FAST-CURING PHENOL-FORMALDEHYDE (PF) RESINS .1. MOLECULAR-WEIGHT DISTRIBUTION OF PF RESINS

A commercial phenol-formaldehyde (PF) resin for fast-curing wood gluin g was analysed by high performance size exclusion chromatography (HPSE C) using styrene-divinylbenzene copolymer columns with tetrahydrofuran (THF) as a mobile phase after the resin was treated by an ion-exchang e resin. The results revealed that the average molecular weights (MnBA R and MwBAR) of the resin were much less than those estimated from the acetylated PF resin. The chromatogram of the ion-exchange treated PF resin contained eight peaks. Two compounds ',5,5'-tetramethylol-4,4'-d ihydroxydiphenylmethane (TMDHDPM) and 2,4,6-trimethylolphenol were syn thesized and used for the identification of five out of these eight pe aks in which TMDHDPM was one of the major components in the resin. Fur thermore, the MnBAR of the ion-exchange treated PF resin determined by the vapour pressure osmometric method and H-1-NMR was found to be low molecular weight which agreed with the results from the HPSEC. Acetyl ation of the ion-exchange treated PF resin gave products with unexpect edly high molecular weights. This may be due to the higher hydrodynami c volume and/or intermolecular association of acetylated higher molecu lar weight PF compounds. Furthermore, polystyrene calibration may not be suitable for the acetylated higher molecular weight PF compounds. H ighly polymerized PF resins were synthesized in the laboratory and ana lysed by the HPSEC method combined with the ion-exchange treatment. Ho wever, more highly polymerized resins were not completely soluble in T HF after treatment with the ion-exchange resin. Therefore, whilst this HPSEC method can be effectively used for many ordinary PF resins, for more highly polymerized resins alternative methods are required.