Dynamic Mechanical Analysis Results Research Articles

Development of butyl rubber nanocomposites in presence and absence of compatibiliser

Chlorobutyl rubber nanocomposites containing organically modified nanoclay (CI-C) were prepared by solution mixing. The nanoclay used in this study was Cloisite 20A. The obtained nanocomposites were incorporated in butyl rubber (IIR) with sulphur as a curing agent. Morphology, curing characteristics, mechanical and gas barrier properties of the nanocomposites were analysed. The morphological studies proved the partial exfoliation along with agglomeration of nanoclay platelets in chlorobutyl rubber, and further incorporation of CI-C in IIR matrix enhance the exfoliation of the nanoclay platelets. Curing study demonstrated shorter scorch time, cure time and increase in maximum torque for the nanoclay loaded IIR compound in the presence of chlorobutyl rubber as a compatibiliser compared to pure and IIR-nanoclay compound without compatibilisers. Dynamic mechanical thermal analysis results showed tremendous improvement in storage modulus and decrease in tan δ value for the one containing a compatibiliser. This particular compound exhibited substantial improvement in mechanical and gas barrier properties.

Nanostructure and dynamic mechanical properties of silane-functionalized montmorillonite/epoxy nanocomposites

In this work sodium montmorillonite (Na-MMT) was functionalized with N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane and the corresponding silylated clay was used to modify epoxy matrix cured with triethylenetetramine. The grafting/intercalation of the aminosilane inside the clay galleries were followed by infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and 29Si cross-polarization magic-angle-spinning nuclear magnetic-resonance (CP/MAS NMR) spectroscopy. Epoxy-based nanocomposites were prepared with different amounts of silylated clay or commercial organoclay, Cloisite 30B, whose intercalating agent consists of a methyl, tallow, bis-2-hydroxyethyl quaternary ammonium salt. The degree of intercalation/exfoliation was estimated by X-ray diffraction experiments and confirmed by small angle X-ray scattering. Nanocomposites prepared with silylated clay displayed no peak in both XRD and SAXS curves whereas those prepared with Cloisite 30B exhibited a clear interference peak corresponding to an interlayer spacing d 001 of 4.1 nm. The former also presented a better dispersion, with a high proportion of tactoids smaller than 2 nm, as estimated by SAXS. From the results of dynamic mechanical analysis it was observed that most of the nanocomposites display higher storage modulus mainly at temperatures above the glass transition temperature. The glass transition temperature is similar or higher than the neat epoxy network for nanocomposites containing 1 wt.% of silylated clay or higher.

Effect of methyl methacrylate content on coatings’ properties of palm oleic acid-based macromer

The macromer was synthesized using medium oil length oleic acid, phthalic anhydride, and glycerol. The synthesized macromer and methyl methacrylate (MMA) were copolymerized by free radical polymerization in toluene. The ratio between the macromer and MMA changed, and the effects on different properties of the copolymers, such as glass transition temperature (T g) and film properties, were studied. The macromer and copolymer structures were characterized by FTIR and 1H NMR spectroscopies. The coatings prepared with the highest ratio of MMA exhibited better overall physico-chemical properties. Alternatively, Tafel polarization curves showed that the corrosion rate value in NaCl solution decreases significantly when the MMA content is increased. Dynamic mechanical analysis results revealed that the increasing amounts of MMA lead to increasing T g values of copolymers.

Thermoreversible supramolecular polyurethanes with self‐complementary quadruple hydrogen‐bonded end groups

AbstractIn this article, a new type of strongly dimerizing 2‐ureido‐4‐[1H]‐pyrimidinone (UPy) with amine group is synthesized and then used as end‐group to prepare a novel series of supramolecular polyurethanes (PUs). The effects of strong and well‐defined hydrogen bonding on material properties of PUs are studied. In these PUs, the UPy groups consequently serve as thermoreversible associations or the “hard blocks” and the bi‐functional PU chains act as the “monomers.” This theoretical hypothesis is proved by the results of dynamic mechanical thermal analysis (DMTA) and rheological test. Thermal analysis shows that the strong hydrogen bonds from end groups restrict the formation of their microcrystalline domains. The supramolecular PUs exhibit good mechanical performance and their self‐assemble mechanism is discussed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Synthesis and characterization of anhydrous conducting polyimide/ionic liquid complex membranes via a new route for high‐temperature fuel cells

The paper deals with the synthesis and characterization of a new series of anhydrous conducting acid‐doped complex membranes based on polyimide (PI) and ionic liquid (IL) for high‐temperature fuel cells via a new route. For this purpose, three imidazolium‐based ILs (RIm+BF4−) with different alkyl chain lengths (R=methyl, ethyl, and butyl) are added into polyamic acid (PAA) intermediate prepared from the reaction of benzophenonetetracarboxylic dianhydride and diaminodiphenylsulfone in different –COOH/imidazolium molar ratios (n = 0.5, 1, and 2). Then, the thermally imidized complex membrane was doped with H2SO4. The conductivities of acid‐doped PI/IL complex membranes prepared by taking n of 1 are found to be in the range of 10−4−10−5 S cm−1 at 180°C, whereas the acid‐free PI/IL complex membranes show the conductivity at around 10−9−10−10 S cm−1. Thermogravimetric analysis results reveal that the acid‐doped PI/IL complex membranes are thermally stable up to 250°C. Dynamic mechanical analysis results of the acid‐doped ionically interacted complex membrane show that the mechanical strengths of the PI/IL complex membranes including 1‐methyl imidazolium tetrafluoroborate (MeIm‐BF4) and 1‐ethyl 3‐methyl imidazolium tetrafluoroborate (EtIm‐BF4) are comparable with those of pristine PI until 200°C. Furthermore, it can be clearly emphasized that the ionic interaction between carboxylic acid groups of PAA's and IL's cations offers a positive role in long‐term conductivity stability by preventing the IL migration at high temperatures. On the other hand, preliminary methanol permeability tests of the acid‐doped membranes show that they can also be considered as an alternative for direct methanol fuel cells. Copyright © 2011 John Wiley & Sons, Ltd.

New Hybrid Materials Based on Modified Halloysite and Unsaturated Polyester Resin

New hybrid materials based on unsaturated polyester resin and modified halloysite with different coupling agents were synthesized. The effect of functional groups grafted on the surface of halloysite against the properties of the final hybrids was studied using different characterization methods. The results of dynamic mechanical analyses showed that the glass transition temperature value of hybrids was strongly influenced by the halloysite modifier type. The concentration of halloysite and the modifier agent type influence the thermal stability of final hybrid materials.

Preparation and Damping property Study of Styrene-Acrylic IPN/Mt Nano-composite Material

In the emulsion system, styrene, acrylate monomers and montmorillonite (Mt) were used to prepare interpenetrating polymer network/montmorillonite (IPN/Mt) nano-composite. X-ray diffraction (XRD), transmission electron microscopy (TEM) and dynamic mechanical analysis (DMA) were used to characterize the structure and damping property of the new material. Results of XRD and TEM showed that the layer structure of Mt was destroyed and Mt dispersed in the polymer matrix by single layer. The result of DMA indicated that the damping property of Styrene-Acrylic IPN/Mt was much better than that of Styrene-Acrylic IPN. Damping value of the Styrene-Acrylic IPN/Mt was well improved and the maximum of tanδ increased from 0.621 to 0.739, with a broad damping domain ranging from -41°C to 140+°C. All these findings indicated that styrene-acrylate IPN /Mt nano-composite of broad damping temperature range and high damping value was successfully prepared.

Characterizing acrylic foam pressure sensitive adhesive tapes for structural glazing applications—Part II: Creep rupture results

This is a second part of a paper on measurements of mechanical characteristics of high-performance acrylic pressure sensitive adhesive (PSA) tapes, an alternate fastening method for structural glazing. The acrylic PSA used in the study was 3M™ VHB™ G23F Tape. For comparison, parallel creep tests were also conducted on 3 silicones: two one-part and one two-part compositions. Mechanical characteristics determined for the acrylic foam PSA include the viscoelastic properties over a range of temperatures and test rates. Creep rupture results are summarized here as the Part II paper while ramp-to-fail strength and DMA (dynamic mechanical analysis) results were summarized in an accompanying paper (Part I paper). Using the time–temperature superposition principle, master curves of VHB™ Tape storage and loss moduli in shear and tension were developed with data from a dynamic mechanical analyzer. The thermal shift factors obtained from these constitutive tests were successfully applied to the creep rupture and ramp-to-fail data collected at 23, 40, and 60 °C, resulting in master curves of ramp-to-fail strength (Part I paper) and creep rupture durability (in Part II) measured in both shear and tension. The creep results revealed some of the design tradeoffs inherent in the application of VHB™ Structural Glazing Tapes versus structural silicones. VHB™ Tape has more time and temperature dependence than the silicones. VHB™ Tape has lower strength than most structural silicones over the time ranges studied, a fact that is addressed by lower design stresses for VHB™ Structural Glazing Tape and larger tape widths for equivalent creep performance to structural silicone sealants. On the other hand, the short-term strength of VHB™ Tape approaches and even exceed that of structural silicones, a feature that may be advantageous in applications like wind loading and protective glazing. While both bonded VHB™ Tape and structural silicone specimens exhibited some voids, there was less sensitivity of time to failure to the voids and defects seen in the VHB™ Tape specimens tested and significantly less scatter in the time to failure data than specimens made with the structural silicones.

Transparent, fluorescent, and mechanical enhanced elastomeric composites formed with poly (styrene‐butadiene‐styrene) and SiO2‐hybridized CdTe quantum dots

AbstractTransparent poly(styrene‐butadiene‐styrene) (SBS)‐quantum dots (QDs) composites (SBS/CdTe QDs) that simultaneously possess strong photoluminescence (PL) and enhanced mechanical properties are presented for the first time based on the facile blending of SiO2‐hybridized CdTe QDs with SBS. UV–vis spectrum and fluorescence measurement show that SBS/CdTe QDs composites exhibit good optical properties. The results of transmission electron microscopy show good dispersion of CdTe QDs in the SBS matrix. The results of dynamic mechanical thermal analysis indicate that the micro‐phase separated structure of the SBS is exist in the composites, and the presence of CdTe QDs can lead to an decrease of glass transition temperatures of polybutadiene (PB) and polystyrene(PS) domains. In addition, mechanical tests reveal that the addition of CdTe QDs is a useful approach to improve the mechanical properties of SBS. Meanwhile, the fluorescent photographs taken under ultraviolet light prove that SBS/CdTe QDs composites possess strong PL. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.

Conversion of sulfuric acid lignin generated during bioethanol production from lignocellulosic materials into polyesters with ɛ-caprolactone

In this study, polyesters were prepared from sulfuric acid lignin (SAL) that was generated as a by-product during the production of bioethanol from lignocellulosic materials using ɛ-caprolactone (CL). Carboxylic groups were introduced into SAL by a hydrothermal reaction under alkali conditions. The acid form (-COOH) of the obtained polymer (HSAL) was dissolved into ɛ-caprolactone and the mixture was heated at 150°C for 12 h with ZnCl2 as a catalyst. The structure of the obtained polymer (PCL-HSAL) was proposed based on results of differential scanning calorimetric analysis, swelling tests, and dynamic mechanical thermal analysis. The hydroxyl group in HSAL participated in the ring-opening polymerization of CL. PCL-HSAL with a high HSAL content formed a three-dimensional network that did not dissolve in organic solvents and did not melt at high temperature. PCL-HSAL showed a high swelling property for a suitable ratio of CL to HSAL.

Influence of mechanical properties, toughness, and barrier properties of PMMA‐EVA‐organoclay nanocomposites with and without in situ crosslinking

AbstractPoly methyl methacrylate (PMMA)‐ethylene vinyl acetate (EVA)‐organoclay nanocomposites were prepared with and without in situ crosslinking using tetrapropoxysilane (TPOS) as a crosslinking agent and dibutyl tin oxide (DBTO) as a catalyst. Brabender Plasticorder experimental results suggest that in situ crosslinking transforms the EVA from a liquid to a viscoelastic solid. Transmission electron micrographs analysis indicates that most of the organoclay was clustered in the crosslinked EVA phase. X‐ray diffraction and morphology indicate that the PMMA‐EVA‐organoclay nanocomposites were intercalated and incompatible. Dynamic mechanical analysis (DMA) results indicate some interaction between PMMA‐EVA‐clay nanocomposites. The in situ crosslinked of EVA and the addition of organoclay increased the modulus properties of PMMA. However, in situ crosslinking slightly reduced the barrier properties of PMMA‐EVA‐organoclay nanocomposites. Copyright © 2009 John Wiley & Sons, Ltd.

Novel hyperbranched polyphenylsilsesquioxane‐modified cyanate ester resins with improved toughness and stiffness

AbstractHigh‐performance thermosetting resins should have good toughness and stiffness, so simultaneously toughening and stiffening is the main target in developing high‐performance resins. A novel modified cyanate ester resin with improved toughness and stiffness was developed by copolymerizing 2,2′‐bis(4‐cyanatophenyl)isopropylidene (CE) with hyperbranched polyphenylsilsesquioxane (HBPPSi). The mechanical properties and their nature were systematically investigated from the viewpoint of structure‐property relations using positron annihilation lifetime spectroscopy and spectral analyses. It is found that a suitable content of HBPPSi in CE resin can effectively improve toughness and stiffness. In the case of the CE resin modified with 10 wt% HBPPSi, its impact and flexural strengths are 21 kJ m−2 and 148 MPa, respectively, about 2.6 and 1.4 times of those of neat CE resin. The flexural modulus increases from 3.0 (for neat CE resin) to 3.4 GPa. The results of dynamic mechanical analyses also corroborate the static mechanical properties. The improved toughness and stiffness of CE resin can be attributed to the synergistic effect resulting from changes of both polymer chain structure and aggregation state structure. These attractive features of HBPPSi/CE resins suggest that the method proposed herein may be a new approach for the development of high‐performance resins for cutting‐edge industries. Copyright © 2011 Society of Chemical Industry

Preparation and properties of high performance phthalide‐containing bismaleimide modified epoxy matrices

AbstractA series of intercrosslinked networks formed by diglycidyl ether of bisphenol A epoxy resin (DGEBA) and novel bismaleimide containing phthalide cardo structure (BMIPP), with 4,4′‐diamino diphenyl sulfone (DDS) as hardener, have been investigated in detail. The curing behavior, thermal, mechanical and physical properties and compatibility of the blends were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), notched Izod impact test, scanning electron microscopy (SEM) and water absorption test. DSC investigations showed that the exothermic transition temperature (Tp) of the blend systems shifted slightly to the higher temperature with increasing BMIPP content and there appeared a shoulder on the high‐temperature side of the exothermic peak when BMIPP content was above 15 wt %. TGA and DMA results indicated that the introduction of BMIPP into epoxy resin improved the thermal stability and the storage modulus (G′) in the glassy region while glass transition temperature (Tg) decreased. Compared with the unmodified epoxy resin, there was a moderate increase in the fracture toughness for modified resins and the blend containing 5 wt % of BMIPP had the maximum of impact strength. SEM suggested the formation of homogeneous networks and rougher fracture surface with an increase in BMIPP content. In addition, the equilibrium water uptake of the modified resins was reduced as BMIPP content increased. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Investigation on the compatibilizing effect of m-isopropenyl-α,α-dimethylbenzyl isocyanate grafted polypropylene on polypropylene and wood flour composites

Wood flour (WF) and polypropylene (PP) composites (WF/PP) were compatibilized by m-isopropenyl-α,α-dimethylbenzyl isocyanate grafted polypropylene (m-TMI-g-PP). The effect of wood flour, m-TMI-g-PP contents on the rheology, dynamic mechanical analysis (DMA), mechanical properties, as well as the morphology of the composites were investigated and discussed. Rheology, DMA results showed that m-TMI-g-PP was an effective compatibilizer for WF/PP composites. The shear modulus (G′) and complex viscosity (η*) of the composites were increased, which implied that the composites probably withstood pronounced shear forces, resulting from strong adhesion at the interface between the matrix PP and WF. The mechanical test indicated that the tensile strength and the flexural strength of the composites were improved with increasing content of m-TMI-g-PP. From the properties tests, the optimum loading of WF in WF/m-TMI-g-PP/PP was found to be 40%, and the optimum loading of m-TMI-g-PP was 6%. Property enhancement is attributed to improved wetting and interactions between the PP matrix and WF, which is supported by scanning electron microscopy analysis.

Influence of Polyphenylene Sulfide on Plasticization and Toughening of Polyarylene Ether Nitrile/Polyphenylene Sulfide Blends

Polyarylene ether nitrile (PEN)/polyphenylene sulfide (PPS) blends were prepared via a melt-mixing process. The melting flow properties, compatibility, thermal and mechanical properties were characterized by melting index test, dynamic mechanical analysis (DMA), thermal analysis, tensile test and the fracture suface morphologies. The melt-mixed PEN/PPS blends displayed the excellent melting flow properties during processing. With the content of the PPS increased in the PEN, the melting index of the blends increased considerably, which is beneficial to the processability of PEN. PPS was found to be incompatible with the PEN by the DMA and DSC results. Morphology examinations reveal that the PPS phase is randomly dispersed as droplets with an average size of about 1~2 μm in PEN matrix, which is the main reason to enhance the toughness of PEN. Importantly, the blending materials maintained the characteristic thermal and thermo-oxidative stability as well as mechanical properties of the PEN as considering the further commercial applications.

Synthesis and characterization of a DOPO-substitued organophosphorus oligomer and its application in flame retardant epoxy resins

Advanced flame retardant epoxy resins with different contents of poly(DOPO substituted phenyl dimethanol pentaerythritol diphosphonate) (PFR) were prepared. PFR was synthesized from the polycondensation of DOPO-disubstituted benzenedimethanol (TDCA-DOPO) with pentaerythritol diphosphonate dichloride (SPDPC). The flame retardancy and thermal stability of the EP/PFR hybrids were investigated by limiting oxygen index (LOI), UL-94 test and thermogravimetric analysis (TGA) in air. LOI values increased from 21.5 for pure EP to 36.0 for phosphorus-containing resins, and UL-94 V-0 materials were obtained with the 15 wt% PFR. The TGA results indicated that incorporation of PFR significantly enhanced the char yield and the thermal stability of char layer at higher temperature. Differential scanning calorimetry revealed that the EP/PFR composites possessed higher glass transition temperatures than phosphorus-free EP, which was consistent with dynamic mechanical analysis results. The thermal degradation behaviors of the EP/PFR composites were investigated by real time Fourier transform infrared spectra (RTFTIR), thermogravimetric analysis/infrared spectrometry (TG–IR) and direct pyrolysis/mass (DP–MS) analysis. The results suggested that the addition of PFR can reduce the release of combustible gas, trap the H and OH radicals by releasing the PO radical and induce the formation of char layer, thus retard the polymer degradation and combustion process.

PMMA-Y2O3 (Eu3+) nanocomposites: Optical and mechanical properties

The results of a study related to the processing and characterization of PMMA-Y2O3 (Eu3+) nanocomposites are presented herein. The nanocomposite samples were prepared using a laboratory mixing molder with different contents of Eu-ion doped Y2O3 nanophosphor powder. The influence of particle content on the optical and dynamic mechanical properties of the nanocomposites was investigated. The intensity of the luminescence emission spectra increased as the nanophosphor content in the composite increased. The results of dynamic mechanical analysis revealed that the storage modulus, loss modulus and glass transition temperature (Tg) of the polymer composites increased with increasing content of the nanophosphor powder. The microhardness data also confirmed that the hardness number increased with nanoparticles concentration in the PMMA nanocomposites. The obtained results revealed a relatively linear relationship between Tg and the Vickers hardness.

Development of a new highly conductive and thermomechanically stable complex membrane based on sulfonated polyimide/ionic liquid for high temperature anhydrous fuel cells

The paper deals with the synthesis and characterization of a new type of acid doped highly conductive complex membrane based on sulfonated polyimide (sPI) and ionic liquid (IL) for high temperature anhydrous fuel cells. For this purpose, 2,4-diaminobenzene sulfonic acid (2,4-DABSA) is reacted with benzophenontetracarboxylic dianhydride (BTDA) to yield sulfonated poly(amic acid) (sPAA) intermediate. Subsequently, IL is added into sPAA to form an interaction between sulfonic acid and imidazolium group of IL followed by acid doping. The ionic conductivity of acid doped sPI/IL complex polymer membrane is higher than that of IL containing composite membranes reported in the literature (5.59 × 10 −2 S cm −1 at 180 °C). Furthermore, dynamic mechanical analysis (DMA) results of acid doped sPI/IL complex membrane show that the mechanical strength of the complex product is slightly changed until 350 °C due to the formation of ionic interactions between sulfonic acid groups of sPI and imidazolium groups of IL. Consequently, the ionic interaction not only provides high ionic conductivity with excellent thermomechanical properties (the storage module of 0.91 GPa at 300 °C) but also results in a positive effect in long term conductivity stability by blocking IL migration through the membrane.

Thermomechanical behavior and nonisothermal crystallization kinetics of poly(ε-caprolactone) and poly(ε- caprolactone)/poly(N-vinylpyrrolidone) blends

AbstractPoly(ε-caprolactone) (PCL) and PCL/Poly(N-vinylpyrrolidone) (PVP) blends are shown to have the potential to be used in a range of biomedical applications and can be processed with successive in-situ polymerization procedures. In this paper, the thermomechanical analysis of PCL and PCL/PVP blends was performed using dynamic mechanical analysis (DMA). The storage and loss moduli as a function of temperature and frequency were recorded. The nonisothermal crystallization kinetics of PCL and PCL/PVP blends were analyzed using Ozawa model and Mo-Liu equation, a combination equation of Avrami and Ozawa formulas. The Ozawa analysis failed to describe the nonisothermal crystallization behavior of blends, whereas the Mo-Liu equation successfully described the nonisothermal crystallization kinetics of PCL and PCL/PVP blends. In addition, the value of crystallization rate coefficient under nonisothermal crystallization conditions was calculated. The PCL/PVP blends compared with the pure PCL and PVP had a restrain effect on the crystallization kinetics of PCL in the blends. Combining the results of DMA and DSC, PVP effectively decreased the crystallinity of PCL and enhanced its damping properties, which indicated that PCL/PVP blends could be more suitable than PCL in some biomedical applications, as it might help in the dissipation of the mechanical energy generated by the patient movements.

Preparation, characterization, and properties of crosslinked hydroxylated poly(styrene‐b‐butadiene‐b‐styrene) triblock copolymer

AbstractHydroxylated poly(styrene‐b‐butadiene‐b‐styrene) triblock copolymer (HO‐SBS), with crosslinked networks, was prepared using various amounts of toluene diisocyanate (TDI). The amount of TDI was 0, 0.5, 1, 2, and 5 wt %. The effects of different contents of TDI on the microstructure, thermal properties, and mechanical properties of the crosslinked networks were investigated in detail. Fourier transform infrared spectra indicates that the reaction between OH and NCO have take place, and the solid‐state nuclear magnetic resonance spectra confirms that the crosslinked structure has been obtained. The results of scanning electron microscopy show that the mode of fracture surfaces transmits gradually from tough fracture to brittle fracture, but the structure of microphase separation is still observed at the same time. Mechanical test indicates that crosslinking is a useful method to regulate mechanical properties of the HO‐SBS. The results of dynamic mechanical thermal analysis display that there are two glass transition temperatures, which also means that the microphase separation is still in existence. Moreover, the glass transition temperature of the polybutadiene domains shifts to higher temperature. Accordingly, the microstructure, glass transition temperature, solvent resistance, and mechanical properties of the HO‐SBS are influenced obviously by the crosslinking of TDI. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011