Bamboo transformation for new industrial applications

Bamboo adaptability let it to become as a sustainable raw resource able to substitute the fossil based materials in a big amount of industrial production chain.

Prosperity Bamboo has been pursuing an industrial model where the starting point consists in the raw material self-production by means of new bamboo plantations close to the transformation factories, in such a way to accomplish two goals: to increase the industrial sector procurements self – sufficiency and to lower the environmental and economic impact of transport. Once the bamboo plantation ripening has reached, it produces at least 40tons per year per hectare of raw material for approximately a century.

First transformation

The bamboo first transformation starts after the culms harvesting. The first transformation changes as function of the desired final product, creating several semi-finished products. This paper does not display technical data like temperatures, solutions percent, working time and further technical pieces of information.

The culms transformation consists in the bamboo fibre extraction from the culm itself by means of several methods: mechanicals, chemicals, thermals, or a combination of the three. The important thing is not to damage the bamboo fibre during its extraction because otherwise its reinforcing function on the final composite could be lost. The most used process consists in the culm division in thin slats up to reaching stick of dimension 1x1x15mm. Then the sticks need a chemical process based on a maceration for a certain time and temperature with a solution of sodium peroxide, distilled water, and acetic acid. At the end, there is a cleaning with distilled water and a drying at room temperature obtaining elementary fibres with 2-3mm length. This semi-finished product can feed several production chains by means of moulding. Short bamboo fibre extraction can also take place only with mechanical machinery, avoiding the chemical solution.

Characteristics

Bamboo fibre has natural antibacterial, bacteriostatic, and deodorant characteristics. There is validation performed by the Japan Textile Inspection Association, which determines that even after fifty wash cycles the bamboo fibre fabric still maintains an excellent anti-bacteriological function.

Bamboo fibre production can take place in ring-spun form, in blends with cotton, viscose or lyocell, and fibres blended with materials such as carbon and polyester. As an alternative to the viscose process, which requires the use of chemical solvents, it is possible to spin bamboo through mechanical spinning which requires longer fibres (5/7mm) but certainly capable of creating a more ethical final product, comparable to fabrics in hemp or flax.

Cellulose

The culms are undergone to decortication and then chipping in such a way to obtain bamboo chips. The bamboo chips processing occur in several ways depending on the final product desired. A further bamboo chip reduction is also possible, creating a sort of vegetable pulp composed by cellulose for 90/100%. The pulp can be used to produce packaging, cardboard or, after bleaching, paper.

Bio plastic

The creation of a compound with a natural fibre reduced to pellet format is underway. This compound would feed, without structural technical modifications, into existing thermos injection machinery to produce components currently made with Polypropylene, Polyethylene, Nylon, etc.

The objective is to create a material that is 100% vegetal where currently there is a mix of fossil origin materials and wood sawdust at 50%.

The bamboo use as bio plastic material can fulfil several industrial applications. As reported by the Bamboo Technology Network, the bamboo sawdust obtained during fibre extraction or other production steps find application as filler in composite materials. Composites of PBS (polybutylene succinate) with 40% of bamboo sawdust have manufactured and have shown good mechanical and chemical properties.

The bamboo fibre mixes with other plant-based compounds, such as sugar cane one, is also possible.

Cold and hot pressing allow the manufacturing of various tableware and containers, which have demonstrated excellent biodegradability in natural conditions within 60 days. They are completely of plant origin, suitable for food contact and have excellent mechanical and chemical resistance (to water and oil).

The company Min Aik, from Taiwan, already markets this type of material. While the FKuR Kunststoff GmbH has produced a filament for 3D printing (Fibrolon? 3D Bamboo) containing bamboo fibre.

Nanofibers

Thanks to a crystalline structure different than the wood pulp nanofibers, the cellulose nanofibers derived from bamboo become an interesting subject of study, suggesting the possibility of obtaining differential properties that pave the way for further applications of this versatile material. In fact, they boast superior mechanical properties, high surface area, low weight, and greater water-repellent tendency (caused by the spatial organization of the nanofibrils themselves).

The nanofibers extraction takes place by means of mechanical process, chemical process, or a combination of both, depending on the part of the culm interested in and the final use you that want to make with the nanofibers themselves. The chemical method is the most used because it is faster and cheaper than the mechanical one. Vice versa, the mechanical process is more sustainable because solvents are not used.

For example, the nanofibers extraction may involve the culm section in between the diaphragms. This section is firstly reduced in strips 20-30cm long and 2-3mm thick and then submerged in a sodium hydroxide solution. The final fibre bundles extraction with a diameter of approximately 200 micrometres takes place by means of a “roller looser”. The fibre bundles need to be neutralized washing them with water and then are submerged in a solution with water and ethanol. The pulp extraction from fibre bundles is possible by means of a mixer. The pulp may than be grinded several times. Finally, a “ball mixing” process take place to separate the nanofibers previously obtained.

Nanofibers extraction from bamboo leaves takes place with another chemical process after leaves reduction in powder, washing with distilled water and heater drying. The powder needs a treatment with a solution of benzene/ethanol to remove chlorophyll, wax, and pigments. A further treatment with sodium chlorite and potassium hydroxide removes lignin and hemicellulose, obtaining cellulose. Then, cellulose need to be submerged in deionized and sonicated water to isolate the nanofibers (a high-pressure homogenizer can also be used).

These are some of the first phases of transformations envisaged by the Prosperity Bamboo industrial development plan, the presentation of which was brought to the attention of the institutions and main industrial groups operating in Italy.