• Macromolecular Research
• /
• v.14 no.3
• /
• pp.318-323
• /
• 2006

We investigated the rheological behaviors and orientation of three different types of layered silicate composite systems under external flow: microcomposite, intercalated and exfoliated nanocomposites. Rheological measurements under shear and uniaxial extensional flows, two-dimensional, small-angle X-ray scattering and transmission electron microscopy were conducted to investigate the properties, as well as nano- and micro-structural changes, of polymer/layered silicate nanocomposites. The preferred orientation of the silicate layers to the flow direction was observed under uniaxial extensional flow for both intercalated and exfoliated systems, while the strain hardening behavior was observed only in the exfoliated systems. The degree of compatibility between the polymer matrix and clay determined the microstructure of polymer/clay composites, strain hardening behavior and spatial orientation of the clays under extensional flow.

• Proceedings of the KIEE Conference
• /
• 1999.11d
• /
• pp.935-937
• /
• 1999

In this study, 1-3 type composite specimens were fabricated with PZT powders prepared by the molten-salt synthesis method and Eccogel polymer matrix. A virtual level-meter was fabricated with a 1-3 type composite probe and electronic unit for underwater application. There was no difference in values between a virtual and measured level on its level meter.

• Polymer(Korea)
• /
• v.28 no.4
• /
• pp.321-327
• /
• 2004

The applications of dental restorative composite resins containing 2,2-bis [4-(2-hydroxy-3-me-thacryloyloxy propoxy) phenyl] propane as a base resin, and triethylene glycol dimethacrylate, as a diluent, were often limited in dentistry due to the relatively large amount of volumetric shrinkage that occurs during the curing reaction. In this study, in order to reduce volumetric shrinkage of the current dental restorative composite resin, asymmetric spiro orthocarbonates were synthesized and then the characteristics of resin composites containing them were explored. The volumetric shrinkage of the dental composites containing spiro orthocarbonates was decreased approximately 45%. However, the curing characteristics and mechanical properties of the new dental composites were slightly poor than those of the commercially available dental composite.

• Advances in nano research
• /
• v.14 no.5
• /
• pp.443-450
• /
• 2023

Carbon nanotubes (CNTs) have received increased interest in reinforcing research for polymer matrix composites due to their exceptional mechanical characteristics. Its high surface area/volume ratio and aspect ratio enable polymer-based composites to make the most of its features. This study focuses on the experimental tensile testing and fabrication of carbon nanotube reinforced composite (CNTRC) beams, exploring various micromechanical models. By examining the performance of these models alongside experimental results, the research aims to better understand and optimize the mechanical properties of CNTRC materials. Tensile properties of neat epoxy and 0.3%; 0.4% and 0.5% by CNT reinforced laminated single layer (0°/90°) carbon fiber composite beams were investigated. The composite plates were produced in accordance with ASTM D7264 standard. The tensile test was performed in order to see the mechanical properties of the composite beams. The results showed that the optimum amount of CNT was 0.3% based on the tensile capacity. The capacity was significantly reduced when 0.4% CNT was utilized. Moreover, the experimental results are compared with Finite Element Models using ABAQUS. Hashin Failure Criteria was utilized to predict the tensile capacity. Good conformance was observed between experimental and numerical models. More importantly is that Young' Moduli of the specimens is compared with the prediction Halpin-Tsai and Mixture-Rule. Although Halpin-Tsai can accurately predict the Young's Moduli of the specimens, the accuracy of Mixture-Rule was significantly low.

• Journal of Mechanical Science and Technology
• /
• v.17 no.2
• /
• pp.171-180
• /
• 2003

One of the most significant problems in the processing of composite materials is residual stress. The high residual stress may cause cracking in the matrix without external loads and degrade the integrity of composite structures. In this study, thermo-viscoelastic residual stresses occurred in an aluminum liner-inserted polymer composite cylinder are investigated. This type of the structure is used for rocket fuselage due to the convenience to attach payloads and equipment to the metal liner by machining. The time and degree of cure dependent thermo-viscoelastic constitutive equations are developed and coupled with a thermo-chemical process model. These equations are solved with the finite element method to predict the residual stresses in the composite cylinder and also in the interface between the liner and the composite during cure.

• Applied Chemistry for Engineering
• /
• v.9 no.4
• /
• pp.579-584
• /
• 1998

Polymer dispersed liquid crystal(PDLC) composite films were made by polymerization induced phase separation method using UV-curing to investigate the effect of fabrication conditions, such as photoinitiator concentration, film thickness, polymerization temperature, and electric field during polymerization, etc., on the electro-optic properties. As the amount of photoinitiator increased, the driving voltage of PDLC device increased due to the increase of small-size liquid crystal phases. This was considered as the results from the increased interfacial area between liquid crystal (LC) and polymer matrix, since LC molecules at the interfacial regions were relatively difficult to response for the applied electric field. When the higher molecular weight oligomer (PTDA-1000) was used as matrix, the initial transmittance was observed to be relatively higher than that for the lower molecular weight oligomer (PTDA-250). Saturation transmittance for PTDA-1000 was observed at relatively lower voltage than that for PTDA-250, of which transmittance was not saturated even at 60 V. As polymerization temperature increased, the initial transmittance of resulting PDLC film increased due to the larger LC droplets formation and the more matched refractive index between LC and matrix than those cases for the lower polymerization temperature. Though driving voltage decreased for the thinner film, it was considered that optimum thickness of the film should be maintained to get some practical contrast, which is the ratio of off- and on-state transmittance. Furthermore, electro-optic properties such as initial transmittance, driving voltage, and response time were observed to be considerably affected by application of external field during polymerization.

• Polymer(Korea)
• /
• v.31 no.6
• /
• pp.491-496
• /
• 2007

In the polymeric dental restorative composites, the resin matrix mainly contains 70 wt% 2,2-bis[4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane (Bis-GMA), as a base resin and 30 wt% triethylene glycol dimethacrylate (TEGDMA) as a diluent. Even though the viscosity of the resin matrix is rapidly decreased by adding TEGDMA, addition of TEGDMA to the Bis-GMA results in reduction in the mechanical properties and increase in the curing shrinkage of the dental composite. In order to fabricate dental composite exhibiting excellent properties by reducing TEGDMA content in the resin matrix, in this study, Bis-GMA derivatives, which do not contain hydroxyl groups, were used instead of Bis-GMA. The curing characteristics of Bis-GMA derivatives were similar with those of Bis-GMA, while the former exhibited lower viscosity and water absorption than the latter. Comparing the curing shrinkage of the dental composite containing Bis-GMA derivative with that prepared from Bis-GMA, the reduction in curing shrinkage was about 25%. Dental composites prepared from new resin matrices also exhibited low water uptake and better properties in mechanical strength.

• Polymer(Korea)
• /
• v.24 no.6
• /
• pp.829-836
• /
• 2000

In order to recyle the FRP waste from SMC bathtubs and rock-crush sludge obtained as a byproduct of stones, the composite consisting of the FRP and rock-crush sludge and the unsaturated polyester matrix resin were prepared. To enhance the interfacial bonding force between the reinforcements and the matrix resin, the rock-crush sludge was treated with silane coupling agent, ${\gamma}$-methacryloxypropyltrimethoxysilane (${\gamma}$-MPS) and their mechanical properties and interface phenomena were examined. The flexural modulus of the composite containing 10 wt% rock-crush powder treated with 3 wt% silane coupling agent showed the maximum value. And also the initial thermal degradation temperature of composites were in the range of 352~359$^{\circ}C$. From these results, we observed that the weight loss of composites was almost constant regardless of the concentration of silane coupling agent. It is confirmed that the interface of the composites containing filler treated with ${\gamma}$-MPS was improved in that there were no pull-out phenomena between the reinforcement and matrix resin.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.24 no.7
• /
• pp.547-553
• /
• 2011

We investigated the dielectric and mechanical properties of ceramic polymer composite xBNT - (1-x)LCP (x= 0, 10, 20, 30, 40 vol.%). The disk shaped BNT ($BaNd_2Ti_4O_{12}$) - LCP (liquid crystal polymer) composite samples were prepared by compression molding method. With increasing the BNT content in composites from 10 to 40 vol.%, the dielectric constant increased but the dielectric loss as well as bending strength of composites reduced. These composites were well described with modified Lichtenecker's model having k = 0.392 and 0.303 for the first and second ball milled BNT filled composites, which means that the BNT filler in composites are well dispersed. The dielectric constant of the composite comprised of the second milled BNT ($D_{50}$ = 1.39 um) was higher that of the composite of the first milled BNT ($D_{50}$= 2.45 um), which seems to be related with the different particle size and dispersion of BNT fillers in LCP matrix. The bending strength of the composite containing the second milled BNT was superior to that of the composite of the first milled BNT.

• Composites Research
• /
• v.21 no.3
• /
• pp.18-23
• /
• 2008

The Rapid Prototyping (RP) technology has advanced in many application areas. In this research, implantable Drug Delivery System (DDS) was fabricated by an RP system, Nano Composite Deposition System (NCDS). The DDS composite consists of 5-fluorouracil (5-FU), as drug particles, and PLGA85/15 as biodegradable polymer matrix. To have larger surface area, the DDS was fabricated in a scaffold shape, and its degradation was tested in vitro environment. Biocompatible Hydroxyapatite (HA) powders were added to the drug-polymer composite in order to control drug release. Test results showed a possibility of controlled release of scaffold DDS over 50 days.