SOME EFFECTS OF TWIST ON STRESS-STRAIN RELATIONSHIPS OF YARNS PRODUCED FROM COTTON-POLYESTER FIBER BLENDS
A THESIS
Presented to
The Faculty of the Graduate Division
by
Yuksel Yesiltepe
In Partial Fulfillment
of the Requirements for the Degree
Master of Science in Textile Engineering
Georgia Institute of Technology
February, 1965 GEORGIA INSTITUTE OF TECHNOLOGY LIBRARY
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^RROWTNG LTRRARV QATE
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**,* SOME EFFECTS OF TWIST ON STRESS-STRAIN RELATIONSHIPS OF YARNS PRODUCED FROM COTTON-POLYESTER FIBER BLENDS
Approved:
t .nairTnan ' !L
Q \ Date Approved by Chairman ^'2^'o5 11
ACKNOWLEDGEMENTS
The author extends his sincere appreciation to Professor R. K.
Flege and Professor R. C. Lathem, both of the A. French Textile
School, for their valuable guidance and assistance. He is grateful to
Siimerbank of Turkey for the fellowship which made this study possible
Special thanks are given to Dr. Joseph Krol of the School of In
dustrial Engineering for his assistance and suggestions regarding the
overall thesis subject matter.
In addition, the author extends his thanks to Mr. R.C. Freeman, and Mrs. J. B. Lesher, technicians of the A. French Textile School, for their assistance. Finally, the author is greatly indebted to the
Professors of the A. French Textile School. iii
TABLE OF CONTENTS
Page
ACKNOWLEDGEMENTS ^^
LIST OF TABLES iv
LIST OF ILLUSTRATIONS V
SUMMARY ^^
CHAPTER
I. INTRODUCTION 1
Statement of the Problem
II. INSTRUMENTATION AND EQUIPMENT 10
Raw Materials Used Processing Equipment Physical Testing Equipment
m. PROCEDURE 18
Preparation of Materials Physical Tests for Breaking Strength and Elonga tion of Yarn
IV. DISCUSSION OF RESULTS 26
V. CONCLUSIONS AND RECOMMENDATIONS 35
Conclusions Recommendations
APPENDIX 37
BIBLIOGRAPHY 41 IV
LIST OF TABLES
Table Page
1. Operating Data for H & B Revolving Flat Card 12
2. Operating Data for Saco-Lowell Roller Top Card 13
3. Operating Data for Saco-Lowell 4 over 5, DS-4 Drawing Frame 14
4. Operating Data for Saco-Lowell Roving Frame FS-2 .... 15
5. Operating Data for Saco-Lowell Spinning Frame Z-2 .... 16
6. Operating Data for Uster Automatic Yarn Strength Tester . . 17
7. Organization of Twist Multipliers and Twist Gears 24
8. Organization of Drafts and Draft Gears 25
9. Average Breaking Strength in Grams, Standard Deviation and Coefficient of Variation for 15's, 20's, 25's and 30's Yarns with Different Twist Multipliers 33
10. Average Per Cent Elongation, Standard Deviation and Coefficient of Variation for 15's, 20's, 25's and 30's Yarns with Different Twist Multipliers 34
11. Fiber Fineness Test Using Sheffield Micronaire, Fiber Fineness Expressed in Micrograms per Inch 38
12. Fiber Strength Test Using Pressley Tester (1/8" Gauge). . . 39
13. Fiber Length Analysis Using Servo-Fibrograph 40 LIST OF ILLUSTRATIONS
Figure Page
1. A Ring, Traveller, Bobbin and Yarn 3
2. A Typical Twist-Strength Curve 5
3. A Hypothetical Yarn Made From Two Parallel Fibers .... 5
4. The Development of the Twist-Strength Curve 6
5. The Twist-Angle of the Fibers in a Yarn 6
6. Sequence of Operations 19
7. Sketch Sho-wing Effects of Yarn Contraction, Traveller Lag and Tape Slippage 27
8. Effect of Twist in Cotton Yarn 29
9. Effect of Twist on Per Cent Elongation of Dacron-Cotton Blend Yarn 30
10. Effect of Twist on Strength of Dacron-Cotton Blend Yarn . . 32 VI
SUMIvlARY
In the past few decades, there has been an increased interest in the blending of synthetic fibers with cotton. This study attempted to es tablish the optimum twist multiplier for maximum yarn breaking strength by using Kochlin's formula, developed for cotton, which is based on the relationship between twist multiplier and yarn number. This investiga tion covered the effects of turns per inch on yarn properties in the yarn nuinber range 15, 20, 25, and 30 where different twist multipliers were used for producing yarns of cotton-Dacron polyester fiber blends.
In this investigation Good Middling Grade American Upland cotton
(one and one quarter inches staple length) and DuPont's polyester fiber
Dacron (one and one half inches staple length and three denier) were se lected. In the laboratory, yarns were produced with various twist mul tipliers. The range of twist multipliers were between 2. 75 and 5. 75.
The yarn specimens obtained were subjected to stress-strain analyses and the data were recorded.
The results of data obtained combined with those from results of previous work have shown that the optimum twist multiplier for cotton
Dacron blend yarns (1. 25" staple length) are 4. 00 where optimum twist multiplier for cotton yarns with same staple length are 4. 40. The breaking strength (in grams) for cotton yarns are greater than that of Vll
cotton-Dacron blend yarns with the same yarn number. For the same
yarn nuinber, the elongation of cotton-Dacron blend yarns at the breaking
point is greater than the elongation of cotton yarns.
The data obtained were fed to the computer in order to determine
average values, standard deviations, and coefficient of variations. These
results from the computer showed that low turns per inch were responsi
ble for unevenness in the yarn. The average breaking and average per
cent elongation were plotted to illustrate the relationship of the variables under study. After an analysis of this graphical presentation, the fol lowing conclusions were reached:
1. The strength of a cotton-Dacron blend yarn is inversely re lated with elongation of the yarn.
2. The strength versus twist multiplier curve follows a concave down parabolic path.
3. The elongation versus twist multiplier curve follows a con cave up parabolic path. CHAPTER I
INTRODUCTION
It has been established that the strength of a cotton yarn is in fluenced by the number of turns in a given section of that yarn. As the turns in the yarn increase, the strength of the yarn increases, and after reaching a certain maximum limit the strength begins to decline.
The rule stated above has long been used for yarns spun from cotton fibers. It is the purpose of this study to determine if the same rule (with some modifications) is applicable for cotton blended yarns.
For a fibrous yarn to have strength, the fibers must be entangled and somehow be held closely together. The holding together is accom plished by twisting the yarn. A force is exerted perpendicular to the yarn axis when the twisted yarn is put under tension. It is this force which causes the fibers to press against one another.
There are two basic methods of investigating the yarn strength as a function of the twist, empirical and theoretical. The completely theoretical approach is best exemplified by the works of R. R.
Sullivan (l). The purely empirical approach has been applied by
Brown and Fiori (2).
Before proceeding further it is in order to define the term
"twist". "Twist" is referred to as being either nominal or actual. Nominal, or mechanical twist, is the revolutions per niinute of the bobbin divided by the inches of yarn delivered at the front rolls of the
spinning frame in one minute. As it is rather difficult to define actual twist, the writer has chosen to describe it by way of an exannple.
Figure 1 is a sketch of a bobbin, ring, traveller, and yarn. The bob bin is such that the circumference is exactly 1.00 inches. Now, when the bobbin turns while holding the yarn, at point A, assuming that there is no yarn contraction due to the twisting action, the traveller will make one revolution for each revolution of the bobbin. Since no yarn is fed, none can be wound up. Now let the bobbin be rotated
100 times and at the same time let the yarn move uniformly from A to
B, a distance of ten inches.
Because the distance around the bobbin is one inch the traveller must make one revolution around the bobbin in order to wind up one inch of yarn. Thus, while the bobbin is making the 100 revolutions, the traveler must make only 90, Because the yarn turns around its axis once for each revolution of the traveller around the ring, there will be
90 turns in the ten inches of yarn. The actual twist per inch in the yarn on the bobbin is therefore 90 turns divided by ten inches and equals nine turns per inch. The mechanical or nominal twist of course is
100 turns divided by ten inches equalling ten turns per inch, a dif ference of ten per cent, more than the actual turns in the yarn on the bobbin. In reality, the difference in the mechanical twist and the Traveler Ring
Figure 1. A Ring, Traveler, Bobbin, and Yarn.
'Source: Landstreet, C. B. , 'Problem of Yarn Strength", Textile Mercury and Argus, February, 1957, p. 321. actual twist in the yarn on the bobbin is in the neighborhood of two per
cent, and depends in part upon the particular diameter about which the
yarn in question is wound.
For a fibrous yarn to have strength, the fibers must be en
tangled or in some way be held closely together. This brings about
the method of twisting. When the twisted yarn is put under tension a force is exerted perpendicular to the yarn axis that causes the fibers to press against one another. This pressure coupled with the fiber friction and entanglement, causes the fibers to resist slipping and is responsible for yarn strength. Figure 2 shows a typical twist- strength curve. It might be well at this point to explain briefly why the curve has this particular shape since it is the maximum point that is of interest in this study. Figure 3 will aid in illustrating the twist strength relationship. Shown here are two parallel fibers that are held together by some outside force P. The fibers are overlapped a distance L, have a coefficient of friction U, and a fiber strength FS.
Suppose for the moment that P is small. The "drag" generated by the pressure and the friction is equal to the yarn strength, that is, the force required to make the fibers slip. As P is increased, the yarn strength will increase until the fibers break. An approximate plot is shown in Figure 4, curve A,
According to the sketch in Figure 3, the axis of the fibers were in the plane of the yarn axis and thus contributed their full strength 180 179 178 177 176 TM = 3. 70 175 Q 174 173 o 172 171 170 - 169 - J L I t _J I LT) sO r^ 00 o o '-* (M en ^ m TWIST MULTIPLIER Figure 2. A Typical Twist-Strength Curve
FS
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FS
When the force produced at the overlap is less than FS the fibers will slip when pulled. When the force produced at the overlap is greater than FS fibers will break when pulled.
Figure 3. A Hypothetical Yarn Made From Two Parallel Fibers.
Source: Landstreet, C. B. , "Problem of Yarn Strength", Textile Mercury and Argus, February, 1957, page 323. —• Curve C
Curve B
Curve A
_i 012345678 TWIST Figure 4. The Development of the Twist-Strength Curve
Figure 5. The Twist-Angle of the Fibers in a Yarn
Source: Landstreet, C. B. , "Problem of Yarn Strength", Textile Mercury and Argus, February, 1957, page 323. to the yarn strength. In reality this is not the case and the fibers lie at some angle to the yarn axis as shown in Figure 5. The higher the twist in a given fiber the higher the twist angle and vice-versa. Be cause of this angle the fiber has only a component of its strength con tributing to the yarn strength. In the example in Figure 5 this com ponent is a function of the cosine of the twist angle and decreases as the angle increases. A plot of this is shown in Figure 4, curve B.
The twist strength curve C, Figure 4 can now be obtained by com- oining the two curves A and B. The two curves A and B show that as the pressure increases yarn strength increases, but at the same time the tv/ist angle is causing the fiber-strength component in the direc tion of the yarn axis to decrease, thus reducing yarn strength. Be cause of these combined actions strength decreases after a certain point although twist continue to increase thus giving the familiar twist- strength curve.
Statement of the Problem
There is a specific number of turns per inch of yarn required to give maximum strength for a particular count of a cotton- synthetic blend. Turns per inch and yarn strength are interrelated.
This is expressed by a constant for that blend, otherwise called the twist multiplier, which is a ratio of the optimum twist to the square root of the count. This relationship is expressed by the formula of
Kochlin (3). Turns per inch = KJ C K = Twist Multiplier C = Yarn Count
It is argued that the above formula is only a mathematical ap
proximation oased on certain assumptions such as "the exposed fibers
are arranged in helices or circular cylinders, and two yarns of dif
ferent counts have the same density when their angles of twist are
equal". This writer believes in the practical value of Kochlin's formu
la and has used it extensively throughout this experimentation. In order
to develop sufficient strength to resist breakage in a twisted strand, of
discontinuous fibers, such as cotton and synthetic fiber blends, the in
dividual fibers must grip each other when the strand is stressed. This
cohesion arises mainly from the twist, which presses the fibers to
gether as the stretching force is applied and so develops friction between pressed fibers. The pressure results from stressing the twisted strand and has its origin in the tension applied to the curved spiral lines of
the individual fibers. The pressure builds up progressively from a low
threshold value at the outer surface of the twisted strand to a compara tively high value as the core of the strand is approached. As the twist in a strand of fibers builds up, the cohesion generated upon stressing
the twisted strand will gradually increase up to the point at which the core fibers miay begin to break when the strand is sufficiently stressed.
In this connection a study of the strength of twisted yarn elements has been made by J. Gregory (4).
Much work has been done to determine the optimum twist mul tiplier for cotton yarns. The object of this experiment is to deter mine if the same observations will hold for blended yarns. Because man-made fibers are becoming so popular, the author hopes to give the mill men some idea of what twist multiplier to use for maximum yarn strength. The blend of cotton and a member of the man-made fibers family (Dacron-polyester) was selected for this study. 10
CHAPTER II
INSTRUMENTATION AND EQUIPMENT
Raw Materials Used
The raw materials used included Good Middling Grade American
Upland cotton having a one and one quarter inch staple length and
DuPont's polyester fiber-Dacron having a one-and-one half inch
staple length, and a denier of three. The data on cotton fiber fine ness, strength and length are shown in Tables 11, 12 and 13 in the
Appendix.
Processing Equipment
The following pieces of processing equipment, were used in these experiments:
1. Cotton opening line including Saco-Lowell Hopper Feeder,
Superior Cleaner. Saco-Lowell Opener and Condenser.
2. Saco-Lowell One - process Picker and Picker Hopper.
3. Whitin one process Picker, Model T, 1949, with Auto-
^ matic Picker feed and Blending Hopper, Model K-6, 1949.
(for synthetic fibers)
4. H and B Revolving Flat Card, Flexible wire clothing.
5. Saco-Lowell Roller Top Card, Model 1, 1948.
6. Saco-Lowell Drawing Frame, Model DS-4, 1957. 11
7. Saco-Lowell 10 1/2" Lap Winder, Model 37, 1948.
8. Saco-Lowell Comber, Model 57, 1959.
9. Saco-Lowell Roving Frame FS-2, 1948.
10. Saco-Lowell Spinning Frame Z-2, 1948.
Physical Testing Equipment
The following physical testing equipment was used to charac terize the experimental products:
1. Sheffied Micronaire, Model D 80400.
2. Pressley Fiber Strength Tester, NO. 1127.
3. Spinlab Servo - Fibrograph, Model 163.
4. Uster Automatic Yarn Strength Tester with Automatic
Bobbin Attachment. 12
Table 1. Operating Data for H & B Revolving Flat Card
Name Diameter Type Clothing R. P. M.
Cylinder 50" Flexible Wire 160
Doffer 27" Flexible Wire 6
Licker-in 9" Metallic 440
Draft Constant 1672
Production Constant 0. 0065 (Pounds per Hour]
Draft Change Gear 17T
Production Change Gear 22T 13
Table 2. Operating Data for Saco-Lowell Roller Top Card
Name Diameter Type Clothing R. P. M
Cylinder 50" Flexible Wire 170
Doffer 27" Flexible Wire 9. 5
Licker-in 9" Metallic 210
Worker Roll 7" Metallic 9
Stripper Roll 3. 5" Metallic 310
Draft Constant 1581
Draft Change Gear 14T to 16T
Production Constant 0. 0104 (Pounds per Hour)
Production Change Gear 22T 14
Table 3. Operating Data for Saco-Lowell 4 over 5, DS-4 Drawing Frame
Bottom Rolls Top Rolls Diameter Type Diameter Type
First 1. 125' Fluted 1.125" Cushion
Second 0.750" Fine Fluted 2. 000" Cushion
Third 1. 375" Fluted
Fourth 1. 375' Fluted 1. 500' Cushion
Back 1. 375' Fluted 1.500" Cushion
Cotton Breaker Dacron Pre Blend Roll Setting: Drawing Drawing Drawing
First to Third 2. 563' 2.563" 2. 563'
Second to Third (Fixed) 1. 500" 1.500" 1. 500"
Third to Fourth 1. 625" 1.625" 1.625"
Fourth to Back 1. 875" 1. 875" 1.875"
Draft Constants and Cotton Breaker Dacron Pre- Blend Draft Gears Drawing Drawing Drawing
Back Draft Constant 0. 059 0.059 0.059
Back Draft Gear 21 21 21
Back Draft 1. 235 1. 235 1. 235
Mid Draft Constant 90 90 90
Mid Draft Gear 50 50 50 Mid Draft 1.8 1.8 1. 8 Front Draft Constant 175 175 175 Front Draft 3.65 3. 65 3. 65 Front Draft Gear 48 48 48 15
Table 4. Operating Data for Saco-Lowell Roving Frame FS-2
Roll Diameter
Front Roll 1. 125"
Middle Roll 1. 070"
Back Roll 1.000
Roll Settings (Center to Center)
Front to Middle 2. 125"
M ddle to Back 2. 000"
Twist Multiplier 1.15
Twist Constant 32. 50
Twist Gear 28T
Tension Gear 48T
Lay Gear 35T
Spring Pressure (in pounds) 25
Spindle Speed 700 R. P. M.
Grain Weight per Yard of Sliver Fed 50
Hank Roving Delivered 1. 67 16
Table 5. Operating Data for Saco-Lowell Spinning Frame Z-2
Machine Details
Spindles per Frame 24
Diameter of Cylinder 10"
Diameter of Whorl 1. 125"
Diameter of Back Roll 1. 000"
Diameter of Front Roll 1. 375"
R. P. M. of Spindles 6150
R. P. M. of Cylinder 530
R. P. M. of Front Roll 70
Type of Drive Tape
Twist Constant 874
Draft Constant 722
Twist Gear See Table 7
Draft Gear See Table 8
Twist Multiplier See Table 7 17
Table 6. Operating Data for Uster Automatic Yarn Strength Tester
Bobbin Attachment:
Number of Bobbins in Creel 8
Number of Breaks per Bobbin 10
Number of Breaks per Lot of Yarn 80
Automatic Tester:
Pretension Disc Setting #5
Length of Jaw Span 20"
Setting for Rate of Loading #6
Loading Time to Break (Seconds) 9+1.5
Complete Cycle Time (Seconds) 20 + 1.5
Range of Breaking Load (Grams) 600 and 1000
Range of Elongation 20 per cent
K Value (Breaking Strength) 2. 1
e Value (Elongation) 0.4
L Value . 0.7 07 18
CHAPTER III
PROCEDURE
Preparation of Materials
The sequence of operations for producing the blend of Dacron polyester fiber and combed cotton is shown in Figure 6. There are several ways that one can blend cotton and man-made fibers. In this experiment they were blended on the drawing frame. The stan dard temperature of 80°F and humidity of 55 per cent were kept con stant in order to secure a uniform blending and fiber distribution.
Conventional opening and picking equipment were used for pro cessing the cotton. The average weight of the picker lap was 13. 5 ounces per linear yard. The picker laps were run through a H & B flat top carding machine to produce eight cans of 55 grain per yard card sliver. A doffer speed of six revolutions per minute was main tained to assure uniform good quality sliver. In order to produce an even breaker drawing sliver, the eight cans of card sliver were di vided into two groups and the necessary draft gear was put on the frame to make a 50 grain per yard drawing sliver.
The necessity of having cotton free of short fibers to blend with Dacron made it desirable to include a combing process in the sequence of operations. At the Saco-Lowell 10 1/2" Lap winder. 19
Cotton Dacron 1 Opening
Picking Picking I Carding
Breaker Drawing
Figure 6. Sequence of Operations 20
20 ends of drawing sliver were fed and 12 laps were made. The
combing operation produced four cans of 50 grain per yard drawing
sliver ready to blend with Dacron.
The method for preparing Dacron sliver differed from that for
cotton sliver. First, the Dacron was processed on a synthetic fiber picker. Then, using a roller top card 50-grain per yard Dacron card
sliver was produced. To reduce the variation from the sliver, the
sliver weight was often checked and necessary adjustments were made. Following carding, the sliver was treated on a drawing frame for pre-drawing. This treatment parallelized and oriented the Dacron fibers similar to cotton fibers.
To have a 50 per cent cotton-50 per cent Dacron blend, four ends of cotton and four ends of Dacron were fed at the drawing frame.
Using the necessary draft gear these eight ends of drawing slivers were reduced to one end of 50 grain per yard drawing sliver. Eight cans of blended drawing sliver were creeled at the roving frame in order to produce eight full bobbins of 1.67 hank roving.
The organization of yarn numbers, draft gears, twist multi pliers and twist gears which were used at the Saco-Lowell Z-2
Spinning Frame are shown in Tables 7 and 8.
Physical Tests for Breaking Strength and Elongation of Yarn
All of the tests were conducted in the A. French Textile School 21
Physical Testing Laboratory. In this laboratory the atmospheric
conditions are kept standard around the clock, at 70° F. temperature
and 65 per cent relative humidity. The tests were made according to
the standards set by the American Society for Testing Materials (5).
The Uster Automatic Yarn Strength Tester was the best choice
to test the breaking strength as well as elongation of the yarn. The
Uster Tester makes use of the inclined plane principle in which the pulling force on the jaw of the machine increases proportionally with the time elapsed. The bobbins to be tested were creeled at the
Automatic Yarn Creel. The machine was dialed to give ten breaks from each bobbin. Eighty breaks were made for each lot of yarn.
While the two counters were recording the cumulative sum of the data for breaking strength and elongation, the recording mechanism of the machine was autographing each individual break and elongation on the separate charts. After completing the tests, the readings from counters were evaluated according to the formulas in the Instruction
Book for the Uster Automatic Yarn Strength Tester (6) to compute the average strength and elongation.
E in per cent = ^ ^ ^^ + n
where:
E = Elongation in per cent
S = Total of the Elongations 22
e = 0. 4 = A machine constant
n = Number of breaks made.
Sp X 10 P in per cent = + K n where;
P. = Breaking strength in per cent
S = Total of the breaking strength XT
K = 2. 1 = A machine constant
n = Number of breaks nnade
P. X M P in grams = _± 100 where:
P = Breaking strength in grams
P = Breaking strength in per cent
M = Weight used in machine in the
order of 600 or 1000 grams.
Individual readings from the chart were tabulated and their standard deviations were found by making use of Burroughs 220 digital computer.
The Uster Breaking Strength Tester also gave the frequency distribution by feeding a small steel ball into the proper vertical slot in a plate corresponding to its value at the end of each individual test. 23
The frequency distribution formed by these small steel balls was
transferred to a ruled chart as a permanent record at the end of each yarn number lot test series. 24
Table 7. Organization of Twist Multipliers and Twist Gears
Yarn No. Twist Con Square Twist Twist Twist (cotton stant of the Root of Multiplier Per Gear system) Spinning Frame YarnNo. Used Inch Used
2.75 10.651 82 3. 25 12. 587 69 3. 75 14. 524 60 4. 25 16. 460 53 15 874 3.873 4.75 18.397 48 5. 25 20.333 43 5.75 22.250 39
2.75 12.301 71 3. 25 14.537 60 3.75 16.774 52 4. 25 19.010 46 20 874 4.473 4. 75 21. 247 41 5. 25 23.483 37 5.75 25.733 34
2.75 13.750 64 3. 25 16.250 54 3. 75 18.750 47 4. 25 21. 250 41 25 874 5.000 4. 75 23. 750 37 5. 25 26.250 33 5. 75 28.750 30
2.7 5 15. 064 58 3. 25 17.804 49 3.75 20. 542 43 4. 25 23. 281 38 30 874 5.478 4.75 26.021 34 5. 25 28.759 30 5. 75 31.420 28 25
Table 8. Organization of Drafts and Draft Gears
Yarn No. Draft Constant Weight of Number Draft (cotton of the Material Actual of Gear system) Spinning Frame Fed Draft Doublings Used
15 722 1.67 H.R. 8. 98 1 80
20 722 1. 67 H.R. 11. 97 1 60
25 722 1.67 H.R. 14. 97 48
30 722 1. 67 H.R. 17. 96 40
Yarn Number Delivered Actual Draft = Yarn Number Fed
Draft Gear = Draft Constant Actual Draft 26
CHAPTER IV
DISCUSSION OF RESULTS
Before discussing the effects of the different twist multipliers on the yarn strength it is best to present the several factors which influence the number of turns per inch actually spun into yarn.
The contraction which takes place during the spinning of a yarn has long been recognized as an important factor in twist calculations
(7). If contraction were the only modifving factor influencing turns per inch, full allowance would have to be made for it. However, there are actually two other factors which tend to offset the influence of con traction. These are (a) traveler lag, and (b) tape slippage. There fore in addition to the normal mechanical arrangement of the spinning frame there are three variables (Figure 7) which govern the number of turns per inch actually spun into yarn:
1. Twist contraction: This factor varies with the twist multi plier employed and tends to increase turns per inch.
2. Traveller lag: This factor varies with the twist per inch and the bobbin diameter. Its effect is to reduce twist per inch.
3. Tape slippage: This factor will vary with the condition of the spinning frame employed and its effect will be to reduce twist per inch. 27
er Lag
- Tape Slippage
Figure 7. Sketch showing Effects of Yarn Contraction, Traveler Lag and Tape Slippage. 28
It is obvious that the normal method of making twist per inch calculations will give correct results only when traveler lag and tape slippage exactly offset the influence of twist contraction.
C. D. Brandt (8) reported the findings on relationship between cotton fiber and twist per inch. Figure 8 shows the effect of twist per inch on the rate of change in strength as the number varies. The higher curve of the 13's yarn shows a rapid rise and a more gradual tapering off after the point of maximum strength has been reached.
This is a characteristic common to all the coarser yarns and would indicate that the twist per inch must be carefully controlled especially within the brackets of softer yarns. Over-twisting of the coarse yarns are not as critical as under-twisting. In the finer numbers over-twisting becomes the critical factor while unde-r-twisting is of less importance. •
Analysis of experimental results indicate that several factors exist which control the yarn strength. Yarns which are 100 per cent
Dacron are stronger than the yarns made from the blending of Dacron and cotton. Similarly, yarns which are 100 per cent cotton are stronger than yarns made from the blending of Dacron and cotton. In a blending situation (cotton and Dacron in this experiment) the lower yarn strength is caused by the fibers having the greater elongation.
The effect of twist on per cent elongation of Dacron-cotton blend yarn is illustrated graphically in Figure 9. It is interesting to note that there is an inverse relationship between twist multipliers 29
100 13's
X H 0 z w H CO 90
I 18's H Z W U p:; w 80
27's
70
60 13 15 17 19 21 23 25 TWIST PER INCH x- igure i Effect of Twist in Cotton Yarn '•'Source: CD. Brandt, "Fibers from Spinners Viewpoint!] The Whitin Review. June 1945, p. 6. 30
11
10
0. 9 ' o H < 8 a o W
7
2.75 3.25 3.75 4.25 4.75 5.25 5.75 TWIST MULTIPLIER Figure 9. Effect of Twist on Per Cent Elongation of Dacron-Cotton Blend Yarn 31
and elongation until the twist multiplier value of 4. 00 is reached. From
twist multiplier value of 2. 75 to 4. 00 the per cent elongation decreases as the twist multiplier increases. Between the range of 4. 00 to 5. 75
is a direct relationship between twist multiplier and per cent elongation.
Per cent elongation increases as the twist multiplier increases. The
overall shape of the curve is parabolic.
Figure 10 was prepared by plotting the experimental data (Table
9). This curve basically has the same concave down shape as 100 per
cent cotton yarn would have. In other words, the twist effect on the cot ton Dacron blend yarn is similar to the twist effect on the 100 per cent cotton. However; it is a known fact that 4.40 twist multiplier gives the maximum breaking strength for pure cotton (1. 25 inches staple length) yarns regardless of their yarn number. From the observations of this experiment it can be stated that for a Dacron-cotton blend yarn maximum breaking strength was reached when the twist multiplier of 4. 00 was used.
An increase in the twist multiplier value had an effect on the yarn strength.
There is a direct relationship between the twist multiplier and yarn strength until the maximum yarn strength is reached. After the maximum yarn strength is reached, the relationship is inverse. In order to investigate the effect of twist multiplier on the yarn strength further. Tables 9 and 10 were prepared. These experimental data suggest that there is an inverse relationship between per cent yarn elongation and yarn strength for Dacron-cotton blend yarns. 32
700
15's
600
500
25's 400
300
200
2.75 3.25 3.75 4.25 4.75 5. 25 5.75 TWIST MULTIPLIERS Figure 10. Effect of Twist on Strength of Dacron-Cotton Blend Yarn 33
Table 9. Average Breaking Strength in Grams, Standard Deviation and Coefficient of Variation for 15's, 20's, 25's and 30's Yarns with Different Twist Multipliers
Average Breaking Per Cent Yarn Twist Strength Standard Coefficient Numb e r Multiplier (in grams) Deviation of Variation
2.75 529. 1 58. 69 11. 13 3. 25 604. 6 63.48 10. 54 3. 75 585. 3 69.71 11. 95 4. 25 606. 0 65. 28 10.81 15 4.75 611. 3 66.67 10.94 5. 25 607. 3 73. 51 12. 14 5.75 583.0 69. 27 11. 92
2. 75 460. 5 44. 27 9.66 3. 25 492.7 51. 57 10. 51 3.75 506.4 50. 94 10. 10 4. 25 518. 5 51. 00 9.87 20 4. 75 510.6 55. 37 10.89 5. 25 474.9 55. 37 11.71 5.75 493.9 49. 84 10. 13
2.75 342.0 32. 82 9.65 3. 25 381.9 39. 07 10. 28 3.75 375.9 37.44 10.02 4.25 382.5 49. 27 13.00 25 4.75 370.2 45. 23 12. 21 5. 25 365. 1 44. 82 12. 35 5.75 345.9 47. 09 13.68
2.75 275.7 36.78 13.44 3.25 287. 1 36. 36 12,76 3.75 302.5 49.62 16. 52 4. 25 280. 3 40. 54 14.57 30 4.75 284. 1 43. 56 15..43 5. 25 294. 3 48.72 16. 69 5.75 273. 3 40.44 14. 92 34
Table 10. Average Per Cent Elongation, Standard Deviation and Coefficient of Variation for 15's, 20's, 25's and 30's Yarns with Different Twist Multipliers
Average Per Cent Yarn Twist Elongation Standard Coefficient Number Multiplier (per cent) Deviation Variation
2. 75 0.0975 0.0260 26.6 3..25 0.0924 0.0137 14.7 3.75 0.0854 0.0136 15.9 15's 4. 25 0.0962 0.0120 12. 5 4. 75 0.0920 0.0116 12.6 5.25 0. 1046 0.0149 14.3 5. 75 0.0974 0.0178 18. 3
2. 75 0.0972 0.0267 27.4 3.25 0.0862 0.0169 19.7 3.75 0.0838 0.0151 18.0 20's 4.25 0.0822 0.0165 20. 1 4.75 0.0876 0.0147 16.8 5.25 0.0962 0.0178 18. 5 5. 75 0.1134 0.0172 15.2
2.75 0.0924 0.0232 25. 1 3.25 0.0832 0.0152 18.2 3.75 0.0812 0.0117 14.4 25's 4.25 0..0858 0.0121 14.3 4.75 0.0867 0.0127 14.3 5.25 0.0874 0.0134 15.4 5. 75 0.0986 0.0149 15. 1
2.75 0.0830 0.0204 24.6 3.25 0.0732 0.0158 21.6 3.75 0.0720 0.0119 16.5 30's 4.25 0.0758 0.0151 19.9 4.75 0.0788 0.0205 26.0 5.25 0.0804 0.0184 22.8 5.75 0.0860 0.0145 16.8 35
CHAPTER V
CONCLUSIONS AND RECOMMENDATIONS
Conclusions
The results of this investigation combined with those based on previous work on twist multiplier — strength relationships have per mitted the following conclusions:
1. The twist multiplier versus breaking strength curve fol lows a parabolic path with maximum point around 4. 00 twist mul tiplier.
2. The per cent elongation versus twist multiplier curve also follows a parabolic path with minimum point around 4. 00 twist multiplier.
3. For Dacron cotton blend yarns, yarn strength and elon gation have an inverse relationship.
4. The twist multiplier has a significant effect on yarn even ness.
5. Twist per inch effect on a cotton yarn is similar to twist per inch effect on a cotton synthetic blend except that optimum twist multiplier 4. 40 for cotton (1. 25 inches staple length) yarn is not the same as for cotton synthetic blend yarns.
6. Decrease of the breaking strength, after the maximum has 36 been reached, is less sharp for cotton synthetic blend yarns than for cotton yarns.
Recommendations
Twist per inch and breaking strength, twist per inch and elongation were observed in this study for Dacron cotton blend. The same study could be made for other synthetic fiber and cotton blends.
The range of twist multipliers could be changed from 2. 75 - 5. 75 to
3. 50 - 6, 50. This new twist multiplier range will make it possible to study higher range of the twist per inch effect on the yarns. The twist multipliers effect on yarn evenness could be checked for other synethtic fiber and cotton blends. APPENDIX 38
Table 11. Fiber Fineness Test Using Sheffield Micronaire, Fiber Fineness Expressed in Micrograms per inch
Test Number Micronaire Reading
1 3,.6 5
2 3,.7 3
3 4.. 00
4 3., 75
5 3.,6 7
6 3. 92
7 3. 70
8 3. 77
9 3. 80
10 3. 80
11 3. 88
12 3. 95
13 3. 76
14 3. 78
15 3. 85
Total 57. 01
Average 3. 80 39
Table 12. Fiber Strength Test Using Pressley Tester (1/8" Gauge)
Breaking Tensile Test Strength Weight Pressley Strength Number (lbs.) (mgs. ) Ratio Index (1000 lbs/in2)
1 13. 20 3.60 3.667 114.95 96. 56 2 13.43 2. 90 4. 631 145.17 121. 94 3 19. 25 5. 15 3. 738 117. 18 98.43 4 11. 38 2. 55 4.463 139.91 117.52 5 15. 10 3. 70 4. 081 127.93 107.46 6 13. 59 3.60 3.775 118.34 99.41 7 16. 65 4. 00 4. 163 130.50 109.62 8 19. 11 5.25 3. 640 114.11 95. 85 9 13.73 3. 55 3. 868 121. 25 101.85 10 17. 80 6. 10 2. 918 91. 47 76. 83 11 14. 25 3. 34 4. 266 133. 73 112.33 12 17.41 4. 58 3. 801 119. 15 100.08 13 14. 91 4. 00 3. 728 116.87 98. 17 14 13.46 3.40 3.959 124. 11 104.25 15 16. 51 4.40 3.752 117.62 98. 80
Total 58.450 1832.29 1539.10
Average 3.896 122.15 102.61
Index and Tensile Strength were calculated using new methods by U.S.D.A.
T J Pressley Ratio ,^^ Index = *• x 100 3. 19
-P -1 c^ ^u Index X 84 Tensile Strength = ——
Where 3. 19 and 84 are the average Pressley Ratio and Tensile Strength of the 1954 U.S. crop. 40
Table 13. Fiber Length Analysis Using Servo-Fibrography
Test M ean Length Upp er Half Mean Uniformity Number (Inches) Len gth (Inches) Ratio (%)
1 0. 844 1. 094 77. 15
2 0. 906 L 156 78. 37
3 0. 844 1. 109 76. 10
4 0. 859 1. 125 76. 36
5 0. 813 1. 141 71. 25
6 0. 891 1. 094 81. 44
7 0. 875 1. 109 78. 90
8 0. 859 1. 110 77. 39
9 0. 875 1. 125 77.78
10 0. 750 1. 109 67.63
11 0. 844 1. 094 77. 15
12 0.906 1. 172 77. 30
13 0.750 1. 109 67.63
14 0. 813 1. 047 77. 65
15 • 0. 813 1. 109 73. 31
Total 12.642 16.703 1135.41
Average 0. 843 1. 114 75. 70
Mean Length ,_„ Uniformity Ratio = r; rr-^—z -; x 100 ^ Upper Mean Length BIBLIOGRAPHY 42
REFERENCES CITED
1. R. R. Sullivan, "A Theoretical Approach to the Problem of Yarn Strength", Journal of Applied Physics, 13:3, March 1942, p. 157.
2. L. A. Fiori, and J.J. Brown, "Effect of Cotton Fiber Fineness on the Physical Properties of Single Yarns", Textile Research Journ- al_, 21, October 1951, p. 750.
3. J. Kochlin, "Paper Read before the Society of Industrialle de Mulhouse", The Indian Textile Journal, October 1945, p. 42.
4. J. Gregory, "The Strength of Twisted Yarn Elements in Relation to the Properties of the Constituent Fibers", Journal Textile Institute, 1953, p. 499.
5. American Society for Testing Materials, ASTM Standards on Tex tile Materials, 1952, p. 337.
6. Uster Corporation, Instruction Book for the Uster Automatic Yarn Strength Tester, p. 24.
7. Whitin Corporation, "Factors Affecting Twist Per Inch", The Whitin Review, June 1941, p. 9.
8. J. D. Brandt, "Fiber from the Spinner's Viewpoint", The Whitin Review, June 1943, p. 1.
9. E. I. DuPont De Nemours and Company, "Processing Blends of Dacron and Cotton", Du Pont Technical Information Bulletin D-151, August 1962, p. 3. 43
OTHER REFERENCES
Barella, A. , "Law of Critical Yarn Diameter and Twist", Textile Research Journal, April 1950.
Bowker, A. H. , and Lieberman, G. L. , Engineering Statistics, Englewood Cliffs, New Jersey, 1959.
Grover, E. B. , and Hamby, D.S., Handbook of Textile Testing and Quality Control. Textile Book Publishers, Inc. , New York, I960.
Landstreet, C. B. , Ewald, P. R. , Hertel, K. L. , and Craven, C.J., "From Cotton Fineness and Length, Chart Gives Twist Multiplier for Maximum Strength", Textile "World, October 1954.
Landstreet, C.B., Ewald, P. R. , Hertel, K. L. , and Craven, C.J., "The Effect of Fiber Length and Fineness on Optimum Twist Mul tiplier for Cotton Yarns", Textile Quality Control Papers, Vol. 1, 1954.
Lord, E. and Pierce, F. T. , "The Fineness and Maturity of Cotton", Journal Textile Institute, 1939.
Pierce, F. T. , "The Weakest Link - Theorems on the Strength of Long and Composite Specimens", Journal Textile Institute, 1926.
Truslow, N. , "A Handbook of Twisting", Textile Bulletin, August, 1954.
Werner, K. R. , "Limitations of the Indirect Untwist- Twist Methods for Determining Twist in Carded Single Yarns", Textile Research Journal, June 1956.