Fibers plasma treatment

M. D. Smith, Suface Modfcation of High-Strength Reinforcing Fibers by Plasma Treatment, AUiedSignal Inc., Kansas City, Mo., July 1991, p. KCP-613-4369. 

Control of fiber friction is essential to the processing of fibers, and it is sometimes desirable to modify fiber surfaces for particular end-uses. Most fiber friction modifications are accomplished by coating the fibers with lubricants or finishes. In most cases, these are temporary treatments that are removed in final processing steps before sale of the finished good. In some cases, a more permanent treatment is desired, and chemical reactions are performed to attach different species to the fiber surface, e.g. siliconized slick finishes or rubber adhesion promoters. Polyester s lack of chemical bonding sites can be modified by surface treatments that generate free radicals, such as with corrosive chemicals (e.g. acrylic acid) or by ionic bombardment with plasma treatments. The broken molecular bonds produce more polar sites, thus providing increased surface wettability and reactivity. 

Fig. 9.5 SEM images of C3 material before and after hydrogen plasma treatment. For experimental details see [59]. (a) and (b) are top views before and after etching of the C3 material perpendicular to its outer surface, (c) is an in-plane view before etching and (d) represents a view along the long axis of a partly etched fiber.

Fig. 5.21. Surface amine concenlralion (O) of aramid fiber and ILSS ( ) of epoxy matrix composites as a function of ammonia plasma treatment time. After Brown et al. (1991).

Ladizesky and Ward (1983, 1989), Ward and Ladizesky (1986) and Ward (1993) reported that plasma treatment of polyethylene fibers in an atmosphere of oxygen is the most effective among the many techniques studied. There are four major mechanisms responsible for improved fiber-matrix interface adhesion ... 

Bascom, W.D., Chen, W.J, (1991). Effect of plasma treatment on the adhesion of carbon fibers to thermoplastic polymers. J. Adhesion 34, 99-119. 

Biro. D.A.. Plcizeicr, G. and Deslandes, Y. (1993a). Application of the microbond technique. HI. Efl ecls of plasma treatment on the ultra-high modulus polyethylene fiber-epoxy interface, J. Mater. Sci. Lett. II, 698-710. 

Gao. S. and Zeng, Y. (1993a). Surface modification of ultrahigh molecular weight polyethylene fibers by plasma treatment. I. Improving surface adhesion. J. Appi. Polym. Sci. 47, 2065-2071. 

Inagaki, N., Tasaka, S. and Kawai, H. (1992). Surface modification of Kevlar 49 fiber by a combination of plasma treatment and coupling agent treatment for silicon rubber composite. J. Adhesion Sci. Technol. 6, 279-291. 

Jang, B.J., Das, H., Hwang, L.R., Chang, T.C. (1988). Plasma treatments of fiber surfaces for improved composite performance. In Proc. ICCI-II, Interfaces in Polymer. Ceramic and Metal Matrix Composites (H. Ishida ed.), Elsevier Sci. Pub. New York, pp. 319-333. 

Oxidation of the surface of wool fibers is known to reduce felting shrinkage as well as improve other properties of wool fibers (37) Oxidation may be proformed or effected in a number of ways including gas phase plasma treatment (38). 

XPS data, on the other hand, showed that the ETC AT treatment of Ar + CF4 and Ar + C2F4 yielded just as good, if not better, fluorination of PET fibers than radio frequency plasma treatment with these gases [14,15]. These examples clearly demonstrate that polymerizable species in plasma polymerization are not photon-emitting species in most cases. This is in accordance with the growth and deposition mechanism based on free radicals, which account for the presence of large amount of dangling bonds in most plasma polymers. 

Substrates used included fiber-reinforced epoxy base polymer [FRP], nylon 66, polytetrafluoroethylene [Teflon], poly(ethylene terephthalate) [PET], phenolic resin, and thermoplastic polyimide [ULTEM, GE]. FRPs were the primary substrates used. Initially, they were cleaned with detergent in an ultrasonic bath followed by rinsing with deionized water and alcohol. For further cleaning, they were treated with oxygen plasma (1.33 seem, 60 W, 5 min) followed by a hydrogen plasma treatment (3 seem, 60 W, 5 min). 

Li et al. have reported results from tensile and pull-out tests on plasma-treated polyethylene fiber eonerete eomposites (/= 12.7mm, if=38pm, Ff = 2%) [32]. Among the three treatments (NH3, CO2, and Ar) investigated, NH3 plasma treatment provided the best improvement in bond strength (up to 35% over untreated fiber eomposites). 

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