Study of phenolic resin/EVA blends by thermal analysis

The properties of polymeric blends originate from the synergistic association of their components. In this investigation, phenolic resins obtained by the reaction of cashew-nut shell liquid (CNSL) and aldehyde are used in several applications. Mixtures of CNSL with industrial reject ethylene-co-vinyl acetate (EVA reject) were prepared with an EVA reject content up to 70%. The thermal compatibility and stability were evaluated by means of thermogravimetry (TG), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC). For blends containing a high percentage of EVA reject, the TG curves clearly show two decomposition stages, one at 350C and the other at 450C (onset 467C). The DIG curves of the blend containing 70% CNSL exhibit decomposition at 240C. The DSC curves show that the samples containing a high percentage of EVA reject are incompatible, withT _g values around –30C.The authors would like to thank PETROBRAS/CENPES/DIQUIM for the NMR facilities and thermal measurements.     

Identification of some sweetening agents by thermal analysis

The thermal behaviours of some artificial sweetening agents — sodium cyclamate, saccharine and sorbitol — were studied by means of a complex thermal method. The quite different thermal behaviours of the different sweeteners are utilized for their identification. An endothermic peak is seen in the DTA curve at about 386° and 94° for saccharine and sorbitol, respectively, which is not accompanied by a weight loss. In the case of sodium cyclamate a characteristic exothermic peak followed by an endothermic one is detected. A semiquantitative method for the determination of sodium cyclamate is described.     

Thermal degradation of polycarbonate-poly(methyl methacrylate) blends by thermal volatilisation analysis

The degradation of bisphenol A polycarbonate (PC), poly(methyl methacrylate) (PMMA) and a 1:1 by weight blend of PC and PMMA have been studied by thermogravimetry, thermal volatilisation analysis and differential scanning calorimetry. Volatile products have been investigated and separated by subambient TVA and characterised spectroscopically. In the degradation of the blend, no change is observed in the nature of the volatile products of degradation, but the rate of degradation of the PC component is increased and the PMMA depolymerisation is retarded. It is suggested that PMMA radicals attack PC macromolecules leading to chain scission in the PC at lower temperatures than required for homolysis in pure PC. This unusual form of interaction involving a macroradical and a macromolecule is made possible by the homogeneous character of the molten blend.     

TMDSC analysis of single-site copolymer blends after thermal fractionation

Temperature-modulated differential scanning calorimetry (TMDSC) has been used to study the melting of a series of blends containing linear low-density polyethylene (LLDPE) and very low-density polyethylenes (VLDPE) with long chain branches. After the blends were subjected to different thermal histories including thermal fractionation by stepwise isothermal cooling, they were examined by TMDSC. TMDSC curves have been interpreted in terms of a combination of the reversing and non-reversing specific heats that result from reversible and irreversible events at the time and temperature, which they are detected, respectively. It was found that crystals formed at different crystallisation conditions had different internal order; hence they showed different amounts of reversing and non-reversing contributions. There is no exothermic activity seen in the non-reversing signal for the thermally fractionated polymers and their blends suggesting formation of crystals approaching equilibrium. In contrast, polymers and blends cooled at 10°C min^-1 cooling rate showed large exothermic contributions corresponding to irreversible effects. In addition, a true reversible melting contribution is also detected for both fast-cooled and thermally-fractionated samples during the quasi-isothermal measurements. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dynamic mechanical thermal analysis of polyamide 6/thermoplastic polyurethane blends

Blends obtained from polyamide 6 and polyester or polyether polyurethanes were investigated by means of DMTA. The blends were prepared by compounding in a twin-screw Brabender —Plasticorder. Changes in composition did not influence the glass temperature of the amorphous fraction of the polyamide, but also no distinct transition for separated polyurethane soft segment was visible. Therefore the blends seem to be multiphase systems, where the elastomeric polyurethane phase is dispersed in a continuous polyamide phase. From changes in the β relaxation region of the polyamide better miscibility of polyester polyurethanes comparing to polyether polyurethanes was explained by hydrogen bonding in the common amorphous phase.     

Phase morphology development in PP/PA6 blends induced by a maleated thermoplastic elastomer

The effects of maleated thermoplastic elastomer (TPEg) on morphological development of polypropylene (PP)/polyamide 6 (PA6) blends with a fixed PA6 content (30 wt %) were investigated. For purpose of comparison, nonmaleated thermoplastic elastomer (TPE) was also added to the above binary blends. A comparative study of FTIR spectroscopy in above both ternary blends confirmed the formation of in situ graft copolymer in the PP/PA6/TPEg blend. Dynamic mechanical analysis (DMA) indicated that un‐like TPE, the incorporation of TPEg remarkably affected both intensity and position of loss peaks of blend components. Scanning electron microscopy (SEM) demonstrated that PP/PA6/TPE blends still exhibited poor interfacial adhesion between the dispersed phase and matrix. However, the use of TPEg induced a finer dispersion and promoted interfacial adhesion. Transmission electron microscopy (TEM) for PP/PA6/TPEg blends showed that a core‐shell structure consisting of PA6 particles encapsulated by an interlayer was formed in PP matrix. With the concentration of TPEg increasing, the dispersed core‐shell particles morphology was found to transform from discrete acorn‐type particles to agglomerate with increasing degree of encapsulation. The modified Harkin's equation was applied to illustrate the evolution of morphology with TPEg concentration. “Droplet‐sandwiched experiments” further confirmed the encapsulation morphology in PP/PA6/TPEg blends. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1050–1061, 2006     

Modification of morphology of polycarbonate/thermoplastic elastomer blends by supercritical CO2

The effect of supercritical CO₂ on the morphological features of blends of polycarbonate and a commercial thermoplastic elastomer was investigated. The as-prepared films of the blend showed phase separated domains of the elastomer. With the combination of pressure and temperature, the large domains were “burst” into smaller domains. Temperatures higher than the critical temperature are required to cause any change in the morphology. The size distribution of the elastomer domains is effectively narrowed by the supercritical CO₂ treatment. The time of exposure also plays a role. It was also seen that above 60 °C, crystallization of polycarbonate begins. Based on the previous work on this system, it is proposed that enhancement of elongation, Young’s modulus and abrasion resistance would occur due to the reduction in the domain size and distribution.     

Brittle–ductile transition in the PETG/PC blends by adding PTW elastomer

In this paper, an elastomer containing epoxy groups, ethylene‐butylacrylate‐glycidylmethacrylate (PTW), was used as toughening modifier for the poly(ethylene glycol‐co‐cyclohexane‐1,4‐dimethanol terephthalate) (PETG)/polycarbonate (PC) blends. A remarkable improvement of toughness was achieved by addition of only 5 wt% PTW. In particular, an obvious brittle–ductile (B–D) transition in impact toughness was found when the PTW content increased from 3 to 5 wt%. The toughening mechanism and observed B–D transition have been explored in detail, combining with electronic microscopy observation, melt rheological investigation and dynamic mechanical analysis (DMA). It is suggested that the B–D transition can be attributed to a better interfacial adhesion between different phases, and importantly, to a continuum percolation dispersed‐phases network formed at appropriate PTW content, in which PC particles are connected with each other by PTW phase. Our present study offers new, profound insight on the toughening mechanism for the elastomer modified amorphous/amorphous plastic blends. Copyright © 2009 John Wiley & Sons, Ltd.     

Thermoplastic elastomer based on high‐density polyethylene/natural rubber blends: rheological,thermal, and morphological properties

Thermoplastic elastomer (TPE) comprising air‐dried sheet or natural rubber (ADS or NR) and high‐density polyethylene (HDPE) was prepared by a simple blending technique. NR and HDPE were mixed with each type of phenolic compatibilizer (HRJ‐10518 or SP‐1045) or liquid natural rubber (LNR) at 180°C in an internal mixer. The mixing torque, shear stress, and shear viscosity of the blends increased with increasing amounts of NR. Positive deviation blend (PDB) for the blends containing active hydroxyl methyl phenolic resin in HRJ‐10518 or dimethyl phenolic resin in SP‐1045 was obtained. PDB was not observed for the blends without the compatibilizers or with LNR. The blends with HRJ‐10518 or SP‐1045 were compatible or partially compatible while the LNR blends were incompatible. In the phenolic compatibilized blends, NR dispersed in the HDPE matrix was found in the NR/HDPE blends of 20/80, 40/60, and 50/50 ratios. HDPE dispersed in NR matrix was obtained in the NR/HDPE blend of 80/20 ratio, and the co‐continuous phase was accomplished in the NR/HDPE blend of 60/40 ratio. The NR/HDPE blend at 60/40 ratio compatibilized with HRJ‐10518 and fabricated by a simple plastic injection molding machine exhibited higher ultimate tensile strength and elongation at break (EB). Incorporation of parafinic oil caused a decreasing tendency in tensile strength with increases in EB. The TPNRs exhibited high elastomeric nature with low‐tension set. Copyright © 2007 John Wiley & Sons, Ltd.     

Investigating poly-(vinyl-chloride)-polyethylene blends by thermal methods

Poly-vinyl-chloride (PVC)-polyethylene (PE) alloys were prepared by melt blending using both low- and high-density polyethylene without applying a compatibilizer. The PVC and the PE are incompatible polymers; in spite of this fact stable microheterogeneous materials were obtained. Mechanical methods e.g. tensile tests generally (measured in the usual concentration range) do not support any compatibility. At higher concentrations, the incompatible parts mask the effect of molecular mixing, easily detected at low PE contents. Dynamic mechanical (DMA), differential scanning calorimetric tests were carried out. Glass transition temperatures were determined by both methods. DMA tests were made at four frequencies, and the energy of activation of PVC main transition was also calculated. The decrease of glass-transition temperatures and energy of activation show that there is a slight mixing of the polymers. Specimens were also investigated by infrared method. From the results of IR spectra, grafting reaction of PE can be assumed onto the PVC because of its dehydrochlorination.     

Morphology and properties of ternary polyamide 6/polyamide 66/elastomer blends

The aim of the work presented is to evaluate the mechanisms and phase interactions in ternary blends based on different polyamides and functionalised elastomers, and to establish a correlation between the morphology controlled by the specific binary interactions, and physical and technological properties, respectively. The properties of the ternary system polyamide 6/polyamide 66/ elastomer depend on the specific blend morphology which is determined mainly by the differences of the surface tension of the components. A phase‐in‐phase structure was observed by microscopic study (AFM) in the ternary polyamide 6/polyamide 66/elastomer blends with maleic anhydride grafted ethene‐octene copolymer, and a “quasi” phase‐in‐phase structure in blends with maleic anhydride grafted ethene‐propene‐diene copolymer as the elastomer phase. An incorporation of polyamide inside of the elastomer particles was observed in the first case due to the difunctionality of polyamide 66. This type of morphology causes an increased elongation at break and toughness of these blends. In comparison to the binary polyamide based blends the ternary blends show an increased elastic modulus, elongation at break and yield stress as well as a high impact strength at low temperatures up to ?20 °C. Copyright © 2003 John Wiley & Sons, Ltd.     

Hydrogen bond effect of azido polyurethane elastomer by dynamic mechanical analysis

Hydrogen bond effects in azido polyurethane elastomers (APUE) have been studied by dynamic mechanical analysis (DMA) and the results show that the hydrogen bond effect has stronger temperature dependence. The activation energy of hydrogen bond dissociation (E_a) and the hydrogen bond density (vs/V) have been evaluated from the elastic modulus–temperature relationship. The calculated E_a in this work is much higher than the reported values of normal polyurethane elastomer (PUE). The values of E_a are 81.3, 68.1, 53.3, and 42.3 kJ/mol at 150, 110, 50, and 20 Hz, respectively, for PUE‐1 (CPPB/HDI trimer elastomer); 94.6, 75.8, 48.4, and 36.9 kJ/mol at 150, 110, 50, and 20 Hz, respectively, for PUE‐2 (APPB/HDI trimer elastomer); 82.1, 74.4, 59.8, and 46.5 kJ/mol at 150, 110, 50, and 20 Hz, respectively, for PUE‐3 (APPB/HDI trimer/EG elastomer); 145, 124, 88.0, and 75.5 kJ/mol at 150, 110, 50, and 20 Hz, respectively, for PUE‐4 (APPB/HDI trimer/BD elastomer); and 72.2, 64.3, 49.8, and 39.9 KJ/mol at 150, 110, 50, and 20 Hz, respectively, for PUE‐5 (APPB/HDI trimer/HD elastomer). The DMA estimations are semiquantitative for it ignores other physical crosslinking effects and the results give relative order of vs/V and E_a. The values of vs/V of crosslinked APUE (PUE‐3, PUE‐4, and PUE‐5) are much higher than PUE‐2. The test frequency could affect the values of vs/V and higher frequency would minify the difference of the values of vs/V for two given temperatures. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2841–2851, 2006     

Benzoxazine-bismaleimide blends: Curing and thermal properties

A blend of bisphenol A based benzoxazine (Bz-A) and a bismaleimide (2,2-bis[4(4-maleimidophenoxy) phenyl] propane (BMI), was thermally polymerised in varying proportions and their cure and thermal characteristics were investigated. The differential scanning calorimetric analysis, supplemented by rheology confirmed a lowering of the cure temperature of BMI in the blend implying catalysis of the maleimide polymerisation by benzoxazine. FTIR studies provided evidences for the H-bonding between carbonyl group of BMI and -OH group of polybenzoxazine in the cured matrix. The cured matrix manifested a dual phase behaviour in SEM and DMTA with the minor phase constituted by polybenzoxazine dispersed in an interpenetrating polymer network (IPN) of polybenzoxazine and cured BMI. The IPN possessed improved thermal stability over the constituent polybenzoxazine. A benzoxazine monomer possessing allyl functional groups, 2,2′-bis(8-allyl-3-phenyl-3,4-dihydro-2H-1,3-benzoxazinyl) propane (Bz-allyl) was reactively blended with the same bismaleimide in varying stoichiometric ratios (Bz-allyl/BMI), where the curing involved mainly Alder-ene reaction between allyl- and maleimides groups and ring-opening polymerisation of benzoxazine. The rheological analysis showed the absence of catalytic polymerisation of BMI in this case. The overall processing temperature was lowered in the blend owing to the co-reaction of the two systems to form a single-phase matrix. The cured resins of both Bz-A/BMI and Bz-allyl/BMI blends exhibited better thermal stability than the respective polybenzoxazines. The T_g of the IPN was significantly improved over that of polybenzoxazine (Bz-A). However, the co-reaction resulted in a marginal decrease in the T_g of the system in comparison to the polybenzoxazine (Bz-allyl).     

Specifics of the structure and mechanical properties of blends of isotactic polypropylene with ethylene-propylene-diene elastomer

The structure of unvulcanized and dynamically vulcanized blends of isotactic PP with ethylene-propylene-diene terpolymer (EPDM) having an EPDM content of 5–85 wt % was studied by means of atomic force microscopy. The systems based on the virgin elastomer and the elastomer plasticized with 50% oligomer were examined. During thermal treatment (molding), the structure of the unvulcanized materials undergoes substantial changes. The morphology of dynamically vulcanized blends containing up to 75 wt % rubber is characterized by a homogeneous distribution of crosslinked rubber particles with a particle size of less than 2 μm in the continuous thermoplastic matrix. During PP blending with the plasticized elastomer, the oligomer diffuses into the thermoplastic phase, with the oligomer being distributed evenly between the blend components. As a result, the stress-strain characteristics of the plasticized systems decline relative to those of the oligomer-free materials. A comparative analysis of the dependence of the elastic modulus on the composition of the blends with the theoretical values obtained in terms of the Kerner, Uemura-Takayanagi, Davies, and Coran-Patel models was performed.     

Reaction kinetics by thermal analysis

The application of thermal analysis in the study of reaction kinetics and reaction mechanisms in combination with presently available powerful analytical tools, in the sphere of materials with particular reference to high energy materials is presented and discussed. Also an attempt has been made to correlate the kinetic data obtained by TA with the performance characteristics, for some important materials.

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Zusammenfassung Es wird die Anwendung der Thermoanalyse bei der Untersuchung der Reaktionskinetik und des Reaktionsmechanismus in Zusammenwirkung mit den gegenwärtig zur Verfügung stehenden leistungsfähigen analytischen Werkzeugen auf dem Gebiet von Materialien mit speziellem Bezug auf energiereiche Stoffe dargestellt Und besprochen. Es wurde auch versucht, die durch TA erhaltenen kinetischen Daten einiger wichtiger Stoffe mit deren Leistungskenndaten in Beziehung zu stellen.

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Study of soils by thermal analysis

The study of soils is very important in the geological and geological engineering researches. A study of ten samples of soils was carried out by thermal analysis, and X-Ray Fluorescence Spectrometry to understand soil evolution in Angra dos Reis region, Rio de Janeiro State, Brazil. The sample collection sites were chosen based on geological characteristics, the soil layer thickness, the soil composition pattern, and whether or not it was moved either by erosion or by gravitational shifts. Because of the humid tropical climatic condition, natural soils tend to show great thickness of weathered mantles with formation of saprolites and saprolite soils. Kaolinite is an important secondary mineral which can be formed from many different minerals, like k-mica and k-feldspar and can be weathered to gibbsite. The results from TG/DTG and DTA indicated which soils had more weathering, and the same results were obtained by XRF, when silica/aluminum ratios from samples are compared with thermal analysis results.     

Identification of nitride inclusions in steel using differential thermal analysis and evolved gas analysis

A preliminary study has been made of the feasibility of applying differential thermal analysis/evolved gas analysis (DTA/EGA) to the identification and estimation of nitrides in residues extracted from iron base alloys. A set of commercially available nitride powders have also been examined.The results showed that EGA traces are more informative than the DTA observations and, additionally, provide an estimate of the total nitrogen present. Residues from steels often contain elemental carbon and this complicates the interpretation of the DTA and EGA traces. It is generally concluded that the DTA/EGA technique is useful in identifying nitrides but should be ancilliary to other techniques such as X-ray diffraction.

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Zusammenfassung Eine Vorstudie wurde durchgeführt um die Einsatzmöglichkeit der Differentialthermoanalyse/Emittierte Gasanalyse (DTA/EGA) zur Identifizierung und Abschätzung der Nitride in aus Eisenbasenlegierungen extrahierten Rückständen zu prüfen. Eine Reihe handelsüblicher Nitridpulver wurde ebenfalls untersucht.Die Ergebnisse zeigten, daß EGA-Spuren informativer sind als die DTA-Beobachtungen und überdies eine Schätzung des Gesamtstickstoffgehaltes gestatten. Rückstände aus Stählen enthalten oft Kohlstoff und dies erschwert die Deutung der DTA- und EGA-Spuren. Im Allgemeinen kann gefolgert werden, daß die DTA/EGA-Technik bei der Identifizierung von Nitriden nützlich ist, doch nur als Ergänzung anderer Techniken, wie z. B. die Röntgendiffraktion, eingesetzt werden sollte.

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Résumé On a effectué une étude préliminaire pour rechercher si l'emploi conjugué de l'analyse thermique différentielle et de l'analyse des gaz émis (ATD/AGE) pouvait servir à l'identification et à l'estimation de la teneur des nitrures présents dans les résidus d'extraction des alliages à base fer. On a également examiné une série de nitrures en poudre disponibles commercialement.Les résultats ont montré que les enregistrements d'AGE fournissent davantage de renseignements que les courbes ATD car ils donnent en plus la valeur de l'azote total présent. Les résidus d'extraction des aciers contiennent souvent du carbone élémentaire, ce qui complique l'interprétation des enregistrements d'ATD et d'AGE. L'étude permet de conclure qu'en général la technique d'ATD/AGE est utile pour identifier les nitrures, mais qu'elle devrait être utilisée comme méthode auxiliaire vis-à-vis d'autres techniques, par ex. la diffraction des rayons X.

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The authors would like to express their thanks to the Directors of the British Steel Corporation, Tubes Division for permission to publish this paper.     

Thermoplastic elastomer based on epoxidized natural rubber/thermoplastic polyurethane blends: influence of blending technique

Epoxidized natural rubber (ENR) and thermoplastic polyurethane (TPU) blends were prepared by simple blend and dynamic vulcanization. The main objective was to prepare a low‐hardness TPU material with good damping and elastic and mechanical properties. It was found that the incorporation of ENR into the blend shows a reduction in Young's modulus, hardness (i.e. <70 Shore A), damping properties (i.e. tan δ < 0.3), and tension set (i.e. <20%) compared with the pure TPU. This indicates the formation of softer TPU materials with superior damping and elastomeric properties. However, incorporation of ENR sacrificed mechanical properties in terms of tensile strength and elongation at break, but these still remain in the range of applicability for industrial uses. It was also found that dynamic vulcanization caused enhancement of mechanical properties, relaxation, damping, rheological properties, and elasticity of the blends. Temperature scanning stress relaxation measurements revealed an improvement in stress relaxation properties and thermal resistance of the dynamically cured ENR/TPU blend. Copyright © 2011 John Wiley & Sons, Ltd.     

Thermorheological analysis of PVC blends

The effect of temperature on dynamic viscoelastic measurements of miscible poly (vinyl chloride) (PVC)/ethylene‐vinyl acetate–carbon monoxide terpolymer (EVA‐CO) and immiscible PVC/high‐density polyethylene (HDPE) and PVC/chlorinated polyethylene (CPE) molten blends is discussed. PVC plasticized with di(2 ethyl hexyl) phthalate (PVC/DOP) and CaCO₃ filled HDPE (HDPE/CaCO₃) are also considered for comparison purposes. Thermorheological complexity is analyzed using two time–temperature superposition methods: double logarithmic plots of storage modulus, G′, vs. loss modulus, G″, and loss tangent, tan δ, vs. complex modulus, G*, plots. Both methods reveal that miscible PVC/EVA‐CO and PVC/DOP systems are thermorheologically complex, which is explained by the capacity of PVC to form microdomains or crystallites during mixing and following cooling of the blends. For immiscible PVC/HDPE and PVC/CPE blends the results of log G′ vs. log G″ show temperature independence. However, when tan δ vs. log G* plots are used, the immiscible blends are shown to be thermorheologically complex, indicating that the morphology observed by microscopy and constitued by a PVC phase dispersed in a HDPE or CPE matrix, is reflected by this rheological technique. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 469–477, 2000