Nanofiller-Polymer Interactions At and Above the Glass Transition Temperature

2000 ◽  
Vol 661 ◽  
Author(s):  
Ai-jun Zhu ◽  
Sanford S. Sternstein
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Strain Amplitude ◽  
Filler Content ◽  
Loss Modulus ◽  
Surface Treatments ◽  
Filler Concentration ◽  
Large Strains ◽  
Chain Entanglement

ABSTRACTRheological data are reported for a series of fumed silica filled PVAc samples, using fillers of different specific surface areas and surface treatments. Data at the glass transition temperature and 45 C above Tg are presented. The addition of filler systematically increases Tg, and all samples obey time-temperature superposition. However, temperature normalized and frequency normalized plots of loss modulus indicate that there is no change in the dispersion of the glass transition, with the only exception being a surface modified with covalently bonded polymer chains. Thus, contrary to expectations, an increase in filler content or change in surface treatment has no effect on the relative shape of the relaxation time spectrum at the glass transition. At 45 C above Tg, different behavior is observed. The filler concentration has a major effect on the nonlinearity of dynamic moduli vs. strain amplitude, with higher filler content reducing the strain amplitude at which nonlinear behavior is observed. Specific filler surface treatments result in major changes in the shape of the loss factor versus strain amplitude relationship. These results suggest that interfacial interactions strongly modify the far-field polymer behavior with respect to chain entanglement slippage at large strains.

Dynamic Mechanical Analysis of Nanosilica Filled Epoxy Nanocomposites

2014 ◽  
Vol 699 ◽  
pp. 239-244 ◽  
Author(s):  
Nurhidayah R. Zamani ◽  
Aidah Jumahat ◽  
Rosnadiah Bahsan
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Epoxy Polymer ◽  
Loss Modulus ◽  
Matrix Material ◽  
Mechanical Analysis ◽  
Dynamic Mechanical ◽  
Mechanical Stirring ◽  
Tan Δ

In this study, Dynamic Mechanical Analyzer (DMA) was used to study the effect of nanoparticles, which is nanosilica, on glass transition temperature (Tg) of epoxy polymer. A series of epoxy based nanosilica composite with 5-25 wt% nanosilica content was prepared using mechanical stirring method. The weight fractions of nanosilica in epoxy were 5 wt%, 13 wt% and 25 wt%. 30mm x 10mm x 3mm size specimens were tested using DMA machine from room temperature up to 180oC at 2°C/min heating rate. From the analysis of the results, dynamic modulus and glass transition temperature of pure polymer and nanosilica filled polymer were obtained. The glass transition of a polymer composite is a temperature-induced change in the matrix material from the glassy to the rubbery state during heating or cooling. Glass transition temperature Tg was determined using several method: storage modulus onset, loss modulus peak, and tan δ peak. The results showed that the presence of nanosilica reduced Tg of epoxy polymer.

The Dynamic Viscoelastic Behavior of Wood-Plastic Composites

2013 ◽  
Vol 815 ◽  
pp. 639-644 ◽  
Author(s):  
Pei Ying Liu ◽  
Zhi Hong Jiang
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Storage Modulus ◽  
Loss Modulus ◽  
Viscoelastic Behavior ◽  
Peak Frequency ◽  
Wood Plastic Composite ◽  
Plastic Composite ◽  
Positive Effect

Wood-plastic composite is a kind of viscoelastic materials. This paper presents the dynamic viscoelastic behavior of WPCs at different temperature, frequency and bamboo flours levels. The storage modulus decreased with the rise of temperature, the loss modulus and tanδ increased as temperature increased but decreased after reaching the peak. Frequency had a little influence on storage modulus and loss modulus, but the glass transition temperature increased with the increase of frequency, while the tanδ decreased. The glass transition temperature of this kind WPCs is about 85°C. The addition of bamboo flours had a positive effect on the dynamic viscoelastic behavior. From the results above, the activation energy of the WPCs was measured using an Arrhenius relationship to investigate the interphase between the wood and plastic.

Characterization of Thermo-Electric Interface Material with Carbon Nanotubes

2007 ◽  
Vol 1056 ◽  
Author(s):  
Piyush R Thakre ◽  
Yordanos Bisrat ◽  
Dimitris C Lagoudas
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Electrical Conductivity ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Epoxy Matrix ◽  
Loss Modulus ◽  
Single Wall Carbon Nanotubes ◽  
Electrical Percolation

ABSTRACTAn approach has been presented in the current work to fabricate and characterize nanocomposite systems for optimizing electrical and thermal properties without sacrificing mechanical properties. An epoxy matrix based nanocomposite system has been processed with different volume fractions of carbon nanotubes. The purpose was to tailor macroscale properties to meet competing performance requirements in microelectronics industy. The nanofiller consisted of comparatively low cost XD grade carbon nanotubes (XD-CNTs) that are optimized for electrical properties. This system was compared with another system consisting of single wall carbon nanotubes (SW-CNTs) as nano-reinforcements in epoxy matrix. The electrical percolation threshold (about seven orders of magnitude increase in electrical conductivity) measured by dielectric spectroscopy was found to be at lower loading weight fraction of SWCNTs (0.015 weight %) as compared to XD-CNTs (0.0225 weight %). However, the electrical conductivity after percolation was higher for XD-CNTs reinforced epoxy with respect to SW-CNTs filled nanocomposites. The governing mechanisms for this phenomenon were investigated using transmission optical microscope. The enhancement in thermal conductivity, measured using differential scanning calorimetry, was found to be moderate at lower weight loadings corresponding to electrical percolation. However, a 90% improvement in thermal conductivity was observed for 0.3 weight percent of XD-CNTs. Dynamic mechanical analysis was performed to measure the storage and loss modulus along with the glass transition temperature. No significant change in modulus values and glass transition temperature was measured for nanocomposites varied filler contents with respect to neat matrix.

Mechanical properties of nylon 6-clay hybrid

1993 ◽  
Vol 8 (5) ◽  
pp. 1185-1189 ◽  
Author(s):  
Yoshitsugu Kojima ◽  
Arimitsu Usuki ◽  
Masaya Kawasumi ◽  
Akane Okada ◽  
Yoshiaki Fukushima ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Glass Transition ◽  
Elastic Modulus ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Loss Modulus ◽  
Nylon 6 ◽  
Heat Distortion Temperature ◽  
Molecular Composites ◽  
Silicate Layers

Various nylon 6-clay hybrids, such as molecular composites of nylon 6 and silicate layers of montmorillonite and saponite, NCH's and NCHP's, respectively, have been synthesized. To estimate the mechanical properties of these hybrids, tensile, flexural, impact, and heat distortion tests were carried out. NCH was found superior in strength and modulus and comparable in impact strength to nylon 6. The heat distortion temperature (HDT) of NCH (montmorillonite: 4.7 wt. %) was 152 °C, which was 87 °C higher than that of nylon 6. In NCHP, saponite had a smaller effect on the increase of these mechanical properties. The modulus and HDT of NCH and NCHP increased with an increase in the amount of clay minerals. It was found that these properties were well described by the contribution of the constrained region calculated from the storage and loss modulus at the glass transition temperature. According to the mixing law on elastic modulus, the following expression was obtained between the modulus E at 120 °C and the fraction of the constrained region C, En = Ecn = C, where the values of n and Ec (modulus of the constrained region) were 0.685 and 1.02 GPa, respectively.

scholarly journals The viscoelasticity and deformation mechanism of Taxodium hybrid ‘Zhongshanshan’ wood by dynamic mechanical analysis

BioResources ◽  
2021 ◽  
Vol 16 (4) ◽  
pp. 6933-6942
Author(s):  
Yuehua Zhu ◽  
Yaoli Zhang ◽  
Biao Pan
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Moisture Content ◽  
Storage Modulus ◽  
Loss Modulus ◽  
Structural Deformation ◽  
Hydrothermal Processing ◽  
Average Loss ◽  
The Difference

The viscoelasticity of Taxodium hybrid ‘Zhongshanshan’ wood, while undergoing hydrothermal processing, was investigated via dynamic thermomechanical analysis. The results showed that the elastic deformation and viscous deformation of the Taxodium hybrid ‘Zhongshanshan’ heartwood were greater than the sapwood. The heartwood average storage modulus and average loss modulus were greater than the sapwood. The difference between the heartwood and sapwood had little effect on the average glass transition temperature of their hemicellulose, which was approximately 74 °C. The radial average storage modulus was greater than the tangential, and the difference between the average loss modulus in the radial and tangential directions was negligible. The average glass transition temperature in the radial direction was slightly lower than the tangential direction. As the moisture content increased, the average storage modulus and its average hemicellulose glass transition temperature decreased. The average glass transition temperature tended to be lower as the moisture content increased. This study revealed the structural deformation and molecular movement of Taxodium hybrid ‘Zhongshanshan’ wood, while undergoing hydrothermal processing; this has important theoretical value for understanding its characteristics as well as its rational and efficient usage.

Physical Modelling and Identification of Polymer Viscoelastic Behaviour above Glass Transition Temperature and Application to the Numerical Simulation of the Hot Embossing Process

2013 ◽  
Vol 554-557 ◽  
pp. 1763-1776 ◽  
Author(s):  
Gang Cheng ◽  
Jean Claude Gelin ◽  
Thierry Barrière
Keyword(s):  
Numerical Simulation ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Storage Modulus ◽  
Loss Modulus ◽  
Maxwell Model ◽  
Hot Embossing ◽  
Finite Element Software ◽  
Generalized Maxwell Model

The experimental processing parameters, such as applied pressure and forming temperature have been analysed during polymer hot embossing of micro-cavities. The viscoelastic characteristics of polymer above the glass transition temperature have been investigated with the classical viscoelastic models. Generalized Maxwell Model has been used to describe polymer behaviours in the glass transition temperature range. The parameters include relaxation time, storage modulus and loss modulus of the Generalized Maxwell Model that have been introduced. The identification of polymer characteristics has been carried out through Dynamic Mechanical Analysis (DMA). The storage modulus, the loss modulus and the damping factor of the selected polymer have been obtained with different imposed frequencies. The master curve of complex modulus has been obtained by applying the time temperature superposition principle. The experimental data has been identified with optimized fitting parameters of Generalized Maxwell Model. A proper agreement between the experimental measurement and the identification of viscoelastic model is observed. The resulting constitutive equations have been implemented in finite element software in order to achieve the numerical simulation of the hot embossing process.

Thermal Viscoelastic Analysis of 3D Fabric Nanocomposites

2008 ◽  
Vol 47-50 ◽  
pp. 1133-1136 ◽  
Author(s):  
Nan Jia Zhou ◽  
Andrey Beyle ◽  
Christopher C. Ibeh
Keyword(s):  
Thermal Analysis ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Loss Tangent ◽  
Viscoelastic Properties ◽  
Vinyl Ester ◽  
Loss Modulus ◽  
Viscoelastic Analysis ◽  
Storage And Loss Moduli

Viscoelastic properties of 3D fabric reinforced Vinyl Ester composites were studied in different directions using Dynamic Mechanical Thermal Analysis (DMTA). Such materials filled by nanoparticles (silicon carbide) with different concentrations were also investigated. The increases of storage and loss moduli with addition of nanoparticles and with increase of their concentrations were observed. The maximal tangent of the angle of mechanical losses was especially compared at below and over glass transition temperature. Below glass transition temperature the presence of nanoparticles increases storage and loss moduli and loss tangent. These effects achieved maximum at glass transition temperature. Over glass transition, the loss modulus and loss tangent are decreased with increase of the concentration of nanoparticles.

Characterizing Properties of Asphalt Cement at Cold Temperatures

1996 ◽  
Vol 1545 (1) ◽  
pp. 59-66 ◽  
Author(s):  
Mary Stroup-Gardiner ◽  
Dave Newcomb ◽  
Rachel DeSombre
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Loss Modulus ◽  
High Reliability ◽  
Cold Temperature ◽  
Tensile Creep ◽  
Test Results ◽  
Cold Temperatures ◽  
Brittle Point

A range of binder test results for Strategic Highway Research Program (SHRP) Materials Reference Library asphalts were used to identify critical low-temperature behavior. Test results were obtained from in-house testing, Minnesota Department of Transportation (Mn/DOT) testing, and previously reported SHRP research reports. Tests used were the Fraass brittle point, bending beam, a dynamic shear rheometer (DSR), and differential scanning calorimetry (DSC) glass transition temperature. A good correlation between the Fraass brittle point and the bending beam rheometer limiting stiffness indicated that the Fraass brittle point represented the behavior of a binder at a stiffness of approximately 200 MPa. Because the traditional method of using the DSR to obtain the glass transition temperature, Tg, from the peak of the loss modulus curve did not provide sufficiently specific results, the temperature at which a minimum phase angle was used to define the Tg instead. These results showed a good correlation with the bending beam results and a strong correlation with the Fraass brittle point. The DSC results were not well correlated with either the rheometer results or the Fraass brittle point. This appears to be due to the intricacies related to interpreting DSC data. Binder results were compared with results reported by SHRP researchers for the indirect tensile creep and thermal stress restrained specimen test. Results indicated that cold-temperature mixture properties are predominantly due to binder properties. Results also indicated that the asphalt source was more important than the asphalt grade in defining cold-temperature properties. The two binders used to construct the Minnesota Road Research facility on I-94 in Otsego were classified by Mn/DOT as PG 58-28 and PG 58-22, respectively. The Canadian SHRP researchers’ equation for estimating the minimum design pavement temperature indicated a cold-temperature design temperature of —28°C, but the SHRP 90 percent reliability grading indicated that a PG 58-40 was needed. Evaluation of the pavement performance over two winters—the first of which was extremely cold even by Minnesota standards—showed that the PG 58-28 had no thermal cracks while the PG 58-22 test sections had 12 transverse cracks. This indicates that the Canadian SHRP equation may be considered a high-reliability minimum design temperature.

Capacitance and Glass Transition Temperature of Nano Structured Alumina Polycarbonate Composites

2013 ◽  
Vol 446-447 ◽  
pp. 73-78
Author(s):  
L.K. Sudha ◽  
Roy Sukumar ◽  
K. Uma Rao
Keyword(s):  
Differential Scanning Calorimetry ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Filler Concentration ◽  
Conductivity Measurements ◽  
Composite Polymer ◽  
Scanning Calorimetry ◽  
Base Polymer ◽  
Ac Conductivity Measurements

This paper describes how glass transition temperature (Tg) and capacitance (Cp) of a nanomodified composite polymer changes as compared to that of its base polymer. Because of its versatile applications, polycarbonate materials (grade PC1100 and PC1220 respectively), which are commercially available, were chosen as the base polymer in this study and nanostructured alumina material was used as filler for fabricating the desired composites by varying the filler weight in the composite materials. The Tg of the composites has been evaluated by differential scanning calorimetry (DSC) technique and Cp of the composites are derived from AC conductivity measurements of the composites. Results show that the Tg decreases as a function of filler load in the composite material whereas capacitance of the composites increase with the filler load in the composites. A filler concentration equal to or greater than 5 wt% in the said composites, the Tg of the composites reduces upto 15°C, whereas Cp shoots up in the pico-farad range with the same level of filler load, as compare to base polymers.

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