Phenoplasts

plastics based on phenolic resins. Aside from the resins (novolacs or resols) themselves, which function as a binder, the principal component of phenoplasts is the filler.

The choice of filler dictates the type of phenoplast obtained. Thus, powder fillers yield phenoplast molding powders, and fiber fillers yield fiber-filled (glass, asbestos) molding compounds. Fillers in the form of continuous webs (glass fabric, asbestos fabric) are used in making phenoplast laminates. Laminates are also made with paper (Micarta) and sheets of wood.

Phenoplasts also include the expanded plastics obtained by introducing a blowing agent (foaming agent). Phenoplasts may also contain hardeners (mainly hexamethylenetetramine, a necessary component in novolac compositions), hardening accelerators (CaO and MgO), lubricants (paraffin, fatty acids, salts of fatty acids), dyes, and inert ingredients.

Articles made of phenoplasts are highly resistant to heat, water, and acids. They have good electrical insulation properties. Their mechanical strength depends on the type of filler and fluctuates within wide limits (Table 1).