Kualitas Kayu Samama (Anthocephalus macrophyllus) dan Peningkatan Kemanfaatannya melalui Teknik Laminasi

Abstract

Indonesia has abundant potency of fast growing tree species. Among those is samama (Anthocephalus macrophyllus (Roxb.) Havil.), an endemic wood in Celebes and Moluccas. Its cylindrical stem with high clear bole has made it as one of “promoting species” which has been intensively planted lately at some areas in Indonesia. Samama has diameter increment of 5.05 cm yr-1 and at 10 years old its volume could reach 1.8 m3 (Bahidin and Marsoem 2012). Wood of samama has been used by local people for furniture, carpentry, and building material. However, its 0.41 specific gravity and 48750 kg cm-2 MOE is equal to woods in strength class IV thus would limit its utilization. Lamination technique can be used to improve the value and extend the utilization of samama wood, considering the highest demand of wood and wood product. Simultaneous studies have been conducted to improve the utilization of samama wood. It started with determination of juvenile and mature woods transition of 8 and 10 years old samama wood. Fiber length, fiber wall thickness, and microfibril angle were fitted on a modified-exponential curve to determine the transition of juvenile to mature part. Secondly, analysis on samama veneers quality by making 1 cm segmentations from pith toward bark. Lathe check, veneer thickness, and shrinkage on each segment were measured prior to regression analysis (best subset regression) on the parameters of wood and veneer quality to determine the dominant factor that affect the number of lathe checks on samama veneer. The third stage was analysis of dynamic wettability of various surfaces of samama wood. Drops of distilated water, UF and PF adhesives were applied at particular size on various surfaces of samama wood and veneer. The next stage was the assembly of 4 types of lamination panel of samama wood to analyze glue-ability of samama wood against isocyanate adhesive as well as analysis of shear modulus. The final stage was analysis of plywood quality made from juvenile and mature wood of samama. The results showed that the first 6-8 segments from the pith were still juvenile, while the subsequent segments were mature wood. Juvenile portion covered 33.3-38.9% of the 8 years old samama wood, while it was 30.4-34.8% of the 10 years old. Moreover, the 8 years old samama wood can be peeled into 1.5 and 3.0 mm veneer with fair thickness variation. Without pretreatment, number of lathe checks of samama veneer was better than those of other fast growing woods. Treatment of boiling at 50 C for 4 hours noticeably decreased the number of lathe checks by 10.91% and 9.93% for 1.5 mm and 3.0 mm veneers, respectively. I also found that number of veneer checks increased by 19.42-24.94% at air dried condition than those at fresh condition. Peeling transforms round wood into sheets of veneer. This research formulated the comparison between veneer thickness with radius and the difference of veneer circumferences, which from this point will be referred as geometry factor. The value of geometry factor elaborates two points: 1) thicker veneer will be stiffer than thinner one, 2) numbers of lathe checks from a round of log are the same, but due to the decrease diameter then numbers of lathe checks per unit length of veneer appear to increase toward pith. The results revealed that geometry factors rather than other wood quality factors (specific gravity, moisture content, fiber length, fiber wall thickness, and microfibril angel) were found to be the dominant factor causing the increasing of lathe checks toward pith. The results of the third stage revealed that tangential surface was the most susceptible to wetting process, followed by radial and RT (it form ±45 angle with radial and tangential surfaces). Both wood and veneer showed a consistent result that juvenile had better wettability than mature portion. Furthermore, samama veneer had an equal wettability with TR surface of lumber in which the loose part of the veneer got wet faster than the tight part. These facts are essential to notice during gluing process of samama wood into laminated product. Sortation and arrangement of lamina types at the fourth stage prominently enhanced MOE and MOR panel lamina, by 27-36% and 26-30%, respectively. Shear modulus of samama wood was 592±183 MPa and contributed to improve Etrue by 2.09-8.03%. Specific gravity of the laminated product was increased, perhaps due to the adhesive filled in between spaces of the lamina surfaces. The delaminated value that met JAS 2007 implied the suitability of isocyanate adhesive to bond samama wood. However, the laminated panels showed lower shear modulus than its solid wood thus further improvement is necessary. In the fifth stage, plywood with UF adhesive was assembled and studied. As expected, bonding strength (KGT) of juvenile portion was lower than that of plywood from mature wood. The 16-20% increased-number of lathe checks would reduce KGT by 6.3-11.9%. It noteworthy, that all of KGTs and moisture contents were met SNI 01-5008.2-1999 for plywood. Moreover, specific gravity of the plywood was 11-23% higher than its solid wood