scholarly journals Structural Arrest and Thermodynamic Scaling in Filler-Reinforced Polymers

2009 ◽  
Vol 82 (2) ◽  
pp. 202-213 ◽  
Author(s):  
C. G. Robertson ◽  
R. Bogoslovov ◽  
C. M. Roland
Keyword(s):  
Glass Transition ◽  
Volume Fraction ◽  
Filler Concentration ◽  
Scaling Exponent ◽  
Segmental Dynamics ◽  
Reinforced Polymers ◽  
Filler Volume Fraction ◽  
Segmental Relaxation ◽  
Filler Network

Abstract The role of small silica particles on the stiffness and glass transition dynamics of polyvinylacetate (PVAc) was examined for filler volume fraction (ϕ) from 0 to 0.28. Whereas the influences of bound polymer and a strain-dependent filler network were clearly noted in the shear properties, the only effect of filler on the bulk modulus was the reduction in deformable polymer. The calorimetric glass transition of PVAc and its dependence on cooling rate were unaltered by the presence of the silica, in agreement with previous dielectric relaxation results. In contrast to the temperature dependence of the segmental dynamics, which was independent of ϕ, the effect of volume on segmental relaxation was amplified by the addition of silica. This resulted in larger values for the thermodynamic scaling exponent (γ), which also increased sharply at the filler concentration corresponding to the development of a percolated filler network.

scholarly journals Glass Transition and Interfacial Segmental Dynamics in Polymer-Particle Composites

2008 ◽  
Vol 81 (3) ◽  
pp. 506-522 ◽  
Author(s):  
C. G. Robertson ◽  
C. M. Roland
Keyword(s):  
Glass Transition ◽  
Relaxation Times ◽  
Polymer Particle ◽  
Polymer Chains ◽  
Nano Particle ◽  
Segmental Mobility ◽  
Segmental Dynamics ◽  
Reinforcing Fillers ◽  
Segmental Relaxation ◽  
Polymer Interaction

Abstract We review the literature concerned with the effect of proximity to a filler surface on the local segmental mobility of polymer chains. This mobility is commonly assessed from either the glass transition temperature, Tg, or the segmental relaxation times measured by mechanical, dielectric, or NMR spectroscopy. Published studies report increases, decreases, or no change in Tg upon the addition of carbon black, silica, and other reinforcing fillers. Similarly, the segmental relaxation times have been found to increase or be invariant to the presence of nanometer-sized particles. Some of these discrepancies can be ascribed to ambiguous methods of data analysis; others likely reflect the variation in filler-polymer interaction among different systems. There are unequivocal examples of polymers that have segmental dynamics and glass transitions unaffected by nano-particle reinforcement. However, the general principles governing the behavior remain to be clarified, with further work, focusing on the micromechanics at the particle interface, required for resolution of this important aspect of rubber science and technology.

Effects of counterion size and backbone rigidity on the dynamics of ionic polymer melts and glasses

2017 ◽  
Vol 19 (40) ◽  
pp. 27442-27451 ◽  
Author(s):  
Yao Fu ◽  
Vera Bocharova ◽  
Mengze Ma ◽  
Alexei P. Sokolov ◽  
Bobby G. Sumpter ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Relaxation Time ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Polymer Melts ◽  
Static Dielectric Constant ◽  
Segmental Dynamics ◽  
Ionic Polymer ◽  
Segmental Relaxation

Backbone rigidity, counterion size and the static dielectric constant affect the glass transition temperature, segmental relaxation time and decoupling between counterion and segmental dynamics in significant manners.

scholarly journals GLASS TRANSITION IN RUBBERY MATERIALS

2012 ◽  
Vol 85 (3) ◽  
pp. 313-326 ◽  
Author(s):  
C. Michael Roland
Keyword(s):  
Glass Transition ◽  
Chemical Structure ◽  
Relaxation Times ◽  
Material Constant ◽  
Scaling Exponent ◽  
Fundamental Understanding ◽  
Thermodynamic Conditions ◽  
Perturbation Frequency ◽  
Thermodynamic Variables

ABSTRACT When the perturbation frequency imposed on a rubber falls within the glass transition zone of its viscoelastic spectrum, energy absorption is maximized. This phenomenon is the operative mechanism for various applications of elastomers requiring large energy dissipation. Nevertheless, a fundamental understanding of the glass transition is lacking. The diversity of properties that depend both on chemical structure and thermodynamic conditions makes modeling difficult and a first principles theory perhaps unachievable; indeed, the number of models for the glass transition seems to be inversely proportional to their ability to accurately describe the myriad behaviors. The progress made at quantifying the role of the thermodynamic variables temperature, T, and density, ρ, on the dynamics is described. An important aspect of the work was the discovery that relaxation times and viscosities of molecular liquids and polymers superpose when plotted against the scaling variable T/ργ, with the scaling exponent γ a material constant sensibly related to the nature of the intermolecular repulsive potential; thus, dynamic spectroscopy measurements can be used to quantify the forces between molecules. Other properties derive from the scaling behavior, including the Boyer-Spencer rule and the correlation of fluctuations in the potential energy with fluctuations in the virial pressure.

Viscoelastic Properties Assessment of Syntactic Foams by Dynamic Mechanical Analysis

2010 ◽  
Vol 636-637 ◽  
pp. 280-286 ◽  
Author(s):  
Carlos Capela ◽  
José A. Martins Ferreira ◽  
José Domingos M. Costa
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Dynamic Mechanical Analysis ◽  
Glass Fibre ◽  
Volume Fraction ◽  
Mechanical Analysis ◽  
Fibre Reinforcement ◽  
Dynamic Mechanical ◽  
Filler Volume Fraction

Low-density sheet moulding compounds incorporating hollow glass micro-spheres are being increasing used namely in automotive industry, boats and deep-water submarines and core materials. This paper presents the results obtained in a current study of the viscous properties on hybrid short fibre/hollow glass microspheres composites fabricated with epoxy binder. Dynamic mechanical analysis (DMA) was used to study the effect of the filler volume fraction and of the addition of glass fibre reinforcement on the dynamic stiffness modulus, damping coefficient and glass transition temperature in tensile mode. The specimens were cut from plates produced by resin transfer moulding in vacuum with microspheres weight contents up to 13%. Elastic modulus decreases significantly with the increasing of filler volume fraction. In contrary, it increases significantly with the glass fibre reinforcement content. Glass transition temperature apparently tends to decrease with microspheres and of glass fibre reinforcement’s content. Tmax temperatures tend to increase slightly with the addition of fibre reinforcements and the microsphere filler. Maximum damping coefficient is much lower for the foams when compared with net resin.

scholarly journals Study on the Effects of the Interphase Region on the Network Properties in Polymer Carbon Nanotube Nanocomposites

Polymers ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 182 ◽  
Author(s):  
Yasser Zare ◽  
Kyong Yop Rhee
Keyword(s):  
Percolation Threshold ◽  
Polymer Nanocomposites ◽  
Volume Fraction ◽  
Excluded Volume ◽  
Positive Role ◽  
Interphase Region ◽  
Network Properties ◽  
High Fraction ◽  
Filler Network

The interphase region around nanoparticles changes the percolation threshold of long and thin nanoparticles, such as carbon nanotubes (CNT) in polymer nanocomposites. In this paper, the effects of the interphase region on the percolation threshold of nanoparticles and the network fraction are studied. New percolation threshold (φP) is defined by the role of the interphase in the excluded volume of nanoparticles (Vex). Moreover, the influences of filler and interphase size on the percolation volume fraction, the fraction of nanoparticles in the network as well as the volume fraction and relative density of the filler network are investigated. The least ranges of “φP” are obtained by thin and long CNT. Similarly, a thick interphase increases the “Vex” parameter, which causes a positive role in the percolation occurrence. Also, thin CNT and a thick interphase cause the high fraction of the filler network in the nanocomposites.

Functionally graded elastomeric composites as microwave shielding media

2016 ◽  
Vol 49 (1) ◽  
pp. 37-46 ◽  
Author(s):  
Raghunandan Sharma ◽  
Sandeep S Ahankari ◽  
Kamal K Kar ◽  
Animesh Biswas ◽  
KV Srivastav
Keyword(s):  
Iron Powder ◽  
Volume Fraction ◽  
Sheet Thickness ◽  
Functionally Graded ◽  
Filler Concentration ◽  
Scattering Parameter ◽  
Filler Volume Fraction ◽  
Microwave Shielding ◽  
Microwave Reflection ◽  
Elastomeric Composites

Magnetic particle-filled elastomeric composites are of significant importance in microwave shielding applications. An attempt has been made to enhance the microwave reflection properties of such composites by introduction of a magnetic filler concentration gradient along the thickness. Iron powder-filled functionally graded elastomeric composites (FGECs) are prepared by a construction-based method, wherein the volume fraction of iron powder is varied along the sheet thickness. The reflection losses of the uniformly dispersed elastomeric composites (UDECs) and of the FGECs, both employing same average amount of filler, has been measured through a reflection method with a vector network analyser, using the complex scattering parameter S11. FGECs with equal sample thickness and filler volume fraction exhibit 2.5 times higher microwave reflection over a broader frequency range, as compared to that of the UDECs. For a volume fraction of 0.39, the reflection losses of FGECs and UDECs at 12.3 GHz are observed to be −50 dB and −19 dB, respectively. The corresponding frequency bandwidth for reflection loss ≤ −15 dB is observed to be 9.4 GHz for FGECs compared to that of 3.5 GHz for UDECs.

scholarly journals FLOCCULATION, REINFORCEMENT, AND GLASS TRANSITION EFFECTS IN SILICA-FILLED STYRENE-BUTADIENE RUBBER

2011 ◽  
Vol 84 (4) ◽  
pp. 507-519 ◽  
Author(s):  
C. G. Robertson ◽  
C. J. Lin ◽  
R. B. Bogoslovov ◽  
M. Rackaitis ◽  
P. Sadhukhan ◽  
...  
Keyword(s):  
Glass Transition ◽  
Coupling Agent ◽  
Volume Fraction ◽  
Polymer Chains ◽  
Styrene Butadiene Rubber ◽  
Butadiene Rubber ◽  
Polymer Filler ◽  
Bound Rubber ◽  
Filler Network ◽  
Styrene Butadiene

Abstract The introduction of silanes to improve processability and properties of silica-reinforced rubber compounds is critical to the successful commercial use of silica as a filler in tires and other applications. The use of silanes to promote polymer–filler interactions is expected to limit the development of a percolated filler network and may also affect the mobility of polymer chains near the particles. Styrene-butadiene rubber (SBR) was reinforced with silica particles at a filler volume fraction of 0.19, and various levels of filler–filler shielding agent (n-octyltriethoxysilane) and polymer–filler coupling agent (3-mercaptopropyltrimethoxysilane) were incorporated. Both types of silane inhibited the filler flocculation process during annealing the uncured rubber materials, thus reducing the magnitude of the Payne effect. In contrast to the significant reinforcement effects noted in the strain-dependent shear modulus, the bulk modulus from hydrostatic compression was largely unaltered by the silanes. Addition of polymer–filler linkages using the coupling agent yielded bound rubber values up to 71%; however, this bound rubber exhibited glass transition behavior which was similar to the bulk SBR response, as determined by calorimetry and viscoelastic testing. Modifying the polymer–filler interface had a strong effect on the nature of the filler network, but it had very little influence on the segmental dynamics of polymer chains proximate to filler particles.

scholarly journals Effect of Filler on Glass Transition of Asphalt Mastics

2012 ◽  
Vol 5 ◽  
pp. 376-381 ◽  
Author(s):  
Meng Guo ◽  
Yi Qiu Tan ◽  
Lei Zhang
Keyword(s):  
Differential Scanning Calorimetry ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Volume Fraction ◽  
Mechanical Analysis ◽  
Scanning Calorimetry ◽  
Filler Volume Fraction ◽  
Asphalt Mastics ◽  
Dsc Method

A study has been carried out of the glass transition of fifteen asphalt-filler mastics in three different filler types. The dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) method were used. The results show that DMA method can measure asphalt Tg of asphalt-filler mastics more accurately than DSC; The glass transition temperature measured by DMA is generally higher by 20~40oC than that measured by DSC; The glass transition temperature of the asphalt-filler mastics increase with the increase of the filler volume fraction, and andesite is the most sensitive; When the volume fraction of filler is greater than 0.5, the enhance capability of glass transition temperature of asphalt-filler mastics is in the order of andesite > granite > limestone; while the volume fraction of filler is smaller than 0.2, the enhance capability is in the order of granite > limestone > andesite.

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