DMA Methods Research Articles

Thermal behavior of DGEBA (Diglycidyl Ether of Bisphenol A) adhesives and its influence on the strength of joints

Adhesives, especially epoxies, are widely used as joints, repairs and corrosion protection in the petroleum onshore and offshore industry. Performance temperature is a key factor for such material. Mainly they are designed by the thermal properties but when they are in real service operation the behavior changes drastically. In this work, three different epoxy adhesives used in the offshore industry are characterized by DSC, DMA and TGA methods. The main objective is to verify if thermo mechanical tests on adhesives produces enough information to use in temperature service situation instead of test single lap joints (SLJ) at different temperatures. From the tests results it can be seen that adhesive SLJ should be tested in order to proper service design.

Formation of nano-plate silver particles in the presence of polyampholyte copolymer

Poly(2-(dimethylamino)ethyl methacrylate-co-acrylic acid) polyampholyte copolymers were synthesized by radical polymerization of the co-monomers in different molar ratios (2–1, 1–1 and 1–2). The water solutions of the obtained materials were used as stabilization agents for the synthesis of silver nanoparticles. XRD, FTIR and DMA methods were used to study the physical properties of the pure co-polymers. It was found that the copolymer is a completely amorphous and inhomogeneous material. The FTIR spectrum was analysed by using literature data and corresponding numerical simulations. TEM analysis showed that the shape of the nanoparticles prepared by reduction of the silver salt in the presence of co-polymers strongly depends on the ratio of DMAEMA and AA co-monomer units. Besides spherical Ag-nanoparticles, reduction in the presence of the polymer with equal molar content of co-monomers also resulted in the formation of nano-plate particles (circular thin plates and thin triangular nanoprisms). The formation of the nano-plate particles was further promoted by heating the mentioned solution at 60°C in air. UV–vis spectroscopy was used to study the change in the surface plasmon resonance behaviour during the growth of the nanoplates. The Ag-nanocomposite thin films of all three co-polymers showed fast antimicrobial activity against the Staphylococcus aureus, Escherichia coli and Candida albicans pathogens (more than 99% reduction after 2h of exposure).

Physical and Mechanical Properties of Rigid Polyurethane Faoms Modified with Selected Flame Retardants or Layered Silicates

The flame retardants: expandable graphite, decabromodiphenyloxid, triethylphosphate and nanofillers: natural montmoryllonite [MMT] – Nanofil®116, natural MMT modified with a quaternary ammonium salt - Cloisite®10A, synthetic layered silicate – Laponite®RD has been used in rigid polyurethane foams (PUFs). The influence of fillers amounts on processing parameters, physical–mechanical properties (compression strength, density, water absorption, brittleness, mass loss and volume change) and thermal properties (thermal stability and storage modulus in DMA methods) of such foams has been analysed. The morphology has been characterized by X-ray diffraction and scanning electron microscopy (SEM). The X-ray diffraction of the polyurethane nanocomposite foams has been indicated the partial exfoliation of the clay in the polyurethane matrix. The flame retardancy and the thermal stability of all polyurethane modified systems was improved by an addition of flame retardants or nanoclays. Best results, in comparison for pure polyurethane foam, was obtained for polyurethane modified with organically modified montmorillonite (Cloisite 10A).

Low amplitude, low frequency elastic measurements using Dynamic Mechanical Analyzer (DMA) spectroscopy

Abstract The applications of DMA methods for the investigation of the dynamical mechanical properties of materials are reviewed. Experimental details of this method are described including the combination of DMA with X-ray rocking curve measurements to investigate the details of the domain patterns. Emphasis is given to the effect of phase transitions, in particular in ferroelastic and co-elastic systems where the ‘easy’ movement of domain boundaries, twin walls and other interfaces lead to super-elastic softening of the material. Thermodynamic constraints, such as in the adiabatic-isothermal crossover are discussed. Smooth, ballistic propagation of domain walls are contrasted with the jerky behaviour of interfaces when phase transitions of first order are investigated. It is shown that for the ballistic behaviour, momentum driven wall movements are common and that their representation in Cole-Cole plots leads to depressed semi-circles, similar to methods used in dielectric spectroscopy. In jerky elastic responses the energy dissipation follows power law dependences. Domain wall pinning and domain wall freezing is discussed in some detail.

Comparative study on the mechanical and thermal properties of two different modified PAN fibers and their Fe complexes

The polyacrylonitrile (PAN) fibers were modified with hydroxylamine and its mixture with hydrazine to prepared the amidoximated PAN fibers (denoted as AO-PAN) and mixing modified PAN fibers (denoted as M-PAN) respectively, and then both of which were reacted with Fe 3+ ions to form two modified PAN fiber–Fe complexes (denoted as Fe–AO-PAN for AO-PAN and Fe–M-PAN for M-PAN). Their mechanical properties were evaluated and compared with respect to the breaking strength and elongation at break in both dry and wet conditions, and two important effecting factors including weight gain rate of the PAN fiber after modification and Fe content remained in the PAN fiber were investigated. Besides, thermal behavior of the modified PAN fibers and their Fe complexes was also examined by DSC and DMA methods. The results indicated that higher weight gain rate imparts the reduced breaking strength to two modified PAN fibers, and which is found to be further lower in wet state. The mechanical properties of the modified PAN fibers-Fe complexes, especially Fe–AO-PAN varied with Fe content ( C Fe–PAN). Moreover, two critical C Fe–PAN values are observed to be 79.75 mg/g for Fe–AO-PAN and 28.35 mg/g for Fe–M-PAN, respectively, at which they show a minimum values of breaking strength and elongation at break. Also, Fe–AO-PAN is much higher than Fe–M-PAN in terms of the critical C Fe–PAN value, which is mainly attributed to the difference in molecular structure between them. Thermal behavior of the modified PAN fibers and their Fe complexes is also greatly affected by their modification methods.

Microstructure and properties of epoxy foams prepared by microwave

AbstractIn this article, epoxy foams comprised of diglycidyl ether of bisphenol‐A (DGEBA) based epoxy resin E31 and E51, polyamide resin, and water were prepared by microwave irradiation method. The structure and properties of epoxy foams were analyzed by FTIR, TGA, SEM, and DMA methods. The density and compressive performance of epoxy foams was also determined. The results indicated that the epoxy foams had excellent compressive performance and the preparation of epoxy foam by microwave irradiation was high efficiency and convenient. The composition has great effect on density, foam structure, dynamical mechanic performance, and thermal degradation behavior of epoxy foams. The epoxy foam with density from 0.08 g cm−3 to 1.05 g cm−3 can be obtained by varying ratio of E51 and E31 to control the viscosity of mixtures. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Henequen/poly(butylene succinate) biocomposites: electron beam irradiation effects on henequen fiber and the interfacial properties of biocomposites

Henequen natural fiber-reinforced poly(butylene succinate) biocomposites were prepared through a resin microdroplet formation on a single fiber and also fabricated by a compression molding technique using chopped henequen fibers, surface-treated with electron beam irradiation (EBI) at various dosages. The effect of EBI treatment on the surface characteristics and dynamic mechanical properties of henequen fibers was investigated using SEM, XPS and DMA methods, respectively. Also, the interfacial behavior of biocomposites was explored through a single fiber microbonding test and fracture surface observations. The result indicates that the interfacial shear strength (IFSS) of biocomposites greatly depends on the EBI treatment level on the henequen fiber surface. This study also suggests that appropriate modification of natural fiber surfaces at an optimum EBI dosage significantly contributes to improving the interfacial properties of biocomposites.

Avaliação de clones de borracha natural crua por ensaios padrão e análise dinâmico-mecânica

A qualidade do látex de borracha natural (Hevea brasiliensis) de diferentes clones (RRIM 600, IAN 873, GT 1, PB 235), uma mistura destes clones e uma borracha comercial foi avaliada por ensaios padrões (plasticidade Wallace, PRI, viscosidade Mooney, % de cinzas, extrato acetônico e % de nitrogênio), DMA, DSC e TG. As borrachas estudadas apresentam propriedades competitivas com as da borracha presente no mercado, ficando dentro dos padrões de qualidade exigidos pela norma brasileira e pelo padrão internacional. Entre os clones, o clone RRIM 600 foi o que apresentou o melhor desempenho, principalmente em relação à viscosidade Mooney e ao PRI.

Synthesis and Properties of PMR Matrix Resins of Poly(Pyrrolone-Benzimidazole)s

PMR type of poly(pyrrolone-benzimidazole) copolymers (PPBI) were synthesized by the polycondensation of monoethyl ester of cis-5-norbornene-endo-2,3-dicarboxylic acid (NE), diphenyl-isophthalate (DPIP), diethyl ester of 4,4′-oxydiphthalic acid (ODPE) and 3,3′-diaminobenzidine (DAB) or 3,3′,4,4′-tetraamindiphenyl ether(TAD) in a mixing solution of anhydrous ethyl alcohol and N -methylpyrrolidone (NMP) under different temperature and pressure procedures. The resulting resin solution showed an excellent solubility in polar organic solvents and good stability at room temperature, while the corresponding PPBI molded powder and molded plate could be prepared by undergoing amidation, imidization, cyclization and crosslinking reactions when the reaction temperature would be increased from 150 to 350°C, especially, the crosslinking structure formed by the reverse Dials-Alder reaction at 270-290°C under 2.5-3.5 MPa pressure displayed by the pressure meter. The chemical reactions and properties of the resulting PPBI molded powders and molded plates were studied by means of FT-IR, TGA, DMA methods, and the results indicate that the PPBI materials obtained hold excellent thermal stability and processability, the initial decomposition temperature > 600°C and its T g defined by the peak temperature in tan δ curve from the DMA method is 448°C (DAB) or 423°C (TAD) for PPBI-20 molded plate.

Synthesis and properties of new polymerized monomer reactants matrix resins of pyrrolone–benzimidazole copolymers containing pyridine unit

AbstractA series of new polymerized monomer reactants (PMR) matrix resins of poly(pyrrolone‐benzimidazole)s containing a pyridine unit (PPBP) were synthesized by polycondensation of monoethyl ester of cis‐5‐norbornene‐endo‐2,3‐dicarboxylic acid, 2,6‐diphenyl ester pyridinedicarboxylic acid or 3,5‐diphenyl ester pyridinedicarboxylic acid, and diethyl ester of 4,4′‐oxydiphthalic acid with 3,3′‐diaminobenzidine in a mixing solution of anhydrous ethyl alcohol and N‐methylpyrrolidone under given temperature and pressure conditions. The resulting resin solutions showed good solubility in polar organic solvents and stability at room temperature. The corresponding PPBP matrix resin, molded powder, and molded plate were prepared by undergoing amidation, imidization, cyclization, and crosslinking reactions when the reaction temperature was increased from 80 to 350°C, successively; the crosslinking structure was formed by the reverse Diels–Alder reaction at 270–290°C under 50 MPa pressure (2.5–3.5 MPa displayed by the pressure meter). The chemical reactions and properties of the resulting PPBP were studied by means of FTIR, TGA, and DMA methods, and the results indicated that the kinds of PPBP materials retain excellent thermal stability and processability; when the initial decomposition temperature was above 620°C the Tg was at 413.5°C for 3,5‐PPBP‐20 molded plate. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3981–3990, 2004

97/04517 Potassium-promoted titania-supported nickel-iron catalysts for Fischer-Tropsch synthesis: Van De Loosdrecht, J. et al. Stud. Surf. Sci. Catal., 1997, 107, (Natural Gas Conversion IV), 201–206

Poly(2-(dimethylamino)ethyl methacrylate-co-acrylic acid) polyampholyte copolymers were synthesized by radical polymerization of the co-monomers in different molar ratios (2–1, 1–1 and 1–2). The water solutions of the obtained materials were used as stabilization agents for the synthesis of silver nanoparticles. XRD, FTIR and DMA methods were used to study the physical properties of the pure co-polymers. It was found that the copolymer is a completely amorphous and inhomogeneous material. The FTIR spectrum was analysed by using literature data and corresponding numerical simulations. TEM analysis showed that the shape of the nanoparticles prepared by reduction of the silver salt in the presence of co-polymers strongly depends on the ratio of DMAEMA and AA co-monomer units. Besides spherical Ag-nanoparticles, reduction in the presence of the polymer with equal molar content of co-monomers also resulted in the formation of nano-plate particles (circular thin plates and thin triangular nanoprisms). The formation of the nano-plate particles was further promoted by heating the mentioned solution at 60 °C in air. UV–vis spectroscopy was used to study the change in the surface plasmon resonance behaviour during the growth of the nanoplates. The Ag-nanocomposite thin films of all three co-polymers showed fast antimicrobial activity against the Staphylococcus aureus, Escherichia coli and Candida albicans pathogens (more than 99% reduction after 2 h of exposure).

A study on the glass transition behavior and morphology of semi-interpenetrating polymer networks

The epoxy resin/polyurethane semi-IPN was prepared and the glass transition behavior of the semi-IPN was discussed with DSC and DMA methods. The results show that the two glass transition temperatures (Tg) referring to epoxy resin and polyurethane respectively get closer. Between the two Tg there exists another Tg related to the interface between the two polymers. SEM indicates that this semi-IPN has a two-phase continuous structure which changes with different weight compositions. This is also proved by testing the Young's modulus. It is found that the IPN system has a cellular structure. Comparatively, the compatibility between the two polymers is the best when the weight ratio of EP/PU is 70/30. © 1996 John Wiley & Sons, Inc.

Study of the Effect of Soft-Segment Length and Concentration on Properties of Polyetherurethanes. II. The Effect on Mechanical Properties

Abstract Three series of segmented polyurethanes with different soft segment lengths and concentrations were examined by TMA, DMA, and mechanical methods. Maximum tensile strengths were obtained when ssc was 40–50%, which was explained by a specific interlocking morphology. No significant effect of soft-segment chain length on maximum strength was found, but higher values were found in the C series when ssc was 60%. Elongation at break increases linearly with ssc but indications that shorter soft segments produce higher extensions was attributed to plastic flow. TMA showed that Tg was independent of ssc in the C and, to a degree, in the B series, while temperature of α-transition in DMA was independent of ssc only in the C series at ssc above 50%.

Thermal and dynamic mechanical investigations on poly[bis(benzimidazobenzisoquinolinones)

A series of new semi-ladder poly[bis(benzimidazobenzisoquinolinones)], obtained by the polycondensation of dinaphthalene dianhydrides and aromatic tetraamines was investigated by TG, DSC and DMA methods. The influence of polymer structure on the thermal behaviour of the poly[bis(benzimidazobenzisoquinolinones)] was examined. The polymers were found to be thermally stable with T d > 723 K in air and T g ranging from 585 to 701 K. A good agreement was obtained in T g values measured by DSC and DMA methods. It was found that some cross-linking processes occurred at temperatures above T g. Some of the isothermal ageing curves were used to find the activation energies of isothermal cross-linking and decomposition.