Biomid is a new 100 percent cellulose-based fiber for use in composites, developed by Gordon Shank Consulting LLC (Burnaby, British Colombia, Canada) and composite materials distributor ENC International (Seoul, South Korea). Reportedly, the fiber’s density is close to that of aramid fiber, its specific modulus is very close to E-glass, and its specific tensile strength is comparable to Innegra Technologies’ (Greenville, S.C.) 8g/denier high-modulus polypropylene (HMPP) fiber.
With an appearance similar to that of glass fiber, Biomid is translucent when wet out (other natural fibers, such as flax, sisal, hemp and kenaf, are brown). Biomid is made in South Korea by dissolving cellulose and spinning the solution from a spinneret. This process, similar to that used to produce Innegra’s HMPP fiber, produces a cellulose fiber with a high degree of crystallinity (95 percent), permitting fiber processing at temperatures as high as 360°C/680°F. Because many commercial resin systems must be processed at up to 200°C/392°F, Biomid is a viable option in situations where most natural fibers, which degrade at 150°C/302°F, can’t be used.
Unlike the discontinuous natural fibers stripped from plant stalks, which vary in length from inches to a few feet, at best, Biomid fibers are spun and, therefore, can be produced continuously. They need not be twisted into bundles, but instead they can be used in parallel, enabling much higher properties and producing thinner fabrics than twisted yarns. This reduces resin puddling at the warp-weft interstices, resulting in a more even resin-to-fiber distribution.
According to the company, spinning enables developers to achieve the smallest filament diameter of any natural fiber — 10 to 11μ (0.39 to 0.43 mil) — and produce consistent, repeatable fiber diameter, reportedly not possible with plant-based fibers. Flax, for example, averages 20μ/0.79 mil but varies from 15 to 30μ (0.59 and 1.18 mil) because there is no way to control the diameter. Biomid will be made first in 1650 denier, which is roughly the same size as a 3K carbon fiber, a 158 tex aramid fiber or a 300 tex glass fiber. It is available now in weights up to 8.5g/denier for less than $5/lb.
The fiber’s raw material is derived, with help from the National Research Council of Canada (NRC, Ottawa, Ontario), from wood pulp and paper-industry waste in Canada. Biomid, therefore, is said to maintain a smaller carbon footprint than other natural fibers. The product doesn’t compete with food crops for land and requires no water or fertilizer for its production. Shank Consulting claims that Biomid fiber manufacturing generates 0.88 kg (1.94 lb) of carbon dioxide (CO2) emissions per metric tonne of fiber, compared to 55 kg (121 lb) for flax fiber and 500 to 600 kg (1,102 to 1,323 lb) of CO2 emitted per metric tonne of produced glass fiber.
The company maintains that the fiber has been optimized at every stage of its development. The partners reviewed more than 500 types of cellulose to find an "optimal proportion between hardwood and softwood” via hundreds of trials. Initial commercialization samples of Biomid are under evaluation by several weavers and are being tested to confirm compatibility with epoxy resins — tests for compatibility with phenolic resins, polyester resins (terephthalate, orthopolyester and dicyclopentodiene-based) and vinyl ester resins are already complete.
Work with bio-based resins also has begun, and the company is exploring reactive sizings that will optimize the fiber-matrix bond and is developing a range of linear densities that can be optimized for specific end-uses.