Purified cellulose fibers show promise in reinforced thermoplastics. (Close-Up: Additives).Purified cellulose fibers could be the next lightweight reinforcements for thermoplastics. Rayonier Performance Fibers, a large maker of specialty pulps, is working with the USDA USDA, n.pr See United States Department of Agriculture. Forest Products Laboratory in Madison, Wis., on reinforcing nylon 6 with cellulose fibers. CreaFill Fibers Corp., a maker of specialty cellulose fibers and powders, is exploring cellulose reinforcement of HDPE HDPE abbr. high-density polyethylene , PP, and PVC PVC: see polyvinyl chloride. PVC in full polyvinyl chloride Synthetic resin, an organic polymer made by treating vinyl chloride monomers with a peroxide. . Potential applications range from molded auto parts Auto parts are components of automobiles. They mainly are, in alphabetic order (only car specific articles or articles with car section):
Cellulose fiber is commercially available in bulk with consistent properties and quality. It has several advantages over glass fiber. It's lower in density, non-abrasive, and less expensive--yet, in a thermoplastic A polymer material that turns to liquid when heated and becomes solid when cooled. There are more than 40 types of thermoplastics, including acrylic, polypropylene, polycarbonate and polyethylene. composite it can still offer roughly two-thirds to three-fourths of the strength properties of glass fiber. Refined cellulose starts in the mid 20 cents/lb range, and prices can go higher, depending on fiber length, purity and form (loose or compressed). Pure cellulose is produced in wood-pulp manufacturing. Bleach strips away the wood lignin lignin (lĭg`nĭn), a highly polymerized and complex chemical compound especially common in woody plants. The cellulose walls of the wood become impregnated with lignin, a process called lignification, which greatly increases the strength and and hemicellulose hem·i·cel·lu·lose n. Any of several polysaccharides that are more complex than a sugar and less complex than cellulose and found in plant cell walls. hemicellulose structural polysaccharide of plants. and leaves acid-free fibers (about 50% of the original wood content) for paper making and specialty applications. Refined cellulose fibers have long been used in thermoset A polymer-based liquid or powder that becomes solid when heated, placed under pressure, treated with a chemical or via radiation. The curing process creates a chemical bond that, unlike a thermoplastic, prevents the material from being remelted. See thermoplastic. plastic applications like injection molded wire caps and electrical outlet boxes. But cellulose fibers haven't been used commercially in injection molded thermoplastics. Targeting auto parts Cellulose was originally thought to be unsuitable for processing at the temperatures required for nylon (435 F) because residual lignins and hemicellulose would degrade and char, causing discoloration dis·col·or·a·tion n. 1. a. The act of discoloring. b. The condition of being discolored. 2. A discolored spot, smudge, or area; a stain. Noun 1. and strong odors. Rayonier was probably the first to find that purified cellulose--from which 99% of the lignins and hemicellulose have been removed--could be safely melt compounded into high-temperature engineering plastics like nylon 6 and PBT PBT Provider Backbone Transport (networking technology adding determinism to ethernet) PBT Polybutylene Terephthalate PBT Profit Before Tax PBT Paper Based Test (education) , which have melting points above 435 F. Rayonier worked with the Forest Products Lab (FPL) under a joint-development agreement and obtained a joint patent in 2001 on the use of more than 80%-pure cellulosic fibers in thermoplastic compounds with melt temperatures above 356 F. The partners targeted automotive-grade engineering resins like nylon 6 and PBT because cellulose fiber "is expensive enough that the benefit is greater in high-performance engineering plastics than in picnic tables and decking made with polyolefins," says FPL research chemist Daniel Caulfield. Rayonier and FPL also developed a way to compress the lowbulk-density cellulose fibers into pellets. The Rayonier/USDA patent (#6,270,883) describes production of pellets by compressing a mixture of wet pulp and a binder (sodium carboxymethyl cellulose Noun 1. sodium carboxymethyl cellulose - a gummy substance that is a sodium salt of carboxymethyl cellulose; used as a thickening or emulsifying agent salt - a compound formed by replacing hydrogen in an acid by a metal (or a radical that acts like a metal) ) into 3- to 6-mm cylindrical pellets using a Kahl Pellet Mill A pellet mill is a type of mill used to create cylindrical pellets from a mixture of dry powdered feedstock, such as flour, sawdust, or grass, and a wet ingredient, such as molasses or steam. The pellets are made by compacting the mash or meal into many small holes in a die. . After drying, the compressed pellets are suitable for shipping in drums or super-sacks. They can be melt compounded in a twin-screw extruder to produce cellulose-filled thermoplastic pellets for injection molding injection molding n. A manufacturing process for forming objects, as of plastic or metal, by heating the molding material to a fluid state and injecting it into a mold. . Loose fibers can also be side-fed into a corotating twin-screw extruder. Rayonier now markets developmental quantities of its purified cellulose pellets under the name TerraCel 10J for hardwood fiber and TerraCel 20F for softwood fiber. Hardwood TerraCel fibers have nominal average length of 0.04 in. (1 mm), while softwood fibers are 0.1 in. (2.5 mm) long. The 2001 patent compares injection molded plaques of nylon containing 30% cellulose and 2% coupling agent with plaques of nylon and 33% glass fiber (see table, p. 36). The data show that cellulose fibers perform well enough for many applications. FPL and Rayonier are sampling around two dozen potential customers for this material in Europe, the U.S., and Japan. Most of them are automotive suppliers. Polyolefin compatible Meanwhile, CreaFill is working to characterize compounds of its CreaTech TC 750 cellulose fibers in lower-temperature resins--HDPE, PP, and PVC. CreaTech TC 750 fibers have a nominal average length of 0.7 mm and width of 0.02 mm, for an aspect ratio of 35:1. CreaFill recently published data comparing compounds of 0.5-MI HDPE and 40% CreaTech TC 750 virgin cellulose fibers with and without coupling agents. Injection molded plaques showed a flexural strength Flexural strength is also known as modulus of rupture, bend strength, or fracture strength. Flexural strength is measured in terms of stress, and thus is expressed in pascals (Pa) in the SI system. of 7570 psi and a reversed notched Izod impact of 2.5 ft-lb/in. When 2% Polybond 3009 coupling agent is added, properties go up: Flexural strength is 7910 psi and reversed notched Izod is 2.6 ft-lb/in. (Polybond is an adhesively modified polyolefin from Crompton Corp., Middlebury, Conn., which performed the tests.) CreaFill says HDPE/cellulose compounds look promising for applications like roofing membranes, pond liners, carpet backing, and automotive components. Cellulose/PVC compounds are aimed at outdoor furniture, siding, and window and door profiles. CreaFill offers both wood-derived virgin fibers and recycled cellulose fibers made from paper. Both come in loose form, pellet-mill chunks, or agglomerated agglomerated of particles, compacted together into a mass. agglomerated feeds particulated feeds compacted or extruded into pellets and similar forms. micropellets. Virgin cellulose is pure alpha cellulose, which is stronger than recycled cellulose and can withstand higher processing temperatures (up to 428 F) without charring, whereas recycled cellulose can be processed only up to 392 F.
CELLULOSE FIBERS VS. GLASS IN INJECTION MOLDED PLAQUES
Softwood Hardwood Glass
Cellulose Cellulose Fiber
Avg. Fiber Length, in. 0.10 0.04 0.125-0.250
% Fiber 30 30 33
% Nylon 6 68 68 67
% Coupling Agent 2 2 0
Tens. Str., psi 11,890 12,620 16,100
Tens. Mod.. kpsi 783 827 1160
Flex. Str., psi 16,530 17,690 21,320
Flex. Mod., kpsi 798 856 1102
Notched Izod, ft-lb/in. 0.47 0.47 0.85
Unnotched Izod, ft-lb/in. 4.6 5.9 7.6
Source: Rayonier, U.S. Patent #6,270,883 B1, Aug. 2001.
NEED TO KNOW MORE? CreaFill Fibers Corp., Chestertown, Md. (800) 832-4662, www.creafill.com Rayonier Performance Fibers, Jesup, Ga. (912) 427-5491, www.rayonier.com |
|
||||||||||||||||||||
Printer friendly
Cite/link
Email
Feedback
Reader Opinion