ESTERIFICATION CHARACTERISTICS AND CROSSLINKING REACTION PARAMETERS BETWEEN WOOD AND POLYCARBOXYLIC ACID THE INTERMEDIATE OF CROSSLINKING REACTION BETWEEN WOOD AND POLYCARBOXYLIC ACID I. Space Effect and Chemical Structure of Polycarboxylic Acid Infection in Vibrancy Efficiency of Wood by Crosslinking Reaction between Wood and Polycarboxylic Acids CROSS—LINKING EFFECT BETWEEN WOOD AND MELAMINE-FORMALDEHYDE