Aramid fibers processing

Fine adjusting and optimization of each step of this process is stiU underway, and a PVA fiber having a single fiber strength as high as 2 N/tex (21 gf/dtex), which is close to that of aramid fiber, has been reported (18). 

Although aramid fiber is by far the most successful fiber made via the liquid crystal route, there are some other important fibers that have been made by this process. For example, poly(p-phenylene benzobisthiazole) (PBT) (Wolfe et al, 1981a, 1981b) is synthesized from terephthalic acid and 2,5-diamino-l,4-ben-zenedithiol dihydrochloride (DBD). The DBD is first dissolved in poly-phosphoric acid (PPA), followed by dehydrochlorination. Terephthalic acid and more PPA are then added and the mixture is heated to 160°C to make a solution. The solution is heated to 180 C and reacted for 18 hours to obtain the... 

Kevlar 29 and versions thereof (K 129 and Kl j.) are also used extensively in lightweight body armor as well as composite liners (with vinylester, polyester or epoxy as the matrix). A quick look at the properties of different Kevlar aramid fibers in Table 4.2 shows why K29 is better than K49 for lightweight body armor applications. K29 has a higher strain to failure than K49. That means that the total work of fracture, i.e. the area under the stress-strain curve, is larger for K29 than K49. Hence, the energy absorbed in the fracture process is higher for K29... 

Riggins P H and Hauser P J, Exhaust process for simultaneously dyeing and improving the flame resistanceof aramid fibers , US Patent4,898,596,1990, assigned to Burlington Industries. 

Wet layup consists of placing a layer of dry reinforcement inside a mold and then applying an uncured, low-viscosity thermoset resin as shown in Fig. 2. Woven glass fibers are the prevalent reinforcing preform utilized in layup processes, although carbon and aramid fibers are also used to a lesser extent. Typical fiber volume fraction of composites manufactured via wet layup range between 30% and 50%. The resin can be poured, sprayed, or brushed on top of the preform layer either by hand or by machine. The fiber preform layer is rolled on or pressed after the application of resin to evenly distribute the resin and remove air pockets. Resin is applied on top after each layer of fiber mats is properly placed. This process is repeated until the desired thickness is reached. To provide a smooth surface finish on the mold side, a thin layer of mold release is often applied prior to starting the layup. Thereafter, pressure and heat are applied to allow the composite to cure. Pressure can be applied... 

Vistamer KF - aramid fiber which has surface activated by a patented reactive gas process DuPont, Wilmington, DE, USA... 

In most other processes, the presence of moisture in filler either requires a process correction in the amount of the active ingredient or the moisture must be removed. In the case of hygroscopic fillers (which are very important to industry), the surface of the filler must be treated to lower moisture uptake. Montmorillonite, glass beads and fibers, silica, titanium dioxide, aramid fiber, mbber particles, and carbon fiber were studied to improve their moisture absorption and impart the hydrophobic properties. "... 

Research and development in fluid jet technology led to its widespread use in film and web processing, mixers, reactors, and fiber processing. Applications to fibers alone includes Taslan bulked yams, jet piddlers, draw-jets, interlaced yams, bulk-crimped carpet fibers (BCF), and spunbonded products such as Reemay polyester, Typar polypropylene (PP), and Tyvek olefins. New fibers also were introduced Nomex aramid, especially suited for high-temperature applications Lycra spandex, an elastic textile yam Qiana nylon, with a silklike appearance and Kevlar aramid, used in products ranging from tires to bullet-resistant vests. 

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