Wood is a porous material composed of cell wall substances, moisture and voids. The density of wood refers to the mass of wood per unit volume, in g/cm3 or kg/m3.
Wood density is an important index to measure wood properties, which directly affects the physical and mechanical properties and processing performance of wood.
Generally speaking, the denser the wood, the higher the strength, the more difficult the processing, the worse the dimensional stability, and the more difficult it is to dry. The main factors affecting the wood density are tree species, late wood rate, moisture content, trunk position, etc. This article introduces the two woods with the lowest density and the highest density known in the world.
The wood with the smallest density in the world - balsa wood
Balsa, Bombacaceae (Bombacaceae), Ochroma tree, scientific name Ochroma pyramidale or Ochroma lagopus, its English name is balsa or balsa wood. Distributed in the Indies, southern Mexico to Peru, Bolivia and other tropical low-altitude areas, as well as my country's Taiwan, Guangdong, Hainan, and Yunnan.
Balsa is the only evergreen medium tree in the family Kapokaceae and the genus Balsa. It is also one of the fastest-growing tree species in the world, which can grow to 5-6 meters in one year, with a diameter of 5-13 centimeters. A 10-year-old balsa tree can reach a height of 16 meters and a diameter of 50-60 centimeters.
Due to the rapid renewal of cell tissue in the body, all parts of the plant are extremely soft and elastic. Its trunk is straight and tall, and its bark is brown. The broad, heart-shaped leaves grow alternately on the branches. The flowers are large, yellow and white in color, and are born in the upper layer of the crown.
Oblong capsules with cottony tufts inside, consisting of five fruit petals. The seeds are obovate, light red or brown, densely covered with fluff outside, like cotton seeds.
Balsa wood is the wood with the lowest density in the world, with a density of about 0.12g/cm3. The wood has straight texture, thin and uniform structure, very light and soft, so its strength and impact toughness are very low, and it is easy to process. But if the planer is not sharp, the surface of the board is easy to hair.
Because of its low density, good dimensional stability, uniform material, low thermal conductivity, and easy processing, balsa wood has advantages that other materials cannot match, and is widely used as insulating materials, sound insulation equipment, life-saving supplies and aircraft Manufacturing and other fields.
In the 1960s, my country began to introduce and try to plant balsa wood. At present, Yunnan, Guangdong, Fujian, Hainan, Taiwan and other provinces have planted it on a large scale.
The densest wood in the world - snake wood
As the densest wood in the world, the heartwood of serpentine wood has irregular black spots and irregular patterns, which resembles the snake pattern and gets its name. In terms of wood density, material color, and structural density, it is superior to red rosewood, and is one of the hardest and most precious woods. Serpentine wood is very expensive and is mainly used for high-end decoration, high-end crafts, high-end furniture, etc.
Snakewood is also known as snake mulberry, Moraceae (Morace), snake mulberry (Piratinera). The scientific name is Piratinea quianensis, and the trade names are Snakewood and Letterwood. Place names Cacique carey (Panama), Palo de oro (Venezuela), Burokoro, Tibicusi (Guyana), Letterhout (Suriname), Boisd amourette (French Guiana). Small crown tree without buttocks, 25m high, 15m trunk, 30-50cm in diameter.
The difference between heartwood and sapwood is obvious, the heartwood is dark reddish brown, the sapwood is wide, light yellowish white. The diameter at breast height is 50cm, and the heartwood is less than 18cm. The diameter at breast height is 38cm, and the heartwood is only 2.5-10cm. The unique dark pattern of the heartwood is formed from resin and has a very decorative effect. Strong luster, fine structure, straight grain.
Diffuse porous wood, the diameter of the vessel is thin, the parenchyma is paratubular, and the wood rays are thin. The wood is very heavy and strong, with an air-dry density of 1.20-1.36g/cm3, which is the densest wood in the world. The heartwood is extremely rot-resistant, insect-resistant, smooth-cut, and well-polished. The radial shrinkage rate is about 6%, the chord shrinkage rate is about 9%, and the end face is prone to cracks.