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Analysis of pulsed microwave processing of polymer slabs supported with ceramic plates
Sankaran Durairaj,
Published in
2009
Volume: 64
   
Issue: 7
Pages: 1488 - 1502
Abstract
A detailed theoretical analysis has been carried out to study the role of ceramic supports (alumina and SiC) and pulsed microwave heating of polymer (Natural Rubber, NR, and Nylon 66) slabs due to various distributions of microwave incidences. Ceramic plates are typical representations as they withstand high temperature without any deformation. It is found that ceramic plates influence the heating processes significantly and local hot spots within samples are governed by specific type of ceramic plates for various sample thicknesses and distributions of microwave incidence (one side or both sides). Optimized pulsing of microwave incidence has been employed to minimize the thermal runaway or hot spots in order to achieve uniform temperature distribution and pulsing is introduced based on two parameters: setpoint (Δ TS) and on-off constraint (T′). Detailed spatial distributions of power and temperature are illustrated for a few representative length scales to demonstrate the role of local maxima in power and temperature on heating rate as well as thermal runaway with or without pulsing. Pulsing ratio (PR) has been defined as PR = toff / tp, where toff is power-off time and tp is the total processing time such that smaller PR denotes large processing rates. It is found that one side incidence gives smaller values of PR for both the ceramic plates whereas SiC plate may be suitable for both sides incidence with large sample thicknesses of NR samples. It is also found that larger values of setpoints also minimize PR. The setpoints along with the on-off constraint play critical role to select the heating strategy as a function of ceramic plates and types of incidence. Pulsing may not be important for smaller thicknesses of Nylon samples and SiC or alumina plates may be recommended for processing larger thicknesses of Nylon samples in presence of pulsing. Current study recommends the efficient microwave heating methodologies for polymer processing attached with ceramic plates by means of optimized pulsing for the first time. © 2008 Elsevier Ltd. All rights reserved.
About the journal
JournalChemical Engineering Science
ISSN00092509
Open AccessNo
Concepts (33)
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    Electric network analysis
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    Heating
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    Knowledge based systems
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    Microwave heating
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    MICROWAVES
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    Polyamides
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    Polymers
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    RAYON
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    Silicon carbide
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    ALUMINA PLATES
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    Ceramic plates
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    CERAMIC SUPPORTS
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    Ceramics
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    HEATING PROCESS
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    HEATING STRATEGIES
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    High temperatures
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    Hot spots
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    Length scale
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    Local maximum
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    MICROWAVE PROCESSING
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    NATURAL RUBBERS
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    NYLON 66
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    OFF TIME
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    Polymer processing
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    PROCESSING RATES
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    PULSING
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    PULSING RATIOS
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    SET-POINTS
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    Spatial distributions
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    Thermal runaway
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    Total processing time
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    TWO PARAMETERS
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    Ceramic materials