Ind. Eng. Chem. Prod. Res.
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Table 11. T' for Various Inks static dynamic ink surface tension surface tension J P 18-2 P44 A014-C % B, 95% H,O Triton X-100, 0.05% H,O solution 5% B, 7% Butyl Carbitol, 88% H,O a
Ronay (1975).
41.8'" 38.8'" 30.3'"
-
30.7
-
43.0
63.0'" 38.9'" 32.OC 30.2'" 34.0' 34.5c 61.0
31.0' 64.5' 66.5'
35.1
35.3'
-
Bruce (1976).
-
65.0 -
Present work.
lower trend of the results, as compared with Bruce, although different, is at least consistent. The liquid containing only an organic dye gives results that are very similar to JP 18-2 which verifies the hypothesis stated above concerning organic dyes. For he P44, the A014-C, and the B dye and Butyl Carbitol inks, it can be seen that the surface tension is independent of surface age. However, when a much smaller quantity of the strong surfactants is present, as in the Triton solution case, the results show a definite dynamic surface tension behavior as postulated. The conclusion is that one must consider the effect of every constituent in an ink jet liquid on the surface tension at an early age because large differences from the static value may occur.
Dev. 1981, 20, 684-688
jet technology. Results using this method are in good agreement with textbook results and previous research results. The method involves measuring the slope of the log V,,vs. break-off distance curve on a given apparatus for water. Similar results are found for the test liquid and a well-known equation by Lord Rayleigh is used to determine the dynamic surface tension. The effects of other variables are removed by maintaining the same apparatus and jet parameters for both tests. When viscosity affects the results, an alternate equation from Weber is used in a similar manner, which requires the measurement of the jet velocity in addition to the slope mentioned above. However, this additional parameter is shown to be easily measured. Hence, the inclusion of viscosity is not detrimental to the method proposed. Because of the high jet velocity and short break-off length employed, the surface age is on the order of 100 ps for these measurements. L i t e r a t u r e Cited Bruce, C. A. IBM J. Res. Dev. 1978, 20, 250. Defay, R.; Petre, G. "Surface and Colloidal Sciences", Vol. 111; Wiiey-Interscience: New York, 1971; p 27. Lamb, H. "Hydrodynamics", 6th ed.;Dover Publications: New York, 1932; pp 471-3. Rayleigh, Lord Proc. Lo&. Math. Soc. 1879, 10, 4. Ronay, M. "Determination of Dynamic Surface Tension of Ink From Capillary Instability of Jets", IBM Technical Report, 1975. Savart, F. Ann. Chem. Phys. 1833, 10, 4. Sweet, R. G. Rev. Sci. Instrum. 1965, 36, 131. Weber, C. 2. Angew. Math. Mech. 1931, 7 7 , 136.
Conclusions
A method has been presented to measure the dynamic surface tension of liquids applying techniques used in ink
Received for reuiew September 19, 1980 Accepted June 23, 1981
Stress Relaxation of Cellular Silicone James W. Schneider
'
The Bendix Corporation, Kansas City Division, Kansas City, Missouri 64 14 7
The long-term ( 10 years) room temperature stress relaxation properties of cellular silicone materials are currently under evaluation. The cellular structure is formed by using urea as a leachable filler. A total of 180 specimen are in test: 90 equilibrium-type samples (random copolymer) and 90 condensation-type samples (block copolymer). Each material was compounded to yield densities of 0.34 and 0.52 g/cm3 for thicknesses of 1.17, 1.52, and 2.54 mm. These density thickness combinations were compressed 20 and 40%. Five samples at each condition are tested yearly. A special fixture is used to maintain a compression on the cellular samples, and a universal test machine is used to acquire the load data. The 10-year predicted percent retention of load is between 57 and 66 % of original load for both sample types.
Introduction
Compression pads serve several functions. They fill gaps between components; they compensate for manufacturing tolerances of adjacent components and they allow for thermal expansion of the components. Compression pads are expected to exert forces at maximum and minimum gaps to maintain the proper positioning between parts in an assembly. A Bendix Kansas City engineering project team is currently evaluating the long-term (10 Operated for the U.S.Department of Energy by The Bendix Corporation Kansas City Division under Contract Number DEAC04-76-SP00613. 0196-4321/81/1220-0684$01.25/0
years) room temperature stress relaxation properties of cellular silicone materials. Previous short-term tests to predict the long-term behavior of compression pads have been inaccurate and unreliable. Previous long-term tests have been hampered by an inefficient number of samples, high costs, and the inability to recalibrate the equpiment during testing. The long-term testing Bendix is presently undertaking is based on separating aging from the measuring portions of a long-term test. Experimental Section Equipment. The key to this test method is to age each
cellular silicone sample in its own fixture and then monitor the load bearing capacity at selected intervals. A fixture 0 1981 American Chemical Society
Ind. Eng. GI".Rod. Res. h v . . Vd. 20. No. 4. 1981 086
t
"
Figure 1. Cross section of compression fixture. Specimen a" prepsed to t h i c k " A. Force memured on universal testing machine on loading cycle.
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655
LOADING f
SAUP1.6 COMPITSSED THlCXNlSs ,mn,
Figure 3. M i d loading and unloading cwven ( n o d d e ) at initial loading and later testing.
m -
e
m
*
e
Figure 2. Compression fixture for aging material.
was designed that would be compatible with the Bendix test machines. The specially designed compression fixture for aging maintains a specific compression on the cellular sample at room temperature. Each fixture was mounted on a universal test machine to acquire the load data. The load was recorded at initial assembly and a t selected intervals thereafter. A cross-sectional view of the compression aging fixture can be seen in Figure 1. The fixture has extremely close tolerances: the flat surface were machined for 0.005 mm TIR (Total Indicator Reading). Each fixture cost approximately $600. With the fixture installed on a test machine, the load bearing properties of the material were checked at selected time intervals. The assembled aging fixture shown on the left side of Figure 2 has a threaded stud that screws into the actuator rod of the test machine. The six nuts and bolts seen in this view clamp down on the cushion during aging. The four cap screws hold a removable detail (plug) that can be changed to vary the amount of compression placed on the sample. The cavity and cushion sample are shown on the right side of the figure. Materials. The cellular silicone materials tested were compounded from two types of base polymer: equilibrium, which is a random copolymer, and condensation, which is a block copolymer. Silicone polymer was reinforced with the addition of silicone dioxide in an intensive mixer. The reinforced base is allowed to age for 28 days. After aging and heat stripping, the material is catalyzed with dichlorobenzoyl peroxide on a two-roll mill and urea (a leachable filler) is incorporated in the intensive mixer. Flat
samples were molded, leached, and oven cured in preparation for this testing. A total of 180 specimens are in tesb 90 equilibrium samples (material in use now) that have been stored for 5 years; and 90 condensation samples (material for future use) that have been stored for 4 years. Each material was compounded to yield nominal apparent densities of 0.34 and 0.52 g/cm3. Three sample variations of 1.17, 1.52, and 2.54 mm nominal thickness were prepared from the lower density produd; two sample variations of 1.52 and 2.54 mm nominal thickness were prepared from the higher density product. Each of the material/thickness combinations was compressed to nominal compressions of 20 and 40%. There are nine replicas at each condition. Five are tested yearly and four are control samples: two are 3-year control samples and two are 10-year control samples. Techniques. The first step in testing was to place the lower half (stud side) of the fixture into the load frame and to place a 50.8-mm-diameter disk of cushion in the center of the cavity. The remaining half of the fixture was then aligned and set on the sample. A small controlled amount of preload was applied to maintain contact between the fixture and the test machine load cell. Force was the feedback variable in this test. Greater force was applied on the fixture at a constant rate up to, and beyond, fixture closure. A t this point, the loading was reversed until the preload was the only force, and the unloading was reversed to return the fixture to the closed position. The unloading-loading sequence was repeated one more time. With the fixture in a closed position, the retaining nuts were placed back on the fixture to maintain compression on the cushion until the sample was checked again. The fixture was removed, and a new fixture could be assembled. Typical results from the initial assembly testing are shown in the upper set of curves in Figure 3. The lower set of curves in Figure 3 is a typical result of later testing. This later testing followed the assembly steps just described with the exception of the starting point. In later testing, assembled fixtures were placed in the load frame and a force greater than the closing force was ap-
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Id.Eng. Chem. Prod. Res. Dev., Vol. 20, No. 4, 1981
I40
I1 j i
Figure 4. Typical loading and unloading curves (expanded scale with tangent drawn) at initial loading and later testing.
plied. The retaining nuts were removed and the test continued as before. The sample was cycled three times before it was locked up until the next testing. Both sets of curves show (1)the force exerted by the sample in fixture closing and (2) the thickness of the sample at minimum load (preload). Figure 3 shows that determining a closure load with any precision is difficult. For this reason, an amplified displacement scale was used for the actual measurement (Figure 4). As before, the upper set of curves is the assembly loading and the lower set the age loading. To determine the closure load, a line tangent to the loading curve was drawn to show its intersection with the vertical closure line. The percent of retention was then determined. These data were plotted vs. the log of the time, as shown in Figures 5 through 8. All the data points were used to determine a leastsquares approximation for each material type and density. The dashed lines in the figures represent the results of the previous year’s test. Curves comparing the current trends are plotted together in Figure 9. The equilibrium material at 0.34 g/cm3
IO0
THICKNESS
(mm) A I 17 A 1.17 8 0 0
COMPRESSION (PERCENT) 20 40 20 40 20 40
1.S2 I52 2.54 2.54
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TIME IN ASSEMBLY ( Y E A R S )
Figure 5. Percent retention vs. log time for equilibrium material, 0.34 g/cm3 nominal density. 100
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THICKNESS
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90 2
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COMPRESSION (PERCENT)
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6
T I M E IN ASSEMBLY ( Y E A R S )
Figure 6. Percent retention vs. log time for condensation material, 0.34 g/cm3 nominal density.
I
7
l
8
l
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Ind. Eng. Chem. Prod.
Res. Dev., Vol. 20, No. 4, 1981 887
100
THICKNESS
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(mm)
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4 A
D-
8
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,
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0
COMPRESSIOY (PERCEKT) 20 40 20 40
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2 E
0 0 LL
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PREVIOUS YEAR DATA
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61
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CURREN? DATA I
sa
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6
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THICKNESS (mm) I52 I52 254 254
A
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COMPRESSION (PERCENT) 20
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EQUILIBRIUM TYPE 40 PERCENT COMPRESSION
2
-
EQUILIBRIUM TYPE 20 P E R C E S T COMPRESSION
CONDE\SATIO\ TYPE 40 PERCENT C O M P R E S S l O h
CONOEYSATIO\ TYPE 20 PERCENT C O M P R E S S l O h
4
I
6
7
8
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2
3
4
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6
7
8
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TIME IN ASSEMBLY IYEARS)
Figure 9. Percent retention vs. log time, comparison of materials.
seemed to have the greatest drop in load retention projected for the 10-year study. Compressed thickness measurements a t the minimum load were recorded as a side
0
I
2
3
4
5
6
TlME I \ ASSEMBLY (YEAR51
Figure 10. Effective compression set vs. aging time.
benefit. Both the measured values of the aged samples and the measured values at assembly were used in a
888
Ind. Eng. Chem. Prod. Res. Dev. 1981, 20,688-693
standard compression set formula. The value calculated was called an effective compression set for the sample. These data were plotted vs. the time in assembly (Figure 10).
Results The rate of load loss for both densities of condensation material was approximately the same. The projected load retention value for the higher density equilbrium material was approximately the same as for the lower density
equilibrium material. Currently, the predicted percent retention of load is between 57 and 66% of original load, with the condensation material having a higher load retention value. If a material has a high load retention, it usually will have a low compression set. Both densities of condensation-type materials seem to prove this point. Samples will continue to be monitored yearly over the 10-year study. Receiued for review July 6 , 1981 Accepted August 28, 1981
Useful Products from Piperazine. Methylpiperazines and an Amorphous Dibasic Acid/Piperazine Polymer W. Tyler Gelger, 111, and Howard F. Rase" Department of Chemical Engineering, The Universiry of Texas, Austin, Texas 78772
Piperazine, a byproduct in ethylenediamine production with declining commercial value, was considered as a raw material for more valuable products. A catalytic process was developed for producing 1-methylpiperazine and 1+dimethylpiperazine in good yield using hydrodesulfurizationcatalysts with piperazine and methanol as reactants at atmospheric pressure and 350 'C. Piperazine was also polymerized with mixed dibasic acids primarily in the C10-C,2 range to yield a unique amorphous product suitable for polymer blends.
Piperazine (NH-CH2-CH2-NH-CH2-CH,) is a cyclic ethyleneamine that is formed as a byproduct in ethylenediamine manufacture. Although it has a number of small-volume uses, its major application as an animal anthelmintic is destined to decline precipitously because of the development of new and more effective drugs. There is thus considerable incentive for converting piperazine to more useful forms either by ring opening reactions or by reacting with other compounds to produce useful products. The purpose of the present study was to suggest and investigate several possible reaction schemes that could yield useful products a t mild conditions and with low-cost reactants. Three areas of investigation were pursued (1) decyclization of piperazine, (2) reaction of piperazine with methanol, and (3) polymerization of piperazine with byproduct mixed dibasic acids. The later two studies yielded potentially valuable processes while the first produced additional insights on the nature of hydrodenitrogenation.
Experimental Equipment and Procedures Catalytic Reactor and Reaction Procedure. All catalytic runs were made using a microreactor previously described by Harrison et al. (1965). Prior to each run the reactor, containing a catalyst charge, was purged for 10-20 min with nitrogen and then calcined for 4 h at 315 "C. This treatment was followed by sulfiding when desired, using a 11.3% H2S-in-H2mixture flowing at 500 (vol/ h)/vol of reactor at 315 "C. Catalysts studied were American Cyanimid commercial hydrodeaulfurization catalysts HDS-2A (Co-Mo/A1203, with 2.34% Co and 9.9% Mo), HDS-3A (Ni-Mo/A1203, with 2.5% Ni and 10.44% Mo), and a blank A1203. All were in form of 1/16-in.extrudates with nominal surface areas of 270, 180, and 200 m2/g, respectively. After sulfiding and purging, the feed of piperazine in xylene or methanol was introduced along with hydrogen or nitrogen. Some carrier gas was essential in order to 0196-4321 /8 I f f220-0688$01.25/0
prevent crystallization of piperazine in the small feed and product lines. Product Analysis. Gas chromatographic analysis of products was employed, using a Hewlett-Packard Model 5750 temperature-programmed gas chromatograph equipped with a thermal-conductivity detector. The column packing was 20% Carbowax 20M and 2% KOH on acid-washed 60/80 mesh Chromosorb W. Sampling was accomplished directly from the microreactor by means of a multiport Biotron sample value. Unknowns were identified by GC/MS analyses and comparison with knowns. Polymerization Techniques. Piperazine polymers were prepared via the salts of piperazine and dicarboxylic acids using the method of Coffman et al. (1947). In preparing the salt of dodecanedioic acid and piperazine, 7.494 g (0.0869 mol) of piperazine and 20.004 g (0.0869 mol) of acid were dissolved in 40 and 200 mL, respectively, of 95% ethanol. The acid solution was heated to completely dissolve the acid. Each solution was filtered, mixed together, and allowed to cool. A fine, white precipitate, which was formed very quickly as the solution cooled, was removed by filtration after 2 h of cooling. The precipitate was then dried and stored in a desiccator. Salts using a mixed acid were prepared in a similar manner using a mixed acid supplied by E. I. du Pont Company, called DBD. Polyamide was formed by placing the precipitated salt in a crucible in a laboratory oven supplied with a nitrogen purge. The oven temperature was held at 165 "C for 3.5 h, 200 "C for 1 h, and finally 230 "C for 35 min. Alternately, polyamide was formed by heating the salt in a vacuum oven at 170 "C and 30 in. HzO pressure for 60 h. The resulting polymers were analyzed by differential scanning calorimetry using a Perkin-Elmer Model DSC-2. Decyclization of Piperazine Ideally, decyclization of piperazine would combine splitting of the piperazine ring and addition of Hz or NH3 0 1981 American Chemical Society
