New technology could offer a cleaner, greener way to strengthen plastic
Competition is heating up among researchers working to develop products using cellulose nanofiber, or CNF, a strong, lightweight material derived from plants.
Since 2015, a number of products made with CNF have appeared on the market, including disposable diapers and ballpoint pens, as the stuff has moved out of the lab and into practical application. Last year, many companies, especially in the paper industry, began installing CNF production equipment. Now the “post-carbon-fiber” wonder material is attracting serious attention.
In December, an environmental products and services trade show, EcoPro 2016, was held in Tokyo. In addition to paper companies such as Oji Holdings and Nippon Paper Industries, machinery and chemical companies also had CNF exhibits. Satoshi Hirata, secretary of the Nanocellulose Forum, which designed a booth on CNF for the trade show, was surprised at the reaction, saying, “Many more people came than we anticipated.”
NATURE’S WAY CNF is made by peeling off microscopic plant fiber from wood products using machines and chemicals. It weighs only one-fifth as much as steel but is three to five times stronger. In contrast to carbon fiber, which is produced by baking acrylic fiber derived from petroleum, CNF comes from renewable resources. “It is a sustainable, natural material, so basically the raw materials will never be exhausted,” said Oji President Susumu Yajima.
Transparency is another a big advantage of CNF. It may be useful in products such as flexible displays. CNF also retains its shape well when exposed to heat, meaning it may have industrial applications.
Because the material is often made from wood pulp, paper companies, which have handled pulp for many years, are taking the lead in cultivating the market. Nippon Paper in 2015 released disposable diapers made with CNF, making use of one of its attributes: odor-absorbing ions. Oji has developed technology that can make CNF into transparent sheets.
Another useful CNF trait is its viscosity. Mitsubishi Pencil, a Japanese maker of writing instruments, took advantage of this property and added it to its ballpoint pen ink. DKS supplies the CNF.
It is also used to give stiffness to food and cosmetics. Compared with conventional additives, CNF is more temperature-resistant, making it easier to achieve the desired amount of smoothness or stickiness. In cosmetics, it combines a silky feel with viscosity.
Anticipating wide-ranging uses in cosmetics and food, Nippon Paper is bringing a CNF plant online in western Japan’s Shimane Prefecture this year. Oji has announced that it will begin selling a thickener made with CNF in April. The product, with 10 to 100 times the viscosity of conventional thickeners, will be sold to manufacturers of cosmetics, consumer products and paints.
CNF was first used as a strengthening resin in the plastics and rubber found in everything from cars to electronics to sneakers. Just as carbon fiber was first used in relatively simple products like fishing rods and golf clubs, making its way into cars and aircraft as the technology advanced, CNF will find more applications as manufacturers become more familiar with its properties.
But for the material to reach its full potential, production costs must fall. At present, CNF costs 5,000 yen to 10,000 yen ($44.50 to $89) per kilogram to make. That compares to 3,000 yen per kilogram for carbon fiber, without accounting for large variations in quality. Steel is much cheaper, at 100 yen per kilogram.
Japan’s Ministry of Economy, Trade and Industry forecasts the market for CNF and related products will be worth 1 trillion yen by 2030, assuming economies of scale and technological advances can lower production costs to between 500 yen and 1,000 yen per kilogram. Research on how to do that is proceeding.
Kyoto University has come up with a technology that could lower costs by a factor of 10. It has taken on researchers from Oji, Nippon Paper and Seiko PMC. These researchers have developed the “Kyoto Process.” First, the pulp is treated chemically and mixed with resin in a special machine. This breaks the fibers down into much finer pieces measuring just a few nanometers (billionths of a meter) in diameter, allowing them to easily penetrate the resin. As this pulverizing and mixing happens in a single step, it could lower CNF production costs to around 1,000 yen per kilogram. Nippon Paper has built a production facility that uses this approach.
In addition to chemical treatments, there are mechanical methods of producing CNF. Sugino Machine, an industrial equipment maker in Toyama Prefecture, 240km northwest of Tokyo, is working on the problem. “We can develop in-house the equipment needed to break down the fibers, which is the most important step in producing nanofibers,” a company spokesman said.
Research and development are also moving forward in Northern Europe, Canada and the U.S. The North American materials are nanofibers, but vary widely in size and are called cellulose nanocrystals (CNC). Because of the differences in strength and other characteristics, Japan’s industry ministry treats CNC and CNF as separate products. It is working on international standards for CNF.
KEYWORD: Plastic-reinforcing fibers
Fibers are often used to enhance the performance of plastics, which by themselves lack the strength of steel needed for use in products such as cars and aircraft parts. Fiberglass and high-performance carbon fibers are typical examples. Such materials can be used in place of metals for many applications.
Carbon fiber reinforced plastics (CFRP) are increasingly used in auto and aircraft manufacturing. The term fiber-reinforced plastics (FRP) often refers to those that incorporate fiberglass. These are used in auto bodies and wind turbines, for example. Although they are not as strong as carbon fiber, they are cheaper and give plastics some additional strength.