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N.M. Garz on-Barrero et al. / International Biodeterioration & Biodegradation 115 (2016) 266e276 271
Table 2
Estimates for the parameters of the proportional chance model of the fungal colonization in the natural exposure and accelerated test (ASTM D 3273-12, 2012).
Parameter covariants Estimate Standard error Z Value Descriptive level (p value)
Material (MDP) 0.1196 0.4238 0.282 0.7778
Surface (Non-coated) 4.5618 0.5982 7.626 <0.001
Face (Back) 1.6782 0.452 3.713 <0.001
Environment (Natural) 0.9301 0.4574 2.033 0.042

where there was no precipitation. Scheffer (1991) stated that, D3273-12 (2012) test. At the end of the 4 weeks of exposure, the
generally in humid climates, the pieces of wood are less conducive test samples without surface coating (ncBCP and ncMDP) subjected
to biodegradation in the occurrence of low temperatures. to the accelerated test presented between 60% and 80% probability
The results of the visual inspection also were illustrated by of obtaining a grade on the evaluation scale of 0 and 1, or rather,
scanning electron microscopy (SEM). Fig. 4a and Fig. 4b show the between 81 and 100% colonization by mold. For the natural expo-
colonization by mold on the surface of the sugarcane particle sure the weathering effect on the front face was observed, where
boards with superficial coating (cBCP) and directly exposed to the colonization probability increased in relation to the back face.
weathering conditions. Besides the presence of the fungi (arrows), Both materials with surface coating (cBCP and cMDP) presented
the front face (Fig. 4a) presents roughness (instead of a smoother 82.6% probability of obtaining a note of 8e9, which corresponds to
back surface, Fig. 4b), possibly caused by the previously mentioned less than 20% mold colonization on the surface of the accelerated
environmental factors. test. However it can be seen that a variation in the probabilities is
Table 3 presents the estimated probabilities by the proportional larger in the natural weathering test. Therefore, the accelerated
chance model for the degree of fungal colonization on the sugar- test, ASTM D3273 12 resulted in a similar pattern as the deterio-
cane bagasse particle boards (BCP) and on MDP in the two condi- ration test for 12 months.
tions evaluated: natural weathering and the accelerated ASTM

Fig. 4. Micrographs of colonized particle boards by mold fungus under natural exposure e 12 months: cBCP (a) front and (b) back faces. The arrows indicate the presence of fungus.

Table 3
Determined probabilities for mold growth interactions between surface coating, face and type of exposition.