BEHAVIOR OF THERMALLY MODIFIED WOOD TO BIODETERIORATION BY XYLOPHAGE FUNGI

Abstract

Thermally modified wood undergoes chemical, physical, and mechanical modifications, resulting  in  changes  in  resistance  to  wood  biodegrading  agents.  The objective of  this  study was to evaluate the resistance to biodeterioration of thermally modified wood by the  industrial  process  VAP  HolzSysteme®  of  Eucalyptus  grandis, Pinus  taeda  and  Tectona grandis,  submitted  to  the  Lentinula  edodes  fungi  (brown  rot)  and  Pleurotus  djamor  fungi  (white rot), and to analyze the chemical properties, contents of holocellulose, lignin, total extracts, and ash, before and after biodeterioration. Three treatments were considered for each species: Control - wood in natura, modified wood at 140 °C and 160 °C. The specimens were made according to ASTM D 1413 (ASTM, 1994), in a total of 108 samples per species, 36 per treatment for each species, with 12 samples submitted to the fungus L. edodes, 12 to P. djamor and 12 correction blocks. Different behaviors occurred among species under fungal action. For E. grandis wood the thermal modification increased the resistance  to  biodeterioration  of  the  wood  under  the  action  of  the  L.  edodes  fungus,  in  the  opposite  way  occurred  for  the  species  P.  taeda.  There  was  little  variation  between  treatments  in  T.  grandis wood for both fungi. Thermal modification conferred chemical alterations on the wood, influencing their behavior the biodeterioration by the fungal action  in  P.  taeda  species  in  a  negative  way,  (increasing  the  degradation  level),  and  E. grandis in a positive way, reducing the biodeterioration. However, in T. grandis species no significant differences were identified in the different treatments by the action of different rotting fungi.