RETENTION OF RED COLOR IN TAIWANIA (TAIWANIA CRYPTOMERIODES HAY.) HEARTWOOD

Taiwania (Taiwania cryptomeriones Hay.) is one of economically importa nt tree species indigenous to Taiwan. The heartwood of Taiwania is yel lowish red with distinguished purplish pink streaks. Unfortunately, th e ''red'' color is susceptible to change to dull black after exposure the heartwood to natural environment. This discoloration is a serious defect that decreases the value of Taiwania products. In order to pres erve the red color of Taiwania heartwood, aliphatic polyurethane (PU) clear coatings containing Tinuvin photostabilizer coupled with pretrea tment using photostabilizers, polyethylene glycol (PEG), semicarbazide (SCB) and acetic acid, were used. The experimental results demonstrat ed that discoloration on the surface of Taiwania heartwood could be pr evented by pretreating it with photostabilizers (Tinuvin-1130 and Tinu vin-292) or PEG or SCB, followed by finishing it with a PU coating con taining Tinuvin-1130 photostabilizer. The discoloration could be reduc ed to 30% of that of the untreated specimen by treating it with photos tabilizers pretreatment or PEG pretreatment followed by finishing it w ith a PU coating containing Tinuvin-1130 photostabilizer. Furthermore, the discoloration was proven to reduce to 10% of that of the untreate d specimen by treating it with SCB pretreatment followed by finishing it with a PU coating containing Tinuvin-1130 photostabilizer.