3. Production of Flax Fibers for Biocomposites

Natural fibers for many and varied industrial uses are a current area of intense interest. Production of these fibers, furthermore, can add to farmer incomes and promote agricultural sustainability. Flax (Linum usitatissimum L.), which has been used for thousands of years, is unparalleled in supplying natural fibers for industrial applications as diverse as textiles and paper, providing high value linseed and fiber from a single plant, and maintaining sustainable agriculture in temperate and subtropical climates for summer or winter production, respectively. As a value-added replacement for glass fiber from a renewable resource, flax fiber is recyclable, biodegradable, and sustainable for the economy, ecology, and society. To the point, DaimlerChrysler reported that natural fibers for automotive components required 83% less energy and were 40% less expensive than glass fiber components. A better understanding of the fiber characteristics that influence composite performance could lead to the development of additives, coatings, binders, or sizing suitable for natural fiber and a variety of polymeric matrices. Stems of flax require retting to separate fiber from nonfiber components and rigorous mechanical cleaning to obtain industrial-grade fibers. Considerable work has been undertaken to improve the retting process using specific cell-free enzymes, especially pectinases, to control and tailor properties for industrial applications. Fiber processing and use in composites are affected by variables such as length, uniformity, strength, toughness, fineness, surface constituents, surface characteristics, and contaminants. One of the main concerns for the composite and other industries in incorporating natural fibers, such as flax, into production parts is the fiber variability resulting from crop diversity, retting quality, and different processing techniques. Standardized methods to assess flax fiber properties, therefore, are needed to maintain quality from crop to crop and provide a means to grade fibers for processing efficiency and applications. Other parts of the plant stalk, notably the waste shive and dust, can potentially be utilized as coproducts to offset costs for producing the major products of fiber and seed.