Nylon wettability

Samples were stored in a desiccator, since Ellison and Zisman [4] have shown that nylon wettability is much influenced by moisture sorbed from the atmosphere. 

Tn the last decades many attempts have been made to obtain attractive - materials by intimate mixing of two polymers with opposite or complementary properties. For example, the impact resistance of brittle polystyrene is increased by mixing with a rubber the wettability of polyacrylonitrile fiber is increased by mixing with hydrophilic saponified cellulose acetate, and the inconvenient flat-spotting of nylon-reinforced tires is suppressed by mixing stiffer polyester fibrils into the nylon fibers. In practically all cases these products acquire their final shape via the liquid state. Thus, the viscous properties of these liquid mixtures are important. 

Roller pumps are among the least expensive and most widely nsed of all sprayer pumps. They provide moderate volumes (8 to 30 gpm) at low to moderate pressure (10 to 300 psi). Often used on low-pressure sprayers, roller pumps are positive-displacement, self-priming pnmps. The rollers, made of nylon, teflon, or rubber, wear rapidly in wettable powders but are replaceable. A pump that will be subjected to such wear should have a capacity at least 50 percent greater than that needed to supply the nozzles and agitator. This reserve capacity will extend the life of the pump. The pump case is usually cast iron or a nickel alloy. Roller pumps are best for emulsifiable concentrates, soluble powders, and other nonabrasive pesticide formulations (Figure 14B). 

Piston pumps are the most expensive of the commonly used sprayer pumps. They deliver low to medium volumes (2 to 60 gam) at low to high pressures (20 to 800 pi). Used for high-pressure sprayers or when both low and high pressures are needed, piston pumps are positive-displacement, self-priming pumps. They have replaceable piston cups made of leather, neoprene, or nylon fabric which make the pump abrasion-resistant and capable of handling wettable powders for many years. The cylinders are iron, stainless steel, or porcelain-lined. The pump casing is usually iron. 

The wettability band for polyamides of the nylon series shifted to show lower slopes and higher critical surface tension intercepts when plotted in the standard Zisman format (7) as the amide group density increased (JO). Unfortunately no theoretical work describes the important factors influencing the slope of such plots which reflect in a general way the strength of solid/liquid interactions. 

The distinction between long, thin cylinders and fibres is quantitative, rather than qualitative. Nevertheless we Shall make the distinction because there is great technical relevance natural fibres (cellulose), synthetic ones (nylon), non-woven fabrics, etc., are materials belonging to this group. The wettability of bundles or mats of fibres and woven fabrics is of prime importance for clothing, tents and several other industrial products. 

Some nine years ago, Ellison and Zisman [4] reported their study of the wettability of 6-6 nylon (polyhexamethylene adipamide) and compared their results to those previously obtained on polyethylene [7]. They found that the nylon was more easily wet than the polyethylene, especially by hydrogen-bonding liquids, and attributed these findings to the presence of amide groups in the nylon surface. 

This paper uses these concepts to correlate wettability with the surface constitution of a homologous series of nylons. These materials... 

FORT Weffabilify of Nylon Polymers Table II. Wettabilities of Homologous Nylons Contact Angle, Degrees 305... 

It was expected that as the average nylon number increased, the contact angles exhibited by hydrogen-bonding liquids on the various surfaces would rise, approaching the wettability of polyethylene as an asymptotic limit (polyethylene might be regarded as nylon oo). Such... 

It was reasoned that the indicated alternation of polymer wettabilities had to result from differences in density, orientation, and/or bonding of the amide groups in the nylon surfaces. Consequently,an attempt was made to relate the observed wettabilities to polymer morphology. 

Figure 1. Variation in wettability with average nylon number...

Finally, it is necessary to consider the effects on wettability of the different separations of the hydrogen-bonded sheets in the extended and twisted chain polymers. These differences are caused by the greater space requirements of the twisted chain structures. Thus, in nylon 6-6 the interplanar distance is 3.7 A. [2] and in nylon 7-7 it is 4.2 A. [11]. Zisman and coworkers [7] have shown that closer packing of hydrocarbon chains leads to more difficult wetting, while closer packing of polar functions has the opposite effect. Since nylons 7-7, 9-9, and 11 all behaved so similarly, the two effects must come near to canceling in the polymers tested. 

PLA fibers are environment-friendly material and the demand for PLA fibers as a substitute for the present synthetic fibers has been growing greatly in recent years. Furthermore, high water vapor transmission rate of PLA makes it a good candidate for fabricating fibers used in garments [e.g., shirts, dresses, underwear, shoes, etc.] to improve their "breathability. While PLA fibers are not as wettable as cotton, they exhibit much greater water vapor transmission than aromatic polyesters or nylon fibers. 

The nature of the supporting membrane also plays an important role in the performance of supporting ILMs. In this context, de los Rios et al. [37] studied the performance of two polymeric membranes, nylon and mitex, as supporting membranes. Nylon membrane was a hydrophilic polyamide membrane with a pore size of 0.45 pm and a thickness of 170 pm. Mitex membrane was a hydrophobic polytetrafluo-roethylene membrane with a pore size of 10 pm and a thickness of 130 pm. It was observed that less IL was absorbed into the mitex membranes, which was explained by the different textural properties and the high hydrophobic character of these membranes, which probably restrict interaction with the hydrophilic ILs used. Simple determination of wettability has also been used as criterion in the selection of a suitable supporting membrane [86]. 

The choice of the membrane depends on several factors chemical and thermal resistance to the process conditions, sharp separation, wettability of the membrane, tendency to adsorb hydrophobic materials and resistance to cleaning. The most common polymeric materials are PTFE, PVDF, PP, PS, CA/CN, CTA, PE, polycarbonate, polyester, poly ether imide and nylon 6. Of these, only PTFE, PVDF and PP have excellent to good chemical stabiHty. Even though hydrophilic CA/CN and CTA membranes have limited chemical stabiHty, they are best suited for treating high fouling feeds using tubular membranes. 

Fort, T., Jr., The wettability of a homologous series of nylon polymers, in Contact Angle, Wettability, and Adhesion, Advances in Chemistry Series, vol. 43, American Chemical Society, Washington, D.C., 1965, p. 302. 

Schonhom, Harold, Ryan, Frank W. (1969), "Effect of Polymer Surface Morphology on Adhesion and Adhesive Joint Strength. II. FEP Teflon and Nylon 6", J. Polym. Sci. 7 (Part A-2), 105-111 (Hara, K., Schonhom, H. (1970), "Effect on Wettability of FEP Teflon Surface Morphology", J. Adhesion 2, 100-105. 

---