Experience Experience from over 20 years of field trials of resin treated wood – Marine borer resistance of MMF and DMDHEU modified wood
M Westin, P Larsson Brelid, A O Rapp, J Habicht
In 1999 a field test of Scots pine treated with MMF (Methylated Melamine Formaldehyde) resin and acetylated Scots pine post treated with MMF resin was started. Six years later a commissioned full NWPC test for BASF of Belmadur® (DMDHEU resin treated wood) was started at the same site.
The testing, according to European Standard EN 275, was done in a bay by Kristineberg Marine Research Station on the Swedish west coast. The marine borer (mainly Teredo navalis) activity at the test site is very high, always resulting in failure of control specimens within a year.
The two sets of CCA-treated reference specimen at low retention level (approximately UC3 level) failed with an average service life of 3.6 and 3.8 years, respectively. The first set of CCA-treated reference specimens at the high retention level (UC5 level) failed with an average service life of 13.5 years.
The two sets of MMF resin modified wood specimens at low and medium treatment level (WPG=11 and 23, respectively) have failed with 4.8 and 15.3 years’ service life, respectively. The set with high MMF treatment level (WPG=47) is only slightly attacked after 21 years. Acetylated wood post treated with MMF resin at low retention level (WPG=19+8) are severely attacked but performing better than CCA at high retention level. Acetylated wood specimens post treated with MMF resin at medium retention level (WPG=21+19) are rated sound after 21 years.
All DMDHEU specimens at all treatment levels (WPG = 28, 35 and 42, respectively) are perfectly sound after 15 years of exposure. DMDHEU seems to provide excellent resistance to borer attack at the treatment levels included in this test.
Keywords: modified wood, Belmadur, DMDHEU, urea derivative, BASF, marine borer, Teredo, shipworm, Limnoria, gribble, durability, field test