dent on the strut thickness and also to a significant extent on the thickness of the unbonded face sheet. The load bearing capability of a series of pads, having a strut height of 2.69 in. and an unbonded face sheet thickness of 0.234 in. and strut thicknesses ranging from 0.10 to 0.22 in., was found to be proportional to the strut thickness raised to the 2.5 power. Another series of pads in which the strut height is 2.80 in. and the unbonded face sheet is only 0.125 in. gave load bearing characteristics proportional to the strut thickness raised to the 2.1 power. As a result of the relatively greater contribution that distortions of the face sheet make to the deformation of the pad, pads having thinner face sheets exhibit less sensitivity of C-D characteristics to strut thickness. Over the range of pad geometries studied, essentially the same compressive stress-percent deflection characteristics result from proportionally linear variations in strut height and thickness. This permits further dimensioning of pad thicknesses by adjusting strut thickness in proportion to the required change in strut height. The study of the reproducibility of the C-D characteristics of one of the pad designs indicates that the data are sufficiently reliable for use in analyzing the effects of the various variables studied in this program. 5.2 Polymer Design. Adjustment of chemical compositions of the polymers is a most important tool in obtaining desired C-D and vibrational damping characteristics. Materials prepared from polyoxytetramethylene-based polyurethane prepolymers, such as Adiprene L100, display excellent resilience (low pseudo-set), low rate sensitivity, but poor vibrational damping, whereas the polyoxyisopropylene prepolymers, such as Conap DP4736, impart poor resilience, high rate sensitivity, but good vibrational damping properties. Since polymers prepared from combinations of both types of materials fortunately have intermediate rheological properties, blends of these materials are employed to obtain suitable compromises. Another means of adjusting the damping and C-D properties is through the processing temperature. Over the range of cure temperatures investigated, the vibrational damping of a series of polymers, prepared from different
ratios of polyoxytetramethylene and polyoxyisopropylene materials, displays an improvement in vibrational damping with increased processing temperature. However, increasing the temperature has the adverse effects of diminishing load-bearing and resilience and increasing the rate sensitivity. Compressive stiffness of the isolator pads is increased by employing relatively lower equivalent weight prepolymers such as Adiprene L167 and the even lower weight L315. These polyoxytetramethylenes, having a high concentrations of polar groups, provide vibrational damping properties that are superior to a higher equivalent weight material such as L100. In systems employing combinations of L167 and L315, the stiffness, rate sensitivity, and damping increase with increasing concentrations of L315. Although employment of L315 is an approach to increasing the excursion to bottoming through the use of' thinner, but stiffer, struts, its use is limited by an undesirable increase of rate sensitivity and loss of resilience. Finally, by using a combination of mechanical and polymer design, cast polyurethane isolator pads can be developed to meet the wide variety of objectives.
Literature Cited Kim, D. S., Rudd, G. E., Westinghouse R&D Center, unpublished work, 1973. Meier, J. F., Rudd, G. E., Rosenblatt, G. B.. J. Appi. Polym. Sa.,16, 559 (1972). Mendelsohn, M. A., Connors, H. J., Runk, R. H., Rosenblatt. G. B., "Missile Launcher Liner Material, Part I. Development of Structural Design." presented at 28th Annual Technical conference of the Society of Plastics Engrs.. New York, N.Y.. May 1970a. Mendelsohn, M. A., Runk, R. H., Connors, H. J., Rosenblatt, G. B.. "Missile Launcher Liner Material, Part II. Effect of Polymer Composition and Processing on Physical Properties," presented at 28th Annual Technical Conference of the Society of Plastics Engrs., New York, N.Y., May 1970b. Mendelsohn, M. A,, Runk, R . H., Connors, H. J., Rosenblatt, G.8.. lnd. Eng Chern., Prod. Res. Dev., 10, 14 (1971). Mandelsohn, M. A,, Rudd, G. E., Westinghouse R&D Center, unpublished work, 1974.
Received f o r reuiew December 9, 1974 Accepted March 11,1975 Presented a t the Division of Organic Coatings and Plastics Chemistry, 168th National Meeting of the American Chemical Society, Atlantic City, N.J., Sept. 9-13, 1974.
Halogenated Allyl Glucoside-Based Flame-Retardant Urethane Foam Carl A. Wilham, Felix H. Otey, Charles L. Mehltretter, and Charles R. Russell" Northern Regional Research Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Peoria, lllinois 6 1604
The free radical addition of halohydrocarbons to propoxylated allyl glucoside offers a feasible route for incorporating high levels of halogens into polyethers. Urethane foams made from these polyethers exhibit normal physical properties and a higher level of flame resistance than might be expected from the amount of halogen added.
Recent demands for consumer products with improved flame resistance have stimulated efforts to develop new polyethers that will yield highly stable, flame-resistant polyurethane foams. One approach toward this objective involves chemically combining halogens with alkoxylated polyols (or polyethers) used in foam formulations. On a
weight basis, usually bromine is superior to chlorine, and increasing the amounts of either gives correspondingly improved flame resistance. However, high halogen content often produces undesirable properties such as high polyether viscosity or poor foam stability. Halogens are less detrimental when incorporated into the polymer molecule Ind. Eng. Chem., Prod. Res. Dev., Vol. 14, No. 3, 1975
189
Table I. Properties of Halogenated Allyl Glucoside-Based Polyethers Pro -
pylene oxide/ Product AGU," no. mol
Polyhalo methane Molecular adduct wt calcd OH no.
Halogen, '% Nitrogen, Found
Corrected" Theory
%
Iodine value
Viscosity, cp, 25" x
493 425 ... ... *.. ... 43.0 50 619 339 16.0 15.3 18.8 0.26 3.5 1500 619 328 18.7 18.1 18.8 0.23 2.9 800 3 CBrC1, 655 301 23.1 22.4 23.3 0.21 1.9 400 B ... 706 298 ... ... *.. ... 30.0 6 4 cc1, 832 257 11.7 11.2 14.0 0.18 5.6 29 5 CBrC1, 868 239 15.6 15.1 17.6 0.15 4.2 15 AGU = anhydroglucose unit. b Hydroxyl number as determined by reaction of the product with acetic anhydride in pyridine. Correction based on O/c nitrogen as ethanolamine hydrochloride. A 1 2
...
4.9 4.9 4.9 4.9 8.6 8.6 8.6
cc1, cc1,
than when present in nonreactive additives. Moreover, the adverse effects of halogens can be minimized by placing them a t certain positions in the polymer molecule. For example, Pitts et al. (1972) obtained improved flame resisH
OCH,CH=CH,
Composition
Wt, g
Polyether" Freon 11 DABCO 33*
70.0 19.0 1.0 0.1 1.0
DBTDL~ DMEA~ DC 193e
I p " i
PA PI^
H-C-O(CH,CHO),H
1.2
54.8
a Polyether No. 3, Table I. A triethylenediamine-based catalyst, made by Houdry Process and Chemical Co. Dibutyltindilaurate catalyst, made by Union Carbide Chemicals Co. Dimethylethanolamine catalyst. e A silicone-based foam stabilizer made by Dow Corning Corp. Polymethylene polyphenyl isocyanate made by Upjohn Co.
I
H-C
H-C-OKH?CHO),,H
I
H C1
I
H
OCH2CHKH,CC1, \C/
I
H-C-O(CH,CHO),H CHJ
I
H(OCHCH2)hO-C-H
I
TH3
H-C-O(CH,CHO),H H-C
0
'/
H-C-O(CH,CHO)~H II
H Allyl glucoside polyether 190
Table 11. Typical Foam Formulation
Ind. Eng. Chem., Prod. Res. Dev., Vol. 14, No. 3, 1975
(1)
tance and foam properties by locating halogens on side groups along the polyether chain. Our study is directed toward placing halogens on the aglycone of a glucosidebased polyether. In a previous study we demonstrated a feasible route for synthesizing halogenated allyl glucoside polyethers and further illustrated their usefulness in preparing good quality, flame-resistant polyurethane foams (Otey et al., 1972). The polyethers produced by direct bromination of propoxylated allyl .glucoside contained a maximum of 2 halogen atoms per molecule and had viscosities ranging from 0.2 to 3 million cP. We have since explored another halogenation procedure for the allyl glucoside polyethers that permits the theoretical addition of up to 4 atoms of halogen per molecule. This approach involves free radical addition of a polyhalohydrocarbon, such as carbon tetrachloride, to the double bond of allyl glucoside polyether as depicted in reaction I, where the sum of a, b, c, and d represents the moles of propylene oxide added per anhydroglucose unit (PO/AGU). We used a copper chloride-ethanolamine complex to initiate the free radical addition according to the procedure of Burton and Kehoe (1970). Experimental Section Propoxylated allyl glucosides were prepared as described earlier (Otey et al., 1972) by heating a t 92' a 1O:l molar ratio of allyl alcohol and glucose in the presence of HzS04 catalyst for about 2 hr. Upon removal of the excess a!cohol by vacuum distillation and addition of KOH catalyst, the crude product was allowed to react with propylene oxide a t 160-170°. The final products prepared by this procedure
Table 111. Polyurethane Foams Foam properties Polyethers from Table I
No.
OH no.
Halogen adduct
Compressive strength, psi Burning' distance, in.
Halogen, * %,
Density, lb/ft3
II
339 cc1, 1.5 8.3 1.97 29 328 cc1, 1.3 9.9 2.48 ... 301 CBrC1, 0.9 12.4 2.05 26 257 cc1, 5 6.8 1.92 21 5 239 CBrC1, 1.3 9.3 2.15 24 a Total distance foam burned by ASTM 1692-68. Calculated amount of halogen in foam exclusive of blowing agent. 1 2 3 4
contained 0.82 mol of allyl groups and either 4.9 or 8.6 mol of propoxyl groups per AGU. Polyhalomethane Addition. In a four-necked, 500-cm3 round-bottomed flask, equipped with stirrer, condenser, thermometer, and nitrogen inlet, 84.0 g (0.17 mol) of propoxylated allyl glucoside, 150 ml (1.5 mol) of carbon tetrachloride, 50 ml of 2-propanol, and 2 ml of ethanolamine were sparged with nitrogen for 30 min at 60'. Then 0.15 g of CuCl2-2H20 was added to initiate free radical addition, and a temperature of 68' and good stirring were maintained for the total reaction period of 6 hr. During this time 2 ml of ethanolamine was added after 2 hr of reaction and again after 4 hr to make a total of 6 ml of amine added. Solvents were then removed by vacuum distillation and the residue was mixed with 25 ml of cc14. Upon cooling, ethanolamine hydrochloride precipitated and was easily removed by filtration. The dried product had an iodine value of 6 as compared to 43 for the starting polyether. A second free radical initiation, as described above, reduced the iodine value to 2.9 (product 2 of Table I). When reductions of 50% for carbon tetrachloride and 40% for 2-propanol were applied to quantities used in general procedure, the halogen addition to the allyl unsaturation decreased from 96 to 81% of theory (product 1 of Table I) although the iodine value of 3.5 was comparable to product 2. The first procedure above was also repeated using bromotrichloromethane instead of CC14. This reaction proceeded more rapidly and a second treatment was not necessary to achieve an iodine value of 3 to 5. Foam Preparation. Rigid urethane foams were made by combining these polyethers with polymethylene polyphenyl isocyanate, blowing agent, catalysts, and emulsifier using hand mix techniques (Otey et al., 1967). The formulations had an NCO to OH ratio of 1.05. A typical foam formulation is given in Table 11. Foam testing was conducted by standard procedures reported earlier (Otey et al., 1967).
Results and Discussion Representative examples of products made by the free radical addition of cc14 and CBrC13 along with their properties and halogen content are listed in Table I. Products A and B, which contain 0.82 mol of allyl groups and two levels of propylene oxide, were the substrate polyethers used for the addition study. Calculated molecular weights reported in Table I are based on the weight increase of the glucose sample after reaction with allyl alcohol and propylene oxide plus the amount of halogen compound that could theoretically add to the allyl groups. Total halogen analysis established the extent of halomethane addition to the allyl double bonds. In addition, analysis of products 3 and 5, which contained both bromine and chlorine (Table I), con-
I 20
... 17 16 17
firmed that the expected amount of bromine was present in these products. Since the products contained nitrogen that could not be removed at 100' and 1 mm Hg pressure, we assumed that small amounts of amine hydrohalide complex remained dissolved which accounts for the corrected percentage of halogen in Table I. Optimum conditions for maximum addition were not necessarily established, but the 80 to 96% of theoretical addition suggests that the process is practical. Although two 6-hr runs were made with the cc14 reagent and one 6-hr run with the CBrCl3, analysis revealed that 70 to 80%of the reaction is complete after only 1 hr. Preliminary experiments confirmed that C C 4 also adds to the allyl unsaturation when activated with either benzoyl peroxide or azobisisobutyronitrile. However, the amount of halogen added was lower than predicted from the loss in iodine value which indicated that these initiators were promoting other reactions with the allyl unsaturation. Unfortunately, the allyl glucoside polyethers show substantial viscosity increases with the addition of either C C 4 or CBrC13. In the previous study (Otey et al., 1972), we observed a tenfold viscosity increase when bromine was added directly to the allyl group. This problem is partially offset in that the compounds readily dissolve in blowing agents to yield solutions with acceptable viscosities for foaming. Pitts et al. (1972) and others have also encountered significant viscosity increases with the incorporation of halogens into polyethers. Preliminary evaluations showed that the new compounds can be incorporated into standard formulations to yield 2 lb/ft3 density foams that exhibit, for the most part, normal physical properties that might be expected for their degree of propoxylation (Table 11). About 4.9 PO/AGU seems optimum. Compounds containing 8.6 PO/AGU did not satisfactorily withstand accelerated humid aging. The most encouraging results were found while testing flammability of the foams (Table 111). With only 8% chlorine, standard specimens of the cc14 based foams burned only 1.4 in. when exposed to a Bunsen flame for 60 sec; with 12% halogen, from the CBrC13, foam samples burned less than 1 in. Lyons (1970) averaged the results of numerous papers and patents and found that some 18 to 20% chlorine is needed to render urethane polymers self-extinguishing. Hence, locating halogens on the aglycone of allyl glucoside polyethers appears to substantially improve their effectiveness as a flame retardant.
Acknowledgments We thank C. E. McGrew, B. R. Heaton, and W. P. Shroeder for microanalyses and W. C. Bury for his assistance with physical measurements. Ind. Eng. Chem., Prod. Res. Dev., Vol. 14, No. 3, 1975
191
Pitts, J. J., Fuzesi, S.. Andrews. W. R.. J. Cell, Plast., 8 (5),274 (1972).
Literature Cited Burton, D. J., Kehoe, L. T., J. Org. Chem., 35, 1339 (1970). Lyons, J. W., "The Chemistry and Uses of Fire Retardants," pp 22-23, Wiley-lnterscience, New York, N.Y.. 1970. Otev. F. H.. Westhoff. R. P.. Mehltretter. C. L.. J. Cell. Plast., 8 (3), 156 (i972).
Otey, F. H., Bennett, F. L., Zagoren, B., Mehltretter, C. L.,
J.
Cell. P&st., 3 (3).
138 (1967).
Received for review November 25,1974 Accepted May 2,1975
Mention of firm names or commercial products does not constitute an endorsement by the U.S. Department of Agriculture.
Drag Reduction of Straight and Branched Chain Aluminum Disoaps Harry C. Hershey,' Jeffrey T. Kuo, and Michael L. McMlllan Department of Chemical Engineering, The Ohio State University, Columbus, Ohio 432 10
Toluene solutions of twelve aluminum disoaps, six straight chain and six branched chain, were studied in laminar and turbulent flow. Molecular weights were determined by light scattering. The straight chain disoaps, which ranged from eight to eighteen carbon atoms, were all effective drag reducers, showing essentially equivalent drag reduction behavior. The branched chain disoaps were even more effective. Aluminum dioctoate and aluminum di-2-methylundecanoate were the two most effective agents found, dioctoate because it required the lowest concentration (0.08 YO)for drag reduction and the di-2-methylundecanoate because of extreme stability with time and shear. The effects of size of side chain group, location of side group, length of main chain, and number of side groups on drag reduction were also studied.
Introduction Drag reduction in turbulent flow has been achieved by using polymers, soaps (association colloids), and suspended solids (Patterson et al., 1969) as well as combinations thereof (Lee et al., 1974). This paper will be concerned only with aluminum disoaps in toluene. The purpose of this investigation was to study the effect on drag reduction of varying the anion characteristics of alluminum disoaps. In this investigation the length of the main chain (backbone) was varied from six carbons to eighteen. All even-carbon straight chain disoaps from Cs (dicaprylate) to CIS (distearate) were studied. Also methyl, ethyl, and pentyl groups were added to the basic backbone a t various locations to study the electronic and steric effects. Related Literature The first study of soap additives as drag reducers was made during World War I1 by Agoston et al. (1954), who discovered the phenomenon. The contribution of Ousterhout and Hall (1961) bridged the time span between Agoston et al. and Savins (1967, 1968,1969), who made the first thorough study of drag reduction in aqueous soap solutions. Important variables studied by Savins include solution pH, temperature, tube diameter, flow rate, electrolyte concentration, and soap concentration. Savins found no minimum threshold shear stress or shear rate where drag reduction begins, as exists in polymer solutions (Hershey 1965; Virk et al., 1966). Rather he found a maximum stress, above which the soap complex degrades reversibly, so that the solution recovers its drag reducing ability upon standing. White (1967) obtained results similar to those of Savins with an aqueous cetyl trimethylammonium bromide solution. Studies of nonaqueous soap solutions in turbulent flow have been made by Baxter (1968), Radin e t al. (1969), 192
Ind. Eng. Chem., Prod. Res. Dev., Vol. 14, No. 3, 1975
Baker et al. (19701, McMillan (1970), McMillan et al. (1971), and Lee and Zakin (1973). Radin et al. (1969) studied solutions of aluminum dioleate and aluminum dipalmitate in toluene. Their results showed that higher concentrations were needed to produce drag reduction in toluene (0.75%) than were needed in water (Savins, 1967; 1968). A second principal difference between aqueous and nonaqueous solutions was the irreversible aging found in nonaqueous solutions. Thirdly, Baxter (1968) found no drag reduction using purified aluminum dioleate. Thus soap additives, a t least in nonaqueous solutions, may be strongly influenced by the presence of impurities. Baker e t al. (1970) studied several lithium and sodium soaps in oil solvents. They found that a strong association colloid was present in those solutions which were drag reducing. Their soap solutions were destroyed by trace amounts of water, with the sodium soap even precipitating. McMillan et al. (1970, 1971) studied aluminum distearate and aluminum dioctoate in toluene. Drag reduction percentages of 80 and 83 were obtained for the dioctoate and distearate soaps, respectively. The effects of solution aging, shear degradation, makeup temperature, dilution, testing temperature, and free fatty acid content of the soap on the drag reducing characteristics were investigated, and the results were interpreted in terms of an equilibrium solution model. I t was discovered that a minimum concentration for stability exists in aluminum disoap solutions. Below this concentration, a metastable structure exists in solution. This structure may be broken down either by exposing to high shear or by aging or by a combination. Above this minimum concentration, the aluminum disoap exists as an association colloid in a dynamic equilibrium. The solution structure may be broken down by high shear, but it reforms upon standing. Aluminum disoap solutions may not be prepared by dilution and then used as if the soap micelle structure were a t
