Chemical constituents, physical, and mechanical properties of Indonesian sugar palm (Arenga longipes Mogea) trunk

Wood density, chemical characteristics, and mechanical properties in the stem (vertical and horizontal) were studied for the Indonesian sugar palm (Arenga longipes) grown in Sumatera Island in Indonesia. This species is widely used industrially and is widely distributed on the island of North Sumatra. A 15-year-old palm tree was harvested (40 cm diameter at breast height) then sampled at seven heights above the ground (1, 2, 3, 4, 5, 6, and 7 m of trunk height) and at five horizontal positions (4, 8, 12, 16, and 20 cm of radius from the bark) at each height. The sections were evaluated for chemical constituents, density, modulus of rupture (MOR), modulus of elasticity (MOE), tensile strength, and compression strength using British Standard BS 373 (1957). The chemistry of the trunk was also evaluated by gas chromatography-mass spectroscopy (GC-MS), Fourier transform-infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The distribution of chemical constituents of A. longipes stem was as follows: 24.97–39.23% α-cellulose, 68.03–78.04% holocellulose, 23.01–34.44% lignin, and 1.62–3.41% ash content. Density varied from 0.13 to 0.75 g/cm3. Modulus of rupture varied from 10.42 to 143.49 MPa, modulus of elasticity varied from 0.35 to 24.92 GPa, tensile strength ranged from 0.55 to 16.03 GPa, and compressive strength ranged from 0.53 to 6.14 MPa. Hexadecenoic acid and octadecanoic acid were both detected, and the latter compound was most common (97.98% of peak area). The FTIR analysis indicated a hydrophilic tendency in the material, which was attributed to the presence of hydroxyl functional groups in cellulose and lignin. Thermal decomposition occurred at temperatures as high as 402°C, representing an 18% degradation. The horizontal variation within the trunk was highly significant for all traits, while the vertical variation was significant only for density and mechanical properties. A strong correlation was observed between density and mechanical properties. A. longipes has potential as an alternative raw material, capable of supplying the industry with valuable timber substitutes, particularly for material from the outer circumference of the stem.