Dynamic Mechanical Analysis Analysis Research Articles

Relaxation and Reinforcing Effects of Polyrotaxane in an Epoxy Resin Matrix

Polyrotaxanes with a low threading ratio of α-cyclodextrin (α-CD) on a poly(ethylene glycol) chain effectively acted as both the relaxation and reinforcing reagents in Novolac-type epoxy resin. The polyrotaxanes were incorporated into the epoxy resin during the curing process to produce transparent and rigid epoxy resin/polyrotaxane (E/PR) alloys. From dynamic mechanical analysis (DMA) of the E/PR alloys, it was found that the polyrotaxane contributed not only as a stress-relaxation component but also as a reinforcing modifier in the epoxy resin matrix. The morphology and chemical structures of polyrotaxanes in the epoxy resin matrices were assumed to be in a nanoscale dispersion, forming an interpenetrate network structure with multi cross-linking bonds on threaded α-CDs. This assumption was made based on their transparency, differential scanning calorimetry, small-angle X-ray scattering, and DMA analyses. This is the first report on the unique properties of polyrotaxanes added in a rigid matrix.

A novel condensation–addition-type phenolic resin (MPN): Synthesis, characterization and evaluation as matrix of composites

This paper reports a novel methylol and propargyl-containing dual-cure-mechanism novolac-based phenolic resin (MPN). MPN resins with varying contents of reactive groups were synthesized by a two-step one-pot method facilly and characterized by Flourier transfer infrared spectra (FT-IR), hydrogen magnetic resonance spectra (1H NMR), gel permeation chromatography (GPC), dynamic scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) techniques. The resins could be thermally cured by two gradual but fused stages: Condensation of methylol groups and addition polymerization of propargyl groups. This novel resin has advantages over conventional condensation-cure and addition-cure phenolic resins in processing capability. The results of DMA and thermogravimetry analysis (TGA) showed the cured resins possessed high thermal properties. Evaluation of MPN as matrices for advanced composites indicated the enhanced crosslink network derived from dense reactive groups in one single molecule was beneficial to the admirable thermal stability, but was detrimental to the mechanical properties of the resultant composites. MPN resin was amongst ideal candidates for matrices of high temperature materials.

Extrusion of pectin and glycerol with various combinations of orange albedo and starch

Microstructural and mechanical properties of extruded pectin and glycerol films with various combinations of orange albedo and starch were determined by universal mechanical testing (UMT), dynamic mechanical analysis (DMA), optical microscopy (OM) and scanning electron microscopy (SEM). A glass transition and a second order transition attributed to the onset of translational motion of the pectin molecules was observed in all films. Observation by OM suggested that extrusion in the presence of dilute HCl was more effective in disintegrating albedo than either water or dilute citric acid. UMT, DMA and SEM analysis revealed that extruded pectin/albedo/starch/glycerol films provided better mechanical properties than pectin/albedo/glycerol films and were comparable in mechanical properties to extruded pectin/starch/glycerol films.

Synthesis and characterization of new ion conductors based on butadiene styrene copolymers

In this work, we report the synthesis, kinetic study and microstructure characterization of a new proton conductor based on sulfonated polybutadiene–styrene copolymer (HPBS). Block copolymer ionomers were prepared through sulfonation of part of the styrene units. The free acid (HPBS-SH) sample was characterized using FT-IR spectroscopy and X-ray Photoelectron Spectroscopy (XPS) to confirm and quantify sulfonation. Microstructural characterization of the samples was carried out using Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), and Impedance Spectroscopy (IS). DMA and DSC analysis have shown that Tg (HPB) remains constant for all the samples studied, while glass transition temperature of polystyrene (PS) measured present an increase about 30 °C after sulfonation. Complex impedance measurements have shown that proton conductivity of HPBS-SH membrane was about 10 −3–10 −2 S cm −1, lower values were observed generally in the case of blends.

Nano Scratching of Clear Coats and Relation to Mechanical Material Properties

ABSTRACTThe nano single scratch experiment has been proven to be a suitable method to evaluate the scratch resistance of a coating. Single scratch damage and its recovery have been studied for a variety of clear coats under dry as well as wet conditions; these investigations were complemented by multi-scratch tests. Bulk mechanical materials properties of free standing films of the clear coats were determined by tensile tests and dynamic mechanical analysis (DMA). It was found that the recovery of the scratch groove is inversely related to the maximum value of the loss tangent (tan δ) as obtained from DMA analysis. The results of our comparative experiments and implications for the evaluation of the scratch resistance of organic coatings will be discussed.

Effect of Moisture Damage on Material Properties and Fatigue Resistance of Asphalt Mixtures

Dynamic mechanical analysis (DMA) has been used successfully to evaluate complex characteristics of fatigue damage and fracture of asphalt binders and mastics by measuring fundamental viscoelastic properties and damage characteristics. DMA was used to define the effect of moisture on fatigue damage and to concentrate on the fatigue damage susceptibility of the sand and asphalt mixture mastic fraction. Dynamic frequency sweep and time sweep tests were performed on cylindrical sand-asphalt samples in a dry state and after being subjected to moisture saturation. Test results clearly indicate that moisture reduces viscoelastic stiffness, fatigue resistance, and eventually fatigue life of sand-asphalt. The mechanistic role of moisture in fatigue was analyzed and quantified by using nonlinear viscoelastic theory based on pseudovariable concepts and a continuum damage fatigue model. The effect of material surface energies, which is strongly related to fracture and damage, is further discussed by using DMA fatigue test results and varying surface energy characteristics of individual mixture constituents. The DMA experimental procedure and analysis is an efficient way to identify the influence of moisture and to compare sand-asphalt mixtures in terms of moisture susceptibility.

Dynamic Mechanical Properties of Poly(propylene) Blends with Poly[ethylene‐co‐(methyl acrylate)

AbstractSummary: Blends of poly(propylene) (PP) were prepared with poly[ethylene‐co‐(methyl acrylate)] (EMA) having 9.0 and 21.5% methyl acrylate comonomer. A similar series of blends were compatibilized by using maleic anhydride grafted PP. The morphology and mechanical properties of the blends were investigated using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) in tensile mode. The DMA method and conditions were optimized for polymer film specimens and are discussed in the experimental section. The DSC results showed separate melting that is indicative of phase‐separated blends, analogous to other PP‐polyethylene blends but with the added polarity of methyl acrylate pendant side groups that may be beneficial for chemical resistance. Heterogeneous nucleation of PP was decreased in the blends because of migration of nuclei into the more polar EMA phase. The crystallinity and peak‐melting temperature did not vary significantly, although the width of the melting endotherm increased in the blends indicating a change had occurred to the crystals. DMA analysis showed the crystal‐crystal slip transition $T_{\rm \alpha }^*$ and glass transition (Tg) for PP as well as a Tg of the EMA copolymer occurring chronologically toward lower temperatures. The storage modulus of PP and the blends was generally greater with annealing at 150 °C compared with isothermal crystallization at 130 °C. The storage modulus of the blends for isothermally crystallized PP increased with 5% EMA, then decreased for higher amounts of EMA. Annealing caused a decrease with increasing copolymer content. The extent of the trend was greater for the compatibilized blends. The Tg of the blends varied over a small range, although this change was less for the compatibilized blends.Storage modulus for PP and EMA9.0 blends annealed at 150 °C.magnified imageStorage modulus for PP and EMA9.0 blends annealed at 150 °C.

Thermal Properties and SSA Fractionation of Metallocene Ethylene‐Oct‐1‐ene Copolymers with High Comonomer Content Cross‐linked by Dicumyl Peroxide or β‐Radiation

AbstractTwo metallocene ethylene‐oct‐1‐ene copolymers, differing in comonomer content and in molecular weight, were cross‐linked either by dicumyl peroxide or β‐radiation. The effect of high comonomer content on the crystalline morphology, once the materials were cross‐linked, was analyzed by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The gel content was determined in boiling xylene, and the cross‐linking process was monitored by FT‐IR spectroscopy. Two endotherms were distinguished: the first one was associated to the primary crystallization, and the second one to the shorter sequences that are excluded from the primary crystallization. The successive self‐nucleation annealing (SSA) technique has revealed that as the comonomer content increases the crystal size distribution is more homogeneous, and therefore, the melting and crystallization behaviour is reversible, because of its fringed‐micellar morphology. In spite of their crystalline morphology with very low crystallites, DCP cross‐linked samples displayed a considerable decrease in crystallinity and in crystal size, whereas β‐irradiated samples showed no significant decline in crystal size. Slight changes in crystallinity were detected and attributed to the heat generation that every irradiation process involves and affects smaller crystallites preferentially. DMA analysis has confirmed DSC results on crystalline size and crystallinity variations induced by both cross‐linking processes. By means of FT‐IR spectroscopy, it was detected that a high comonomer content induces oxidation during cross‐linking. Moreover, β‐irradiation samples exhibited a lower degree of oxidation than DCP cross‐linked samples.The heating scan of DCP cross‐linked EG8411 after being submitted to successive self‐nucleation annealing.magnified imageThe heating scan of DCP cross‐linked EG8411 after being submitted to successive self‐nucleation annealing.

Preparation and Characterization of Polyketone/Clay Nanocomposites

Nanocomposites of Polyketone (PK)/Cloisite 30B clay were prepared by the melt intercalation technique. The nanocomposites were characterized for their microstructure using wide-angle x-ray diffraction (WAXD), transmission electron microscopy (TEM), and dynamic mechanical analysis (DMA). An increase in the “d” spacing of silicate layers, as revealed by WAXD analysis, indicated the intercalated structure of the nanocomposites. A uniform dispersion of clay layers in polymer matrix was confirmed by TEM micrographs. The DMA analysis indicates improved storage modulus over the temperature range studied and an increase in the glass transition temperature of the nanocomposites.

Pad Degradation During CMP Process: Effect of Soak in Slurry and Water on Thermal and Mechanical Properties of the CMP Pads

AbstractSoak of polyurethane-based CMP pads in tungsten slurry and de-ionized water and its effect on retention of thermal and mechanical properties of the pads was studied using Dynamic Mechanical Analysis (DMA), Thermal Mechanical Analysis (TMA), Thermal Gravimetric Analysis (TGA), and Modulated Differential Scanning Calorimetry (MDSC). Simultaneous cross-linking and plastisizing due to soak were established using DMA and MDSC analysis. The stable operating temperature range and its dependence on soak time were determined using TMA analysis. Substantial difference in diffusion behavior of the “soft” and “hard” pads was discovered: diffusion into the hard pads followed Fickian law [1], while diffusion into the multi-layer soft pads was dominated by the fast filling of the highly porous pad surface with liquid.During a traditional CMP process, which involves application of polishing pads and slurry, the pad properties can be substantially and irreversibly changed as the result of slurry/rinse water absorption.The retention of the pad properties after exposure was monitored using such thermal and mechanical techniques, as Thermal Mechanical Analysis (TMA), Dynamical Mechanical Analysis (DMA), Modulated Differential Scanning Calorimetry (MDSC), Thermal Gravimetric Analysis (TGA).

Films of PLLA/PHBV: Thermal, morphological, and mechanical characterization

AbstractBlends of poly(L‐lactic acid)/poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PLLA/PHBV), both semicrystalline polymers, were prepared in different compositions (100/0, 80/20, 60/40, 50/50, 40/60, 20/80, and 0/100) and characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), polarized light microscopy (PLM), and tensile tests. Although PLLA/PHBV blends do not present clear phase separation by SEM, the analyses by TGA, DSC, and DMA showed that the PLLA/PHBV blends are immiscible. The cross sections observed by SEM showed that the morphology of the blends changes from porous to dense, due to the composition. DSC and DMA data showed two distinct glass transition and melting temperatures. However, the DMA analysis related to frequency variation showed partial molecular interactions between PHBV and PLLA. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2898–2906, 2002

Comparative Morphological Study of Poly(dioxolane)/Poly(methyl methacrylate) Segmented Networks and Blends by 13C Solid-State NMR and Thermal Analysis

Nanostructured amphiphilic segmented networks based on poly(1,3-dioxolane) (PDXL) and poly(methyl methacrylate) (PMMA) have been synthesized by radical copolymerization of α,ω-diacrylate PDXL with methyl methacrylate (MMA). The corresponding polymer blends have been prepared by the radical polymerization of MMA in the presence of α,ω-dihydroxy-PDXL. The multiphase behavior of the segmented networks and polymer blends have been compared by making use of solid-state 13C CP/MAS NMR spectroscopy, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and thermogravimetrical analysis (TGA). For the network structures, the combined analysis of the proton spin−lattice relaxation times (T1H) and proton spin-lock relaxation times (T1ρH) revealed small PDXL domain sizes between 1 and 20 nm. DSC and DMA analysis also showed the forced compatibility of the network components. In the case of the polymer blends, the phase morphology strongly depends on the PDXL weight fraction. For blends with PDXL fractions higher than 20 wt %, T1H relaxometry, DSC, and DMA analysis evidenced the presence of a heterogeneous phase morphology (domain sizes > 20 nm) that allows for the crystallization of the PDXL-rich domains.

On the viscoelastic properties of poly(vinyl alcohol) and chemically crosslinked poly(vinyl alcohol)

AbstractPoly(vinyl alcohol)(PVA) films chemically crosslinked with glutaraldehyde(GA) in the presence of HCl were prepared by casting from aqueous solutions. The PVA and PVA gels were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA); their swelling characteristics and tensile strength were also determined. The DSC results for the gels displayed depressions of the melting and crystallization temperatures, as well as a decrease of the heat of fusion, when compared to those of PVA free of crosslinker. The DMA analysis revealed that: (1) The glass transition temperature of the wet PVA was lower than that of the dry one, indicating that the water had a plasticizing effect. (2) The gels had a lower glass transition temperature than PVA. (3) The glass transition temperature of the wet gels increased with increasing crosslink density. Possible explanations are provided for these observations. Whereas the thermogravimetric curves of PVA exhibited a single degradation peak, two degradation peaks were detected for the crosslinked PVA. The wet PVA and PVA gels displayed lower tensile strengths and higher elongations than the dried ones. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1816–1823, 2001

Viscoelastic properties of plasticized methylcellulose and chemically crosslinked methylcellulose

Films of methylcellulose (MC), poly(ethylene glycol)400 (PEG400) plasticized MC, and MC gels (MC crosslinked with glutaraldehyde (GA)) were prepared by casting from aqueous solutions. The swelling test has shown that the MC gels were insoluble in water and that their crosslinking density increased with increasing GA and HCl concentrations. The effect of the addition of PEG400 or GA to MC was investigated through dynamic mechanical analysis (DMA). The DMA analysis of PEG400/MC blends has shown that PEG400 was compatible with MC and was an effective plasticizer since the curves of tan δ against temperature exhibited single peaks (corresponding to a single glass transition temperature), which were displaced to lower values with increasing PEG400 content. The thermogravimetric analysis (TGA) indicated that the thermal stability of MC was not affected by the chemical crosslinking. The tensile strength was slightly increased through crosslinking while the elongation was slightly decreased. The presence of moisture in MC hydrogels decreased the tensile strength and enhanced the elongation while the addition of PEG400 decreased the tensile strength but sharply increased the elongation.

High temperature lifetime of polyimide/poly(silsesquioxane)-like hybrid films

Decomposition kinetics in thermogravimetric analysis (TGA) and dynamic mechanical relaxation in dynamic mechanical analysis (DMA) are used to study the high temperature lifetime of the new type of polyimide/poly(silsesquioxane)-like (PI/PSSQ-like) hybrid films, which are designed to form three-dimensional structures with linear polyimide blocks and a crosslinked PSSQ-like structure. Both TGA and DMA analysis reveal that the PI/PSSQ-like hybrid films have a longer lifetime (are more reliable) with regard to their thermal and mechanical characteristics than that of pure PI. Even just 2 wt% of p-aminophenyltrimethoxysilane (APTS) in a PI/PSSQ-like hybrid film can significantly improve the service lifetime by as much as at least four times in a TGA decomposition kinetic study. The dynamical relaxation data are well fitted to the calculated WLF (Williams-Landel-Ferry) master curves. In a series of X-PIS (PI modified with APTS) hybrid films, decreasing the PI block chain length increases the decomposition activation energy, lifetime (in both TGA and DMA) and relaxation modulus. In a series of X-PIS-y-PTS [PI modified with APTS and phenyltrimethoxysilane (PTS)] films, the decomposition activation energy and lifetime (in TGA) increase with the PTS content. Interestingly, the dynamic mechanical relaxation modulus of 10000-PIS-100-PTS film is lower than that of the corresponding 10000-PIS film at frequency > 102 rad/sec, but higher at frequency < 102 rad/sec. The 10000-PIS-100-PTS has a lower relaxation time than the 10000-PIS at the modulus 5×108 Pa, but the relaxation time of the former becomes higher at 5×107 Pa.

Effect of water sorption on the structure and mechanical properties of an epoxy resin system

The characteristics of sorption and diffusion of water in an amine-cured epoxy system based on tetraglycidyl diaminodiphenylmethane and a novolac glycidyl ether resin were studied as a function both of the polymer microstructure, known from previous works, and the temperature. Water-sorption experiments and dynamic mechanical analysis (DMA) were performed. Tensile stress–strain and Rockwell hardness tests were conducted to investigate the effects of absorbed water on the mechanical properties of the material. Competing effects of the sorption of water in the free volume and of strong interactions between water molecules and polar groups of the network were used to explain the diffusional behavior observed, which followed Fick's second law. DMA analysis seemed to be sensitive to the water effects and the viscoelastic behavior was related both to the water-sorption processes and to the microstructure of the system. An important impact of water uptake on the tensile properties at break was also appreciated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 71–80, 2001

Mechanical behavior of tetrafunctional/phenol novolac epoxy mixtures cured with a diamine

An amine-cured epoxy system based on tetraglycidyldiaminodiphenylmethane and a novolac glycidyl ether resin was studied. Epoxies were prepared by varying the cure schedules and using the isothermal time-temperature-transformation diagram of the system. The materials were characterized using dynamic-mechanical analysis (DMA), tensile stress-strain tests over a range of temperatures and testing speeds, impact, and hardness tests. Optical microscopy was used to study the fracture surfaces of the samples. Some interrelations between the behavior and the microstructure of the system are discussed. In addition, the effect of thermal aging on the mechanical properties has been studied. DMA analysis seemed to reveal a structure that tended to be less heterogeneous with increasing the crosslink density. The advance in the etherification reactions or the thermal aging has reduced the mechanical properties related with the consumption of energy to break. The optimal cure schedule according to the global properties has been established. The morphology of fractured surfaces by optical microscopy showed a clear correlation with the variation of the tensile properties.