Fiber-based additive manufacturing

Fiber-based additive manufacturing technology for open porous impiants with complex geometries... 

Spandex stretch fiber, based on polyurethanes, was developed by DuPont and appeared in 1962. From this time, polyurethanes would account for the greater part of demand for anilines. Aniline production alone had more than doubled, to over 100 million lbs. per year, between 1939 and 1957, in part to satisfy demand in products other than dyes. Half the US output was consumed in the production of rubber additives, mainly diphenylamine and cyclohexylamine, the latter used as a chain stopper in manufacture of polyurethanes (also as a boiler water additive and, in the US until banned in 1970, in the manufacture of cyclamate sweeteners). Other polymers, such as epoxy resins, relied on the bulk availability of various aromatic amines (Chapter 14). 

Polyolefins, Polyethylenes, Polyisobutylenes, Poly(Methyl Methacrylates), and Poly(Styrene Sulfonates), In addition to polyurethane foams, polyethylene and polypropylene fibers can be manufactured as alternative polymeric sorbents. However, based on sorbent capacity, cost, and availability, these materials would be considered inferior to polyurethane. 

Figure 18.5 Biomimetic scaffold for tympanic membrane replacement based on poly(ethylene oxide terephthalate)-co-poly(butylene terephthalate) and fabricated using additive manufacturing to deposit radial and circular fibers onto an electrospun basement mesh. Zoomed-in micrograph shows human mesenchymal stromal cells stained with methylene blue.

Employees who point out that their hands feel hot may need a different glove model than the one they are currently wearing. Today many gloves are manufactured with ventilation holes to address this issue. In addition, the liner fabric of the glove can make a huge diffaence in worker comfort. For example, gloves with a cotton liner base are generally cooler to wear than those built on a synthetic fiber base. 

Acrylic acid is an important chemical building block used in the manufacture of polyacrylates and commodity acrylates. Commodity acrylates, such as methyl, ethyl, n-butyl, and 2-ethylhexyl acrylate, are utilized in various industrial applications, including coatings, adhesives and sealants, textiles and fibers, polymer additives/impact modifiers, and films. Polyacrylates are extensively used as super absorbent polymers. Bio-based acrylic acid can be obtained through the fermentation of carbohydrates to 3-hydroxypropionic acid (3-HPA), and further dehydration of 3-HPA gives acrylic acid. 3-HPA could also be used as a precursor to other important chemical building blocks, such as PDO, acrylonitrile, and acrylamide. Via another route, glycerol can be chemically converted to acrylic acid, either by dehydration to acrolein followed by oxidation to the final product or in a one-step oxydehydration. 

The other major benefit of RF heating was in reduced presstimes. A typical steam-heated MDF press was operated at about 163°C. Presstimes, not including deadtime, for 19-mm (3/4 in.) board would be about 7 min. With RF, this time could be reduced to about 5 min. It will be noted that these presstimes, even with the use of RF, are longer than those requited for particleboards and this, in addition to the more costiy base fiber and the higher resin requirements, explains much of the manufacturing cost differential between MDF and particleboard. 

Fire and Wind Hazards. Weather resistance of roof covetings is not necessarily correlated to fire and wiad resistance. Underwriters Laboratory and the Factory Mutual System test and rate fire and wiad hazard resistance, and some durabiUty tests. Organic felt or fiber glass mat base shingles are commonly manufactured to meet minimum UL requirements, which, ia addition to minimum mass, require wiad and fire resistance properties. 

In addition to electrical uses, epoxy casting resins are utilized in the manufacture of tools, ie, contact and match molds, stretch blocks, vacuum-forrning tools, and foundry patterns, as weU as bench tops and kitchen sinks. Systems consist of a gel-coat formulation designed to form a thin coating over the pattern which provides a perfect reproduction of the pattern detail. This is backed by a heavily filled epoxy system which also incorporates fiber reinforcements to give the tool its strength. For moderate temperature service, a Hquid bisphenol A epoxy resin with an aHphatic amine is used. For higher temperature service, a modified system based on an epoxy phenol novolak and an aromatic diamine hardener may be used. 

Uses. About 60% of the MA produced is used to make unsaturated polyester and aikyd resins, which are formed by reaction of MA with glycols. Polyester resins are used in the fabrication of glass fiber reinforced parts. Applications include boat hulls, automobile body parts, patio furniture, shower stalls, and pipe. Aikyd resins are mostly used in coatings (paint, varnish, lacquers, and enamels). MA also is widely used as a chemical intermediate in the manufacture of plasticizers and dibasic acids (fumaric, maleic, and succinic). About 15% of MA production goes into the manufacture of viscosity index improvers and dispersants used as additives in lube oils. Several agricultural chemicals are based on maleic anhydride, the best known being Malathion. 

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