Hexamethylene diamine , covalent bonding

One technique being used is to bond solid wood with monomeric materials that are highly reactive with hydroxyl groups such as those in the wood fiber wall. For example, Schoring et al. (65) synthesized particleboards using as a binder hexamethylene diamine and polyvinyl chloride at 140°C. They postulated that the polyfunctional amine covalently linked the wood components, especially lignin, to the polyvinyl chloride. 

The van der Waals bonds between monomer molecules are replaced by covalent bonds between the monomeric units in polymerization. Since van der Waals bond lengths are about 0.3-0.5 nm and covalent bond lengths are, in contrast, about 0.14-0.19 nm, a general contraction occurs. The contraction increases with decreasing monomer molecule size, since more van der Waals bonds per unit mass must be eliminated. Thus, ethylene contracts by about 66%, vinyl chloride by about 34%, styrene by about 14%, and W-vinyl carbazole by as little as about 7.5%. Polymerization of ethylene oxide leads to a volume contraction of 23%, of tetrahydrofuran to one of about 10%, but that of octamethyl cyclotetrasiloxane, however, to a contraction of only 2%. Some strained bicyclic ring systems even polymerize with an expansion. With polycondensation, the volume contraction is smaller with decreasing size of eliminated residue. Polycondensation of hexamethylene diamine with adipic acid leads to a contraction of 22% (water elimination), that of hexamethylene diamine and dioctyl phthalate, on the other hand, to one of 66% (elimination of octanol). 

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