I
H. L. GUNNERSON and J. P. GALLAGHER The Goodyear Tire & Rubber Co., Akron, Ohio
Non-Newtonian Flow Behavior of Vinyl Resin Plastisols An evaluation of the flow properties of these pastes is important, to predict their behavior in a particular type of application and to select the most suitable resin product
VINYL
resin plastisols are dispersions of small particles in organic plasticizers. They are converted to a film or plastic coating by heating, which solvates the resin and fuses it to a homogeneous product. Plastisols are used under widely different conditions varying from high shear coating and spreading operations to low shear slush molding, dipping, or casting processes.
formula (the power 1aF.v) has frequently been used (4, 5, 7, 8 ) . One way to express it is
log T = lag
where T = shear stress, D = rate of shear, C = non-Newtonian consistency, and n = index of non-Newtonian behavior or non-NeLvtonian index.
Experimental
Plastisols were prepared from four different types of vinyl resin (A, B, C, and D) in concentrations of 60, 66.5. 80, 90, 100, and 110 parts of dioctyl phthalate plasticizer (DOP) per 100 parts of resin by weight. The resin and plasticizer were thoroughly mixed and deaerated. After 4 hours, the flow characteristics were determined with a plate and cone viscometer. The viscosity measurements were repeated after aging for 1 day, 1 week, and 1 month. Apparatus
The plate and cone viscometer is a rather new innovation in rotational viscometers, but a number of variations have been described (1-3, 6). The Goodyear instrument consists essentially of a flat plate which is rotated by a variable-speed drive at a rate indicated by an attached meter, and a freely rotating cone mounted above the plate at a fixed clearance. The sample is placed between the plate and the cone. A torque exerted on the cone by hanging weights is balanced by rotating the plate at such a rate that there is no rotation of the cone. Each pair of readings of plate speed and applied weight gives a point on a force-flow curve. Theory
In describing the flow behavior of non-Sewtonian fluids, a generalized
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Taking the log of both sides of Equation l , the expression
Table 1. Plastisols Become More Nearly Newtonian and Approach Equal Consistency Values at Lower Resin Concentrations D, n, at
Iiesiii/UOP Ratio
2340 Dynes/ S q . Cm.
See.-’ at 2340 Dynes/ Sq. Cm.
100/60 100/66.5 100’80 100/90 loo/100 100/110
Resin A 4.14 9.44 3.16 13.4 2.20 25.5 1.71 54.9 1.53 74.5 1.49 103
100/50 100/66.5 100/80 100/90 loo/ 100 100/110
0.747 1.10 1.17 1.19 1.12 1.02
C 20.4 63.7 188 233 254 260
Resin B 2.39 6.76 15.3 26.8 48.0 52.7
123,000 28,700 6,400 4,490 3,620 3,070
Resin C 100/69 100/66.5 lOO/SO 100/90 loo/ 100 100/110
1.25 1.29 1.14 1.13 1.08 1.03
l00/60 100/66.5 lOO/SO 100/90 100/100 loo/ 110
1.23 1.14 1.07 1.11 1.03 0.960
11.6 21.5 38.9 84.3 106 131
11,300 7,630 3,570 2,370 1,860 1,570
Resin D
INDUSTRIAL AND ENGINEERING CHEMISTRY
33.1 45.3 77.0 120 196 268
3,590 2,610 1,490 1,150 1,030 1,010
C 100
-
+ n log D
(2)
is obtained. By plotting log 7’ us. log D ,a curve is obtained for a given fluid in which n is the slope. ATewtonian materials give a log-log force-flow curve which is a straight line with a slope of unity, in which case Equation 1 reverts to the usual Kewtonian expression. Loglog f l o ~ vcurves or portions thereof for which n is greater than unity denote dilatant flow, whereas if n is less than unity, pseudoplastic flow is indicated. Thus, this is a generalized relationship in which Neivtonian flow is merely a special case. This generalized equation is used to interpret separate straight sections for which n and C are constant of log 7’ us. log D curves. Each different and constant value of n probably denotes a different mechanism in the flow of a material, and portions of curves whose slope is changing indicate transition states for ivhich these equations have no significance. Values of both n and C are required io describe completely the flow properties of a non-A-ewtonian material at a given shear stress or raie of shear. Determination of n and C Values
The log T us. log D flow curves for the 100160 resin-DOP plastisols aged 1 day for each of the four types of resin are plotted in Figure 1. To compare the flow properties of the various plastisols on an equivalent basis, the slope of the straight-line section, n, at a selected shear stress of 2340 dynes per sq. cm. was determined. Using the values of n and D at the selected shear stress, values of C were calculated by Equation 1. These data are listed in Table I for plastisols aged one day.
3,8E -
100/60 RESIN/PLASTICIZER
4.0
RATIO
PLASTISOLS OF MIXTURES
OF RESINS A AND R AGED ONE MONTH
PLASTISOLS AGED ONE DAY
R RESIN/DOP 9ATIO
2.5
SLOPE OF LINE I(
-
20
q-
-m
r 7
3.0C
’5 I5
2.8
E
z --I-
v RESIN
A RESIN C
$ / 0
IO B
I
I
02
1
05
& RESIN D
1
0.4
1
1 1 0.6
1 1 08
1 I 1.0
I l 1.2
l I4
0.0 0.0
LOG RATE OF SHEAR (SEC-I)
Figure 1 .
By comparison with the Newtonian reference line, the resin A plastisol i s dilatant and the resin B paste is pseudoplastic The flow character of these two plastisols would probably change from pseudoplastic through Newtonian into dilatant as the resin C plastisol does, if the range of rate of shear were great enough
Aging Characteristics
When n and log C were plotted us. the log of the aging time, approximately straight-line relationships were obtained for all four resins a t all concentrations. In general, plastisols tend to become less dilatant during aging. A consistent trend of increasing C values with increasing aging time was obtained for all the plastisols. Blending of Samples
Same Type of Resin. Values of n were determined for plastisols prepared from different samples of the same type of resin at a 100/80 resin-DOP ratio. Portions of these resin samples were then blended, and a plastisol made from the resin blend was evaluated. The n values of the individual samples were weighted according to the proportion of each sample in the blend and averaged (Table 11). Such data on plastisols aged 1 day displayed somewhat better agreement than those evaluated after 4 hours of aging, and better results were obtained for dilute than for more concentrated plastisols. When flow properties of plastisols of resin blends and component resins in the blends were determined in other ways-by measuring the Brookfield viscosity, for instance-no such additive relationship was found. Two Different Types of Resin. T o investigate the possibility of obtaining flow properties not available with any of the four pure resins tested, plastisols of blends of regins A and B which tend to
-
0.2
- nB = KFA -k k
(3)
may be used to present blending data. Here nM = the non-Newtonian index of plastisols made from blends of resins A and B, nB = non-Newtonian index of plastisols of pure resin B, FA = weight
Table II. Averaged and Actual n Values for Plastisol of Resin A Blend Sample Weighted No. n n 1 2 3 4 5 6 7 8 9 10
11 12 13
0.4 0.5 0.6 07 0.13 OB OF RESIN A IN BLENDS OF A AND B
IO
The data deviate from a straight line only when resin A is present in large excess. k is zero. A plot of the logarithms of the slopes of these straight lines vs. the weight fraction of total resin in the mixture yields a straight line
form pseudoplastic and dilatant plastisols, respectively, were made. Resin A-resin B ratios of 40/60, 60/40, and 80/20 were used in resin-DOP concentrations of 100/60, 100/66.5, 100/80, and 100/110. Again viscosity measurements were made at aging times of 4 hours, 1 day, 1 week, and 1 month. T h e effects of concentration and age on C and n values of plastisols of these resin blends were thus determined. Assuming that resin B predominates over resin A in the effective control of the rheological properties of plastisols made from blends, the relationship nM
0.3
WEIGHT FRACTION
Figure 2. Variation of non-Newtonian index as function of resin A-resin B ratio
Log-log flow curves of vinyl plastisols
Whether pseudoplastic or dilatant, plastisols tend to become more nearly Newtonian and approach equal values of consistency at lower resin concentrations (Table I).
0.1 FA
1.6
1.94 2.10 1.76 2.20 1.66 1.45 1.49 2.28 2.27 2.17 1.82 2.26 1.72
0.127 0.164 0.116 0.161 0.144 0.157 0.102 0.189 0.156 0.149 0.149 0.167 0.134
-
Average n (from weighted values)
1.92
Actual IZ (plastisol made from blend)
1.90
fraction of resin A in blends of resins A and B, and K and k are constants. Figure 2 is a plot of (nM - nB) us. FA. Conclusion
The non-Newtonian index and the non-Newtonian consistency determined from measurements made with a plate and cone viscometer furnish a useful and practical basis for describing the flow properties of vinyl resin plastisols. With the type of data on blending presented here one could mix two types of resin, one which produces dilatant and the other pseudoplastic pastes, to yield plastisols with almost any desired nonNewtonian index at a given total resin concentration. Acknowledgment
The permission of T h e Goodyear Tire & Rubber Co. to publish this paper, and the advice and counsel of M. B. Palmer, Chemistry Department, Kent State University, are appreciated. literature Cited (1) Hig inbotham, R. S., J . Sei. Instr. 27, 139 8950). (2) McKennel, R., Proc. Second Intern. Congr. on Rheology, Oxford (1953), p. 350, 1954. (3) Markovitz, H., Elyash, L. J., Padden, E. J., Jr., DeWitt, T. W., J . Colloid Sci.10, 165 (1955). (4) Metzner, A. B., Reed, J. C . , A.I.Ch.E. Journal I , 434 (1955). (5) Mooney, M., J . Rheol. 2,210 (1931). (6) Pollet, W. F. O., Cross, A. H., J . Scz. Instr. 27, 209 (1950). (7) Rabinowitsch, B., 2. physik. Chem. 145A. 1 (1929). (8) Schbfield, R:, J. Appl. Phys. 4, 122 (1933).
RECEIVED for review January 15, 1959 ACCEPTEDApril 15, 1959 VOL. 51, NO. 7
JULY 1959
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