Thermoplastic Nanocomposites from Cellulose Fibers
Blacksburg, Va. August 24, 1999 - Researchers at Virginia Tech have developed a one-step process for creating thermoplastic nanocomposites from cellulose fibers.
Hiroyuki Matsumura, research scientist at Daicel Chemical Industries, Ltd. of Japan, and Wolfgang Glasser, wood science professor at Virginia Tech, will present their research at the 218th American Chemical Society National Meeting, which is being held in New Orleans Aug. 22-26. The researchers have discovered that by reacting wood pulp fibers in a solvent medium that does not fully penetrate the fibers, then hot-pressing the partially modified pulp fibers at elevated temperature, a semi-transparent polymer sheet is formed that is actually a nanocomposite of cellulose esters and unmodified cellulose.
The wood pulp raw material starts out looking like pulled apart tissue paper. After the solvent is added, the fibers look much the same, but actually the surfaces of the microfibrils within each wood pulp fiber have become melt-flowable like plastics. "By hot-pressing these partially modified pulp fibers, the cellulose ester surfaces of the modified microfibrils fuse to form a continuous material," explains Matsumura. "The fused microfibrils contain unmodified cellulose at their core. The nanocomposite consists of a mixture of cellulose and cellulose ester (plastic) in which each component has a dimension several nanometers."
The resulting material has the virtues of thermoplastics, in that it is resistant to water, can be shaped by heat, and is expandable. Because it is a nanocomposite rather than a blend, the material also retains the virtues of cellulose fibers, which nature uses as reinforcement. "The unmodified cellulose adds strength and biodegradability," says Matsumura. "It is also cheaper than the more highly processed cellulose ester materials commercially available. It comes from a renewable resource and we have developed a low-input process both in terms of time and materials."
He anticipates the thermal nanocomposites may be used not only where strength, resistance to moisture, and resistance to heat are desired, such as panel products in transportation industries and casings for electrical products and appliances, but also "where a pleasant feel is valued, such as board products for furniture."
Biodegradability is important for agricultural materials and trays for food products. "There are many such uses where we don't want the wrap to outlast the content. When you send garbage to the landfill in a plastic bag, you would like the bag to degrade in addition to the content," Matsumura points out.
The paper, "Thermoplastic nanocomposites from cellulose" (CELL 55), will be presented Tuesday, Aug. 24, at 10:45 a.m. in Convention Center Room 256.
Daicel Chemical Industries, Ltd., which makes cellulose and petroleum-based products, sent Matsumura to Virginia Tech two years ago to study with Glasser, who heads the biobased material/recycling research program in the College of Natural Resources. Matsumura will return to Japan this fall. A patent is pending on the thermoplastic nanocomposite cellulose material.