Detergency Studies w i t h .
.
Sulfated Tallow Alcohols LLOTD OSIPOW, DOROTHEA MARRA, CORNELIA T. SNELL, AI\'D FOSTER DEE SNELL Foster D . Snell, Inc., JYew York 11, ,V. Y.
T
SOLUBILITY
L4LLOFV-available as a surplus niateiial becauqe of decreasing soap production-can be reduced from the glyceride to mixed fatty alcohols and then sulfated. The sodium salts of the tallow-alcohol sulfates are detergents similar in cheniical composition t o the so-called sodium "lauryl" or dodecyl sulfate made from coconut oil. Like the coconut oil-based products, the tallow-based detergents contain a milture of fatty acid radicals, but a higher proportion of CISand CISgroups-the latter soinetimes both saturated and unsaturated. Two methods of preparing tallow alcohols are used: 1eduction of tallow by sodium and by hydrogenolysis. Unsaturated groups such as those present in oleic acid are unchanged by sodium reduction; they are changed to saturated groups by hydrogenation. The object of this study n a s to determine how the t n o types of surfactants produced originally by sodium I eduction and by hydrogenolysis would compare n ith one another in detergent and surface-active properties. Would the presence of unsaturated bonds aid or detract from detergencv? Cornpalison lras also made with commercial spnthetic detei gents based on sodium
Table I.
...
100
..
100
...
25
...
25
50
...
25
...
...
50
...
25
... 25
25
... 1. 2. 3.
Anionic 1. SO^, active dodecylbenzenesulfonate (Sacconol NRSF) Anionic 2 . 90% active dodecyl sulfate (Duponol LIE) Anionic 3. 30% active triethanolamine salt of lauryl sulfate (Stepanol WAT)
Sonionic 1. 100% active polyoxyethylene condensate of isooctyiphenol (Triton X-100)
Appearance of Solutions Containing Tallow-.llcohol Sulfates after 48 Hours at Indicated Temperatures
Tallow-Alcohol Suliate Saturated Unsaturated
0.
Because some syndets axe sold in liquid form or as a solution, the solubility of the tallon--alcohol sulfates was determined qualitatively alone and mixed with commercial syndets. I n this discussion, names of syndets are abbreviated by omitting "sodium salt of," as shown in Table I. Aqueous solutions were prepared by heating. The solutioiiq were then held in a thermostat at t h e appropiiate temperatuies for 48 hours and observed for clarity, Keither saturated nor unsaturated tallorr sulfates were soluble a t 20" to 60" C., a t a concentration as low as 570. Solubility can be increased eomewhat by mixture with other syndets.
Anionic 1
Anionic 2
Nonionic 1
3 3 3 0
.. 75
72
..
.. ..
30 50
,.
,J
..
---I J
C.
20'
.. .. .. 73 7;
5% Solution 40' C. 60' C. 3 3 3 3 0 0 0 0
1
0
3
0
7
0
3
0 0 0
3 0
20' C. 3 3 3 0 3 3 3 3 3 0
10% Solution 40' C. Coo C .
3 3 2
3 3 2
0 0
0 1 0 0 0
30° C .
3 3
20% Solution 40° C. 60° C ,
3
3
2 0 2 0 1
3 1
0
Clear Sljght turbidity Slight precipitate Moderate precipitate
dodecyl sulfate and sodiuni dodec)-lbeiieeiiesulfoiiate. The latt,er two, particularly the second, are the types of products current,ly most used in industry. The talloir-alcohol sulfates, a term used for brevity but meaning the sodiuni salts, were prepared by knom-n methods. They were salt-free and contained 0.5 t o 1.0% of unsulfated tallow alcohol..
Table 11.
Konionic 2 .
(xino'
This is more often t h e case with the unsaturated tallow-alcohol sulfate product than with the corresponding saturated productfor example, a 20% solution can be made containing 25 parts of unsaturated tallow-alcohol Sulfate and 75 parts of either dodecylbenzenesulfonate or the polyosyethylene condensate of isooctylphenol, even a t 20" C. Surface Tensions and Interfacial Tensions at Room Temperature (Suifaces aged 15 seconds)
Formula
100% active amide condensate of lauric acid and di-
Tallow-Alcohol S u l f a t e Saturated Unsaturated
~$~~~~~ ~ ~ sulionate
Sulfate
Surface Tension, sodiull1 d ~ Dynes/Cm. ~ ~ Sulfate 0.05yo 0 1%
492
I n t e l iacia Tension against Nu j ol lDynes/&. 0 05% O.lyo
SURFkCE A S D INTERFACIAL TEN S I O S S
In Table 11, the values for surface tension and inteifacia1 tension, obtained with the D u A-ouy tensiometer, are seen to be similar for saturated and u n s a t u r a t e d tallow-alcohol sulfates, either alone or with added syndets.
INDUSTRIAL AND ENGINEERING CHEMISTRY
March 1955
493
Addition of dodecylbenzenesulfonate to the tallow-alcohol sulfates reduces both surface tension and interfacial tension against refined mineral oil. Addition of sodium sulfate does not reduce interfacial tension in the way it does when added t o dodecyl sulfate. FLASH SUDS AND FOAM STABILITY
Values for initial foam capacity and foam stability as measured by the Ross-Miles (1)method are given in Table 111. Results with unbuilt or light-duty tallow-alcohol sulfates showed the saturated tallow-alcohol sulfate to foam poorly, much less than the unsaturated. However, the unsaturated compound did not foam as strongly as dodecyl sulfate. I n built products corresponding t o heavy-duty formulations, little difference was found in foaming ability between the built saturated and unsaturated tallow-alcohol sulfates, either as such or mixed with other detergents. EMULSIFICATION
N
The results of qualitative tests made under standardized conditions by shaking 2 volumes of a 0.3% detergent solution with 1 volume of Nujol mineral oil containing a trace of dye are shown in Table IV. Little difference in emulsifying power between the saturated and unsaturated tallow-alcohol sulfates appeared. Both were improved by admixture with dodecglbenzenesulfonate. MANUAL DISHWASHING
The method followed was that developed by t h e General Aniline & Film Research Laboratory for washing dishes by hand under standardized conditions. Each flat dinner plate was soiled with a half teaspoonful of 80%'rnelted Crisco, 20% flour, and sufficient Oildag (black) for visibility. The soiled plates were washed one after another in a 0.1% detergent solution until the foam no longer completely covered the wash solution and until grease appeared on the surface of the water in the dishpan. The first end point was a measure of the foam stability in the presence of soil; the second was a measure of the relative effectiveness of a particular detergent solution.
lo
The results, given in Table V, show t h a t when admixed with dodccylbenzenesulfonate, with or without further addition of fatty amide, the unsaturated and saturated tallow-alcohol sulfates gave about t h e same results (formulas A and B). Addition of fatty amide increased both foam stability and detergent ability of the solution (formulas C and D). \\"hen triethanolamine dodecyl sulfate and fatty amide were mixed with the tallow sulfate (formulas E and F), the saturated tallow-alcohol sulfate was superior in foam stability and performance t o the unsaturated tallow-alcohol sulfate. This combination with t h e saturated tallow-alcohol sulfate (formula F) gave the best results in hand dishwashing. WASHING OF FABRICS
Using commercial soiled cloth swatches (sold as FDS artificially soiled cotton by Foster D. Snell, Inc.) in a Launder-ometer under standardized conditions, the effectiveness of various detergent combinations was determined, both in removing soil and in preventing its redeposition. Both effects are equally important in evaluating a detergent. Soil removal was determined under the test conditions shown herewith Soil redeposition or antigraying action was measured by washing clean swatches in the detergent solution containing an added 0.025% of carbon black soil. With this amount and under the washing conditions, substantial deposition of carbon black on the cloth occurred. The higher the number for soil removal, the better the result The smaller the absolute value of t h e number for soil redeposi-
494
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 47, No. 3
Results with cotton in Launder-onieter tests, as given in Table VI, show decreasing order of eff ect,ivrnessfor combinations 4, 1, and 5 in soil removal, and 1, 3, and 5 for soil redeposition. This indicates t h a t a 1 to 1 saturated-unsaturated tallow-alcohol sulfate combination in a heavy-duty 107, active formulation was very effective. Combinations of tallorr--alcohol wlfates with nonionics and other anioiiics gave poorer washing results, and poorer results in soil redeposition, than without added surfactants. TEST CONDITIONS From Table TTI i t is seen t h a t detcrgent samples 5, 6, 9, 11, and 16 gave the better res.uIts for soil removal in 2-grain water; IO0 nil. Amount of solution per jai Mechanisal washing assistants per jar 8 rubber bails samples 1, 5 , 6, 7, 8, 9, and 13 in I5-grairi vrater. 111preventing 3/a-inch diameter 600 c. Temperature soil redeposition samples 2, 5 , 6, 9, and 11 gave the hetter result,s 40 r.p.m. Speed of rotation of jars in 2-grain water; samples 5 , 6, 9, 12. arid 16 i n 15-grain wat,er. 15 minutes Time for nasliing Rotate 2 minutes r i t h 150 nil. of Rinsing procedure Comparison of the four sets of figures s h o w that in over-all remater of same hardness as mash water sults for both soil removal and prevention of soil redeposition Two swatches of F D S soiled cotton, Fabrics per jar samples 5 , 6, and 9 gave consistently favorable results. These 3 X 2 inches Hunter multipurpose reflecReflectance reading were mixtures of saturated and unsaturated tallow eulfatcs in B % n ~ e t e r set to read 100 on magnesia block proportions varying from 1 part of the first to 3 parts of the second, up to 3 parts oC the first to 1 part of the secorid. The mistures of the two tdloiv-alcohol sulfates appeared to bc Washing Cotton. The detergent effectivenrss of the tallow more effective than the same amount of either one alone; also sulfates on cotton, with and without addition of other surlartants, more effective than tlodecylbenzenesulfona te ttnd dodecyl sulfate, is ehown in Tables VI, 1'11, and VIII. These are average reeither alone or coinbiiied with the t:Lllon.-alcohol sulfates. sults obtained in tests run a t different times; the estimate of the Tallow-alcohol sulfates had better detei.genc>- alone thaii after standard deviation is 1.45 for soil removal arid 2.10 for soil readdition of fatt>yamide. deposition. \Tit11 only 20% of active surfactant plus 80% of builders, as showi in Table YIII, the Table 11'. Emulsification at 25" C. with Rlineral Oil arid Detergent at 0.3% Concentration results for cotton detergency Detergent Building were somewhat different than Emulsion Rating A B C D with the 40% active material. 40 20 100 40 1. Excellent no emulsion break for 30 minutes Active detergent I n 2-grxin.water hetter results 32 40 , . . .. 2 . Good, noktnulsion break for 1.5 t o 20 minutes Sodium tripolyphosphate 8 10 . . . . . 3 . Fair eiiiulsion break in 3 t o 5 minutes Tetrasodium pyrophosphate were ohtained in soil removal 10 10 4. Poor, emulsion break in less t h a n 2 iiiinutes Sodium metasilicate, pentahydrate n-ith sample.: 1, 2: 5 , arid 8; 10 20 : : : 60 Sodium sulfate in 15-grain water with sainDodecylTallow-Alcohol Sulfate benzeneDodecyl Detergent ples 1: 2, 5 , and 10. Samples - Saturated Building Eitiulsion Rating Unsaturated sulfonate Sulfate 5 , 0 ) and 10 were omitted in c 2 100 the soil deposition studies. 2 .. C 100 ... C 1 ,.. 75 25 Of tlio remaining samples, bet1 25 75 C ... C 2 ... .. ter resiilts were ohtained in 50 > 50 .. C ... 2-grain water with 1, 2, 7 , and D 2 ... .. 40 2 .5 D 40 .. ... 8; in the 15-grain water also 1 ... .. u ... .4 1,i 20 with 1, 2, 7 , and 8 . For soil 20 ... 16 A 1 20 removal, the tallon--alcohol -4 1 20 20 ... ... .. B 1.5 20 sulfate-, alone or conihined, B a 20 .. ... 1 . .5 compared favorably with var... 10 B 10 10 10 B 2 ious niixt,ures. They also COIU1 10 B 5 (+z 'idnionic 2 ) 10 B 1 ... 5 ( +.j &;ionic 2) pwed favorably iri preventing 10 B 1 ,.. soil deposition, but coniliinatioiis with dodec~lbeneer~esulfonate plus fatty nmide were Table V. Hand Dishwashing Test at 43" C. a i d 0.1% Formulation Concentratioii also good. Basic Ileteigent l'ormulasa W a s h i n g W o o l . Rcsuits A B C D E 1' wool detergency are given with Anionic 1 I5 1. i 10 10 .. in Table TX. The technique Anionic 3 ,. .. 10 I0 Unsaturated tallow-alcohol is similar to that, shown for sulfate .5 .. 1 .. 5 .. Saturated tallow-alcohol cotton, escept, for a tempera.. o 1 .. 2 sulfate ture of 43' C. and the use of > J 5 J Nonionic 2 io 80 so 80 so Water FDS artificially soiled wool. Clear Slight Clear Slight Clear Clear Appearance amber turbidity, amber turbidity, amber amber -4s tjhe LOOTo active agenamber amber no inorganic salt,s addecl-t,he Total Nnmher of Dishes saturated taliow-alcohol sulDetergent Before foam breakdown Before grease appearance fate was the most effcctivc foi -4 8, 9 8, 9 washing XI-oolin 2-grain water. B 9, Q 9,9 14, 13 c 10,ll The 100% unsaturated tallowD 12, 13 12.13 E 13, 14 alcohol sulfate was low in de9,9 F 1B,16 24,24 t ergent effectivcness. a All proportions on active agent basis Resulte v i t h heavy-duty formulations areshorr-nin Table S.
tion-that is, the less the negative figure-the better the result. The latter results are interpreted as indicating the relative effectiveness of a detergent in preventing soil froin redepositing on fabric during an actual washing operation. Both cotton and n-ool were used in soft (2-grain or 34 p.p.m ) and hard (15-grain or 255 p,p.m.) L$-ater. All these variables are of importance in detergent problems.
sa
~~~
March 1955
INDUSTRIAL AND ENGINEERING CHEMISTRY Table VI.
Cotton Launder-ometer Test Results
(Brightness units gained.
0.2% 2-grain water, 60' C.) Heavy-Duty Detergent Building A B 40 20 32 40 8 10 10 10 10 20
Magnesium oxide = 100.
I
Active detergent Sodium tripolyphosphate Tetrasodium pyrophosphate Sodium metasilicate, pentahydrate Sodium sulfate Dodecylbenzenesulfonate
Tallow-Alcohol Sulfate Saturated Unsaturated
Sample 1 2
20 20
4 5 6 7 8
..
..
..
20
..
.
Table VII.
3
4 5 6 7 8 9 10 11 12 13
9.6
-29.8
-33.8
7.7 8.1 0.0
-28.0 -40.6 -52.3
-32.6 -42.2 -52.5
Cumulative Values for Cotton Detergency
14
15 16 17 18 (
a
Tallow-Alcohol Sulfate ~ Saturated Unsaturated .. 40 40 .*
..
4
5 7
8 9 10
2
10 30
.. ..
40
36 10
20
..
30
20 20
io
20 10
*.
..
..
.. .. ..
30
..
..
..
~
..
40
.. .. ..
20 20 10 10 10 20 10
..
.. .. .. ..
..
10
..
a
I
1
-23.'2'(8) -26 5.4 5 (8) (8) - 2 6 . 9 (4) - 2 4 . 3 (4)
..
..
..
..
~
Soil Deposition %grain 15-grain -30.3 (12) - 3 3 . 4 (4) -28 3 (12) - 3 2 . 5 (4) -34 2 (12) - 3 7 . 6 (4) -31 4 (12) - 3 6 . 3 (4) -40'.6' 12) - 3 0 . 0 {12) - 2 8 . 1 (12)
..
indicates number of replicates.
Sample
Tallow-Alcohol Sulfate Saturated Unsaturated 100 ... ... 100 25 ... 25 ... 50 ... 50 40 ... ... 40
...
6 7 8 9 10 11 12 Water
:
~ Soil Redeposition 2-grain 15-grain - 2 5 . 4 (4) - 3 2 . 3 4) - 3 0 . 8 14) - 2 3 . 3 (4) -34.7(12) -35.6 (12) - 4 0 . 9 (4) - 3 7 . 3 (4) -23.1 (8) -20.6 (8) - 2 3 . 9 (4) -28.1(4) -23.4(24) - 2 9 . 9 (20) - 2 6 . 8 112) - 2 7 . 3 (8)
Cumulative Values for Cotton Detergency
...
.. 10 .. ..
0.2yo-grain water, 43' C.
... ...
10
...
...
-4i:z
(4) -33.8(4) - 3 2 . 6 (4)
...
...
...
Detergent building B , Table 111, with 20% active surfactant.
Wool Launder-ometer Test Results
(Brightness units gained.
la
N ~ i~ ~ ~-Soil iRemovala ~ ~ i ionic 2 2-grain 15-grain .. 1 1 . 2 4) 1 3 . 4 (4) . . 1 1 . 6 14) 1 2 . 6 (4) .. 10.5 (12) 1 0 . 5 (12) .. 1 1 . 9 (4) 1 3 . 2 (4) .. 12.6 (8) 1 4 , s (8) , . 1 2 . 7 (8) 1 3 . 4 (8) 10 1 1 . 7 (4) 1 3 . 7 (4) 10 13.4(4) 10.8 (4) , . 1 2 . 3 24) 1 4 . 0 ( 1 6 ) .. 1 2 . 0 LO) 9 . 5 (16) .. 1 2 . 5 (12) 6 . 7 (4) 1 1 . 0 (8) .11.9 (8) i6 1 3 . 3 (4) .. 11 i ' ( 8 ) 1 1 . 6 (8) .. 10,2 (8) 190..89((8) 12) .. 12 ( 8 ) .. 1 1 . 2 (4) 1 2 . 3 (4) 10 1 1 . 7 (4) 1 1 . 7 (4)
Detergency building A, Table 111, with 40% active surfactant.
Table IX.
2 3 4 5
Magnesium oxide = 100)
(Brightness units gained. Magnesium oxide = 100) Tallow-Alcohol Sulfate ~ ~ ~ i ~ N ~ ~ i ~ ~-Soil i Removala ~ ~ i Saturated Unsaturated 1 2 ionic 2 %grain 15-grain' 20 .. .. 1 3 . 6 (18) 1 4 . 6 10) .. .. .. 20 1 3 . 4 (18) 1 1 . 4 LO) 10 12 3 18) 10 8 . 2 (10) io 10 6 . 7 (4) 1 2 : 2 112) i0 10 1 2 . 7 (6) 1 2 . 5 (6) .. .. 1 1 . 5 (12) 1 2 . 1 (12) 5 5 5 1 2 . 7 12) 5 .. 7 . 7 (4) .. 4 8 9 . 6 i6) 8.4(6) 4 8 8 11.8(6) 13.5 (6)
..
6
i
..
Table VIII.
a ()
1
20 io 10 10 10 15 15 15 15 15 15 ) indicates number of replicates.
Sample 1 2 3
~ ~
.. ..
-30.2 -34.7 -31.1 -33.4 -32.5 -37.6 -36 3
12.1
(Brightness units gained. Sample 1 2
-24.0 -30.9 -27.4 -30.5 -28.1 -34.7 -31.5
12.7 B 11.5 2.5 15-grain water, 4 replicates.
B
10 10
..
soil Removala 2-grain 15-grain 13.5 15.0 12.6 7.9 12.5 6.7 14.0 15.4 13.7 11.6 12.2 7.4 12.2 6.7
B
10
5 IY.5
nonionic 2)
10 (10 anionic 1) 11 Water a 2-grain water, 12 replicates.
I
10 10
10
5js5 nonionic 2)
9
20 20
20
10
Detergent Building A A A B B B B
..
20
.. 20 ..
3
495
Magnesium oxide = 100)
~~"n",",~ Dodeoyl sulfonate
Sulfate
..
.. .. ..
..
75 75
..
30 30 40
1 through 9, 8 replicates.
50 50
Sodium Sulfate
.. .. .. .. ..
..
..
60
46
60 60 60 60
60
Soil Removal 13.7 4.8 7.8 6.0 8.4 6.1 6.9 6.3 12.5 11.7 8.5 12.0
10 through 12, 6 replicates.
Soil Redeposition with 0.025570 Added Carbon Black -30.7 -38.9 -32.4 -35.7 -36.2 -36.9 -42.7 -38.0 -43.3 -37.9 -39.3 -39.8 -61,l
496
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 47, No. 3
With formulas -4 coiitaiiiiiig
4OYOof surfactant the beal results for both soil removal and prevention of soil deposition n-ere obtained with mixtures of the saturated and u w a t urated tallow sulfates. Replacement in p a r t h y dodecylbenzenesulfonate mis a deterrent rather than ail improvement. With the 20% formulation, the best results for soil removal from n-ool n-ere obtained with the saturated tallow-alcohol sulfate. Partial replacement of the saturated tallow-alcohol aulEate with an amide nonionic plus dodecylbenzenesulfonate gave f a i ~ l y good soil removal, although not as good as the sat'urated tallow-alcohol sulfate at 207,.
Table X.
Wool Launder-onleter Test Results at 43' C. and 0.2Y0 Concentration (Brightness units gained.
l l a g n e s i u m oside = 100.
. i c t i r c detercent Sodiiini tripolyphosphate Tetrasodiuni pyrophosphate Sodium metasilicate, pentahydrate Sodium sulfate
Talloii--.ilcoliol Sulfonate
~
~
Saturated
Unsaturated
..
..
70 20
10 30 10 IYater 20
_
Dodecylbenzene_ sulfonate
Detergent Building
10
.i (A 3 nonionic 2 )
..
(10 anionic 2 )
i.7 7 3
20
10
30
i.l 11 . o
10 0
3 ( + 3 nonionic 2 )
SUMM.4RY AND CONCLUSIONS
Sodium tallow-alcohol sulfates are not sufficiently soluble by t,heiiiselvesto he suit,ed for w e in liquid detergentfi. Solubility of the unsaturated tallow-alcohol sulfate is increased somewhat by combination with other syndets. Saturated talloi\-alcohol sulfate is a low foamer aiid unsaturated tallow-alcohol sulfate is a moderate foamer, in comparieon with dodecyl sulfate. Although t,allon--alcohol sulfates are fairly good emulsifier,q of niiiieral oil, they are improved by combinntion with other pyndets. Saturated tallow-alcohol sulfate appeared to be Poniei~-hatmore effective than unsaturated foi iiinnual dishn-ashing, particularly when combined with nonio, ic surfactants. For both cotton and woo1 detergency, a 1 to 1 coinhination of misaturated and saturated tallon-a,lcohol sulfates in heavy-duty formulations proved very effective in thew tFst.5, and was superior
10 8 7 9
.5 3
7 0 7 1
d
10 10 10
10
..
8 0 0 3 11 0
9.3
R
15-grain
lL.0
..
..
..
~
2-grain
20
20
io
Soil_Reinoi-al __ _ ~ ___
40
20
4 replicates)
Detergent Building A B 40 20 32 40 8 10 IO 10 IO 20 Soil Deposition with 0.02555 Added C a r b o n Black 2-grain ]%grain -30 9 -30.1 -10.4 -28.6 -23 3 -24 0 -61.1
-31 3 -31.i
-30.0 -30.3 -35
e
-30.3 -61
5
x
10 10
to coml)ination~with other syndets. 1Titho:it builders, the l than saturated tallox--alcohol sulfate as it better ~ o o detergent the unsaturated. The properties of the ti1-o tallow-alcohol sulfates dhow that each may havc special field? of usefulness, while their combinntioii should be very effective in heavy-duty proc1uc.t~. .4CKNOW'LEDG\IEVT
'Phi? 1 ~ 0 1 ~was 1 ~ carried out uiider a grant, from the Satioriitl Distillei.!: Prodiict,s Cory. LITERATURE CITED
( I ) Ross. J., and JIiIes, G . D., Oil & S o a p , 5, 99-10? (1941). RECEII.EDfor ieviem J u n e 16,1934. .~)ICCEPTEI> Octoher 28, 1854. I'sosented before rhe Dirision of Colloid Cliemietry a t t h e 126th Meetixg C I I E 1 I I C . 4 L SOCIETY,New l-ork. S . Y,, 19.54. of t h e .IXIERICAS
Effect of Milling on Branching and Distribution of Hot GR-S W. K. TAFT .4ND JUXE DUKE Gocernntent Laboratories, Unicersity of A k r o n , iikrort, Ohio
K
UIlN and Kuhn ( 7 ) point, out that the theory that branched molecules occupy less space in dilute solution than linear molecules, and therefore give less viscous solutions, is in semiquantitative harmony with experimental data, but in conrentrated solutions branched eopolymws show inordinately high viscosities ($). Baker and Mullen ( 1 ) state that for branched or netted particles, the slope of the curves of the natural logarithm of the relative viscosity divided by the concentration plotted against the concentration, is zero or positive when in the concentration range of 10 to 15% solids. Or, an increase in the value of the positive slope means more branching. The papeis of Rueche ( 3 )and Bestul and coworkers (2) substantiate the corieepts of Baker and JIuIlen.
Piper and Scott (9) found that, initially, hot milling is lesi. effective than cold in producing a soft material, but after a time the positions reverse and the hot treatment becomes more eflective. The reason for the reversal of eff'ectiveriets was thought to he differences in the manner of breakdoiyn of GR-S,wlirther by inechanical rupture of the chain, occurring in cold milling, or 17)- oxidation ir-hich is accelerated by hot milling. Theories contributed by Kauzmann and Eyring ( 6 ) and discussed b. TT-atson (11 ) suggested that, cold mastication ruptures primary chemical bonds of the polymer molecules, aiid the react'ive fragments may recombine or produce oxygenat,ed radicals which stabilize t,heniselves by side reactions, and that a t temperahres belorr 100" C., oxygen merely intervenes to repress recombination after molecu-
