1038
Vol. 36, No. 11
INDUSTRIAL AND ENGINEERING CHEMISTRY
to 200' F. Prolonged exposure to 180" F.has 110 effect so long as nonvolatile plasticizers are used. Like most vinyls, the butyral has tt tondcncy to stiffen at low temperatures, Young's modulus changing from 200 pounds per square inch at +77" F. to 16,000 pounds a t -5" F., 40,000 pounds at -40' F., and 235,000 pounds at -70' F. However, brittle temperatures are usually very low, generally below -40' F., and some stocks are below -90" F. The specific gravity of the base resin is 1.06; finished compounds can run as high as 1.4. Since the covering power and most of the properties are not seriously affected and since resin cost is high, high loading is usually very economical. Color possibilities are infinite since the base stock is clear and colorless. The butyral will not yellow in sunlight over long periods of time, and there is also no danger of tendering of fabric or other harmful effects of decomposition. Few solvents except alcohols and some esters and aromatics affect the cured product to any degree other than by extraction of plasticizer. I n prolonged exposure t o aliphatic hydrocarbons, there is no swelling but only a gradual stiffening from plasticizer extraction. The plastic normally supports combustion but can be' made t o burn very slowly. Properties for a typical vinyl butyral compound are given in Table I. An interesting departure from conditions expected in rubber is the behavibr of butyrals during cure. Standard methods for determining cure are either to measure the plasticity in such a machine as the Tinius-Olsen flow tester or the degree of swelling in alcohol. A typical curve of plmticity (measure as inches of flow through an orifice under 100 pounds per square inch pressure at 225' F.) plotted against time of cure a t various temperatures is given in Figure 1A. A similar curve of swelling in alcohol us. time of cure is shown in Figure 1B. Despite the gradual nature of these curves, investigation of tensile strength changes during
(sure shows a more abrupt change and, contrary to rubber, a change downward. Figure 2 presents such a curve with tensile strength plotted agninrt alcohol swelling for three different curing temperatures. It is evident that overcuring is harmful chemically and that optimum cure is obtained where the curve starts to drop. No explanation is given for this behavior as yet, but since the overcure point is far beyond most practical cures, this phenomenon does not appear to be serious. APPLICATION
Military applications have consumed all the vinyl butyrals since the stoppage of safety glass manufacture. Chief uses have been army raincoats, double-textured waterproof clothing, water, food, and clothing bags, and flotation gear. On a smaller scale, production items include 18-ton pontoons, heavy-duty hose, film for waterproof (but not vaporproof) packaging, soft and hard sponge, miscellaneous tubing and molded parts. A specialty use has taken advantage of its resistance t o mustard and other vesicant gases for the coating of large quantities of fabric for the Chemical Warfare Service. For civilian applications the properties of beauty, attractive softness, and chemical resistance will be of advantage. The possibilities in waterproof fabrics and film ranging from crib sheeting to industrial aprons, clothing to tablecloths, are infinite. It may even be an ingredient of the experimental but much discussed plastic shoe sole. Vinyl butyral is not to be considered a competitive material for crude or synthetic rubber. It offers some properties unavailable in rubber, combined with ability t o be processed by rubber mills. It is thus a now raw material available to the rubber industry for expansion into the field of plastics. PRZSSNTED before the spring meeting of the Diviaion of Rubber Chemistry, AMZRICAN CHZMICAL SOCIETY, in New York, N. Y., 1944.
DAVID A. EDWARDS AND CHARLES F. BONILLA The Johns Hopkins University, Baltimore,
0 styrene an open Ostwald viscometer was employed o the standard type suitable for liquids of medium vis!sity. The upper bulb held roughly 2 ml., the capillary was 8.0 cm. long, and the average head during a run was eome 12 cm. The volume of liquid added was about 5 ml., enough t o fill the lower bulb always t o the same level with the liquid warmed to the temperature of the run. The viscometer waa immersed in a transparent water jacket with a stirrer and calibrated thermometer. Calibrating runs with distilled water were made at nine temperatures between 24' and 77" C. Water is a suitable cali-
Md.
brating liquid because its kinematic viscosity is close to that of styrene. The temperature in the water runs was vaned in order t o cover a range of viscosities, since the principal eource of error under the conditions was end effects ( 6 ) . The viscometer constant in the form v l e was plotted against 8 - 3 . This is a convenient plot, since a straight line should be obtained if the head lost in end effects is proportional t o the velocity head. This may be shown by writing Poiseuille's law explicit for head and adding the term a(u*/g). On rearranging,
The viscosity of liquid styrene and liquid butediene monomers was determined in Ostwald type viscometers over a usetul renge of temperatures. The primary purpose of the experiments was to obtain values of viscosity which are sufficiently accurate for the design of heat transfer equipment involvins these compounds.
HD'g l28QL
I
e
On plotting the water runs in this way it was apparent that a straight line was a satisfactory curve. The line obtained by the method of averages gave an average deviation in u/B, for all the points, less than 0.5% from the line, From the slope, a waa calculated t o be 0.78; from the
November, 1944 Table 1.
Viscosity of Liquid Styrene and Liquid Butadiene
at Atm. PressurVbOktY Density T p m , $obea enti- rtoka Centi- G ! f k l .
-Styrene
o
IO
W,
26 80 86
1.060 0.883 0.7~1 O.eg6 0.660
o
607 o:667
46 M)
0.sa4 0.604
66 60
0'478 0.455 0.436 0.414
66 70
''
80 90 100
110 120
INDUSTRIAL AND ENGINEERING CHEMISTRY
0.a94
0.876 0.340
o.aio
0.290 0.270 0.250 0.2S8 0.225
1 . 1 ~ 6 0.8240 0.968 0.9148 0.829 0.gOw 0.778 0.9010 0.726 0.8866 o 681 0 8919 0:640 0:8878 o*606 0.674 0.8827 0.8781 0.8689 0'87a6 0.624 O eM7 0.608 0.8648 0.482 0.8697 0*461 0'8661 0.440 o . 8 ~ 0 6 0.404 0.8414 0.872 0.8822 0.862 0.8280 0.832 0.8188 0.811 0.8047 0.298 0.7066 0.284 0.7909
-Butadiene
'T%?? -20 -16
-io
$ ",;
at Satn. PrauurV e d t Y ti' D e d t y a!fd1.
0.246 0.229 0.216
%% 0.886 0.846 0.827
0.6687 o.etia1 0.6674
- f :::ti 8:@ l$ g:$# t:%g!:%# 1s 20 26
0 . 1 ~ 8 0.262 0.6274 0.149 0.240 0 . 6 ~ 1 2 0.141 0 . ~ 2 9 0.6160
66 60
0:WS
g8 :::%% g:;i$ g:g$$ !g:: !:$E 60 0.106 0.188 0 . 6 8 ~ 2 0 101
0.176 0.168
0.5764
1039
From the calibration curve and the observed 8, v then p were calculated from given values of p (4). A differential Porter plot against benzene was prepared by plotting the temperature of the styrene viscosity runs against the difference between t b t temperature and the temperature a t which benzene would have the same viscosity (3). The average deviation of the temperature dserence points from the smooth curve waa less than 0.3' C. By this method of interpolation I.( and u for styrene were obtained for eaoh 6' c. interval from 25" to 76" C., and v checked weU with a direct plot of the original kinematic viscosity-temperatwe data. The values are listed in Table I and probably are not in error by more than 1%. The values of p and v down t o O' and up to 146" C. were obtained by extrapolating a linear Porter plot against water (3)and are probably correct within 2 to 8%.
ECAUSE of the low viscosity of butadiene, theend-effect
mrrection would be considerable in the usual Ostwald viscometer. Since i t was also desired to exceed atmospheric pressure, a s p i e l sealed viscometer with a long helical capillary was conetructed. The capillary had L 63 cm., D = 0.0570 cm. ( m d with mercury), and i t waa smoothly coiled into almost three turns, 7 cm. in diameter. The measuring bulb held 2.80 intercept, D was 0.0494cm. These values are Only aPPrOXh8b since &, L, and the average value of H were not meamred a ~ u - 00. and had thick walls which would not expand appreciably By filling with mercury and weighing the mercury, D under Preesure, The total charge was some 4.1 cc. The averrye rat&. equaled 0.0491 om. The u/@ intercept at 6 = 0 ~.o001080 head during 8 run between 7 and 8 cm. The viscometer is illustrated in Figure 1. The upper or stoke per second, and v/6 decreased about 6% over the range of the tats. This hold-up bulb is desirable t o obtain smooth operation a t the st& of the run. method of calibration assumes Q is a p The opening between i t and the measproximately the same for both liquids, uring bulb should not be very small; which seems reasonable in view of ita about 1/16 inch is satisfactory. It would practical constancy for water over the probably be desirable t o locate the retemperature range used. ceiving bulb vertically below the meaaThe atyrene was shipped in a 6-gallon from the Institute, W. Va., plant uring bulb (6). In this case, however, i t was not deemed necessary since of Csrbide & Carbon Chemicals Corpothe liquid levels were measured during ration on September 21, 1943. Their each run in any case. White (6) analysis showed: showed that error due to curvature of Sp gr 20 20° C 0.9069 the capillary (using a smoothed curve &re& by wk. 99.08 through his tabulated values) is negliAldehydes (aa benmaldehyde), % by wt. 0.011 gible for a value of the Reynolds numPeroxidea (uhydrogen peroxide),
