21
Polyester Processability i n Texturing as a F u n c t i o n
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o f S p u n Yarn M o r p h o l o g y J. H. SOUTHERN, R. W. MILLER, and R. L. BALLMAN Monsanto Company, Pensacola, FL 32575 The effects of polyester (polyethylene terephthalate) spinning variations on continuous filament spun yarn (POY) morphology and the resulting tensile properties and shrinkage have been previously reported, together with the textured yarn (PTY) dyeability dependency on POY and PTY structure. (1) The research reported herein describes representative results concerning textured yarn processability, as defined by the number of broken filaments per unit length. The PTY broken filament number is examined as a function of POY spinning conditions, tensile properties, and structure.
Single position spinning machine and texturing units have been previously described in detail.(1) For this study, spinning variables are defined in Table I. The texturing unit is operated at 600 meters per minute and 29+2 gram T2 tension (measured between the cooling plate and Barmag Type 5 9-disk twist aggregate; see Figure 1 schematic). All textured yarns have 70 denier, 34 filaments, 3.3 (+1) gm. tenacity, and 18 (+ 2) % elongation. Instron tensile breaks are measured at 30.5 cm/min. extension rate with 25.4 cm initial gauge length. PTY broken filaments are defined with a Toray Fray Counter (model DT-104, Type F detector using 60 meters-per-minute yarn transport speed at 15 grams tension, with broken filaments averaged over a 10 minute interval). POY yarns were also examined for broken filaments, with negligible counts observed (0-0.8/100 meters). X-Ray, birefringence, and density techniques used to obtain crystalline and amorphous contents and Hermans-Stein orientation functions have also been defined in detail previously. (1-2) The orientation function is directly related to the angle ((j)) that the average chain segment makes relative to the fiber axis and is defined as follows. (3) f
2
=
3
> •z a
Vi
70
m
3
70
O
*r\
vi
m
O
21.
SOUTHERN ET AL.
Spun Yarn Morphology
341
where f » -0.5; a l l chain segments perpendicular to f i b e r axis. = 0; average chain segment orientation i s random. = +1;
a l l chain segments p a r a l l e l to the f i b e r a x i s .
The percent c r y s t a l l i n i t y data herein are derived from density measurements (1_), while the amorphous o r i e n t a t i o n data are derived from a combination of sonic modulus, density and wide angle x-ray measurements (2). Discussion As evidenced by the Table 1 data, POY t e n s i l e strength increases and % elongation decreases with increasing spinning speed (consistent with e a r l i e r studies) (4-5), polymer molecular weight (proportional to IV) and reduced melt temperatures; a l l spinning changes y i e l d i n g increased threadline tension. POY structure, as measured by c r y s t a l l i n e content and amorphous o r i e n t a t i o n , generally increases with the above spinning variable changes (e.g., F i g . 2). For the various POY yarns textured at constant tension to a fixed tenacity and elongation target (3.3 grams per denier tenacity; 18% elongation), the number of broken filaments generated by the texturing operation decreases with increased yarn structure (Table 1). Interestingly, the best POY structure versus PTY broken filament number c o r r e l a t i o n i s achieved with the r e c i p r o c a l product of amorphous o r i e n t a t i o n (fa) and c r y s t a l l i n e content (x)' Frays - -4.47
+ 3.485 (1/fa)
r
2
= 0.910
(2)
Frays = -.048
+ .320
r
2
= 0.863
(3)
Frays = 1.024
+ 0.0745 (1/xfa)
r
2
= 0.945
(4)
(1/x)
2
where r i s the amount of variance accounted f o r by each of the above equations. The Figure 3 (1/xfa) c o r r e l a t i o n i s best understood from the following observations and t h e s i s . Based on previous observations (2-6), increased amorphous orientation y i e l d s increased yarn tenacity at room temperature test conditions; however, for conventional polyester texturing conditions i n the 200-240°C range, yarn tenacity should also be governed by c r y s t a l l i t e s , which act as the physical crosslinks preventing chain slippage f o r temperature between the polyester glass (110°C) and melt (255°C) t r a n s i t i o n s , as well as amorphous orientation; hence, the excellent broken filament correlation with the product of c r y s t a l l i n i t y and amorphous o r i e n t a tion. E s s e n t i a l l y , polyester can be treated to a f i r s t approximation at conventional texturing temperatures as a rubbery network (7), with the c r o s s l i n k density and molecular extension increasing with cryst a l l i n i t y content and amorphous o r i e n t a t i o n , respectively. Thus the mechanism for reducing PTY broken filaments i s straightforward: increased POY structure implies increased POY tenacity at texturing temperatures which, i n turn, y i e l d s fewer breaks under the constant stress condition used to texture the Table I samples.
Arthur et al.; Polymers for Fibers and Elastomers ACS Symposium Series; American Chemical Society: Washington, DC, 1984.
POLYMERS FOR FIBERS AND ELASTOMERS
Figure 1. Single p o s i t i o n drawtexturing unit schematic.
1.0 0.8 - -
0.6 0.4 i
%CRYSTALLINITYM
0.015" S P T . DIA. 0.007" 0.2-1AMORPHOUS
• • 3000
4000 SPINNING
ORIENTATION (f^
0.015" 0.007" 5000
6000
SPEED(YPM)
Figure 2 POY c r y s t a l l i n i t y and amorphous orientation versus spinning speed
Arthur et al.; Polymers for Fibers and Elastomers ACS Symposium Series; American Chemical Society: Washington, DC, 1984.
SOUTHERN ET AL.
Spun Yarn Morphology
15
0
1
I i i 1 —• •— • 0 .20 .40 .60 .80 1.00 120 1.40 1/CPOY CRYSTALLINITY x AMORPHOUS ORIENTATION)
Figure 3.
PTY broken filaments versus POY
morphology.
Arthur et al.; Polymers for Fibers and Elastomers ACS Symposium Series; American Chemical Society: Washington, DC, 1984.
344
POLYMERS FOR FIBERS AND ELASTOMERS
I t i s of i n t e r e s t to point out the Figure 2 spin l i n e c a p i l l a r y diameter e f f e c t on the POY yarn structure, where the 7 m i l (0.018 cm) diameter c a p i l l a r y yielded no amorphous orientation change, but a s i g n i f i c a n t c r y s t a l l i n i t y reduction r e l a t i v e to the 15 m i l (0.38 cm) c a p i l l a r y . From the above discussion, the generally equal POY tens i l e properties for yarns spun from the two c a p i l l a r i e s are predicted from the equal amorphous o r i e n t a t i o n values at equivalent spinning speeds (Table I ) . The greatly reduced PTY broken filament count f o r the yarn textured from the higher c r y s t a l l i n i t y POY spun from the 15 mil c a p i l l a r y i s also consistent with the above discussion. Thus, the r e s u l t s herein support the conclusion that improved POY texturing, as measured by reduced broken filament counts, can be attained v i a increases i n either the spun yarn amorphous o r i e n t a t i o n or c r y s t a l l i n e content. These desired morphological changes can be achieved v i a increased spinning speed, molecular weight, c a p i l l a r y diameter, and reduced melt temperature. The a p p l i c a b i l i t y of these polyester conclusions for other synthetic f i b e r s i s under study and w i l l be reported i n the future. Acknowledgments Yarn samples and physical property data were provided by J . A. Burroughs, D. R. Gates, J . W. S e c r i s t , G. T. Reeves and L. J . H i l l ; morphology data by B. J . Senn. We wish to express our appreciation to J . H. Saunders for his support of this work and to the Monsanto T e x t i l e s Company for permission to publish i t .
Literature Cited 1. 2. 3. 4. 5. 6. 7.
Miller, R. W.; Southern, J . H.; Ballman, R. L . ; Textile Research Journal 1983, 53, 670. Samuels, R. J., "Structured Polymer Properties"; Wiley-Interscience, New York, 1974. Stein, R. S.; J . Polymer Sci. 1958, 31, 327. Huisman, R.; Heuvel, H. M.; J . Appl. Polymer Sci. 1978, 22, 943. Heuvel, H. M.; Huisman, R.; J . Appl. Polymer Sci. 1978, 22, 2229. Simpson, P. G.; Southern, J . H.; Ballman, R. L . ; Textile Research Journal 1981, 50, 7. Bueche, F.; "Physical Properties of Polymers"; John Wiley, New York, 1962, p. 37.
RECEIVED January 10, 1984
Arthur et al.; Polymers for Fibers and Elastomers ACS Symposium Series; American Chemical Society: Washington, DC, 1984.
