INDUSTRIAL AND ENGINEERING CHEMISTRY
760
producing substance, but fell back to the original rate when a defoamer was added. When molasses was caused t o foam in the evaporator, there was a n initial increase in rate followed by a rapid and complete scaling of the heater tube. Superheating of the films due t o the foaming apparently aggravated the tendency to scale. Thus, where a solution has scale-forming potentiality, foaming in the evaporator should be combated by the use of defoamers or by suitable changes in evaporator design. The data are presented on a laboratory scale and up t o the present time very few experimental data have been obtained on plant equipment. However, the authors have some evidence that the conclusions drawn will be comparative t o some extent with industrial oractice. LITERATCJRE CITED
Ames, W.M., Chemistry & Indzistrg, 1946, 194-5. Badger, W. L., and Caldwell, H. B., Chem. & M e t . Eng., 32, 616-17 (1925).
Bott. E. C. B.. J . SOC.Chem. Ind.. 56, 453-6 (1937). Hall, R. E . , IND.EXG.CHEM..17. 283-90 (1925).
(5)
Vol. 41, No. 4
Hewlett. A. M.,Mulfekuhler, A . F., and Lui, E., 8ugur. 42 30-1 (1947).
Hildebrandt, F. M., FoodPnd., 13, No. 12, G2-4 (1941). (7) Kerr, E. W., Louisiana Expt. Sta., Bull. 149 (1914). (8) Lamb, C. J., Chem. Inds., 60, 411 (1947). (9) McAdams, W. H., “Heat Transmission,” 1st ed., pp. 301-5, New York, McGraw-Hill Book Co., 1933. (10) McCabe, W. L., and Robinson, C;., IND.ENG.CHEM.,16, 47H (6)
(1924).
(11) Mitchell, D. T., Shildneck, P., and. Dustin, J . , IND. I 3 . s ~CHEM., . A N ~ LED., . 16, 754-5 (1944). (12) Olin, H. L., Dowell, W. H., and Toynbee, C. M . , Chem. & M e t Em.. 31. 116-19 (19241. (13) Othmer. D. F.. Ixu. ENG.CHEII.. 21. 876-7 (1929) (14; Pridgeon, L. A., and Badger, W. L., Ibid., 16, 474-9 (1924). (15) Reavell, B. N., Chemistry & Industry, 1946, 254-5. ENG,CHEM.,16, 458 (1924). (16) Van Marle, D. J., IND. (17) Webre, A. L., and Robinson, C. S., “Evaporation,” pp, 189-92, Kew York. Chemical Catalog Co., 1926. KECPSVED \Inrcli 3, 1948.
WRINKLE RESISTANCE OF FABRICS I. J. GRUNTFEST AVD D. D. GAGLIARDI Rohrn & Haas Compun.y, Philadelphia 57, Pa.
T h e results of experiments described in this paper show that the wrinkle resistance of a fabric is determined by the extent of its multifilament character and by the ability of the separate fibers of which it is composed to recover from tensile deformations. The extent of multifilament character depends on the ratio of fiber diameter to fabric thickness. This ratio determines the minimum strain with which a fold may be made. The extent to which the minimum strain is realized depends on the ease with which the separate fibers can move relative to one an-
T
other. This is, in turn, regulated by the structure of thp fabric, the presence of sizing or lubricating agents, the smoothness of the fiber surface, and the stiffness of the fibers. Selected urea-formaldehyde resins, formaldehyde alone, and glyoxal, which have access to the inside of the fiber, improve the ability of cellulose fibers to recover from deformations and increase their stiffness. Resin deposited on the outside of the fibers impairs the niultifilament character, stiffens the fabric, and reduces i t a ability to recover from folding.
H E properties of a fabric must be determined by the riature ment material. A represents a single-filament yarn (homoof the fibers of which it is composed, its structural features, geneous beam) being bent through a 90” angle. The path, end the type and distribution of finishing materials which rnay be which an imaginary element on thc outside of the bend must present. The details of the relations among these variables and traverse, is greater than the original length of this element Consequently, when the bend is made, the element must be the properties of the finished fabric are very complicated, however, and it is not likely that a complete and exact analysis will be stretched. Similarly, the element on the inside must be comgiven for some time. The experiments to be discussed here propressed, since the path length in this position is smaller than the original length of the element. Somewhere in the middle of vide a limited and qualitative analysis of these relations, which is a step ton-ard understanding the factors determining the wrinkle the beam there are elements which are neither stretched nor compressed when a bend is made. These me said to be in the neutral resistance of fabrics. This study was initiated because, although chemical treatments have been used for some time to improve the plane of the deformation. For any imaginary elements in this beam, the amount of deformation suffered depends on the digwrinkle resistance of fabrics, the mechanism by whirh these tance from the neutral plane of the deformation. Figure 1, B, effects are produced has not been altogether clear. Before the experiments are described, the general considerashows one way in which both tensile and compressiv~strain? mhv he relieved when a multifilament yarn is bent; the separate. tions which led t o their design will be discussed. When anv fibers slip by one another rather than stretch out. C illustratei sheet material is folded, a permanent nrinkle or crease will br produced if the deformations accompanying the fold are so great another mechanism by which bending deformations ran be rrthat the material cannot recover its original form. Fabrics differ from other sheet materials, such as cellophane, by being knitted or woven from yarns made of many small fibers 01 filaments. As a result of this rnultifilamcnt character, fabrics are much more easily folded and more winkle resistant, because the deformations which accompany folding can be relieved by adjustment of the relative positions of the separate fibers or filaments. FIGURE IA FIGURE I5 FIGURE I C HOMOGENEOUS B E A M M ULTI FILAMENT YARN MULTlFlLAMENT YARN Figure 1 illustrates the mechanism by which bending strains ran he rclicvcd in a multifilaFigure 1. Mechanism of Strain Reduction in RIuZtidilament Yarns
INDUSTRIAL AND ENGINEERING CHEMISTRY
April 1949
m
II
I
761
tained by dialyzing resin B and retaining the nondiffusible fraction; all of this resin would be expected to be found outside of the fibers of the fabric. Viscose filament twill fabrics (yarn size 150/40) were kindly supplied by C. 8. Venable of the American Viscose Company, The resins were applied in the usual way by padding these rayon fabrics through solutions of the appro riate concentrations, to which a catalyst had been added. !'he samples were then framed t o their original dimensions, cured in a gas-fired oven for 10 minutes a t 300" F., and conditioned at 65% relative humidity and 70" F. for 24 hours. Wrinkle resistance and stiffness were then measured. The change in wrinkle resistance was determined by a slightly modified Shirley Institute tester (8). Briefly, the test consists of placing a folded fabric specimen under a 500gram load for 5 minutes and measuring the recovery from creasing by the angle left in the specimen after relaxation. T o measure this angle, one end of the specimen is laced in a clamp mounted on the face of a protractor, and t i e angle is noted when the free end of the specimen hangs vertically. 180" angle represents 100% recovery from a crease, and 0 angle, no recovery. The stiffness of the fabrics was measured by the heart loop method (1). Table I shows the data obtained for the treated fabrics.
4
/
I
i
R2
RI
S STRAIN
Figure 2.
Stress-Strain Diagram for Various Fibers
lieved in a multifilament yarn; the separate fibers are shown to be gathered near the neutral plane of the bend, where the strains are not so pronounced. The tensile strains produced in a monofilament material by forming a close fold (180" bend) are of the order of 100%. Few materials are capable of surviving and recovering from such deformations. I n multifilament materials, under favorable conditions, the strains which accompany folding may be equal to the ratio of the thickness of the fibers to the thickness of the fabric. For common fabric constructions this ratio may be of the order of 5 t o 10%. Since, in any fabric, strains are produced in the fibers no matter how highly developed the multifilament character, the ability of the fibers t o recover from tensile deformation must also be taken into account. Figure 2 shows three stress-strain curves for hypothetical fibers from which fabrics are assumed to be made. The wrinkle resistance of a fabric made of type I fibers would be poor, since the-recovery from strain E, produced in folding the hypothetical fabric, is small. T h e fabric of type I11 fibers would also wrinkle easily because the fibers fail before reaching strain 8. Curve I1 represents the stress-strain relation for a n intermediate fiber which has improved strain recovery. Fabrics made of shch a fiber would, therefore, be expected t o be more wrinkle resistant than either of the other two! These considerations seem to provide a reasonable picture of the phenomenon of wrinkling or creasing and of the factors which determine the wrinkle resistance of a fabric. EFFECT OF FINISHING TREATMENT ON MULTIFILAMENT CHARACTER
The experiment selected for demonstrating the importance of the multifilament character of a fabric in determining wrinkle resistance is also relevant in connection with the question of the location of the resin in resin-treated fabrics, already discussed by others (6, 6). Urea-formaldehyde treated fabrics have been compared which have essentially the same 'gross composition but differ only in respect t o the distribution of the resin. The samples were repared b y controlling the diffusibility in cellulose of the urea!ormaldehyde composition. Resin A was essentially monomeric, and was capable of diffusing easily and rapidly through a cellulose membrane (cellophane); 'this resin presumably had access to the interior of the fibers of the viscose fabric. Resin B was a precondensate, of which approximately 50% could diffuse in cellulose; a t least half of this resin, then, would be expected t o be outside of the fibers of the treated fabric. Resin C was ob-
Resin A produces changes in fiber properties which will be discussed in detail later. It is condensed inside the fibers and does not impair the multifilament character of the fabric. Wrinkle resistance is high, and the fabric stiffness is relatively unchanged, even though the fiber stiffness is markedly increased.
TABLEI. WRINKLE RESISTANCEAND STIFFNESSDATAFOR RESIN-TREATED RAYONFABRICS Location of Resin Control (no resin) 1 5 7 resin A (completely diffusible) 15d resin B (half diffusible) 15% resin C (nondiffusible)' 5
Wrinkle Resistance, % Recovery 46
70 40 25
Stiffness Rating, Heart Loop Height, Cm.a 9.2 8.9 5.5 5.5
The height of the heart loop is greater, the lower the fabric stiffness.
The sizing effect of the nondiffusible portion of resin B nullifies the effort toward improving fiber properties produced by the diffusible fraction. The material condensed outside the fibers interferes with their easy movement relative to one another, reduces the multifilament character of the fabric, and increases its stiffness. The extremely poor wrinkle resistance of the fabric treated with resin C, which cannot affect the properties of the separate fibers, shows how serious the impairment of multifilament character can be. To emphasize this point further, samples of a fabric previously treated with a 20% solution of resin A (completely diffusible) were subsequently treated with small concentrations of resin B and glue. The changes produced in the "wrinkle-proofed" fabric follow: ,
Glue
7 -
yo added
% crease recovery
% added
0
72 63 53
0 1 3
1
3 5
48
5
Resin B---. % crease recovery 72 69 68 55
The effect of the resin is similar t o t h a t of glue, a familiar sizing agent. These results can be attributed to interference with the multifilament character of the fabric. The fact t h a t a resin is 100% diffusible in the cellulose does not imply that after curing all the resin will be found within the fibers. During drying and curing, migration and separation of the polymer phases may occur, and some polymer may be deposited outside the fibers. T h a t some surface resin is present on the fabric is suggested by noting the crease resistance ratings of a treated fabric after cure and after a modified Sanforize wash. Presumably the wash restores the multifilament character t o some extent,
INDUSTRIAL A N D ENGINEERING CHEMISTRY
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Vol. 41, No. 4
as slio\m by the following data on effect o i laundering on wrinkle resistance of a viscosc fabric treated with various concentration of resin A; this effect does not appear to be due to fabric shrinkage since this resin also stabilized the fabrics:
400
'
350
15% RESIN Q Resin A Treatment, 70 2
TROL
6 10
300
--Crease Recovery, %-Before wash After wash 47 50 49
52 63
20
c
BO
55 66
ILIICROSCOPIC EXAMINATIONS 250
The determination of the location of a nitrogen-containing thermosetting resin in textile fabrics has been studied by several investigators (8,5, 6). Monfbe (6) used Anthraquinone Blue BY, Color Index No. 1054, t o stain resin-treated fibers, and this dye was adopted for the present work on urea-formaldehydc. The specimens for microscopic examination were prepared by casting the fabric into highly plasticized methyl methacrylatc according to the method used by Yelland (9). The specimens mere dyed first and then cast and sectioned. The materials examined consisled of viscose filament iabrici which had been treated with resins A, B, and C. The following observations were made on cross sections of the dyed fabric. These results support the conclusions drawn from diffusion measurements and mechanical examinatin of resin-treated fahrirs:
cn
3ia
,
W
200
v) v)
W
a
I-
v,
150
100
so
Treatment Untreated 0 0
0.5
1.0
1.5
2.0
2.5
3.0
STRAIN IN INCHES (18" SPECIMEN)
Figure 3. Effect of Wrinkle-Proofing Agents o n Fiber Properties of Viscose Filament Yarn (150 Denier)
350
15% RESIN Q
%: 20% resin C
Observations of Stained Fabrics N o coloration of fibers
Deep uniform coloration inside fibers, no ooloration outside Faint coloration inside a n d very deep coloration on exterior of fibers Very faint coloration inside and very deep coloration on exterior of fibers
EFFECT OF WRINKLE PROOFING OX FIBER PROPERTIllS
The second experiment was designed to examine the relation between the stress-strain properties of the fibers and thc wrinkle resistance of the fabric. Urea-formaldehyde resins were used, but some studies were also made with glyoxal and formaldehyclc. Fabrics were again treated with resins and other agents by padding, framing, and curing for 10 minutes a t 300 F. One-ply 150/40 yarns were used. The choice of both filament yarns and filament fabric was made because it was felt that the stred+strain properties of the yarns reflected directly the stress-strain properties of the separate viscose filaments. The yarns were mound around a U-shaped metal frame, 20 inches wide, and the resins or other solutions mere brushed on. The excess liquor was abiorbcd by biotting, and the "harp" was then 'huspended in an oven, kept a t 300" F., and cured for 10 minutes. Either an acid or an ammonium salt was used as catalyst for all treatments. After CUI'ing, the harps were removed t o a conditioning room and kept a t 65% relative humidity and 70" F. for 24 hours. Stress-strain properties of the treated filament yarns were measured on a Scott IP-2 tester. T h e deformation-recovery curves were obtaincd with a one-minute loading-unloading cycle. Table I1 shows data obtained from the stress-strain curves of untreated viscose filaments and those for filaments treated with 20% solution of resin A. Treatments of both fibers and fabrics with wrinkle-proofing agents are seldom exactly reproducible. There are several possible sources of variations, such as differences in fibers and fabrics, volatilization prior to curing, penetration and migration of thc resin, and variations in curing temperatures throughout the sample. Nevertheless, although a certain treatment may not give the same numerical ansxers from day t o day, it does produce consistent results in so far as the gross effects are concerned. Thus a 10% application of formaldehyde under certain conditions will always improve the wrinkle resistance even though the actual amount may vary. The data presented in the following O
STRAIN
Figure 4.
-
%e
Strain-Recovery Curves of Modified Filament Viscose Yarns (150 Denier)
INDUSTRIAL AND ENGINEERING CHEMISTRY
April 1949
TABLE11. STRESS-STRAIN
PROPERTIES OF A
FILAMENT RAYONYARN
Treatment Control 20% resinA
Breaking Load, Grams Dry Wet 305 158 278 423
Load t o Produce 5% Elongation, Grams Dry Wet 60 160 105 340
Breaking Elongation,
%
Dry 17.2 10.6
RESIN-TREATED
Wet 19.0 14.7
Recovery from 5% Elon ation, Dry 18 44
6Wet 14 21
TABLE111. EFFECT OF WRINKLE-PROOFING AGENTSON FIBER PROPERTIES (FILAMENT YARN) Treatment, % Control Resin A, 20 Resin B, 20 Resin Q" 18 Rormalddhyde, 4 Glyoxal, 5 a
Breaking Load, Grams 336 405 342 375 315 290
Load t o Recovery Produoe 5% from 6% Elongation, Grama Elongation, % 150 18 350 42 220 33 315 49 285 64 268 56
Breaking Elongation,
%
15.6 10.0 13.6 9.2 7.2 6.7
wrinkle resistance increases with' increased strain recovery of the fibers. This is exemplified by uncondensed ureaformaldehyde, glyoxal, and formaldehyde, which are 100% diffusible in cellulose. Figure 5 shows that, for any one strain recovery, the wrinkle resistance of the glyoxal and formaldehyde samples is lower than that produced by urea-formaldehyde. This difference is probably due t o the fact that the increase in fiber stiffness accompanying a particular improvement in strain recovery produced by the aldehydes is less than that shown by the urea-formaldehyde (Table IV and Figure 6). The greater stiffness leads to a more highly developed multifilament character in the fabrics containing the resin-Le., more force is available to promote the strain-relieving fiber displacements, which are importa$ in determining the multifilament character of the fabric.
TABLE IV. RELATION BETWEEN FIBER PROPERTIES AND FABRIC WRINKLERESIBTANCE
Water-soluble, 100% diffusible material. Treatment, yo Control
tables, therefore, represent the type of results which are generally obtained. Table I1 shows that treatment with uncondensed urea-formaldehyde greatly alters the mechanical properties of the cellulose fibers. Not only does i t increase the.wet and dry strength of the filaments, biut more important, i t improves their ability to recover immediately from a deformation (raises the elastic limit) and increases their stiffness (Young's modulus). The modification of the stress-strain properties of cellulosic fibers is a characteristic of all agents which are capable of producing wrinkle-resistant fabrics. Table I11 presents further data to show the effects of urea-formaldehyde compounds and other :winkle-proofing agents on the properties of a viscose filament yarn. Figure 3 shows complete stress-strain curves of several filament yarns treated with the agents given in Table 111. Figure 4 gives typical deformation-recovery curves to show the improved resistance of the fibers t o permanent deformation. RELATIONS BETWEEN FIBER PROPERTIES AND FABRIC WRINKLE RESISTANCE
To show that the wrinkle resistance of a fabric is directly related to the properties of its fibers, samples of filament viscose fabric (made from 150/40 yarn) were treated with various amounts of urea-formald e h y d e resins a n d other wrinkle-proofing agents. Starch was also applied, and the fabrics were tested for wrinkle resistance. S e v e r a1 warp yarns were then removed from each fabric for e x a m i n a t i o n . T h e stressstrain properties of these filament yarns were measured as previously described. H o w ever, precautions had to be taken t o eliminate the crimp of the yarns. Table IV and Figure 5 show that in the absence of sizing complications, the
763
Wrinkle Reeistanoe Load t o Produce 6% Elongation of Fabric, % Recovery (Yarn), Grams 38 173
Recovery from 5% Elongation (Yarn), % 22 31 36 38 42
Resin A, 10 15 20 30
59 69 71 73
Resin B, 5 10 15 20
33 26 29 24
195 195 216 223
27 33 39 42
Resin C, 5 10 15
24 27 24
180 178 172
28 26 28
Formaldehyde, 2 4 6 10
48 56 66 77
190 235 240 270
34 48 58 67
Glyoxal, 4 6 10
50 59 69
240 265 270
43 52 56
Staroh, 1 2 6
30 21 25
1ti6 173 168
21 22 22
80
RESIN A
-
(P
70
0 a
m
a b
60
>-
a W
>
0
ix
50
se I
W
0 z
40
U
I-
v, (I) W
a
30
X
W -I Y
z a
3
20
20
25
30
35
40
45
50
55
60
65
% STRAIN RECOVERY FROM 5 % EL. (FIBER)
Figure 5.
Relation between Fiber Strain Recovery and Fabric ;S8'rinkle Resistance, and Effect of Sizing
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
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Vol. 41, No. 4
the fibers, produces only slight changes in fiber properties, and the effect on the fabrics is similar t o t h a t of starch treatments. These results illustrate the relation between fiber properties and fabric wrinkle resistance, and also show the importance of maintaining multifilament character. The data plotted in Figure u, 350 7 were obtained from a n experiment on three pieces of viscose (r rayon fabric treated with the same concentration of resin Q (wa(3 ter soluble and 100% diffusible). One solution contained 1% I z Triton K-60, a cationic softener-Le., a fiber lubricant-and tho 0 jZ 3 0 0 other, 1% solids of Rhoplex ER, which acts essentially as a sizing 4 (3 agent. The curves of Figure 7 show t h a t sizing decreases the z wrinkle resistance whereas the softening agent increases it, as w predicted in the earlier discussion. No changes are produced by these two agents on the strain recovery of the fibers. g 250 The wrinkle-proofing treatments discussed also have some efIfect on other properties of the fabrics. Table V presents data 4 showing that urea-formaldehyde actually improves the breaking c) 4 strength of a staple viscose fabric. This effect is also evident in 0 -1 200 Tables I1 and I11 dealing with the properties of filament yarns. Formaldehyde and glyoxal usually produce fabrics of lowcr strengths. All these treatments reduce the tear strength of fabrics, with formaldehyde giving the lowest values. The decrease in tear strength, abrasion resistance, and flexural endurance of some I I I I I IS0 10 20 30 40 50 60 70 wrinkle-resistant fabrics (6) is not altogether due t o degradation % STRAIN RECOVERY FROM 5 % EL. (FIBER) of the cellulose (either hydrolytic or oxidative), but results, as a natural consequence, from the increase in the stiffness of thc celluRelation between Stiffness and Strain Recovery Figure 6. lose fibers. Various workerg (3,4,7') have shown that these propof Modified Filament Rayon Yarns (150 Denier) erties deDend mainlv on the toughness of m m s or fibers, so t h a t any treatment which reduces elongation can be expected t o give fabrics of lower tear TABLE v. EFFECTO F WRINKLE-PROOFING AGENTSON FABRIC PROPERTIES" strength, abrasion resistance, and flexural enWrinkle Breaking Elongation Tear durance. Shrinkageb, Resistance, Strengthc, a t Break, Strengthd, Treatment % % Recovery Lb. % Lb. This paper has discussed mainly the mechanical Control* 12.2 43 47 18.3 6.3 aspects of the wrinkle proofing of cellulosic fabrics. 72 58 8.7 3.6 2.2 Resin A T h e problem of wrinkle proofing (improving the 89 24 4.2 1.0 0.8 Formaldehyde, 10% 66 33 8.6 2.8 2.5 Glyoxal, 10% strain recovery and increasing the stiffness of a Some fabric stiffness d a t a are given i n Table I. fibers) is similar t o that encountered in connecb After one Sanforize wash. tion with the vulcanization of rubber and other 0 Raveled strip method. d Trapezoid tear test. high polymers. Treatments which can cross link Staple visoose rayon. cellulose chains, either chemically or physically, can be expected t o reduce the creep of fibers, inerease their stiffness, and raise their elastic limit. Table IV and Figure 5 show t h a t resin B (only partially Also, treatments which can cause the exclusion of water from diffusible in cellulose) modifies fiber properties somewhat but the interior of the cellulose can modify fiber properties t o give much less than does resin A. T h e wrinkle resistance of the fabwrinkle-resistant fabrics. This follows from the fact t h a t water rics is not improved, as a result of the sizing action of the nonis a good plasticizing agent for cellulose. T h e wrinkle resistance diffusible fraction. Resin C, which can polymerize only outside of cellulose fabrics is much better when no water is present in the fibers. Heating in air at high temperature gives fabrics which are temporaril). wrinkle resistant. As moisture is again taken up from the air, the wrinkle resistance decreases unt>ilthe original state of the fibers is reached. RESIN Q + I % 400
a
s
TRITON ACKSOWLEDGMEYT
RESIN Q
The authors are grateful to H. B. Walker and 0. B. Hager, formerly of this laboratory, for their encouragement in this work. LITERATURE CITED
40
'
90
I
I
I
e6
50
35
I
40
45
% STRAIN RECOVERY FROM 5% EL, (FIBER)
Figure 7.
Effect of Softening and Stiffening Agent on Wrinkle Resistance of Resin-Treated Fabric
(1) Federal Specifications, Textiles, CCC-T-19la, p. 10 (1945). (2) Gordon, C. M., J . SOC.Chem. Ind., 63,272 (1944). (3) Hager, 0. B., Gagliardi, D. D., and Walker, H. B., Teztile Research J., 17, 376 (1947). (4) Hamburger, W. J., Ibid., 15, 169 (1945). (5) Landells, G., J . TeztiZeInst., 37, 328 (1946). (6) Monroe, IC. P.,Am. DuestuffReptr., 35, 13 (1946). (7) Schiefer, H., J . Research Nutl. BUT.Standards, 29, 69 (1942). (8) Shirley Inst. Bull., 12, 349 (1939). (9) Yelland, W., Tertile Research, 9,285 (1939). RECEIVED February 11, 1948. Presented before the Division of Industrial Chemistry at the second Rleeting-in-Miniature of t h e Philadelphia Sent,ion, AAIEHICAN CHEMICAL SOCIETY, January 22, 1948.
