INFLUENCE OF PMUF RESINS PREPARATION METHOD ON THEIR STRUCTURE AND PERFORMANCE AS ADHESIVES FOR PLYWOOD

The preparation method of a PMUF resin manufactured in a single synthe sis procedure has been shown to have fundamental importance both at th e molecular level and for the resin application performance. C-13 NMR spectra of PMUF resins present excellent correspondence with applied t ensile strength results of plywood prepared with the same resins. PMUF resins prepared by initial reaction of phenol with formaldehyde follo wed by standard MUF preparation procedures present better results than resins prepared with the phenol either added during the preparation o r added at the end of the MUF resin preparation. The reason for this i s the reaction procedure itself which ensures that the phenol is copol ymerized with the main MUF chain to form a block copolymer and that bo th PF and MUF resin blocks still present consistent amounts of reactiv e methylol groups. Progressive deviation from these molecular level re quirements during the course of PMUFs preparation also ensures a progr essive deviation from their optimal performance, even leading to PMUF resins of worse performance than their corresponding MUF resin to whic h phenol has not been added.