Alternative procedures for the recycling of sheet molding compounds

To establish the parameters for converting sheet molding compounds (SMCs) to useful products, various technical approaches, viz., solvent extraction, hydrolysis, and pyrolysis, have been explored. Thermogravimetric analysis of an SMC sample indicated that it contains about 25% by weight organics and 75% inorganics, mainly glass fibers and CaCO3 as filler. Solvent extraction of ground SMC with acetone, methylene chloride, chloroform, or chloroform : benzene (1 : 1 vol) yielded low quantities of a gummy, viscous extract. Hydrolysis of the extracted SMC sample under strong alkaline conditions was also studied. A unit structure was postulated for the hydrolysate based upon elemental and molecular weight analysis. Pyrolysis of both extracted and unextracted SMCs in nitrogen at 500°C and in air at 400°C yielded organic oils. These oils were characterized for their calorific values. The products of pyrolysis consisted of mainly aromatics along with some oligomers. The extract and the oil from pyrolysis appear to be compatible with epoxy systems. Their use as an extender for epoxy systems, while that of the inorganic residue (glass fibers and CaCO3) as a filler for epoxy system, have been explored. © 1993 John Wiley & Sons, Inc.