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Dynamic Mechanical Thermal Analysis (dynamic + mechanical_thermal_analysis)
Selected AbstractsMechanical and functional properties of composites based on graphite and carboxylated acrylonitrile butadiene rubberJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Jian Yang Abstract In this study, carboxylated acrylonitrile butadiene rubber (xNBR)/expanded graphite (EG) nanocomposites were prepared with a latex compounding technique by ultrasonic stirring. The dispersion of EG in the xNBR matrix was investigated with transmission electron microscopy, scanning electron microscopy, and X-ray diffraction analysis. EG could be exfoliated into lots of nanosheets dispersing in the xNBR matrix. More EG loading resulted in the presence of a few incompletely exfoliated agglomerates. The mechanical properties (hardness, tensile modulus, and tensile strength) of the xNBR/EG composites were determined. Dynamic mechanical thermal analysis was also performed, and it showed that the nanosheets of EG somewhat immobilized the motion of rubber macromolecular chains and led to the shifting and broadening of the tan , peak toward higher temperatures. Many other functional properties of EG-filled xNBR composites were studied, and it was established that the composites had excellent electrical conductivity as well as gas-barrier and wear properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] On the Interrelationship of Transreactions with Thermal Properties and Dynamic Mechanical Analysis of PTT/PEN BlendsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2009Seyed-Hassan Jafari Abstract An attempt was made to explore the effects of interchange reactions on the crystallization, melting, and dynamic mechanical behavior of binary blends based on poly(trimethylene terephthalate) (PTT)/poly(ethylene 2,6-naphthalate) (PEN). 1H NMR spectroscopy is used to verify the occurrence of interchange reactions at the interface, which are increased upon an increase in the melt processing time and temperature. The crystallinity of PTT was reduced while that of PEN was increased on blending. In addition, the crystallization temperatures of both phases showed depression. A single composition-dependent glass transition temperature (Tg) was detected in the second and subsequent heating thermograms of the blends, which is indicative of miscibility. The cold crystallization of the PTT phase was observed to increase while that of PEN was suppressed on blending. Each phase crystallized individually and a melting point depression was evident, which suggests a certain level of miscibility. Dynamic mechanical thermal analysis corroborated differential scanning calorimetry results. A constructive synergism was observed in the glassy state storage moduli of the blends, which is suggestive of a reduced specific volume of the system because of enhanced interactions and crystallinity. [source] Tensile creep behaviour of polymethylpentene,silica nanocompositesPOLYMER INTERNATIONAL, Issue 6 2010Andrea Dorigato Abstract For the first time, poly(4-methyl-1-pentene) (PMP) nanocomposites were prepared by melt compounding 2 vol% of fumed silica nanoparticles, in order to study the role of the nanofiller surface area and functionalization on the tensile mechanical response of the material, with particular focus on its creep behaviour. The high optical transparency of the polymer matrix was substantially preserved in the nanocomposites, while the mechanical properties (in particular the creep stability) were improved. Dynamic mechanical thermal analysis showed an improvement of the storage modulus, more evident above the glass transition temperature of the polymer matrix. Uniaxial tensile tests evidenced that the elastic modulus of the material was positively affected by the presence of silica nanoparticles, even if a slight reduction of the strain at break was detected. The reduction of the tensile creep compliance was proportional to the surface area of the nanofiller, being more evident at high stresses and elevated temperatures. Findley's law furnished a satisfactory fitting of the creep behaviour of the composites, even at high temperatures. It clearly emerges that the incorporation of fumed silica nanoparticles in PMP can be an effective way to overcome the problem of the poor creep stability of polyolefins, especially at high temperatures and high stresses. Moreover the possibility of retaining the original transparency of the material is fundamental for the production of completely transparent PMP components. Copyright © 2010 Society of Chemical Industry [source] Preparation and properties of ternary polyimide/SiO2/polydiphenylsiloxane composite filmsPOLYMER INTERNATIONAL, Issue 11 2006Zhenping Shang Abstract A series of novel ternary polyimide/SiO2/polydiphenylsiloxane (PI/SiO2/PDPhS) composite films were prepared through co-hydrolysis and condensation between tetramethoxysilane, diphenyldimethoxysilane (DDS) and aminopropyltriethoxysilane-terminated polyamic acid, using an in situ sol,gel method. The composite films exhibited good optical transparency up to 30 wt% of total content of DDS and SiO2. SEM analysis showed that the PDPhS and SiO2 were well dispersed in the PI matrix without macroscopic separation of the composite films. TGA analysis indicated that the introduction of SiO2 could improve the thermal stability of the composite films. Dynamic mechanical thermal analysis showed that the composite films with low DDS content (5 wt%) had a higher glass transition temperature (Tg) than pure PI matrix. When the content of DDS was above 10 wt%, the Tg of the composite decreased slightly due to the plasticizing effect of flexible PDPhS linkages on the rigid PI chains. The composite films with high SiO2 content exhibited higher values of storage modulus. Tensile measurements also showed that the modulus and tensile strength of the composite films increased with increasing SiO2 content, and the composite films still retained a high elongation at break due the introduction of DDS. The density and water absorption of the composite films were also characterized. Copyright © 2006 Society of Chemical Industry [source] Biocomposites based on Alfa fibers and starch-based biopolymerPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 12 2009R. Belhassen Abstract Biocomposite materials based on Alfa cellulose fibers (esparto grass plant) as reinforcing element and starch-based biopolymer matrix were prepared and characterized in terms of mechanical performance, thermal properties, and water absorbance behavior. The fibers and the matrix were first mixed in the melted state under mechanical shearing using a plastograph and the obtained composites were molded by injection process. The tensile mechanical analysis showed a linear increase of the composite flexural and tensile modulus upon increasing the fiber content, together with a sharp decrease of the elongation at break. The fibers, incorporation into the biopolymer matrix brings about an enhancement in the mechanical strength and the impact strength of the composite. Dynamic mechanical thermal analysis (DMTA) investigation showed two relaxations occurring at about ,30 and 35°C. The addition of Alfa fibers enhanced the storage modulus E, before and after T,, which is consistent with the reinforcing effect of Alfa cellulose fibers. Copyright © 2008 John Wiley & Sons, Ltd. [source] Structure of reactively extruded rigid PVC/PMMA blendsPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 6 2005Y. Haba Abstract A novel route for producing polymer blends by reactive extrusion is described, starting from poly (vinyl chloride)/methyl methacrylate (PVC/MMA) dry blend and successive polymerization of MMA in an extruder. Small angle X-ray scattering (SAXS) measurements were applied to study the monomer's mode of penetration into the PVC particles and to characterize the supermolecular structure of the reactive poly(vinyl chloride)/poly(methyl methacrylate) (PVC/PMMA) blends obtained, as compared to the corresponding physical blends of similar composition. These measurements indicate that the monomer molecules can easily penetrate into the PVC sub-primary particles, separating the PVC chains. Moreover, the increased mobility of the PVC chains enables formation of an ordered lamellar structure, with an average d -spacing of 4.1,nm. The same characteristic lamellar structure is further detected upon compression molding or extrusion of PVC and PVC/PMMA blends. In this case the mobility of the PVC chains is enabled through thermal energy. Dynamic mechanical thermal analysis (DMTA) and SAXS measurements of reactive and physical PVC/PMMA blends indicate that miscibility occurs between the PVC and PMMA chains. The studied reactive PVC/PMMA blends are found to be miscible, while the physical PVC/PMMA blends are only partially miscible. It can be suggested that the miscible PMMA chains weaken dipole,dipole interactions between the PVC chains, leading to high mobility and resulting in an increased PVC crystallinity degree and decreased PVC glass transition temperature (Tg). These phenomena are shown in the physical PVC/PMMA blends and further emphasized in the reactive PVC/PMMA blends. Copyright © 2005 John Wiley & Sons, Ltd. [source] The Effect of Rapid High Temperature Excursions on the Moisture Absorption and Dynamic Mechanical Properties of Carbon Fibre Epoxy Composite MaterialsASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1-2 2004G. M. Mcnally The effect of elevated temperature excursions (thermal spiking) on the moisture absorption characteristics and dynamic mechanical properties of Cycom 8 HS carbon fibre epoxy laminates was investigated. Cured laminate samples were preconditioned (65d,C, 95%R.H.) and these samples were exposed to various thermal spiking (150d,C/2min) programmes. Dynamic mechanical thermal analysis (DMTA) techniques measured the changes in glass transition temperature (Tg) storage modulus (log E') and damping (Tan , max) of the laminates as a result of exposure to these environments. The thermal spiking programme was shown to cause an increase in both the amount and rate of moisture absorption of the laminates. These increments were accompanied by a significant decrease in Tg, log E', and Tan , max. Scanning Electron Microscopy (SEM) analysis also showed the progressive growth of both interlaminar and translaminar micro-cracks as a result of thermal spiking. [source] Physicochemical and biological evaluation of plasma-induced graft polymerization of acrylamide onto polydimethylsiloxaneJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008A. Parvin Abstract Polydimethylsiloxane (PDMS) rubbers exhibit good mechanical properties for biomedical and industrial applications, but their inherently high hydrophobicity limits biomedical applications of this material despite its favorable mechanical properties. In this work, surface modification of PDMS by radio-frequency glow discharge and subsequently graft polymerization of acrylamide was studied. PAAm-grafted, oxygen plasma-treated, and control (untreated) PDMS rubbers were characterized using attenuated total reflectance Fourier transform infrared, scanning electron microscopy, dynamic mechanical thermal analyses, zeta potential, and contact angle techniques. Fibroblast (L929) cell attachment and growth onto these surfaces were examined by optical microscopy. The data from in vitro assays showed that cell attachment onto control surface was very negligible while significant cell attachment and growth was observed onto oxygen plasma-treated and PAAm-grafted PDMS surfaces. The method developed in this work offers a convenient way of surface modifications of biomaterials to improve attachment of cells onto substrates. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 [source] Generation of Compositional-Gradient Structures in Biodegradable, Immiscible, Polymer Blends by Intermolecular Hydrogen-Bonding Interactions,ADVANCED FUNCTIONAL MATERIALS, Issue 10 2005B. Hexig Abstract A biodegradable, immiscible poly(butylenes adipate- co -butylenes terephthalate) [P(BA- co -BT)]/poly(ethylene oxide) (PEO) polymer blend film with compositional gradient in the film-thickness direction has been successfully prepared in the presence of a low-molecular-weight compound 4,4,-thiodiphenal (TDP), which is used as a miscibility-enhancing agent. The miscibilities of the P(BA- co -BT)/PEO/TDP ternary blend films and the P(BA- co -BT)/PEO/TDP gradient film were investigated by differential scanning calorimetry (DSC). The compositional gradient structure of the P(BA- co -BT)/PEO/TDP (46/46/8 w/w/w) film has been confirmed by microscopic mapping measurement of Fourier-transform infrared spectra and dynamic mechanical thermal analysis. We have developed a new strategy for generating gradient-phase structures in immiscible polymer-blend systems by homogenization, i.e., adding a third agent that can enhance the miscibility of the two immiscible polymers through simultaneous formation of hydrogen bonds with two component polymers. [source] Modification of cellulose acetate with oligomeric polycaprolactone by reactive processing: Efficiency, compatibility, and propertiesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2009Szilvia Klébert Abstract Oligomeric polycaprolactone (oPCL) was used for the modification of cellulose acetate by reactive processing in an internal mixer at 180°C, 50 rpm, 60 min reaction time, and 45 wt % caprolactone (CL) content. The product of the reaction was characterized by several analytical techniques and its mechanical properties were determined by dynamic mechanical thermal analysis and tensile testing. The synthesized oPCL contained small and large molecular weight components. The small molecular weight fraction plasticized cellulose acetate externally and helped fusion. Although composition and structure did not differ considerably from each other when CL monomer or polycaprolactone oligomer was used for modification, the grafting of a few long chains had considerable effect on some properties of the product. The large molecular weight chains attached to CA increased the viscosity of the melt considerably and resulted in larger deformability. oPCL homopolymer is not miscible with cellulose acetate and migrates to the surface of the polymer. Exuded polycaprolactone oligomers crystallize on the surface but can be removed very easily. More intense conditions may favor the grafting of long chains leading to polymers with advantageous properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Radiopaque, barium sulfate-filled biomedical compounds of a poly(ether-block-amide) copolymerJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Xiaoping Guo Abstract Various radiopaque compounds of a poly (ether- block -amide) copolymer resin filled with fine barium sulfate particles were prepared by melt mixing. Material properties of the filled compounds were investigated using various material characterization techniques, including thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic rheometry, uniaxial tensile test, and dynamic mechanical thermal analysis (DMTA). The effects of the filler and its concentration on the measured material properties are evaluated. It has been found that in addition to its well-known X-ray radiopacity, the filler is quite effective in reinforcing some mechanical properties of the copolymer, including modulus of elasticity and yield strength. More interestingly, it has been observed that at low loading concentrations near 10 wt %, the filler may also act as a rigid, inorganic toughener for the copolymer by improving the postyield material extensibility of strain hardening against ultimate material fracture. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Influence of fillers on the properties of a phenolic resin cured in acidic mediumJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008J. M. Laza Abstract The curing behavior of a phenolic resol resin in the presence of p -toluensulphonic acid is reported herein. The gel time of different systems has been determined by thermal scanning rheometry. Thermal and mechanical properties of the resin have been modified by the addition of varying amounts of fillers, talc, and kaolin. dynamic mechanical thermal analysis is used to determine the mechanical properties of the systems and the influence of the fillers and the postcuring. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Some factors influencing exfoliation and physical property enhancement in nanoclay epoxy resins based on diglycidyl ethers of bisphenol A and FJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007S. Ingram Abstract An investigation of the factors influencing the degree of exfoliation of an organically modified clay in a series of epoxy resins is reported. The use of sonication, choice of curing agent, effect of the moisture content of the clay, and the cure temperature were examined. The dispersion was characterized using a combination of rheological measurements, X-ray diffraction, and dynamic mechanical thermal analysis. Rheological analysis of the clay dispersion in the epoxy monomer indicated that at high clay loads Herschel,Bulkley type behavior is followed. Higher cure temperatures and higher levels of clay moisture were found to influence the extent of exfoliation. Improvements in physical properties were observed through the addition of nanocomposites. The DGEBA/DDM and DEGEBA/DDS exhibited 2 and 4°C increase, respectively, in Tg per wt % of added clay. DGEBF showed virtually no enhancement. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Miscibility and rheological properties of poly(vinyl chloride)/styrene,acrylonitrile blends prepared by melt extrusionJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Hyun Sik Moon Abstract Styrene,acrylonitrile (SAN) with acrylonitrile (AN) concentrations of 11.6,26 wt % and ,-methylstyrene acrylonitrile (,MSAN) with a wide range of AN concentrations are miscible with poly(vinyl chloride) (PVC) through solution blending. Here we examine the rheological properties and miscibility of PVC/SAN and PVC/,MSAN blends prepared by melt extrusion for commercial applications. We have investigated the rheological properties of the blends with a rheometer and a melt indexer. The PVC/SAN and PVC/,MSAN blends have a low melting torque, a long degradation time, and a high melt index, and this means that they have better processability than pure PVC. The miscibility of the blends has been characterized with differential scanning calorimetry, dynamic mechanical thermal analysis, and advanced rheometrics expansion system analysis. The miscibility of the blends has also been characterized with scanning electron microscopy. The SAN series with AN concentrations of 24,31 wt % is immiscible with PVC by melt extrusion, whereas ,MSAN with 31 wt % AN is miscible with PVC, even when they are blended by melt extrusion, because of the strong interaction between PVC and ,MSAN. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Morphology and mechanical and viscoelastic properties of rubbery epoxy/organoclay montmorillonite nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Amar Boukerrou Abstract The morphology and mechanical and viscoelastic properties of rubbery epoxy/organoclay montmorillonite (MMT) nanocomposites were investigated with wide-angle X-ray scattering (WAXS), transmission electron microscopy (TEM), tensile testing, and dynamic mechanical thermal analysis. An ultrasonicator was used to apply external shearing forces to disperse the silicate clay layers in the epoxy matrix. The first step of the nanocomposite preparation consisted of swelling MMT in a curing agent, that is, an aliphatic diamine based on a polyoxypropylene backbone with a low viscosity for better diffusion into the intragalleries. Then, the epoxy prepolymer was added to the mixture. Better dispersion and intercalation of the nanoclay in the matrix were expected. The organic modification of MMT with octadecylammonium ions led to an increase in the initial d -spacing (the [d001] peak) from 14.4 to 28.5 Å, as determined by WAXS; this indicated the occurrence of an intercalation. The addition of 5 phr MMTC18 (MMT after the modification) to the epoxy matrix resulted in a finer dispersion, as evidenced by the disappearance of the diffraction peak in the WAXS pattern and TEM images. The mechanical and viscoelastic properties were improved for both MMT and MMTC18 nanocomposites, but they were more pronounced for the modified ones. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 103: 3547,3552, 2007 [source] Ageing of soft thermoplastic starch with high glycerol contentJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Rui Shi Abstract In this study, a soft and thermoplastic starch with an improved ageing-resistant property was prepared by melt blending method for a biodegradable biomaterial. The glycerol content varies from 30 to 60 wt %. The aging temperature and humidity of the glycerol-plasticized thermoplastic starch (GTPS) was 37°C and 50 ± 5 RH %, respectively. The retrogradation was characterized by X-ray diffraction (XRD), dynamic mechanical thermal analysis (DMTA), Fourier transform infrared (FTIR), and the stress-strain mechanical properties. The XRD results suggest that high content of glycerol promotes the formation of single helix structure of V-type, but inhibits double helix structure of B-type. Changing of the tan ,, storage modules (E,), and the glass transition temperatures as a function of glycerol content and ageing time was detected by DMTA. FTIR result shows that the shifting speed of the peak of hydroxyl group stretching fell as the glycerol content increased. The glycerol content has no obvious effect on the mechanical properties when it is high enough. Results from all characterizations demonstrate that the ageing speed is closely relative to the plasticizers content. The higher content of glycerol possesses an obviously inhibitory effect on the ageing. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 574,586, 2007 [source] Effect of Moisture Content on the Thermomechanical Behavior of Concentrated Waxy Cornstarch,Water Preparations, A Comparison with Wheat StarchJOURNAL OF FOOD SCIENCE, Issue 3 2002A. Rolée ABSTRACT: The rheological behavior of waxy cornstarch preparations at intermediate moisture contents (30 to 60% w/w) was studied by dynamic mechanical thermal analysis (DMTA). Differential scanning calorimetry (DSC) and electron spin resonance (ESR) experiments were also performed in parallel. The results were compared to those obtained previously for wheat starch. DMTA results evidenced a critical moisture content (between 50 and 55%) for waxy cornstarch that delimited a radical change in the rheological behavior both at room temperature and during heating. This critical water content was around 45% for wheat starch. [source] New thermosets obtained by the cationic copolymerization of diglycidyl ether of bisphenol A with ,-caprolactone with an improvement in the shrinkage.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2007Abstract Diglycidyl ether of bisphenol A was cured with different proportions of ,-caprolactone with ytterbium triflate as an initiator. The curing was studied by means of differential scanning calorimetry and Fourier transform infrared in the attenuated total reflection mode. The latter was used to monitor the competitive reactive processes and to quantify the conversions of the epoxide, lactone, and intermediate spiroorthoester groups. A partial depolymerization process from the cured material to free ,-caprolactone was also identified. The formation of a stable carbocation and the coordinative capability of ytterbium triflate were the reasons for this unexpected process. The thermal and dynamic mechanical properties of the cured materials were determined with differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical thermal analysis. An increase in the proportion of ,-caprolactone resulted in an increased curing rate, a decrease in the shrinkage after gelation, and a significant decrease in the glass transition temperature. The introduction of ester linkages into the three-dimensional structure led to more thermally degradable thermosets. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1968,1979, 2007 [source] Lightly crosslinked, mesomorphic networks obtained through the reaction of dimeric, liquid-crystalline epoxy,imine monomers and heptanedioic acidJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2006David Ribera Abstract We reacted various dimeric, liquid-crystalline epoxy,imine monomers, differing in the length of the central aliphatic spacer or the dipolar moments, with heptanedioic acid. The resulting systems showed a liquid-crystalline phase in some cases, depending on the dimer and on the reaction conditions. The systems were characterized with respect to their mesomorphic properties and then were submitted to dynamic mechanical thermal analysis in both fixed-frequency and frequency-sweep modes in the shear sandwich configuration. The arrangement in the liquid-crystalline phase seemed to be mainly affected both by the polarization of the mesogen and by the reaction temperature, which favored the liquid-crystalline arrangement when it was lying in the range of stability of the dimer mesophase. In agreement with other recent literature data, dynamic mechanical thermal analysis results suggested that the presence of the mesogen directly incorporated into the main chain increased the lifetimes of the elastic modes both in the isotropic phase and in the liquid-crystalline phase with respect to side-chain liquid-crystalline elastomers and that the time,temperature superposition principle did not hold through the liquid-crystalline-to-isotropic transition. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44:6270,6286, 2006 [source] N,N -dimethylaminopyridine as initiator in the copolymerization of diglycidylether of bisphenol A with six-membered cyclic carbonatesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2006Roser Cervellera Abstract N,N -Dimethylaminopyridine (DMAP) was used as initiator to cure mixtures of diglycidylether of bisphenol A (DGEBA) and 1,3-dioxan-2-one (TMC) or 5,5-dimethyl-1,3-dioxan-2-one (DMTMC). The curing was studied by differential scanning calorimetry (DSC) and Fourier transform infrared in the attenuated-total-reflection mode (FTIR/ATR). FTIR/ATR was used to monitor the competitive reactive processes and to quantify the evolution of the groups involved in the curing. We observed the formation of five-membered cyclic carbonates and anionic carbonate groups that remain unreacted at the chain ends. The formation of these groups was explained by the attack of the anionic propagation species on the methylene carbon of the carbonate group, which leads to an alkyl-oxygen rupture. By performing the cure in the thermobalance we could evaluate the loss of CO2 produced in the samples containing carbonates. The kinetics were studied by DSC and analyzed with isoconversional procedures. The addition of carbonates slows down the curing rate. Thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA) experiments were used to evaluate the properties of the materials obtained. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2873,2882, 2006 [source] Synthesis of polyethylene-octene elastomer/SiO2 -TiO2 nanocomposites via in situ polymerization: Properties and characterization of the hybridJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2005Chin-San Wu Abstract In this study, a silicic acid and tetra isopropyl ortho titanate ceramic precursor and a metallocene polyethylene-octene elastomer (POE) or acrylic acid grafted metallocene polyethylene-octene elastomer (POE-g-AA) were used in the preparation of hybrids (POE/SiO2TiO2 and POE-g-AA/SiO2TiO2) using an in situ sol-gel process, with a view to identifying a hybrid with improved thermal and mechanical properties. Hybrids were characterized using Fourier transform infrared spectroscopy, 29Si solid-state nuclear magnetic resonance (NMR), X-ray diffraction, differential scanning calorimetry, thermogravimetry analysis, dynamic mechanical thermal analysis, and Instron mechanical testing. Properties of the POE-g-AA/SiO2TiO2 hybrid were superior to those of the POE/SiO2TiO2 hybrid. This was because the carboxylic acid groups of acrylic acid acted as coordination sites for the silica-titania phase to allow the formation of stronger chemical bonds. 29Si solid-state NMR showed that Si atoms coordinated around SiO4 units were predominantly Q3 and Q4. The 10 wt % SiO2TiO2 hybrids gave the maximum values of tensile strength and glass transition temperature in both POE/SiO2TiO2 and POE-g-AA/SiO2TiO2. It is proposed that above this wt %, excess SiO2TiO2 particles caused separation between the organic and inorganic phases. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1690,1701, 2005 [source] Poly(ester urethane)s with polycaprolactone soft segments: A morphological studyJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2002Juliana Kloss Abstract Two series of poly(ester urethane)s were prepared, containing polycaprolactone (PCL) as the soft segment with molecular weights of 530 and 2000. In each series, the soft-segment/hard-segment ratio was varied, and the morphological changes were monitored with differential scanning calorimetry, dynamic mechanical thermal analysis, wide-angle X-ray scattering, and scanning electron microscopy techniques. The polyurethanes with longer PCL segments retained their crystallinity, whereas those with shorter PCL segments did not. A morphological model is proposed, in which a continuous PCL-rich matrix contains both PCL crystallites and domains of urethane hard segments. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4117,4130, 2002 [source] Physicochemical properties and application of pullulan edible films and coatings in fruit preservationJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 10 2001Tony Diab Abstract The effects of water, sorbitol and a sucrose fatty acid ester (SE) on the water sorption behaviour and thermal and mechanical properties of pullulan-based edible films as well as the physiological responses of fruit coated with pullulan have been studied. Incorporation of sorbitol or SE in pullulan films resulted in lower equilibrium moisture contents at low to intermediate water activities (aw), but much higher moisture contents at aw,>,0.75; estimates of monolayer values (within 4.1,5.9,gH2O,kg,1 solids) were given by application of the Brunauer,Emmett,Teller (BET) and Guggenheim,Anderson,DeBoer (GAB) models. A single glass,rubber transition (Tg), attributed to the polysaccharide component, was detected by calorimetry and dynamic mechanical thermal analysis (DMTA) at a sorbitol level of 15,30% DM. With both tests the strong plasticising action of water and polyol was evident in the thermal curves, and the Tg vs moisture content data were successfully fitted to the Gordon,Taylor empirical model. Multifrequency DMTA measurements provided estimates for the apparent activation energy of the glass transition in the range of , 300,488,kJ,mol,1. With large-deformation mechanical testing, large decreases in Young's moduli (tensile and three-point bend tests) were observed as a result of water- and/or polyol-mediated glass-to-rubber transition of the polymeric films. In the moisture content range of 2,8%, increases in flexural modulus (E) and maximum stress (,max) with small increases in moisture content were found for films made of pullulan or pullulan mixed with 15% DM sorbitol; a strong softening effect was observed when the water content exceeded this range. Addition of sorbitol increased the water vapour transmission rate of the films, whereas addition of SE had the opposite effect. Application of a pullulan/sorbitol/SE coating on strawberries resulted in large changes in internal fruit atmosphere composition which were beneficial for extending the shelf-life of this fruit; the coated fruit showed much higher levels of CO2, a large reduction in internal O2, better firmness and colour retention and a reduced rate of weight loss. In contrast, similar studies on whole kiwifruits showed increased levels of internal ethylene, which caused acceleration of fruit ripening during storage. © 2001 Society of Chemical Industry [source] Tandem Action of TpMsNiCl and Supported Cp2ZrCl2 Catalysts for the Production of Linear Low-Density PolyethyleneMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 9 2006Maria Cristina A. Kuhn Abstract Summary: Linear low-density polyethylene (LLDPE) samples with different properties were prepared from ethylene, without the addition of an , -olefin co-monomer, using a combination of the catalyst precursors TpMsNiCl (TpMs,=,hydridotris(3-mesitylpyrazol-1-yl) and Cp2ZrCl2/SMAO-4, by varying the nickel loading mole fraction (xNi). Upon activation with methylaluminoxane (MAO), this binary catalytic system showed activities varying from 12.3 to 309.1 kg of PE,·,(mol[M],·,atm,·,h),1. The properties of the polymeric materials are influenced by xNi as well as by the temperature of polymerization, affording the copolymers with a melting point (Tm) between 118 and 135,°C. The GPC results show that the molecular weight () of the polymers is sensitive to the xNi. In all of the cases studied, the GPC curves displayed monomodal molecular weight distributions (MWDs) with the average molecular weight varying from 30,000 to 507,000 g,·,mol,1. Studies using dynamic mechanical thermal analysis (DMTA) show that the formation of different polymeric materials is associated with the branching content, with the stiffness varying according to the xNi and the temperature used in the polymerization reaction. Overview of the copolymerization process, from ethylene in the presence of MAO, mediated by catalysts 1 and 2/SMAO. [source] Polyamides X.34: A New Class of Polyamides with Long Alkane SegmentsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 13 2003Moritz Ehrenstein Abstract A new series of semi-crystalline polyamides (PA), which comprise extended aliphatic segments between the amide moieties and which display an interesting amphiphilic character has been synthesized and characterized. The polymers PA-2.34, PA-4.34, PA-8.34, PA-10.34, and PA-12.34 were prepared by melt-polycondensation of salts of tetratriacontanedioic acid and the respective short-chain diamine. The thermal properties of these polymers were investigated by differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical thermal analysis. The new polyamides exhibit melting temperatures that depend on the length of the diamine and range between 166 (PA-12.34) and 190,°C (PA-2.34). Solid transitions were observed between 38 and 57,°C. The materials displayed a rather limited solubility in common polyamide solvents, but readily dissolved in alkylsulfonic acids. All members of the series formed thermo-reversible gels in the highly polar sulfuric acid and 1,2,3,4-tetrahydronaphthalene, reflecting their interesting amphiphilic character. Young's moduli and tensile strengths of melt-processed, isotropic films of the polyamides investigated were in the range of 0.5,0.7 GPa and 20.30 MPa, respectively, independent of the length of the diamine used. Melting temperatures of polyamides PA-X.34 (x) and 1,2,3,4-tetrahydronaphthalene/PA-X.34 gels (37.5 wt.-% polyamide, determined from the second DSC heating scans) (+). [source] Effect of mold temperature on the long-term viscoelastic behavior of polybutylene terepthalatePOLYMER ENGINEERING & SCIENCE, Issue 5 2008K. Banik The effect of mold temperature variation during injection molding on the long-term viscoelastic behavior of polybutylene terepthalate (PBT) was studied by dynamic mechanical thermal analysis (DMTA) and flexural creep tests. The time,temperature superposition (TTS) principle was applied to the experimental data and the master curves were created to predict their long-term behavior. The WLF and Arrhenius models were verified for the shift data in the investigating temperature range and the activation energies for the deformation process were calculated based on the Arrhenius equation. Further a four-element Burger model was applied to the creep results to represent the creep behavior of the PBT processed at two different mold temperatures and to better understand the deformation mechanism. Differential scanning calorimetry (DSC) and density measurements were accomplished to characterize the process-dependent microstructures. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Thermal properties of biaxially deformed in situ compositesPOLYMER ENGINEERING & SCIENCE, Issue 8 2004Youngwook P. Seo The thermal properties of biaxially blown poly(etherimide) (PEI) films containing a thermotropic liquid crystalline polymer (TLCP) were studied using differential scanning calorimetry, thermogravimetric analysis, wide-angle X-ray diffraction and dynamic mechanical thermal analysis. The effects of the compatibilizer and thermal annealing on the thermal properties of biaxially oriented TLCP films were investigated. Though the compatibilizer (poly(ester imide)) improved deformation of the TLCP phase (poly ester amide) and adhesion between the matrix and the TLCP phase, which improved mechanical properties, it did not significantly affect the thermal properties of the in situ composite films. The film degradation behavior corroborated the role of the compatibilizer. Since a relatively small amount of TLCP (10 wt%) was added to the matrix and the matrix PEI was amorphous, the effect of annealing on the TLCP structure was not obvious. By the same token, while the effect of the deformation in the circumferential direction (a change in the blow-up ratio) was manifest in mechanical property improvements, its effect on the thermal properties was not obvious. All films showed similar thermal expansion behaviors, regardless of the thermal history and of the compatibilizer addition. Thus, there is an optimum amount of the compatibilizer required to obtain optimal mechanical properties for in situ composite films without causing a deterioration of their thermal properties. Polym. Eng. Sci. 44:1419,1428, 2004. © 2004 Society of Plastics Engineers. [source] The study of morphology, thermal and thermo-mechanical properties of compatibilized TPU/SAN blendsPOLYMER ENGINEERING & SCIENCE, Issue 5 2004M. Ulcnik-Krump The compatibilizing efficiency of three different compatibilizers in thermoplastic polyurethane/styrene-co-acrylonitrile (TPU/SAN) blends was investigated after their incorporation via melt-mixing. The compatibilizers studied were poly-,-caprolactone (PCL), a mixture of polystyrene-block-polycaprolactone (PS-b-PCL) and polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA), and a mixture of polyisoprene-block-polycaprolactone (PI-b-PCL) and polybutadiene-block-poly(methyl methacrylate) (PB-b-PMMA). All compatibilizers were synthesized by living anionic polymerization. Investigations of thermal and thermo-mechanical properties performed by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DTMA), respectively, were systematically classified into two groups, i.e. blends of TPU or SAN with 20 wt% of different compatibilizers (so-called limit conditions) and TPU/SAN 25/75 blends with 5 wt% of different compatibilizers. In order to determine the compatibilizer's location, morphology of TPU/SAN 25/75 blends was studied with transmission electron microscopy (TEM). Different compatibilization activity was found for different systems. Blends compatibilized with PCL showed superior properties over the other blends. Polym. Eng. Sci. 44:838,852, 2004. © 2004 Society of Plastics Engineers. [source] Recycling of poly(ethylene terephthalate) as polymer-polymer composites,POLYMER ENGINEERING & SCIENCE, Issue 4 2002M. Evstatiev Microfibrillar reinforced composites (MFC) comprising an isotropic matrix from a lower melting polymer reinforced by microfibrils of a higher melting polymer were manufactured under industrially relevant conditions and processed via injection molding. Low density polyethylene (LDPE) (matrix) and recycled poly(ethylene terephthalate) (PET) (reinforcing material) from bottles were melt blended (in 30/70 and 50/50 PET/LDPE wt ratio) and extruded, followed by continuous drawing, pelletizing and injection molding of dogbone samples. Samples of each stage of MFC manufacturing and processing were characterized by means of scanning electron microscopy (SEM), wide-angle X-ray scattering (WAXS), dynamic mechanical thermal analysis (DMTA), and mechanical testing. SEM and WAXS showed that the extruded blend is isotropic but becomes highly oriented after drawing, being converted into a polymer-polymer composite upon injection molding at temperatures below the melting temperature of PET. This MFC is characterized by an isotropic LDPE matrix reinforced by randomly distributed PET microfibrils, as concluded from the WAXS patterns and SEM observations. The MFC dogbone samples show impressive mechanical properties,the elastic modulus is about 10 times higher than that of LDPE and about three times higher than reinforced LDPE with glass spheres, approaching the modulus of LDPE reinforced with 30 wt% short-glass fibers (GF). The tensile strength is at least two times higher than that of LDPE or of reinforced LDPE with glass spheres, approaching that of reinforced LDPE with 30 wt% GF. The impact strength of LDPE increases by 50% after reinforcement with PET. It is concluded that: (i) the MFC approach can be applied in industrially relevant conditions using various blend partners, and (ii) the MFC concept represents an attractive alternative for recycling of PET as well as other polymers. [source] Blends of bitumen with polymers having a styrene componentPOLYMER ENGINEERING & SCIENCE, Issue 7 2001A. H. Fawcett The properties of a 100 penetration grade bitumen are modified considerably, and in a number of ways by the addition of 10 to 40 parts per hundred (pph) of a homopolystyrene and graft, block and random copolymers of styrene with butadiene and acrylonitrile. At low temperatures some blends have a similar stiffness to or even lower stiffness than the bitumen, but generally the blends are more than one order of magnitude stiffer, even when a rubber is added. The contrasting behavior is displayed by a polystyrene and a high impact polystyrene, ,3% to 4% of grafted rubber on the latter being sufficient to cause the enhancement, even at the 10 pph level, by two different random styrene-butadiene copolymers, and also by blends consisting of different amounts of SBS block copolymer. Some polymers apparently trigger a Hartley inversion of the micellar structure of the asphaltene micelles. High low temperature stiffness correlates roughly with a lower Tg' as measured by the peak maximum in the E, plots of the dynamic mechanical thermal analysis (DMTA) and by the steps in the differential scanning calorimetry (DSC) curves at temperatures below O°C. Tan , maxima and DSC traces detected the glass transition in the continuous phase and in the dispersed phases, but none of these amorphous polymers formed a crystalline phase, though the DSC traces of the polystyrene and the SBS blends suggested that the polymer-rich phases underwent an aging/ordering process on cooling. Our SBS blends differ in phase inversion behavior and the pattern of loss processes from others that had a smaller asphaltene component. [source] | |||||||||||||