• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.2
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• pp.348-353
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• 2007

This paper presents design specifications and characteristics of bridge expansion joints to develop new type-joints in fiber reinforced polymer decks. Based on properties of the fiber reinforced polymer decks and fundamental process to calculate their expansion length, new expansion joints fur fiber reinforced polymer decks on typical steel or concrete girder are developed and proposed.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1438_1438
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• 2009

In this describes the results of a study on the thermal expansion of FRP tube/flange for improved tightness characteristics of polymer bushing. The thermal expansion of FRP tube and flange were investigated. The thermal expansion of flange, FRP tube were studied by TGA, TMA. AS winding tension is increased glass fiber contents was increased in the range of 70.89~78.74 and thermal expansion coefficient was decreased in the range of 29.90~13.50.

• Transactions of Materials Processing
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• v.18 no.1
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• pp.20-25
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• 2009

A finite element analysis was carried out for a 4:1 planar contraction die for polymer melts using the viscoelastic constitutive equation of Leonov. Viscoelastic fluids showed significant differences in pressure drop and birefringence in contraction and expansion flows. The pressure drop was higher and the birefringence smaller in expansion than in contraction flow. The difference increased with increasing flow rate. The nonlinear Leonov model was shown to describe the viscoelastic effects observed in experiments.

• Polymer(Korea)
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• v.31 no.2
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• pp.98-104
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• 2007

The expansion behavior of polystyrene (PS) chains with various molecular weights has been investigated above Flory $\Theta$temperature by viscometry after dissolving in the three different mixed solvents systems such as benzene/n-heptane, 1,4-dioxane/isopropanol, and 1,4-dioxane/n-heptane. Two different regimes are observed as increasing temperature: one regime is for the expansion of chain and the other is for the contraction. For the higher molecular weight sample of PS, the higher peak temperature showing its maximum expansion is obtained. Within a certain system of Ps/mixed solvents, the $\tau/\tau_c$ parameter shows universality for the variation of molecular weight. But while each system of Ps/mixed solvents has shown its own different slope, the universality breaks down in the overall system of mixed solvents. However after introducing a new empirical $b^{2/3}\tau/\tau_c$ parameter, all data points of three different systems have dropt on one master curve and the universality of chain expansion has recovered again. Here $\tau$ and $\tau_c$ are defined as $(T-\Theta)/\Theta$ and $(\Theta-T_c)/T_c$, respectively and $T_c$ is the critical solution temperature, and b of Schultz-Flory equation is corresponding to the effective slope in the plot of $1/T_c$ against $1/M_w^{1/2}$.

• Korean Journal of Materials Research
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• v.25 no.12
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• pp.678-682
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• 2015

The electrical property of polymer matrix composites with added carbon powder is studied based on the temperature dependency of the conduction mechanism. The temperature coefficient of the resistance of the polymer matrix composites below the percolation threshold (x) changed from negative to positive at 0.20 < x < 0.21; this trend decreased with increasing of the percolation threshold. The temperature dependence of the electrical property(resistivity) of the polymer matrix composites below the percolation threshold can be explained by using a tunneling conduction model that incorporates the effect of the thermal expansion of the polymer matrix composites into the tunneling gap. The temperature coefficient of the resistance of the polymer matrix composites above the percolation threshold has a positive value; its absolute value increased with increasing volume fraction of carbon powder. By assuming that the electrical conduction through the percolating paths is a thermally activated process and by incorporating the effect of thermal expansion into the volume fraction of the carbon power, the temperature dependency of the resistivity above the percolation threshold can be well explained without violating the universal law of conductivity.

• Polymer(Korea)
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• v.31 no.3
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• pp.206-214
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• 2007

The theoretical study is developed for predicting the thermal expansion changes of composites which include complex inclusion, which is used three-dimensional ellipsoid model ($a_1>a_2>a_3$), which has two aspect ratios (the primary aspect ratio, $\rho_{\alpha}=a_1/a_3$ and the secondary aspect ratio, $\rho_{\beta}=a_1/a_2$). We can predict the feature of general thermal expansion factors by theoretical approach of matrix with aligned ellipsoidal inclusion using the Eshelby's equivalent tensor. The coefficients of longitudinal linear thermal expansion ${\alpha}_{11}$ decrease to those of inclusions, ${\alpha}_f$, as both aspect ratios increase. The coefficients of transverse linear thermal expansion of composites ${\alpha}_{33}$ initially increase and show the parabolic corves with maximum values, as the concentrations of filler increase. The coefficient of thermal expansion, ${\alpha}_{22}$ in the transverse direction decreases, as $\rho_{\alpha}$ increases, however, ${\alpha}_{22}$ increases as $\rho_{\beta}$ increases. The coefficient of linear thermal expansion of composites, ${\alpha}_{33}$ in the normal direction increases, as $\rho_{\alpha}$ increases, while ${\alpha}_{33}$ decreases as $\rho_{\beta}$ increases.

• Journal of the Korea Concrete Institute
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• v.24 no.4
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• pp.491-498
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• 2012

This study examines setting shrinkage, coefficient of thermal expansion, and elastic modulus of unsaturated polyester( UP)-methyl methacrylate(MMA) polymer concrete, which is generally used for repair of portland cement concrete pavement and manufacturing of precast products. In this study, a series of laboratory test were conducted with variables such as UP-MMA ratio, shrinkage reducing agent (SRA) content, and test temperature. The results showed that the setting shrinkage ranged from 29.2 to $82.6{\times}10^{-4}$, which was significantly affected by test temperature. Moreover, the findings revealed that the coefficient of thermal expansion, elastic modulus and ultimate strain of UP-MMA based polymer concrete ranged from 21.6 to $31.2{\times}10^{-6}/^{\circ}C$, 2.8 to $3.3{\times}10^4$ MPa, and 0.00381 to 0.00418, respectively. The results of this study will be used as important data for design and application of UP-MMA based polymer concrete.

• Polymer(Korea)
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• v.31 no.2
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• pp.160-167
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• 2007

This paper proposes a model for the solutions predicting the coefficient of thermal expansion of composites including fiber-like shaped$(a_1>a_2=a_3)$ and disk-like shaped$(a_1=a_2>a_3)$ inclusions like two dimensional geometries, which was analyzed by one axis and a single aspect ratio, $(\rho_\alpha=a_1/a_3)$. The analysis follows the procedure developed for elastic moduli by using the Lee and Paul's approach. The effects of the aspect ratio on the coefficient of thermal expansion of composites containing aligned isotropic inclusions are examined. This model should be limited to analyze the composites with unidirectionally aligned inclusions and with complete binding to each other of both matrix and inclusions having homogeneous properties. The longitudinal coefficients of thermal expansion $\alpha_{11}$ decrease and approach the coefficient of thermal expansion of filler, as the aspect ratios increase. However, the transverse coefficients of thermal expansion $\alpha_{33}$ increase or decrease with the aspect ratios.

• Journal of the Korea Institute of Building Construction
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• v.8 no.5
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• pp.85-91
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• 2008

Prepacked concrete has recently been used in the special constructions fields such as underwater concrete work, heavy-weight concrete work, underground structure work, partial repair works for damaged reinforced concrete structures. and polymer-modified mortars have been employed as grouting mortars for the prepacked concrete. The purpose of this study is to recommend the optimum mix design of polymer-modified grouting mortars for prepacked concrete. Polymer-modified mortars using SBR and EVA emulsions as admixture of grouting mortars for prepacked concrete are prepared with various mix proportions such as sand-binder ratio, fly ash replacement ratio, polymer-binder ratio. and tested for flowability, viscosity of grouting mortars, bleeding ratio, expansion ratio, flexural and compressive strengths of grouting mortars and compressive and tensile strengths of prepacked concretes. From the test results, it is apparent that polymer-modified mortars can be produced as grouting mortars when proper mix design is chosen. We can design the mix proportions of high strength mortars for prepacked concrete according to the control of mix design factors such as type of polymer, polymer-binder ratio, sand-binder ratio and fly ash replacement ratio. Water-binder ratio of plain mortars for a constant flowability value are in the ranges of 43% to 50%. SBR-modified mortar has a little water-binder ratios compared to those of plain mortar, however, EVA-modified mortar needs a high water-binder ratio due to a high viscosity of polymer dispersion. The expansion and bleeding ratios of grouting mortars are also controlled in the proper value ranges. Polymer-modified grouting mortars have good flexural. compressive and tensile strengths, are not affected with various properties with increasing fly ash replacement to cement and binder-sand ratio. In this study, SBR-modified grouting mortar with a polymer-binder ratio of 10% or less, a fly ash replacement of 10% to cement and a sand-binder ratio of 1.5 is recommended as a grouting mortar for prepacked concrete.

• Korean Journal of Materials Research
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• v.30 no.2
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• pp.93-98
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• 2020

Effective control of the heat generated from electronics and semiconductor devices requires a high thermal conductivity and a low thermal expansion coefficient appropriate for devices or modules. A method of reducing the thermal expansion coefficient of Cu has been suggested wherein a ceramic filler having a low thermal expansion coefficient is applied to Cu, which has high thermal conductivity. In this study, using pressureless sintering rather than costly pressure sintering, a polymer solution synthesis method was used to make nano-sized Cu powder for application to Cu matrix with an AlN filler. Due to the low sinterability, the sintered Cu prepared from commercial Cu powder included large pores inside the sintered bodies. A sintered Cu body with Zn, as a liquid phase sintering agent, was prepared by the polymer solution synthesis method for exclusion of pores, which affect thermal conductivity and thermal expansion. The pressureless sintered Cu bodies including Zn showed higher thermal conductivity (180 W/m·K) and lower thermal expansion coefficient (15.8×10^-6/℃) than did the monolithic synthesized Cu sintered body.