Beginning of WPC Thermosetting Materials

The hrst WPC—in the 1960s—were thermosetting molding compounds containing cellulose hber as hller. 

For example, U.S. Pat. No. 3,367,917 [15] describes a thermosetting melamine-formaldehyde-benzoguanamine resinous molding composition containing a hbrous hller, such as a-cellulose pulp, in an amount between 25 and 42% by weight. 

154 [16] and 3,407,155 [17] describe thermosetting urea-formaldehyde and aminoplast resinous molding composition comprising fusible reactive urea-formaldehyde and aminotriazine-formaldehyde resin, respectively, and purihed a-cellulose hbers (14-25% by weight) as a hller. 

The next innovations in this area are described in U.S. Pat. Nos. 4,282,119 [18] and 4,362,827 [19]. In accordance with these patents, particleboards were produced employing a binding agent that was a combination of a polyisocyanate with an aminoplast resin containing 0.25-0.65 mole of formaldehyde per mole equivalent of amino groups. 

158 [20] describes a flooring composition involving a terpolymer, a nonflbrous filler (calcium carbonate, silica, clay, kaolin, and carbon black) and a fibrous filler, such as wood flour, cellulose fibers, and asbestos. Compositions may include 25-53% by weight of nonfibrous filler and 17-40% by weight of fibrous filler, with the fillers accounting for 50-80% of the total composite weight. 

---