rotation of the phenylenegroups (at 63°C). The crystallinity of Nylon M5T strongly depends on the rate of cooling from the melt. The isothermal crystallization data are melt temperature dependent: two-dimensional crystallization takes place when the samples are crystallized from higher melt temperatures, and this phase changes into a spherulitic structure during cooling to room temperature. Spherulitic crystallization occurs when lower melt temperatures are used. This polymer has three crystal forms as indicated by DSC, DMA and WAXS data. The crystal to crystal transitions are clearly visible when amorphous samples are heated in the DSC, or the DMA curves of as-spun fibers are recorded. It is experimentally shown that a considerable melting of the lower temperature crystal forms takes place during the crystal to crystal transitions. The equilibrium melting point as measured by the Hoffman-Weeks method, has been determined to be 339°C.

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Abstract  

With the aid of thermal analysis, epoxy (EP) resins have been characterized from the curing of the components all the way to disposal. The methods employed for the investigations were DSC, TMA, DMA, TG and TG-QMS. The experimental results obtained will be used here to demonstrate the typical possibilities offered by these methods for characterization of an epoxy resin from cradle to grave.

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