• Macromolecular Research
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• v.15 no.7
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• pp.676-681
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• 2007

A process designed to synthesize rigid polyurethane foam (PUF) with insulative properties via the modulation of PUF cell size via the addition of clay and the application of ultrasound was assessed. The blowing agents utilized in this study include water, cyclopentane, and HFC-365mfc, all of which are known to be environmentally-friendly blowing agents. The rigid PUFs were prepared from polymeric 4,4'-diphenylmethane diisocyanate (PMDI) and polyether polyol with a density of $50kg/m^3$. In addition, rigid PUFs/clay nanocomposites were synthesized with clay modified by PMDI with and without the application of ultrasound. The PUF generated using water as a blowing agent evidenced the highest tensile strength. The tensile strength of the PUF/nanocomposites was higher than that of the neat PUF and the strength was even higher with the application of ultrasound. The cell size of the PUF/clay nanocomposites was less than that of the neat PUF, regardless of the type of blowing agent utilized. It appears that the higher tensile strength and lower cell size of the PUF/clay nanocomposites may be attributable to the uniform dispersion of the clay via ultrasonic agitation. The thermal conductivity of the PUF/clay nanocomposites generated with HCFC-141b evidenced the lowest value when PUF/clay nanocomposites were compared with other blowing agents, including HFC-365mfc, cyclopentane, and water. Ultrasound has also proven effective with regard to the reduction of the thermal conductivity of the PUF/clay nanocomposites with any of the blowing agents employed in this study. It has also been suggested that the uniformly dispersed clay particles in the PUF matrix function as diffusion barriers, which prevent the amelioration of the thermal insulation property.

• Journal of the Korean Institute of Gas
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• v.8 no.2 s.23
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• pp.1-7
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• 2004

The physical properties of rigid polyurethane foam(PUF) synthesized using various types of blowing agents such as water, HFC-365mfc, HFC-245fa, HCFC-l4lb, CFC-11 and n-pentane were studied. The blending effect of blowing agents were also studied. The thermal conductivity, reaction rate, and cell morphology of the PUF with various blending ratio of blowing agents were investigated. The PUF blown by water shows the highest compressive strength among other single blowing agents. The thermal conductivity of PUFs blown by HFC-245fa and HFC-365mfc are close to that of PUFs blown by CFC-11. When HFC-365mfc was mixed with HFC-245fa(30mo1e$\%$) as coblowing agent, the mechanical property shows the highest value among other coblowing agents. It is that the thermal conductivity of PUFs depends on cell size of PUFs as well as thermal conductivity of blowing agent in gaseous form.

• Elastomers and Composites
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• v.58 no.4
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• pp.208-215
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• 2023

In this study, the properties of polyurethane-polydimethylsiloxane (PU-PDMS) hybrid foams containing different types and contents of physical blowing agents (PBAs) were investigated. Two types of blowing agents, namely physical blowing agents and thermally expandable microspheres (TEM), were applied. The apparent density was measured using precisely cut foam samples, and the pore size was measured using image software. In addition, the microstructure of the foam was confirmed via scanning electron microscopy and transmission electron microscopy. The thermal conductivities related to the microstructures of the different foams were compared. When 0.5 phr of the hydrocarbon-based PBA was added, the apparent density and pore size of the foam were minimal; however, the pore size was larger than that of neat foam. In contrast, the addition of 3 phr of TEM effectively reduced both the apparent density and pore size of the PBAs. The increase in resin viscosity owing to TEM could enhance bubble production stability, leading to the formation of more uniform and smaller pores. These results indicate that TEM is a highly efficient PBA that can be employed to decrease the weight and pore size of PU-PDMS hybrid foams.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.6
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• pp.17-22
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• 2013

Recently, microcellular polymer films have been widely used as absorbents, support cells, and sensors in the industrial fields of IT, NT, BT, and ST. The conventional fabrication methods of microcellular polymer films are not only more complicated than those of non-microcellular polymer films, but also require a longer production time. In this paper, we propose a new hybrid fabrication method for microcellular polymer films; films can be rapidly made using UV laser processing with chemical blowing agents. The experimental results show that the number of the micropores increased with respect to the laser fluence and the concentration of the chemical blowing agents.

• Journal of the Korean Applied Science and Technology
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• v.16 no.2
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• pp.179-185
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• 1999

The effect of blowing agents and inner temperature on the machanical properties of the flexible polyurethane foams were investigated. In the study used that chemical blowing agents is $H_2O$ and support blowing agents. CFC-11, HCFC-114b, dichloromethane, n-penthane, iso-pentane, cyclopentane. The flexible polyurethane foams were foamed by the density of $0.015{\pm}0.002g/cm^3$ and $0.024{\pm}0.002g/cm^3$ which were used in mechanical properties measurements. Inner temperature was measure as long as the preparation of the flexible polyurethane foams of each blowing agents. The density, tensile strength, elongation, tear strength, compression strength and compression set were measured after 48 hours hardening. The result of the study was optimized dichloromethane and cyclopentane at the support blowing agents.

• Applied Chemistry for Engineering
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• v.16 no.3
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• pp.379-384
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• 2005

Polyurethane foams (PUFs) were prepared from polymeric 4,4'-diphenylmethane diisocyanate (PMDI), seven polyols with different functionalities and OH values, silicone surfactant, two catalysts, and three blowing agents. Chlorofluorocarbon (CFC-11), hydrochlorofluorocarbon (HCFC-141b) and hydrofluorocarbon (HFC-365mfc) were used as blowing agents. The effect of gelling and blowing catalysts on basic properties and cell structure of PUF with HCFC-141b was investigated. The cell size of the PUF decreased with an increase in the amount of catalyst from 0 to 2 pph (parts per hundred polyol). In the case of gelling type catalyst, the compressive strength increased from 11.9 to $12.66kg_f/cm^2$ with an increase in the amount catalyst from 0 to 2 pph but the density did not change significantly. The gelling time, density, and compressive strength of the PUF with three different blowing agents were measured. There was no detectable change in their properties. However, the cell structure of PUF with HCFC-141b was not uniform as in the other systems.

• Macromolecular Research
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• v.17 no.1
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• pp.44-50
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• 2009

Rigid polyurethane foams (PUF)s were synthesized with environmentally friendly blowing agents such as a cyclopentane/distilled water (10.0/1.0, pphp) mixture and distilled water only for four different silicone surfactants having different silicone/polyether ratios. An attempt was made to reduce the thermal conductivities of the PUF samples by varying the concentration and the silicone/polyether ratio of the various silicone surfactants. The scanning electron microscopy (SEM) results indicated an optimum concentration of the silicone surfactant of about 1.5 to 2.5 phpp for various surfactants to reduce the cell size and lower the thermal conductivity. The silicone surfactant having a higher silicone/polymer ratio showed a smaller cell size and, therefore, demonstrated the lower thermal conductivity of the PUF samples. From the relation between the thermal conductivity and the cell size of the PUF samples, the smaller cell size improved the thermal insulation property of the rigid PUF for both the PUF samples blown by the cyclopentane/distilled water (10.0/1.0, pphp) mixture and distilled water only. If the blowing agent is fixed, then the cell size is an important factor to decrease the thermal conductivity of the PUF samples. These results indicated that rigid PUF samples having lower thermal conductivity can be obtained by choosing a silicone surfactant containing a higher silicone/polyether ratio, as well as an optimum content of the surfactant.

• Journal of the Korean Institute of Gas
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• v.20 no.2
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• pp.30-34
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• 2016

In this study, we synthesized a phenol foam using a resol-type phenol resin as a research for replacing the polyurethane foam used as an insulator for cryogenic temperature, such as LNG or LPG. Foaming agents for synthesizing a phenolic foam was used HCFC-141b or n-pentane, cyclopentane, n-hexane, cyclohexane and a mixture of HFC-365mfc and HFC-227ea respectively. Cyclohexane as a blowing agent exhibited the most superior insulating performance and compressive strength. The heat resistance of polyurethane foam and phenolic foam blown by the cyclohexane, was higher than polyurethane foam.

• Macromolecular Research
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• v.16 no.3
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• pp.218-223
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• 2008

In order to obtain crosslinked poly(butylene succinate) (PBS) foams with a closed-cell structure, a commercial-grade PBS was first modified in the melt using two different branching agents to increase the melt viscosity. The rheological properties of the branched and crosslinked PBS were examined by varying the amount of the branching agents. The complex viscosity of the crosslinked PBS increased with increasing amount of the branching agent. However, it decreased with increasing frequency. When 2 phr of the branching agent was added to PBS, the storage modulus (G') was higher than the loss modulus (G") throughout the entire frequency range, showing that the addition of a branching agent increases the melt viscosity and elasticity of PBS effectively. Closed-cell PBS foams were prepared by mixing the chemical blowing agent with the crosslinked PBS. The effect of the foaming conditions such as temperature and time, and the amount of the crosslinking agent on the structure of the expanded PBS foams were also investigated.

• Journal of the Korean Institute of Gas
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• v.5 no.4 s.16
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• pp.79-84
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• 2001

In this study, the effect of polyol structure(OH-value, functionality) on the reactivity, mechanical property and cell morphology of polyurethane foam and the possibility of replacing HFC-36smfc was examined by evaluating how each blowing agent(CFC-11, HCFC-l4lb, HFC-36smfc) affects the reactivity, mechanical property and cell morphology. Results of the experiment showed that as the functionality and OH-value of polyol increased, there was an increase in the temperature profile, reaction rate, density and compressive strength. However. as the functionality and OH-value increased. the ceil size became smaller The use of different kinds of blowing agents did not appear to have and significant influence on the temperature profile, reaction rate, density and compressive strength. The foam using HFC-365mfc produced more uniform cells compared to the foam using HCFC-l4lb.