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Issue 05/2016

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Materials Mineral

Materials Mineral plastic A new class of plastics has been inspired by nature and is easily degradable Conventional plastics are based on crude oil and it is widely accepted that they potentially can cause problems for the environment. One aspect in these discussions is, that most of them are not degradable. The research group around Helmut Cölfen, professor of physical chemistry at the University of Konstanz, has now produced an entirely new mineral plastic whose structure copies biomaterials. The plastic is a so-called hydrogel that can be produced at room temperature from calcium carbonate and polyacrylic acid in water. The material can directly be recycled or transformed and is self-healing in its gel state. In the dry state, the material has the consistency of a crab shell and is pliable. The nontoxic plastic material might partly replace conventional plastics in the future and thus contribute to avoid possible environmental problems. The paper has been published in the scientific journal “Angewandte Chemie” [1]. Conventional plastics are usually not biodegradable, and the recycling process also requires energy. The research group from Konstanz used the guiding principle of green chemistry for the production of their mineral plastic. The process was inspired by mineralisation in nature, which is based on calcium carbonate. The hydrogel, which might replace plastics, consists of calcium carbonate nano particles. Polyacrylic acid is used to link these particles. The hydrogel can be produced without energy input at room temperature and is malleable and self-healing. Cracks, for example, will close again after applying a drop of water. Two separate components can be joined together in the same way. The gel can also be used as a temperature sensor, as it changes its colour when heated. Recycling the gel is no problem because it can be re-shaped without energy input. By adding water and a weak acid, such as acetic acid or citric acid, the gel will dissolve by releasing carbon dioxide. The residual polyacrylic acid is non-toxic. “The production process of the hydrogel can directly be adapted by the industry, especially since the source materials are industrially produced at low cost,” Helmut Cölfen explains. Once the material has dried, it takes on the distinctive qualities of plastic, as it is both durable and pliable at the same time. This makes it a suitable replacement for conventional plastics in dry applications, for example in electronic components. A further development of this substance might be cover material, which should not, however, affect the recycling process. The special swelling capacity combined with its hardness after drying makes the material suitable in building applications to fill cracks. In contrast to biominerals, which are hard once they are finished, e.g. bones or teeth, the hydrogel is pliable. In addition to examining natural processes, the research group around Helmut Cölfen is now very interested in systematically changing the properties of such gels to produce other mineral plastics for specific applications. Future research projects will also consider possible medical applications for this new class of substance. The researchers will test other minerals as source material and they have planned to use polyaspartic acid as a potential cross-linking agent. This acid is completely biodegradable. MT References: [1] Hydrogels from Amorphous Calcium Carbonate and Polyacrylic Acid: Bio-Inspired Materials for “Mineral Plastics” Shengtong Sun, Li-Bo Mao, Zhouyue Lei, Shu-Hong Yu and Helmut Cölfen. Angewandte Chemie International Edition (DOI: 10.1002/anie.201602849). 30 bioplastics MAGAZINE [05/16] Vol. 11

Materials The elegance of traditional Japanese lacquerware NEC Corporation (Tokyo, Japan), in collaboration with the Kyoto Institute of Technology and a representative Japanese lacquerware artist, Dr. Yutaro Shimode, recently announced the development of a bioplastic using cellulose based resin [1] from grasses, trees and other non-edible plant resources that features the highly regarded URUSHI BLACK color of Japanese traditional lacquerware. In order to create the new cellulose-based bioplastic, NEC developed a unique technology for mixing additives to adjust coloration and light reflectance of the material, enabling, for the first time, the realization of optical properties (low brightness, high glossiness, etc.) similar to the deep and shiny URUSHI BLACK color of high-grade Japanese lacquerware. The new plastic balances a high level of environmental friendliness and decorativeness and makes it possible to mass produce products of various shapes and patterns using the usual molding process for ordinary plastics. “In response to the depletion of resources and food shortage problems, the need for non-edible-plantbased plastics is increasing. In addition to NEC’s history in the development of a unique cellulose-based plastic (NeCycle ® [2]) using non-edible plant materials for use in durable electronic products, we have now developed a new bioplastic that, in addition to high functionality, realizes the decorativeness of Japanese lacquerware, which is highly evaluated throughout the world, and illustrates a beauty well beyond what petroleum-based plastics can provide,” said Dr. Masatoshi Iji, Research Fellow, IoT Devices Research Laboratories NEC Corporation. This development was carried out in collaboration with the Kyoto Institute of Technology’s Future-Applied Conventional Technology Centre and Dr. Yutaro Shimode [3], a prominent Japanese lacquerware artist. The development process involved the fabrication of a Japanese lacquerware URUSHI CRAFT model by Dr. Shimode as a first step. The model, a transparent resin plate repeatedly coated with Japanese lacquer and polished by hand, served as the standard for the advanced optical properties exhibited by highquality Japanese lacquerware. Scientific analysis was performed on Japanese lacquerware at the Kyoto Institute of Technology. Based on the results, NEC then developed an optimized technology for modifying and mixing of the additives. Going forward, NEC will pursue business partnerships aimed at commercializing the new bioplastic in durable products and high-grade materials that require a high level of decorativeness, such as the interior components of luxury cars. Key features of the URUSHI BLACK bioplastic Use of non-edible plant materials that are readily available as the main ingredient. The new bioplastic uses cellulose resin produced from cellulose that is widely available from non-edible plant resources, such as grasses, the stalks of cereal crops and wood, and has the potential to be used as a substitute for petroleum. Realizes the advanced optical properties (Urushi black) of high-grade Japanese lacquerware. Black coloring agents and highly refractive organic ingredients were mixed with the above cellulose resin as special additives to adjust the resin’s coloration and light reflectance properties. By dispersing the additives into fine particles, NEC became the first to achieve the advanced optical properties exhibited by high-grade Japanese lacquerware with a bioplastic material. The new bioplastic can be mass-produced into products of various shapes using existing process technology. Conventionally, lacquerware is produced by coating the surface of substrates with lacquer and polishing them. For this newly developed bioplastic, the materials can be heated, melted, and injected into molds (mirror-finishing) to form shapes (injection molding), as with ordinary plastics. This makes it possible to mass-produce the bioplastic into products of various shapes and patterns. NEC is scheduled to present this technology at the 24 th Material Processing Technical Conference (M&P 2016) to be held at Waseda University in Tokyo from November 25 to 26, 2016. MT References: [1] Cellulose resin: Resin made using cellulose that is the main ingredient of the stems of cereal crops and wood, and is not suitable for human consumption. [2] NeCycle ® : Brand name of bioplastic material developed mainly by NEC. [3] Japanese lacquerware artist, Dr. Yutaro Shimode: a third-generation president of Shimode makie-studio who is a leading lacquerware artist in Japan. bioplastics MAGAZINE [05/16] Vol. 11 31

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