scholarly journals In Search of the Driving Factor for the Microwave Curing of Epoxy Adhesives and for the Protection of the Base Substrate against Thermal Damage

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2240
Author(s):  
Satoshi Horikoshi ◽  
Yuhei Arai ◽  
Nick Serpone
Keyword(s):  
Microwave Heating ◽  
Thermal Damage ◽  
Driving Factor ◽  
Heating Efficiency ◽  
Microwave Curing ◽  
Epoxy Adhesives ◽  
Ionic Intermediates ◽  
Electrically Charged ◽  
Base Substrate ◽  
Lower Heating

This study used controlled microwaves to elucidate the response of adhesive components to microwaves and examined the advantages of microwave radiation in curing epoxy adhesives. Curing of adhesives with microwaves proceeded very rapidly, even though each component of the adhesive was not efficiently heated by the microwaves. The reason the adhesive cured rapidly is that microwave heating was enhanced by the electrically charged (ionic) intermediates produced by the curing reaction. In contrast, the cured adhesive displayed lower microwave absorption and lower heating efficiency, suggesting that the cured adhesive stopped heating even if it continued to be exposed to microwaves. This is a definite advantage in the curing of adhesives with microwaves, as, for example, adhesives dropped onto polystyrene could be cured using microwave heating without degrading the polystyrene base substrate.

scholarly journals Research on Electromagnetic Sensitivity Properties of Sodium Chloride during Microwave Heating

2020 ◽  
Vol 39 (1) ◽  
pp. 54-62
Author(s):  
Hua Chen ◽  
Junjiang Chen ◽  
Weijun Wang ◽  
Huan Lin
Keyword(s):  
Sodium Chloride ◽  
Electric Field ◽  
Water Content ◽  
Heating Rate ◽  
Microwave Heating ◽  
Resonant Cavity ◽  
Relative Dielectric Constant ◽  
Heating System ◽  
Heating Process ◽  
Heating Efficiency

AbstractThe multimode resonant cavity is the most common cavity. The material often shows on selective heating performance during the heating process due to the effect of microwave heating having a closely relationship with the electromagnetism parameters. This paper is based on finite difference time domain method (FDTD) to establish the electromagnetic-thermal model. The electromagnetic sensitivity property parameters of sodium chloride including relative dielectric constant, loss angle tangent and water content of sodium chloride is studied during the heating and drying process. The heating rate and the electric field distribution of sodium chloride, at the different water content, were simulated with the electromagnetic characteristic parameters changing. The results show that with the electromagnetic sensitivity property parameters varying, the electric field strength, heating rate and steady-state temperature of the heating material will all have a variety in the cavity. Some measures are proposed to improve the heating efficiency and ensure the stability of the microwave heating system in the industrial application.

Application of Microwave Heating for Adhesive Joining

1999 ◽  
Author(s):  
Erik T. Thostenson ◽  
Tsu-Wei Chou
Keyword(s):  
Microwave Heating ◽  
Composite Structures ◽  
Material Selection ◽  
Adhesive System ◽  
Conventional Heating ◽  
Joint Interface ◽  
Microwave Curing ◽  
Composite Joint ◽  
High Dielectric ◽  
Microwave Techniques

Abstract In conventional joining of composite materials and sandwich structures, reductions in processing time are limited by inefficient heat transfer. In conventional processing the thermal energy must diffuse through the composite layers to heat the joint interface and cure the thermosetting adhesive, and this outside-in process of heating results in excessive processing times and wasted energy. The purpose of the current work is to examine microwave heating as an alternative to conventional heating for joining of composite structures. Through proper material selection, microwaves are able to penetrate the substrate materials and cure the adhesives in-situ. Selective heating with microwaves is achieved by incorporating interlayer materials that have high dielectric loss properties relative to the substrate materials. In this study, a processing window for elevated temperature curing of an epoxy paste adhesive system (HYSOL EA 9359.3) was developed and composite joint systems were manufactured using conventional and microwave techniques and tested in shear. Microwave curing resulted in both enhanced shear strength and less scatter in experimental data.

Formulation for Continuous Vulcanization in Microwave Heating Systems

1971 ◽  
Vol 44 (1) ◽  
pp. 294-306 ◽  
Author(s):  
J. Ippen
Keyword(s):  
Microwave Heating ◽  
Continuous Process ◽  
Heating Systems ◽  
Rubber Industry ◽  
Microwave Curing ◽  
Hot Air ◽  
New Development ◽  
Curing Method

Abstract For a number of years the rubber industry has been trying to make its processes as continuous as possible. Techniques which dispense with interruptions are particularly desirable in the production of strip and hose, for extrusion is a continuous process whose interruption for the purpose of enabling the goods to be cured is both illogical and unsatisfactory. Several continuous vulcanization methods, such as the use of hot air and the liquid curing method, are receiving attention. A new development in this field is the use of microwave for vulcanization. Microwave curing is a valuable supplement to other continuous vulcanization methods, in comparison with which it offers advantages in some respects.

Microwave-Assisted Chemistry: a Closer Look at Heating Efficiency

2009 ◽  
Vol 62 (3) ◽  
pp. 236 ◽  
Author(s):  
Richard Hoogenboom ◽  
Tom F. A. Wilms ◽  
Tina Erdmenger ◽  
Ulrich S. Schubert
Keyword(s):  
Microwave Heating ◽  
Microwave Power ◽  
Large Scale ◽  
Small Scale ◽  
Passive Heating ◽  
Conductive Heating ◽  
Heating Efficiency ◽  
Medium Scale ◽  
Microwave Assisted ◽  
Demineralized Water

Nowadays, microwave heating has evolved into a common tool for chemists based on its numerous advantages over conventional conductive heating. Surprisingly, the efficiency of microwave-assisted heating is still rather unexplored. In this contribution, we report our investigations concerning the heating efficiency of a variety of solvents including polar and apolar substances. Moreover, the effects of adding salt or passive heating elements on the microwave heating efficiency will be addressed. Finally, the heating efficiency of demineralized water is discussed at different volumes and with different microwave power levels in both monomode and multimode microwave synthesizers, demonstrating maximum average heating efficiencies of 10% for small-scale vessels (5 mL), 20% for medium-scale (50 mL), and 30% for large-scale microwave heating (400 mL).

Influence of Curing on Calcined Kaolin-Based Geopolymer

2016 ◽  
Vol 690 ◽  
pp. 200-205
Author(s):  
Narumon Lertcumfu ◽  
Sukum Eitssayeam ◽  
Kamonpan Pengpat ◽  
Tawee Tunkasiri ◽  
Denis Russell Sweatman ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Portland Cement ◽  
Microwave Heating ◽  
Production Line ◽  
Room Temperature ◽  
Ordinary Portland Cement ◽  
Microwave Curing ◽  
Alternative Material ◽  
Calcined Kaolin

The object of this work was to use calcined kaolin-based geopolymer as an alternative material to replace ordinary Portland cement (OPCs) by applying geopolymerization processes. Geopolymer slurry was prepared from calcined kaolin and alkali activators, which consisted of 10 M NaOH and Na2SiO3 solution. The fresh slurry was cast into plastic molds and then cured at room temperature for 24 h. Reaction temperatures were measured (for 24 hours after casting). Compressive strength of the geopolymer was tested after curing at room temperature and after microwave heating. The mechanical properties increased with added plaster for microwave curing of 5 min. It is believed that this process can increase the efficiency of the production line for geopolymer.

scholarly journals Simulation and Analysis of Oleic Acid Pretreatment for Microwave-Assisted Biodiesel Production

Processes ◽  
2018 ◽  
Vol 6 (9) ◽  
pp. 142 ◽  
Author(s):  
Weiquan Ma ◽  
Tao Hong ◽  
Tian Xie ◽  
Fengxia Wang ◽  
Bin Luo ◽  
...  
Keyword(s):  
Porous Media ◽  
Oleic Acid ◽  
Microwave Heating ◽  
Rapid Heating ◽  
Experimental System ◽  
Biodiesel Production ◽  
Heating Process ◽  
Acid Pretreatment ◽  
High Loss ◽  
Heating Efficiency

Oleic acid needs to be heated when it is utilized for biodiesel production, but, as a low-loss solution, oleic acid is difficult to heat by microwave. An efficient heating method for oleic acid is designed. A high loss material porous media is placed in a quartz tube, and a microwave directly heats the porous medium of the high loss material. The oleic acid flows through the pores of porous media so that the oleic acid exchanges heat during this process and rapid heating of oleic acid is achieved. A coupling model, based on the finite element method, is used to analyze the microwave heating process. The multiphysics model is based on a single mode cavity operating at 2450 MHz. An elaborate experimental system is developed to validate the multiphysics model through temperature measurements carried out for different flow velocities of oleic acid and different microwave power levels. The computational results are in good agreement with the experimental data. Based on the validated model, the effects of different sizes, porosities, and materials on microwave heating efficiency are analyzed.

scholarly journals Modelling microwave heating of an oil palm mesocarp

2018 ◽  
Vol 240 ◽  
pp. 01017 ◽  
Author(s):  
Ming Law ◽  
Jessie Chang
Keyword(s):  
Moisture Content ◽  
Microwave Heating ◽  
Oil Palm ◽  
Electromagnetic Waves ◽  
Oil Quality ◽  
Three Dimensional ◽  
Three Dimensional Model ◽  
Heating Efficiency ◽  
Heating Model ◽  
Palm Fruits

An oil palm mill often uses steam in sterilization and fruit detachment processes. Consequently, a large amount of wastewater is produced. To reduce the wastewater, microwave (MW) heating of oil palm fruits has been studied and positive results were reported in open literature. Nevertheless, MW heating of oil palm fruits requires proper control to avoid overheating, which deteriorates the oil quality. MW heating efficiency depends not only on the electromagnetic strength, but also on the complex permittivity of oil palm fruits. This study reports the MW heating model of an oil palm mesocarp. The three-dimensional model solved Maxwell’s Electromagnetic waves equation, diffusion equation of moisture content, and heat conduction equation. The model was validated with mesocarp’s experimental data of moisture content and temperatures. The electromagnetics, moisture, and temperature distributions of the mesocarp were studied. The simulation results showed that the volumeand surface-averaged temperature were similar, thus the surface temperature might be used as a good approximation to the volumetric temperature. Besides, the model also showed that radiation and convection were the main heat loss mechanisms. This validated model can be used for designing a microwave heating reactor for oil palm fruits.

scholarly journals Investigating the microwave heating behaviour of lunar soil simulant JSC-1A at different input powers

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sungwoo Lim ◽  
James Bowen ◽  
Giulia Degli-Alessandrini ◽  
Mahesh Anand ◽  
Aidan Cowley ◽  
...  
Keyword(s):  
Microwave Heating ◽  
Lunar Soil ◽  
Input Power ◽  
Thermal Runaway ◽  
Resource Utilisation ◽  
The Moon ◽  
Heating Efficiency ◽  
Microwave Apparatus ◽  
Mechanical Strengths ◽  
Available Resources

AbstractFor a sustainable human presence on the Moon, it is critical to develop technologies that could utilise the locally available resources (a.k.a. in situ resource utilisation or ISRU) for habitat construction. As the surface soil is one of the most widely available resources at the Moon, we have investigated the viability of microwave heating of a lunar soil simulant (JSC-1A). JSC-1A was thermally treated in a bespoke microwave apparatus using 2.45 GHz frequency, using five different microwave powers in the range of 250 W to 1000 W. The structural properties of the resulting products were analysed to determine whether their microstructures and mechanical strengths differ under different input powers; and whether input power plays a crucial role in triggering thermal runaway, for identifying the optimum power for developing a microwave-heating. Our key findings are: (i) the higher input powers (800 W and 1000 W) generate the highest yields and microstructures with the greatest mechanical strengths, at the shortest fabrication times, and (ii) thermal runaway improves the microwave heating efficiency despite the rapid increase in temperature, once it is triggered. Our findings are of key importance for developing a microwave-heating payload for future lunar ISRU demonstration missions, contributing towards 3D printing-based extra-terrestrial construction processes.

Microwave curing of carbon nanotube/epoxy adhesives

2014 ◽  
Vol 104 ◽  
pp. 97-103 ◽  
Author(s):  
Ping-Cheng Sung ◽  
Tzu-Huan Chiu ◽  
Shih-Chin Chang
Keyword(s):  
Carbon Nanotube ◽  
Microwave Curing ◽  
Epoxy Adhesives
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