Dynamic Mechanical Analysis Measurements Research Articles

Prospects of poly (vinyl alcohol)/Chitosan/poly (styrene sulfonic acid) and montmorillonite Cloisite®30B clay composite membrane for direct methanol fuel cells

A proton conducting polymer electrolyte nanocomposite membrane has been fabricated by using poly (vinyl alcohol) (PVA), Chitosan, and poly (styrene sulfonic acid) (PSSA) polymers and montmorillonite Cloisite®30B clay with the objective of its application in direct methanol fuel cells. Comparative studies of a PVA/PSSA/Chitosan/Cloisite30B clay composite membrane with a base PVA/PSSA membrane has been carried out by using thermal gravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, X-ray diffraction, methanol permeability and proton conductivity measurements. Properties of the membrane have been compared with Nafion®117 at identical test conditions. Methanol permeability of the PVA/PSSA/Chitosan/Cloisite30B clay composite membrane has been found to be superior to that of PVA/PSSA as well as Nafion117 membranes. Water uptake of the membrane is much higher compared to the Nafion117 membrane. Proton conductivity of the membrane has been found in the range of 10−2 S cm−1 at room temperature and 70% relative humidity. Selectivity of the membrane is in the range of 104 S s cm−3, which is better than that of Nafion117.

Effect of CO2 fixation reaction on the thermal and dynamic mechanical properties of tetrafunctional epoxy resin

A tetrafunctional epoxy resin was modified using CO2 fixation process in the presence of tetra-n-butyl ammonium bromide as catalyst. The unmodified tetrafunctional epoxy resin (UMTE) and CO2 fixated modified tetrafunctional epoxy resin (CFMTE) were cured by diethylenetriamine. A bifunctional glycidyl ether compound was used as a reactive diluent to control the viscosity of CFMTE. The activation energy of curing reaction was computed using the advanced integral isoconversional method. The activation energy, which depends on the conversion, was considerably changed due to the CO2 fixation process. The thermal stability parameters including the initial degradation temperature, the temperature at the maximum rate of weight loss (T max), and the decomposition activation energy (E d) were determined by thermal gravimetry. Dynamic mechanical thermal analysis measurements showed that the CO2 fixation decreases the T g of the epoxy resin. The surface morphology of UMTE and CFMTE were determined by scanning electron microscope. It is concluded that CO2 fixation reaction improves the properties of tetrafunctional epoxy resin.

Effects of mesoporous silica coated multi-wall carbon nanotubes on the mechanical and thermal properties of epoxy nanocomposites

Mesoporous silica coated multi-wall carbon nanotubes (denoted as CNTs@MS) were prepared using sodium silicate as the silica source and gelatin as the surface-activation agent. The effects of CNTs@MS on the mechanical and thermal properties of epoxy composite are investigated in this study. The electron microscopy images and Fourier transform infrared spectra demonstrate integral coating of the mesoporous silica on the CNTs. Because of the polar silica shell, the CNTs@MS exhibited uniform dispersion in epoxy-based nanocomposite. The thermal and mechanical properties of nanocomposites were characterized using dynamic mechanical analysis (DMA), thermo-mechanical analysis (TMA) and thermal conductivity measurement. These results show that the storage modulus and thermal conductivity increased along with the amount of CNTs@MS (0.25, 0.5, 1.0 and 2.0wt%). The coefficient of thermal expansion decreased gradually, because the dipole–dipole interactions between the silica and epoxy polymer and confinement space of the mesoporous structure reduced the thermal mobility of the epoxy polymer inside the mesopore space.

Modification of bifunctional epoxy resin using CO2 fixation process and nanoclay

A bifunctional epoxy resin was modified by using a CO2 fixation solution process in the presence of tetra n-butyl ammonium bromide (TBAB) as catalyst and the modified treated resin was treated by cloisite 30B as nano additive. The Unmodified epoxy resin (UME), CO2 fixated modified epoxy resin (CFME), and CFME/clay nano composite (CFMEN), were cured by diethylenetriamine (DETA). A cycloaliphatic compound as a reactive diluent was used to control the viscosity of high viscose CFME. The exfoliation of organoclay in UME and CFME was investigated by X-ray diffraction and activation energy was computed using the advanced integral isoconversional method. The activation energy dependency demonstrated that the mechanism of UME curing did not change in the presence of nanoclay. In contrast, the CO2 fixation results showed a significant change in the activation energy dependency. The Thermal stability parameters include the initial degradation temperature (IDT), the temperature at the maximum rate of weight loss (Tmax), and the decomposition activation energy (Ed) were determined by thermal gravimetry analysis. Dynamic mechanical thermal analysis measurements showed that the presence of organoclay in CFME increases the Tg of nano composite in contrast to UME. The fracture roughness of UME, CFME and CFNE were determined by scanning electron microscope. The exfoliated UME/1%clay nanocomposite was confirmed by TEM image.

Effect of Rubber Contents on Tribological and Thermomechanical Properties of Polybenzoxazine

Bisphenol-A/aniline based polybenzoxazine (PBZ) modified with amine terminated butadiene–acrylonitrile (ATBN) were prepared. The tribological and thermomechanical properties as well as thermal stability of the PBZ/ATBN copolymers were investigated by ball-on-disc tribometer, dynamic mechanical analysis (DMA), universal test machine and thermogravimetric analysis (TGA). The inclusion of ATBN at a mass fraction of 5% was found to greatly increase friction coefficient and wear resistance of the copolymers. DMA measurements showed that the storage modulus and the glass transition temperature of the PBZ can be maintained with an addition of ATBN in the range of 1-5wt%. Moreover, flexural property measurements indicated that the flexural strength of the copolymer increased with increasing of ATBN content up to 10wt% whereas TGA results revealed that an increase of the PBZ content can help improve thermal stability of the copolymers.

Small and large signal ferroelectric properties of single lead zirconium titanate fibers

Ferroelectric fibers based on a commercial lead zirconium titanate powder were investigated by a new characterization method to measure single fiber properties, such as large signal polarization and longitudinal free strain, and small signal properties, such as piezoelectric constant. To verify the measurements, the free strain data were compared with dynamic mechanical analyzer measurements. For this investigation, lead zirconate titanate fibers were sintered in lead-rich atmosphere at different temperatures. Microstructure and phase composition were analyzed by scanning electron microscope and X-ray diffraction. By increasing the temperature from 1150°C to 1200°C, the electromechanical behavior of the fibers could be improved: an increase in remnant and saturation polarization occurred. A d33 as of ∼430 and ∼400 pm/V could be measured for 1150°C and 1200°C, respectively. These d33 values are very close to the one reported on the data sheet of the material.

Preparation and properties of cyclopentadiene-containing monomer modified polydicyclopentadiene

A series of 1,4-dicyclopentadienylmethyl benzene (DMB) enhanced polydicyclopentadiene (DMB/polyDCPD blends) and 2,2′-dicyclopentadienyl ether (DCPE) toughened polyDCPD (DCPE/polyDCPD blends) were prepared via the ring-opening metathesis polymerisation (ROMP). The curing behaviour, thermal and mechanical properties were investigated. Differential scanning calorimetry (DSC) investigations of the DMB/polyDCPD blends showed the samples exhibited similar singular exothermic peak, and the exothermic peak of blends shifted to a higher temperature direction compared with the unfilled polyDCPD. However, the exothermic peak of the DCPE/polyDCPD blends presented two exothermic peaks. Dynamic mechanical analysis (DMA) measurements exhibited that the glassy modulus was enhanced as the DMB content increased. Thermal performance of DMB/polyDCPD has been enhanced with an increasing amount of DMB which was investigated by thermo gravimetric analysis (TGA) measurements. Whereas, the thermal stabilities of the DCPE/polyDCPD blends have been weakened with an increasing amount of DCPE. Moreover, the toughness of the DCPE/polyDCPD blends displayed a maximum performance at 60 wt% loading of DCPE.

Effects of partial miscibility on the structure and properties of novel high performance blends composed of poly(p-phenylene sulfide) and poly(phenylsulfone)

Although super-engineering plastics show superb thermal stabilities and long lifetime, their mechanical properties are often insufficient due to their molecular stiffness, as observed for poly(p-phenylene sulfide) (PPS). In the present study, a novel blend of two super-engineering plastics, PPS and poly(phenylsulfone) (PPSU), was investigated in detail. Differential scanning calorimetry and dynamic mechanical analysis (DMA) measurements revealed for the first time that the PPS/PPSU blends showed partial miscibility. The desirable interfacial adhesion achieved by the partial miscibility and the segmental mobility of PPSU, observed as a transition peak at approximately −100 °C in the DMA measurements, most likely contributed to remedying the brittleness of PPS. Furthermore, small-angle X-ray scattering measurements revealed that the PPSU chains intruded into the amorphous region between the PPS lamellae during the crystallization of PPS as a result of the interlamellar segregation of the PPSU chains, which were partially miscible with PPS in the molten state. Thermogravimetric analysis measurements under a nitrogen atmosphere demonstrated that the thermal stabilities of PPS blends were significantly improved by the addition of PPSU.

Acoustic composite laminates with unidirectional fiber reinforcement by novel pultrusion drawing

Three types of composites prepared by special pultrusion technology are tested for acoustic suitability as designed for industrial production of vibrating rods. Thermosetting pultrusion as a novel technique is introduced in more details. Isophtalic polyester matrix (Ashland S 599) reinforced by glass roving (OCV) discharged optimum results providing best listening tests in accordance with the dynamic mechanical analysis measurements of relative bend factor (Young’s modulus) and glass transformation temperature (Tg) as well as with the transverse vibrational frequencies and the sound attenuation in impact tests.

Tensile behavior and dynamic mechanical analysis of novel poly(lactide/δ-valerolactone) statistical copolymers

Lactide-co-δ-valerolactone copolymers (PLVL) have not attracted as much research interest as the more popular poly(lactide-co-ε-caprolactone) (PLCL) elastomeric materials. In this work the study of the mechanical performance is focused on the former with the aim of identifying the potential advantages of these thermoplastic elastomers for their application in the biomedical field. Mechanical testing (at 21°C and at 37°C) of at least 5 specimens and dynamic mechanical analysis (DMA) in duplicate were carried out on various PLVL, which include a moderately blocky l-lactide/δ-valerolactone copolymer (~70% of l-LA and R=0.68) and several that showed a random distribution of sequences (R~1): some terpolymers based on l-lactide, d-lactide and δ-valerolactone (with a lactone content of ~25 and ~14%) and a series of copolymers of l-LA and δ-VL having l-LA molar contents ranging from 69 to 74%. In view of the results, it can be concluded that noteworthy improvements in stiffness and strength were achieved by adding δ-VL to the reaction mix instead of ε-CL, although both monomers have analogous chemical properties. For example, a PLVL with a 75:25M composition of l-LA/δ-VL at 21°C presented a secant modulus of 213.7±36.5MPa and σu=14.7±1.4MPa whereas a previously studied PLCL of equal composition had a secant modulus and an ultimate stress value of 19.4±1.3MPa and 3.2±0.6MPa, respectively. At 37°C, the differences in the mechanical properties between the different PLVLs of this work were far less relevant, with most of them showing a fully elastomeric behavior. Referring to the DMA measurements, the reduction in the peak of tan δ (from ~2.5 to 0.5) through the glass transition was a clear indicator that crystalline domains formed during hydrolytic degradation in some of the polymers. However, the more amorphous PLVLs with short l-LA average sequence lengths (ll-LA<2.91) did not undergo changes in the storage modulus and tan δ curves after two weeks submerged in PBS at 37°C.

Viscoelastic properties and long-term stability of polystyrene-carbon nanotube nanocomposites. Effect of the nature of the carbon nanotubes and modification by ionic liquid

Abstract Dynamic mechanical analysis (DMA) measurements have been used for determining the viscoelastic behaviour of polystyrene (PS) nanocomposites containing a 1 wt.% of single- or multi-walled carbon nanotubes, both pristine (SWCNT and MWCNT) and modified by previous treatment with a room-temperature ionic liquid (SWCNTm and MWCNTm). Two sets of multiple frequency tests have been carried out. The Arrhenius relationship has been used to estimate the apparent activation energies for the glass transition. Master curves have been generated using the time–temperature superposition principle. The nanocomposites show an increase of the activation energy up to an 8% with respect to PS, in the order PS + MWCNT > PS + MWCNTm > PS + SWCNTm > PS + SWCNT > PS. The nanophases also induce a displacement of the onset of the storage modulus to longer times following the order PS + SWCNTm > PS + SWCNT > PS + MWCNT > PS + MWCNTm > PS, at 40 °C. At higher temperatures, the storage modulus onset is very similar for all materials. In the case of PS + SWCNTm, the period of time for the onset of the storage modulus is multiplied by a factor of 28 with respect to PS. The surface modification of the SWCNT by the ionic liquid could improve the interfacial compatibility. The results described here show that a very low proportion of carbon nanotubes can effectively improve the long-term stability of PS under service temperature conditions.

Mechanical investigation of confined amorphous phase in semicrystalline polymers: Case of PET and PLA

The effect of confinement onto the mechanical properties of the amorphous phase of Polyethylene terephthalate (PET) and poly(lactic acid) (PLA) was investigated. These polymers have the advantage of being in bulk amorphous or in semicrystalline state allowing mechanical and physical investigation of the amorphous phase on bulk and confined configuration. Based on small angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA) experiments, the micro-structural arrangement of the amorphous and crystalline phase, the rigid amorphous fraction, and the visco-elastic mechanical properties of the different semicrystalline samples were investigated. DSC results help quantifying the rigid amorphous fraction dependence on the crystallinity. DMA measurements lead to quantify the viscoelastic properties of the free and confined amorphous phases for PET and PLA polymers. Indeed, based on the DMA tests, where the maximum of tan(δ) peak is usually related to the glass transition temperature, shifts upon crystallization, the mechanical properties of the restricted and mobile amorphous phase were determined. This result was correlated along with the amorphous phase thickness distribution determined by SAXS results. This observation was bolstered based on literature results about geometrical confinement configurations and their effect on the glass transition temperature of polymeric materials. POLYM. ENG. SCI., 55:397–405, 2015. © 2014 Society of Plastics Engineers

Preparation and properties of high performance phthalide‐containing bismaleimide reinforced polydicyclopentadiene

ABSTRACTA series of phenolphthalein‐containing bismaleimide (PPBMI) reinforced polydicyclopentadiene blends (PPBMI/polyDCPD) were prepared via the ring‐opening metathesis polymerization of DCPD in the presence of PPBMI. The crosslinked networks between PPBMI and polyDCPD backbones resulted in the reinforced structures. The curing behavior, thermal, and mechanical properties were investigated. Differential scanning calorimetry investigations showed the samples exhibit similar singular exothermic peak, and the exothermic peak of the PPBMI/polyDCPD blends slightly shifted to a lower temperature direction compared with the unfilled polyDCPD, meanwhile, the exothermic peak of the PPBMI/polyDCPD blends slightly shifts back to a higher temperature direction with the PPBMI content increased. Both dynamic mechanical analysis and thermo gravimetric analysis measurements revealed the optimal thermal performance of PPBMI/polyDCPD was obtained with 20 wt % loading of PPBMI. In addition, while PPBMI content increased, the weight loss peak at 100–200°C disappeared and the temperature of maximum rate of decomposition (Td,max) increased. Moreover, bending tests showed the best mechanical performance was achieved at 5 wt % loading of PPBMI in blends. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40474.

Semi-interpenetrating polymer networks prepared from in situ cationic polymerization of bio-based tung oil with biodegradable polycaprolactone

In situ cationic polymerization of bio-based tung oil in the presence of poly(e-caprolactone), a crystallizable, biodegradable, and biocompatible polymer, was performed to produce novel semi-interpenetrating polymer networks (IPNs). The macromolecular structure and properties of these IPNs were investigated as a function of composition using small amplitude oscillatory shear flow rheology, FT-IR spectroscopy, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). This versatile and low-cost strategy successfully produced bio-polymer blends with various degrees of miscibility, morphology, and crystallization behavior. The carbon–carbon double bonds in tung oil were consumed quickly after adding the cationic initiator to form a three-dimensional (3D) crosslinked network in all measured samples as confirmed by FT-IR. A complete miscible structure with a single glass transition temperature and one-phase morphology was observed for a tung oil/PCL 90/10 blend. On the other hand, a two-phase structure exhibiting a nanoscale morphology of the dispersed minor phase as small as 100 nm was observed for blends with 20 and 30 wt% PCL. For a 50 wt% PCL blend, an interconnected, co-continuous microstructure of the two phases was also detected. DMA and DSC measurements confirmed the miscibility (or partial miscibility) of the blends by following the changes in the glass transitions of phases as a function of the composition. The value of the elastic modulus (E′) in the glassy state as obtained from the DMA measurements was strongly dependent on the composition, reaching a maximum at 20 wt% PCL.

Relationship between polishing performance and viscoelasticity of epoxy resin polishing pads

Polishing performances of glass using epoxy resin polishing pads from the aspect of their mechanical properties are described. Material removal rates are independent to the hardness of the epoxy resin pads. The different types of epoxy resin pads are produced by varying the composition of the resin and the curing agent. Dynamic mechanical analysis (DMA) of the epoxy and conventional urethane resin polishing pads was conducted to investigate the relationship between the material removal rates and the mechanical properties of the epoxy resin polishing pads. DMA measurement indicates that the epoxy resin polishing pads showed a significant difference in the storage and loss modulus compared to the conventional urethane pads. Moreover, the epoxy resin pads showed a higher loss tangent (tan δ) than the urethane resin polishing pad. From the investigation of the relationship between the material removal rates and tan δ of the polishing pads, the strong positive correlation between the material rate and tan δ is observed. Finally, the dependence of polishing conditions on the material removal rate by the epoxy and urethane resin pads is evaluated. It is found that the difference in the material removal rate between the epoxy and urethane resin pads becomes larger under a condition of a low abrasive concentration and a high rotation rate.

Structure and properties of thermoplastic polyurethanes based on poly(dimethylsiloxane): Assessment of biocompatibility

Properties and biocompatibility of a series of thermoplastic poly(urethane-siloxane)s (TPUSs) based on α,ω-dihydroxy ethoxy propyl poly(dimethylsiloxane) (PDMS) for potential biomedical application were studied. Thin films of TPUSs with a different PDMS soft segment content were characterized by (1) H NMR, quantitative (13) C NMR, Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), contact angle, and water absorption measurements. Different techniques (FTIR, AFM, and DMA) showed that decrease of PDMS content promotes microphase separation in TPUSs. Samples with a higher PDMS content have more hydrophobic surface and better waterproof performances, but lower degree of crystallinity. Biocompatibility of TPUSs was examined after attachment of endothelial cells to the untreated copolymer surface or surface pretreated with multicomponent protein mixture, and by using competitive protein adsorption assay. TPUSs did not exhibit any cytotoxicity toward endothelial cells, as measured by lactate dehydrogenase and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide assays. The untreated and proteins preadsorbed TPUS samples favored endothelial cells adhesion and growth, indicating good biocompatibility. All TPUSs adsorbed more albumin than fibrinogen in competitive protein adsorption experiment, which is feature regarded as beneficial for biocompatibility. The results indicate that TPUSs have good surface, thermo-mechanical, and biocompatible properties, which can be tailored for biomedical application requirements by adequate selection of the soft/hard segments ratio of the copolymers.

Biomaterials from blends of fluoropolymers and corn starch—implant and structural aspects

The development of polymeric blends to be used as matrices for bone regeneration is a hot topic nowadays. In this article we report on the blends composed by corn starch and poly(vinylidene fluoride), PVDF, or poly(vinylidene fluoride-trifluoroethylene), P(VDF-TrFE), to obtain biocompatible materials. Blends were produced by compressing/annealing and chemically/structurally characterized by micro-Raman scattering and Fourier transform infrared (FTIR) absorption spectroscopies, dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM), besides in vivo study to evaluate the tissue response. Vibrational spectroscopy reveals no chemical interaction between the polymers and starch, absence of material degradation due to compressing/annealing process or organism implantation, and maintenance of α and ferroelectric crystalline phases of PVDF and P(VDF-TrFE), respectively. As a consequence of absence of interaction between polymers and starch, it was possible to identify by SEM each material, with starch acting as filler. Elastic modulus (E′) obtained from DMA measurement, independent of the material proportion used in blends, reaches values close to those of cancellous bone. Finally, the in vivo study in animals shows that the blends, regardless of the composition, were tolerated by cancellous bone.

Influence of g-C3N4Nanosheets on Thermal Stability and Mechanical Properties of Biopolymer Electrolyte Nanocomposite Films: A Novel Investigation

A series of sodium alginate (SA) nanocomposite films with different loading levels of graphitic-like carbon nitride (g-C3N4) were fabricated via the casting technique. The structure and morphology of nanocomposite films were investigated by X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. Thermogravimetric analysis results suggested that thermal stability of all the nanocomposite films was enhanced significantly, including initial thermal degradation temperature increased by 29.1 °C and half thermal degradation temperature improved by 118.2 °C. Mechanical properties characterized by tensile testing and dynamic mechanical analysis measurements were also reinforced remarkably. With addition of 6.0 wt % g-C3N4, the tensile strength of SA nanocomposite films was dramatically enhanced by 103%, while the Young's modulus remarkably increased from 60 to 3540 MPa. Moreover, the storage modulus significantly improved by 34.5% was observed at loadings as low as 2.0 wt %. These enhancements were further investigated by means of differential scanning calorimetry and real time Fourier transform infrared spectra. A new perspective of balance was proposed to explain the improvement of those properties for the first time. At lower than 1.0 wt % loading, most of the g-C3N4 nanosheets were discrete in the SA matrix, resulting in improved thermal stability and mechanical properties; above 1.0 wt % and below 6.0 wt % content, the aggregation was present in SA host coupled with insufficient hydrogen bondings limiting the barrier for heat and leading to the earlier degradation and poor dispersion; at 6.0 wt % addition, the favorable balance was established with enhanced thermal and mechanical performances. However, the balance point of 2.0 wt % from dynamic mechanical analysis was due to combination of temperature and agglomeration. The work may contribute to a potential research approach for other nanocomposites.

EFFECT OF POLYSULFANE SILANIZED SILICA ON THE MORPHOLOGY AND MECHANICAL PROPERTIES OF BROMBUTYL RUBBER VULCANIZATES

ABSTRACT Polysulfane silanized white silica particles were prepared by treating with various loadings of bis(3-trie-thoxysilylpropyl)tetrasulfide (TESPT) in a high-speed mixer. Brombutyl rubber (BIIR) vulcanizates filled with the silanized silica were prepared by compression molding. Compared with BIIR/untreated silica vulcanizate, the mechanical properties of BIIR/silanized silica vulcanizates improved prominently with the increase of TESPT loading and reached peak value with the TESPT loading increasing up to 2 phr but declined slightly with the continuous increment of the TESPT. Effects of various loadings of TESPT on the mechanical properties of BIIR vulcanizates were investigated by testing mechanical properties, vulcanizing properties, bound rubber, scanning electron microscopy, and dynamic mechanical analysis (DMA) to determine the extent of rubber-filler interaction. As shown in vulcanizing properties, bound rubber, and DMA measurements, the bound rubber content, cross-link density, and storage and loss modulus of BIIR vulcanizates clearly increased with the TESPT loading increasing from 0 to 2 phr and then reduced somewhat with a continuous increase of TESPT; the tanδmax value decreased significantly with the increment of TESPT loading from 0 to 2 phr and increased sharply with the TESPT content increasing to 4 phr. These experimental results indicate that the improvement in the mechanical properties of BIIR vulcanizates was mostly attributed to a strong BIIR–silica interaction and an effective dispersion of the silica. On the other hand, the decline of mechanical properties can be explained by the excess TESPT, as a kind of physical diluent, having an adverse effect on the silica dispersion and cross-link reaction. By forming the silica aggregates on the mixing, the poor dispersion of silica could cause the decline of relative volume content of silica in the matrix.

Physical and Gas Transport Properties of Asymmetric Hyperbranched Polyimide-Silica Hybrid Membranes

Physical and gas transport properties of the asymmetric hyperbranched polyimide (HBPI) -silica hybrid membranes prepared with a dianhydride, 4,4’-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), and an asymmetric triamine, 2,4,4’-(triaminodiphenyl)ether (TADE), were investigated and compared with those of the symmetric HBPI-silica hybrid membranes prepared with a symmetric triamine, 1,3,5-tris(4-aminophenoxy)benzene (TAPOB). The HBPI-silica hybrid membranes were prepared via sol-gel reaction using hyperbranched polyamic acid of which end groups were modified with silane coupling agents, water and tetramethoxysilane. The thermal mechanical and dynamic mechanical analysis measurements confirmed that the rigidity of asymmetric HBPI was higher than that of symmetric HBPI because of the rigid and asymmetric structure of TADE monomer. In addition, the degree of branching of asymmetric HBPI is lower than that of symmetric HBPI because of the different reactivity of the three amino groups included in TADE. The rigidity and linearity of HBPIs had an effect on the progression of sol-gel reaction, consequently the gas transport properties. The increasing of the gas permeability coefficient of the asymmetric dianhydride(DA)-HBPI-silica hybrid membranes with increasing silica content was smaller than those of symmetric DA- and amine(AM)-HBPI-silica hybrid membranes. In addition, the gas permeability coefficient of the asymmetric AM-HBPI-silica hybrid membranes decreased with increasing silica content. This was due to the fact that the dispersibility of silica in the asymmetric HBPI-silica hybrids, of which polymer chain was more rigid and linear than those of symmetric HBPI-silica hybrid, was not as fine as in the symmetric HBPI-silica hybrids, and that the long and tortuous diffusion path was newly formed by hybridization with silica.