Peculiarities of Quasi-Isothermal Foaming of the SCF-Plasticized Polylactide: the Effect of Transition from Foam Expansion to Its Collapse

2020 ◽  
Vol 14 (7) ◽  
pp. 1236-1243
Author(s):  
D. A. Zimnyakov ◽  
E. O. Epifanov ◽  
A. V. Kalacheva ◽  
N. V. Minaev ◽  
S. A. Minaeva ◽  
...  
Keyword(s):  
Foam Expansion

Parameter Identification by Inverse Analysis Coupled with a Finite Pointset Method for Polyurethane Foam Expansion

2014 ◽  
Vol 611-612 ◽  
pp. 868-875 ◽  
Author(s):  
Hichem Abdessalam ◽  
Boussad Abbès ◽  
Yu Ming Li ◽  
Ying Qiao Guo ◽  
Elvis Kwassi ◽  
...  
Keyword(s):  
Parameter Identification ◽  
Reaction Temperature ◽  
Inverse Analysis ◽  
Stokes Equations ◽  
Foam Height ◽  
Test Tube ◽  
Navier Stokes ◽  
Foam Expansion ◽  
Mesh Free ◽  
Mesh Free Method

This paper deals with the parameter identification for polyurethane foaming process simulation by using an inverse analysis coupled with a Finite Pointset Method. Simultaneous measurements of the foam height rise, the reaction temperature and the viscosity on a cylindrical cardboard test tube are obtained by using the foam measurement system (FOAMAT). The simulation of the foam expansion is obtained by solving unsteady Navier-Stokes equations coupled with the energy equation, the curing reaction (reaction of isocyanate with polyol) and the foaming reaction (reaction of isocyanate with water to emit the CO2 gas) by using a mesh-free method. The inverse identification method consists in determining the parameters by comparing the computed quantities (height rise, reaction temperature and viscosity) computed by the finite pointset method to those measured experimentally.

scholarly journals The Impacts of Shell Thickness of Thermally Expandable Microspheres on the Application of Vehicle Underbody Coating

2019 ◽  
Author(s):  
Jin-Wook Park ◽  
Sang-Jin Lee ◽  
Sang-Hoon Ji ◽  
Hae-Na You ◽  
Ji-Hoo Kim ◽  
...  
Keyword(s):  
Heat Resistance ◽  
Shell Thickness ◽  
Prolonged Exposure ◽  
Outer Shell ◽  
Industrial Scale ◽  
Cross Linking ◽  
Cross Sectional ◽  
Foam Expansion ◽  
Maximum Expansion ◽  
The Cross

This research was conducted to manufacture thermally expandable microspheres (TEMs) for vehicles’ underbody coating and to apply them on an industrial scale. TEMs heat resistance was studied depending on the ratios of a cross-linking agent and an initiator. This research focused on the content of a cross-linking agent and how it affected the results. The TEMs’ outer shell was thickened to solve the problem of the foam expansion ratio’s reduction that occurred due to the shrinkage after the maximum expansion (Tmax) was reached. After foaming, the cross-sectional thickness and surface of the sample with thickened outer shell were observed. The TEMs with the thickened shell showed the least shrinkage, which indicated excellent shrinkage stability, even after prolonged exposure to heat.

Foaming and thermal characteristics of bio-based polylactic acid–thermoplastic polyurethane blends

2018 ◽  
Vol 54 (6) ◽  
pp. 931-955 ◽  
Author(s):  
Mohsen Barmouz ◽  
Amir Hossein Behravesh
Keyword(s):  
Polylactic Acid ◽  
High Cell Density ◽  
Thermoplastic Polyurethane ◽  
Research Work ◽  
Thermal Characteristics ◽  
High Cell ◽  
Foam Expansion ◽  
Foaming Process ◽  
Cell Densities

This paper reports a research work on characterization of foamed biocompatible polylactic acid–thermoplastic polyurethane blends in terms of microstructural, thermal, and physical properties. The brittleness of the polylactic acid is compensated via blending with an elastoplastic phase of thermoplastic polyurethane. A range of low bulk density foam with a high cell density was produced in a solid state foaming process. Addition of thermoplastic polyurethane phase acted against the cell growth and thus foam expansion, apparently due to its inherent lower storage modulus, which weakens the polymer matrix and leads to gas escape phenomenon. Evaluation of thermal properties showed a tangible effect of blending and foaming process on crystallization of the specimens, which confirmed that the sensitivity of polylactic acid’s crystallinity to CO2 gas saturation was reduced as a result of thermoplastic polyurethane addition. Measurement of cell diameters and cell densities of the foamed samples demonstrated formation of the fine closed cells structure as a result of suitable foaming parameters that were able to deal with stiffness and strength of the polymeric matrix.

AFFF Spread Over Liquid Surface with Different Foam Expansion

2017 ◽  
Author(s):  
Bao-Wei Wang ◽  
Shen-Shi Huang ◽  
Qi-Ze He ◽  
Shou-Xiang Lu
Keyword(s):  
Liquid Surface ◽  
Foam Expansion

THERMAL CHARACTERISTICS OF FOAMS AND DISCHARGE FROM FIRE-EXTINGUISHMENT FOAM SPRAY NOZZLE

2009 ◽  
Vol 23 (03) ◽  
pp. 381-384
Author(s):  
YOUN-JEA KIM ◽  
JIN-SOO PYO
Keyword(s):  
Heat Flux ◽  
Temperature Gradient ◽  
Thermal Characteristics ◽  
Expansion Ratio ◽  
Experimental Results ◽  
Orifice Diameter ◽  
Spray Nozzle ◽  
Foam Expansion ◽  
Fire Extinguishment ◽  
Air Hole

To evaluate the performance of discharged foam agents used to protect structures from heat and fire damages, the thermal characteristics of fire-extinguishment foams were experimentally investigated. Especially, two different parameters of a spray nozzle, that is, the number of air holes and the orifice diameter, were considered. A simple repeatable test for fire-extinguishment foams subjected to fire radiation was performed. Experimental results showed that the expansion ratio of the discharged foam with the small orifice throat ( d 0= 9.5 mm ) and opened air hole ( N h =9) was large. Results also showed that although the temperature gradient in the foam increased as the foam expansion ratio is increased, it remained constant as the intensity of heat flux increased.

scholarly journals Extreme Foaming Modes for SCF-Plasticized Polylactides: Quasi-Adiabatic and Quasi-Isothermal Foam Expansion

Polymers ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1055 ◽  
Author(s):  
Dmitry Zimnyakov ◽  
Roman Zdrajevsky ◽  
Nikita Minaev ◽  
Evgeniy Epifanov ◽  
Vladimir Popov ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Bubble Radius ◽  
Initial Pressure ◽  
Critical Value ◽  
Expansion Ratio ◽  
External Pressure ◽  
Pressure Derivative ◽  
Specific Internal Energy ◽  
Foam Expansion ◽  
Foam Volume

The experimental evidence on depressurization foaming of the amorphous D,L-polylactide, which is plasticized by subcritical (initial pressures below the critical value) or supercritical (initial pressures above the critical value) carbon dioxide at a temperature above the critical value, relates to two extreme cases: a slow quasi-isothermal foam expansion, and a rapid quasi-adiabatic expansion. Under certain conditions, the quasi-isothermal mode is characterized by the non-monotonic dependencies of the foam volume on the external pressure that are associated with the expansion-to-shrinkage transition. The quasi-adiabatic and quasi-isothermal expansions are characterized by a significant increase in the degree of foam expansion under conditions where the CO2 initial pressure approaches the critical value. The observed features are interpreted in terms of the energy balance in the foam volume and the phenomenological model based on the equation of the foam state. The expansion-to-shrinkage condition is based on the relationship between the average bubble radius and the pressure derivative of the surface tension for the plasticized polylactide. The maximum expansion ratio of the rapidly foamed polylactide in the vicinity of the critical point is interpreted in terms of the maximum decrement of the specific internal energy of the foaming agent (carbon dioxide) in the course of depressurization.

Recovery and Recycle of HCFCs by Activated Carbon Adsorption

1993 ◽  
Vol 36 (2) ◽  
pp. 33-36
Author(s):  
P. Logsdon ◽  
R. Basu
Keyword(s):  
Activated Carbon ◽  
Carbon Tetrachloride ◽  
Ozone Depletion ◽  
Stratospheric Ozone ◽  
Potential Contribution ◽  
Stratospheric Ozone Depletion ◽  
Activated Carbon Adsorption ◽  
Foam Expansion ◽  
Carbon Adsorption ◽  
Methyl Chloroform

Various chemicals, such as chlorofluorocarbons (CFCs) methyl chloroform, carbon tetrachloride, and halons will be phased out globally by 1995 because of their potential contribution to stratospheric ozone depletion. Hydrochloroflurocarbons (HCFCs) are considered as replacements for the CFCs in certain applications (e.g., solvents and foam expansion agents). In a number of applications, CFCs are recovered using adsorption on activated carbon and reused. In this paper, we have described how to use activated carbon to adsorb 1,1-dichloro-1-fluoroethane (HCFC-141b) from an airstream and later recover and recycle using steam desorption. The capacity of commercially available carbons to adsorb HCFC-141b and conditions to be used in the process are described.

Development of Firefighting Equipment for Efficient Firefighting Strategy (Development of New Nozzle)

2015 ◽  
Vol 10 (4) ◽  
pp. 620-626
Author(s):  
Takumi Sasaki ◽  
◽  
Yoshiaki Miyazato ◽  
Junji Inamoto ◽  
Takahiro Yamamoto ◽  
...  
Keyword(s):  
Fire Fighting ◽  
Compressed Air ◽  
Strategy Development ◽  
Foam Expansion ◽  
New Type

We have developed a new type of hose nozzle, which uses either water or compressed air foam (CAF), as a more efficient fire-fighting strategy. In this paper, a description of the measured spray range and foam expansion of both the prototype nozzle and conventional nozzles is given. The results show that the spray range of the prototype nozzle is equal or superior to that of conventional nozzles. The foam expansion capability of the prototype nozzle is far superior to that of existing nozzles. From these results, it was confirmed that the new type of hose nozzle suggested in this paper will be an effective addition to existing firefighting equipment, resulting in a more efficient firefighting strategy.

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