Biconstituent Nylon-Polyester

Several other polyamides have been introduced for use as fibers in specialty applications where certain combinations of properties are desired. The major specialty nylons include Qiana, nylon 4, nylon 11, nylon 6,10, and biconstituent nylon-polyester. Their particular characteristics are outlined below. 

Other elastomeric-type fibers iaclude the biconstituents, which usually combine a polyamide or polyester with a segmented polyurethane-based fiber. These two constituents ate melt-extmded simultaneously through the same spinneret hole and may be arranged either side by side or ia an eccentric sheath—cote configuration. As these fibers ate drawn, a differential shrinkage of the two components develops to produce a hehcal fiber configuration with elastic properties. An appHed tensile force pulls out the helix and is resisted by the elastomeric component. Kanebo Ltd. has iatroduced a nylon—spandex sheath—cote biconstituent fiber for hosiery with the trade name Sidetia (6). 

These systems, whose phase characteristics resemble those of the polyblends discussed in Chapter 3, can be prepared by first blending the molten polymers together until the minor component is dispersed in the form of droplets that are small in comparison to the fiber diameter desired (Allied Chemical Corp., n.d. Buckley and Phillips, 1969 Hayes, 1969 Mumford and Nevin, 1967 Papero et a/.,1967). The material is then melt-spun and drawn in order to orient both constituents and cause the dispersed phase to form elongated cylinders or fibrils. For satisfactory dispersion, the viscosities of both components must be comparable (for a discussion of rheological effects in molten polymer blends, see Section 9.6). An important biconstituent system is based on a combination of nylon 6 with a linear polyester poly(ethylene terephthalate), with nylon 6 as the continuous phase (Buckley and Phillips, 1969). As shown in Figure 9.5, fibrils of polyester... 

Figure 9.6. Micrograph showing polyester fibrils isolated from a polyester-nylon (30/70) biconstituent fiber after treatment with formic acid. (Buckley and Phillips, 1969.)...

Polymer Blends.—In addition to the work on polyester—polyamide blends reported in Section 2, several other papers describe the characteristics of various polymer formulations with polyamides. Biconstituent fibres have been formed from nylon-6 and poly(ethylene terephthalate). The same polyamide and nylon-12 have been blended with acrylonitrile-butadiene-styrene copolymer and the temperature and the concentration dependence of the dynamic modulus evaluated. The rheological properties of acrylonitrile-styrene copolymer/nylon-6 mixture have also been reported. Fourier transform infrared studies of nylon-6 and PVC have indicated the presence of specific interactions between the two polymers in both the molten and solid states. Finally X-r y studies carried out on injection-moulded blends of nylon-6, -12, and -66, have revealed that the addition of small amounts of the second component initiates formation of the y-crystalline phase within the nylon-6 polymer matrix. ... 

Biconstituent fiber of nylon 6 with polyester microfibrils dispersed throughout the fiber matrix has been marketed under the trade name Source (Allied). The fiber is reported to have unique optical and dyeing properties and a higher strength and lower regain than nylon 6,6 and is used primarily in carpets. A sheath-core bicomponent fiber containing a nylon 6 sheath and a polyester core has been reported al so. It is said to have properties that are intermediate between both fibers. 

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