Journal of Microwave Power and Electromagnetic Energy (JMPEE)
TITLE	Microwave Drying of Resin Impregnated Paper [PDF]
AUTHORS	S. Minami and R. Branion 1972 7 2 87-98
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Abstract A pilot scale apparatus was constructed for impregnating paper with water soluble phenol formaldehyde resin and subsequently microwave drying it. Comparison of the properties of the papers dried at various microwave power application levels with the properties of similar papers dried in a hot air, natural convection oven showed that the microwave dried papers had a more uniform resin concentration distribution across the sheet thickness, were superior in internal bond strength and in surface abrasion resistance. The surface abrasion resistance and internal bond results support the contention that the resin distribution is more uniform in the microwave dried papers. No significant differences were observed in the tensile breaking strength, stretch, or Young's modulus between papers which were microwave dried or oven dried. Results obtained in a bending test suggest, but do not unequivocally prove, the microwave dried papers are more flexible. The results are used to support the hypothesis that in conventional drying, where the highest temperature are found at the sheet surface, resin migrates to the surface and tends to polymerize most rapidly there leaving a relative deficiency of resin in the middle of the sheet. This is to some extent ameliorated by microwave drying because the highest temperatures in such a process are somewhere in the interior of the paper sheet.