ABSTRACT
The classical thermosetting resins are supplied as solid powders which may be melted by the addition of heat and then chemically cured by a continued supply of heat. The classical thermosets comprise a large range of resins: phenolics, amino compounds, alkyds, and glyptal based materials. This chapter discusses the phenolics as a typical system; they are more properly described as phenol-formaldehyde resins. They are formed by the condensation of phenol and formaldehyde. The thermal and electrical properties of amino resins are inferior to those of the phenolics but are generally superior to most thermoplastics. Alkyd resins are essentially polyester-based resins; the term alkyd is derived from the "alcohol and acid" precursors of this family of polymers. Fillers are essential components of many thermosetting resin compounds. The organic fillers are very widely used in general purpose molding compounds. They are generally cellulosic in nature and include such materials as wood flour, cotton flock, cotton seed hulls, ground walnut, and cork dust.
