Effects of hot oil treatment on properties and durability of three species of Philippine bamboo

The hot oil treatment of bamboo altered a number of its properties. The extent of the changes varied with the treatment temperature and duration as well as with the species used. The color of the bamboo samples were altered producing a darker appearance. A low temperature can be compensated for by longer duration in order to achieve the same coloring effect produced a higher temperature. The treated samples have a smoky smell which eventually disappeared after some time. The texture of the samples were also affected as manifested with the presence of corrugations. The treatment caused reductions in the weight of the samples. The hygroscopicity of bamboo was generally reduced as measured by the percentage water absorption. The dimensional stability was also enhanced as measured by the percentage thickness and volumetric swelling. The resistance against Fomes lividus and Lenzites striata was greatly improved. The major drawback of the hot oil treatment is the loss of mechanical properties. The reduction generally increased with increased treatment temperature and duration. The Modulus of Elasticity (MOE) was reduced by as much as 26.36 percent. Likewise, the treatment caused reductions in the Modulus of Rupture (MOR) and toughness to as much as 60.54 and 61.57 percent, respectively. Results of the study reveal that variations in the properties are mostly dependent on temperature. Duration may or may not have significant effect. There were some indications that samples treated at lower temperature but longer duration can resemble the effects at higher temperature but shorter duration. Hot oil treatment at 200 deg C generally produces a bamboo material with considerable strength loss. Such harsh treatment however, is required to increase the fungal resistance. There seems to be some sort of threshold for process temperature and duration after which the losses in strength increase greatly. In this study, it was found out that hot oil treatment of Bambusa blumeana, B. vulgaris and Dendrocalamus asper at around 180 deg C for approximately 60 to 120 minutes can be tolerated before any severe loss of properties occurs with smaller improvement in fungal resistance.