Structural Flakeboards and Composites 3055 



described an operation utilizing a shaping-lathe headrig (fig. 18-104abcd) to 

 yield solid and molded-flake hardwood products, and concluded that it should be 

 economically feasible if molded pallets can be proven serviceable. 



24-24 MOLDED PRODUCTS BONDED WITH FOAMED 



URETHANE 



Deppe (1969) noted that particleboard made with a foamed-plastic binder can 

 be lightweight with low hygroscopicity, and yet have high strength and excellent 

 insulating properties. The high cost of plastic foams, such as urethane, has 

 prohibited their use in the manufacture of flat panels, however. 



Marra et al. (1975) studied the technical and economic potential of using high- 

 density southern hardwoods comminuted into particles having a three dimen- 

 sional branched shape (fig. 18-285), bonded with foamed resin to form low- 

 density molded, as well as flat, products (fig. 24-63). By this procedure, 

 particles are charged to a mold, binder is meter-mixed and added, and the mold 

 is closed and compacted if necessary. The finished part is extracted 10 to 30 

 minutes later; no heat is required to cure the resin. Pressures of 3 to 5 psi are 

 normally generated by expanding foam on the surfaces of the mold — greater if a 

 large excess of resin is introduced. For most wood-foam products below 24 Ib/cu 

 ft density, a counter pressure of 10 to 20 psi is needed to obtain the necessary 

 compaction. Higher densities require proportionately higher compaction 

 pressure. 



Figure 24-63. — Guitar case molded from hardwood particles bonded with foamed 

 urethane. (Photo from Marra et al. 1975.) 



