Prediction of the viscoelastic response of filler network in highly nanofilled polymer composites

Journal of Elastomers & Plastics

Mortezaei

et al. 2016

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Highly filled systems, such as dental materials and tires, have some exceptional properties that make them very special for particular scientists and engineers. In this study, the thermal and dynamic properties of highly nanosilica-filled polystyrene were investigated. Thermal study predicts a phase in the filled system, named as adsorbed polymer, that has a different glass transition temperature (T g ) compared with the neat polymer. The adsorbed polymer seems to be responsible for special thermal properties of the highly filled system. The dynamic properties of the filled system are observed to have a similar trend as the thermal behavior at different particle sizes and concentrations, both increasing linearly with the increase of volume fraction of adsorbed polymer. However, at higher volume fractions or for smaller particles, this trend changes and the filler networking mechanism is considered to be the reason for this change. Effect of the filler network is studied through the Han plot and it is found that the contribution of the filler network to the dynamic behavior of the highly filled system increases by reducing the particle size and increasing the particle loading. Beside the particle size and concentration, the effect of filler surface physics on dynamic and thermal behavior of the highly filled system is investigated and it is found that surface modification of the particle surface with nonpolar groups tends to lower T g and volume fraction for the adsorbed phase and lower strength of the filler network. In this work, the samples were prepared using the method of stabilizing suspension in polymer solution. For viscoelastic investigation, the dynamic rheometry in sweep mode was chosen, also for studying the thermal Downloaded from behavior, differential scanning calorimetric tests were performed. In addition, in order to study the structure of filler in low and highly filled samples, atomic force microscopic imaging was employed.

Section: Resultsmentioning

confidence: 94%

“…40 From this figure, one can infer that the T g of nanocomposites is only a function of amount of adsorbed polymer.…”

Section: Thermal Studymentioning

confidence: 94%

Highly nanofilled polystyrene composite

Journal of Elastomers & Plastics

Mortezaei

et al. 2016

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“…Available surface area, adsorbed layer thickness and density of particle structure are estimated from the density of nanocomposites. 33 The value of is determined from the WLF equation at 193 C, i.e. 7 C lower than test temperature, 25 and the test temperature (200 C) is considered as the reference temperature.…”

Section: Comparison With Experimental Resultsmentioning

confidence: 99%

Modeling the rheological properties of highly nano-filled polymers

Mortezaei²,

Journal of Composite Materials

et al. 2016

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Organic and inorganic materials are usually added to polymers in order to achieve some benefits such as reducing the product cost, as well as achieving higher modulus and strength. Addition of these materials would change polymers' behavior. Adding nano-materials to polymers on the other hand is a new challenge in the field of polymer composites where previous studies were unable to achieve good correlation with nano-composites at higher particle volume fractions. In this research, Yamamoto network theory is developed to investigate the behavior of highly nano-filled systems. For this purpose, five different types of sub-chain and two types of junctions are considered and the effect of particle size, concentration, and the model parameters in association with the behavior of the junctions are studied. Moreover, some experiments are performed on polystyrene filled with nano-silica at different particle size and concentration values in frequency mod in the linear region. At last, we compared the results of our final model with the experiments in order to evaluate its accuracy, which confirmed a very good agreement.

“…Also, smaller particles or higher concentrations result in stronger network in nanocomposites. 28 Replacing polar groups on particle surface with nonpolar ones reduces particle network strength.…”

Section: Theorymentioning

confidence: 99%

“…properties of adsorbed polymer) and filler network properties. 28 On the other hand, these parameters are affected by some other variables. Effect of hydrodynamic motion of particles in media on filled systems properties is function of particle volume fraction and shape.…”

Section: Theorymentioning

confidence: 99%

Mixing challenges for SiO₂/polystyrene nanocomposites

Journal of Thermoplastic Composite Materials

Mortezaei³

et al. 2017

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Morphology of a nanocomposite, which has indisputable effects on its properties, is determined by its dynamic and thermodynamic conditions. While physical properties of the components of a nanocomposite as well as the interaction between them are the parameters controlling the morphology thermodynamically, their dynamic condition is related to the issues like intensity of mixing and geometry of mixer. In this research, we investigate the mixing process of solution casting method by studying the effects of mixing intensity on the dynamics of the particle structure and hereby its morphology using sedimentation test. In these experiments, mixing is performed at various durations, input energies, and energy types for suspensions containing different particle sizes and concentrations as well as diverse polymer concentrations. We found that increasing mixing time and input energy along with using ultrasonic wave decrease the size of aggregates. Sedimentation test revealed improvements of dispersion and distribution states of suspension by using ultrasonic waves and high shear mixing, respectively. Finally, particle-particle interaction data show increase in the probability of restructuring after mixing with reduction in particle size and increase in particle volume fraction.