Dyne fibers

Fluorochemicals repel both water and oU because they produce an extremely low energy surface (18—26). The effectiveness of the fluorochemicals depends upon uniform surface coverage and orientation of the molecules on the fiber surface so that the perfluoroalkyl chains are directed away from the surface. The result is a GST as low as 5—10 mN /m (dyne/cm). Fluorochemical finishes are often formulated with nonfluorinated resin-based water-repeUent extenders. These water repeUents not only reduce the cost of the finish but may also improve durabUity (27,28). 

The water repeUency of sUicone finishes results from the low CST (ca 22 mN/m or dyne/cm) produced by the methyl groups in the sUicone that are oriented away from the fiber surface. The CST is lower than that produced by any class of compounds except for fluorochemicals. 

Kaelble, D.H., Dynes, P.J. and Mans, L. (1974). Surface energy analysis of treated graphite fibers. J. Adhesion 6, 239-258. 

The ink for inkjet printers is essentially colored water, and the current formulation of ink is about 75% water, plus dye and glue (Kang 1991, Le 1998, Pond 1999). The ink should flow readily from ihe inkwell to the nozzle, and then to the paper, without dripping or clogging. The viscosity of current inkjet ink is from 2 to 8 cP. The droplets formed should be very uniform in size, and should be as small as possible to increase the resolution. When the droplet hits the paper, the droplet should penetrate the fibers without splatter, which would increase the diameter of the dot on the printed text or picture. The surface tension of current ink is around 45 to 50 dynes/cm, which is much lower than water at 70 dynes/cm. It is believed that if the surface tension is raised from 45 to 65 dynes/cm, the spread (or ratio of diameter of spot on paper/diameter of droplet) would decrease from 3.3 to 1.1. Much higher resolutions... 

Surface Tension Range dynes/cm. CST of Fiber Material from Ref. 5,... 

Since the fiber is heavier than the liquid, it would sink when placed on the liquid if it were not sustained by an upward force caused by the surface tension of the liquid. This force is exerted at the three-phase air-liquid-fiber boundary lines. If the contact angle 0 and the surface tension y are high enough, this upward force can become sufficient to balance the sinking force, and the fiber will come to rest when the two forces become equal, at an equilibrium depth corresponding to a definite value of < . In this situation, as shown in Figure 1, the force exerted vertically upward on a unit length (1 cm.) of fiber, measured in dynes, will be ... 

A perfluoroacrylate monomer was flash evaporated at 100 millitorr and exposed to polypropylene fibers pretreated in a plasma field within one second while the fabric was traveling at 50 m/min. The condensed monomer layer was then cured in-line by electron beam radiation within 100 milliseconds resulting in a 0.1 pm perfluoroacrylate coating on the material surface. The product had an adequate repellency for both water and oil and a surface energy of 27 dyne/cm. 

The slopes of the stress-strain curves in both yield and post-yield regions decrease with decreasing disulfide content and approach zero at zero disulfide content. With fibers stressed at a rate of about 10 dyne cm min the ratio of these slopes remains constant at about 10 1. 

Stretching a hair fiber in water and the curve at the top of the chart represents stretching at 65% RH. In the Hookean region of the load-elongation curves, the stress (load) is approximately linear to the strain (elongation), and the ratio of stress to strain in this region is the elastic modulus (Es), commonly called Young s modulus. The elastic modulus is usually expressed in dynes per square centimeter and may be calculated from this simple expression ... 

The elastic modulus for stretching human hair, determined in our laboratories at 60% RH and room temperature, is 3.89 x 10 °dynes/cm. Methods other than load-elongation have been used to determine the elastic modulus of hair fibers. These methods [10,11] are described later in this chapter. 

The vibrascope is a device that applies an oscillatory force of known frequency to a filament under tension. The fiber cross-sectional area (A) in cm may be computed from the lowest (natural) frequency if) in cycles per second that produces mechanical resonance. The tension (T) on the fiber is in dynes, the fiber length (L) is in cm, and its density is 1.32g/cm. ... 

TABLE 8.20 Transverse Modulus of Some Plant Fibers Fiber Mean width (xlO" cm) Transverse Modulus (+ Std Error 10 dynes/cm )... 

Fiber Mass per unit length (p.g/cm) RH (%) Approximate porosity incl. lumen (%) Shear modulus (10 dynes/cm )... 

Uses Silicone for damping, heat transfer, hydraulic fluids, mbber/plas-tics, polishes, cosmetics/toiletries, aq. defoaming prods. thread/fiber lubricant for textiles mold release for tires, rubber, plastics base fluid for greases flow control agent, mar resist, aid, gloss aid in paints Properties Sp.gr. 0.968 vise. 100 cSt pour pt. -67 F flash pt. (PMCC) 575 F ref. index 1.4030 surf. tens. 20.9 dynes/cm sp. heat 0.36 Btu/lb/ F dissip. factor 0.0001 dielec. str. 35 kV dielec, const. 2.74 vol. resist. 1x10 ohm-cm 100% silicone SF96 (350 CSt) [GE Silicones]... 

Properties Yel. fiber pulp 12 p particle size sp.gr. 1.44 bulk dens. 5.0 lb/ ft surf, energy 55+ dynes/cm (water wettable)... 

Uses Film-former for applies, such as binder or surf, treatment for glass fiber textiles and other substrates, overprint coatings Features Solventless produces light-stable films zero VOC Properties Milky liq. char, odor 2 p particle size sp.gr. 1.04 dens. 8.7 Ib/gal vise. 500 cps max. flash pt. (PMCC) > 100 C pH 7 surf. tens. 39 dynes/cm Film props. tens. str. 4450 psi tens, elong. 700% (ultimate) nonionic 35% solids Witcobond W-506 [Uniroyal]... 

Fio. 50. Equilibrium melting temperature as a function of pH for A, tyrosyl-carboxylate ion, B, tyrosyl-histidine, and C, carboxyl-carboxyl hydrogen bonds, all at a constant force of 3 X 10 dynes per square centimeter for the hypothetical fiber discussed in the text (Scheraga, lOOOd). 

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