Antonios N Papadopoulos 
email: antonios1974@hotmail.com
  
Durability of particleboards made from wood particles chemically modified with propionic anhydride: Results after six years in ground stake-test

   

Durability of particleboards made from wood particles chemically modified with propionic anhydride: results

after six years in ground stake-test

Antonios N. Papadopoulos

Introduction

Chemical modification has been used to improve decay resistance of wood. The majority of research investigating this area was concerned with the reaction of acetic anhydride with wood. It was shown that acetylation imparts excellent protection against decay, provided that a certain degree of acetylation is reached [START_REF] Rowell | Chemical modification of wood: Advantages and disadvantages[END_REF][START_REF] Hill | Wood modification ---chemical, thermal and other processes[END_REF]). This paper examines the decay resistance in ground stake test of particleboards made from wood chips modified with propionic anhydride and is an update of an earlier paper [START_REF] Papadopoulos | Natural durability in ground stake test of propionylated particleboards[END_REF].

Papadopoulos AN, Gkaraveli A (2003) 

  . Dimensional stabilization and strength of particleboard by chemical modification with propionic anhydride. Holz Roh-Werkst

	61(2):142-144		
	Table 1. Decay rating of control and propionylated boards in ground stake test (a
	rating of 10 means no decay, 9 slight decay, 7 moderate decay, 4 severe decay and 0
	means total decay)	
	Tabelle 1	Befallsgrad der Kontrollproben und propionylierten Proben im
	Erdkontakt (10 = kein Befall, 9 = leichter Befall, 7 = mäßiger Befall, 4 = starker
	Befall, 0 = vollständig zerstört)
				Decay rating
	Exposure time	Control	Propionylated (12.2%)
	72 months	0	0
	60 months	0	4
	48 months	0	4
	36 1 months	4	7
	24 1 months	7	10
	12 1 months	10	10
	1. Data from Papadopoulos (2007)

Experimental

The propionylation of wood chips (weight gain of 12.2% after 60 minutes at 120°C) and the laboratory manufacture of boards are fully described in a previous paper (Papadopoulos and Gkaraveli 2003). The ground stake test was carried out as described earlier [START_REF] Papadopoulos | Natural durability in ground stake test of propionylated particleboards[END_REF].

Results and discussion

The performance of propionylated stakes during the testing period is shown in Table 1. It was reported earlier [START_REF] Papadopoulos | Natural durability in ground stake test of propionylated particleboards[END_REF]) that after three years of exposure in ground stake test the propionylated stakes were moderately attacked, whereas the control stakes were severely attacked (grey part in Table 1). The upper part of Table 1 shows the performance of the stakes during the following three years. It can be seen that the control stakes were totally decayed during the fourth year of the test. The propionylated stakes showed severe attack after five years of testing and total decay after six years.