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A kenaf-fiber-reinforced bioplastic jointly developed by Unitika and NEC is now being used as an environmentally sound plastic for mobile phones. Developed due to strong interest by both companies in environmental problems such as global warming and the depletion of resources, the new bioplastic adds kenaf fiber (Note 1)—which is an effective plant in preventing global warming—to a corn-based polylactic acid (Note 2). This kenaf-fiber-reinforced bioplastic is intended to replace conventional oil-based plastics and is made using a unique blending method to satisfy the fall impact, formability and other characteristics needed for mobile phones.
Polylactic acid, a bioplastic derived from renewable plant-based resources, has recently been attracting considerable attention. However, improvements in heat and strength resistance were required before it could be used in electronic equipment. The industry has therefore been studying how to blend polylactic acid with conventional oil-based plastics.
A combination of NEC's original plant softening and formability-enhancing agents and a formula that improves resistance to excess moisture developed by Unitika has achieved the highest level plant constituent ratio for a bioplastic to be used in electronic equipment (about 90%*2), as well as the fall impact (Note 3), heat resistance (Note 4), and formability characteristics required for mobile phone casings.
This bioplastic made its debut in the casings of NTT DoCoMo's mobile phone model "FOMA (R) N701iECO"*1 launched in March. To utilize the unique texture of this material, the mobile phone incorporates new ideas in design (new color, no plating or painting), demonstrating a harmony with the environment.
(*1: "FOMA" is a registered trademark of NTT DoCoMo *2: Quantity of plant constituents in plastic.)
Note 1: Kenaf
Kenaf has a considerably fast growing speed (usually growing at a speed of three to 9 times that of the average plant), and has a preeminent carbon fixation effect (1.5t of CO2 in the air is absorbed per 1t of kenaf). Although conventional uses include material for paper and feed etc., an effective use for kenaf has not been discovered to date.
Note 2: Polylactic acid (PLA)
This is plastic in which polymerization of the lactic acid is achieved through fermentation of materials such as corn. It is already in mass production. Presently the biomass-based plastic has insufficient heat resistance and strength for use in electronic devices.
Note 3: Fall impact
A method to evaluate the damage to an object, such as a cell phone, when it is dropped from a predetermined height.
Note 4: Heat resistance
Evaluation by applying heat until an object changes its form while a load is being applied. By adding kenaf fiber, the temperature at which a PLA changes form can be improved by over 20 degrees Celsius.
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