Ind. Eng. Chem. Prod, Res. Dev. 1981, 20, 163-166 Dehaan, F. P.; Covey, W. D. J. Am. Chem. Soc. 1978, 100, 5944-5. Duniop, A. P.; Peters, F. N. “The Furans,” Relnhold Pubikhlng Corp.: New York, 1953; pp 400, 411, 557. Qraves, (3. D. US. Patent 2077409, 1937. Iseki, T.; Suglura, T. J . Biod”. Jpn. 1939, 30, 113. Isekl, T. 2. Physlol. Chem. 1933, 216, 130. Katrkzky, A. R. A&. Hetemycl. Chem. 1963, 1 , 38. Merck Company. Inc., British Patent 887300, 1902. Newth, F. H. Adv. Carbohydr. Chem. 1951. 6 , 83. Pasto, J.; Johnson, C. R. “Organic Structure Determination”. Prentlce-Hall, Inc.: Englewocd, N.J., 1909 p 383.
163
Pless, J. J. olg. Chem. 1973, 39, 2644-6. Szmant, H. H.; Chundwy. D. J . Appl. Chem. Blotechnol. 1981r, in press. Szmant, H. H.; Chund D.,1981b, manuswlpt in preparation. Szmant, H. H.; Basso? . J. J. Am. Chem. Soc. 1952, 74, 4397. Terai, T. Japanese Patent 1111, 1951. Turner, J. H.; Rebers, P. A.; Barrick, P. L.; Cotton, R. H. Anel. Chem. 1954, 28. s9s.
Received for review July I, 1980 Accepted November 6 , 1980
Tough Plastics and Reinforced Elastomers from Renewable Resource Industrial Oils. A Short Review Leslie H. Sperllng,’ John A. Manson, Shahld Qureshl, and Ana M. Fernandez Materiels Research Center, Lehbh UnIversHy, Bethlehem, Pennsylvania 180 15
Industrial oits, botanical oils, and vegetable oils all refer to the oils pressed or extracted from oll-bearing seeds. Some of these oils contain chemically reactive groups, besides double bonds, that permit new classes of tough plastics and reinforced elastomers to be made. Many of these materials are nonedible but Industrially useful. This paper reviews recent and current research on interpenetrating polymer networks and simuttaneous interpenetrating networks made from castor oil (hydroxyl group), Vernonia dl (epoxy group), and epoxldized Nnseed dl (epoxy group), combined with cross-linked polystyrene. Possible applications are discussed.
polyurethane or polyester of castor oil, both of which are soft elastomers. These polymers were combined with cross-linked polystyrene to form an interpenetrating polymer network, IPN (14-16). An IPN may be defined as a combination of two polymers in network form, at least one of which was polymerized and/or cross-linked in the immediate presence of the other. Both sequential ‘IPN synthesis (2-8) and simultaneous interpenetrating network, SIN,syntheses were undertaken (9-13). The latter, involving simultaneous but independent polymerizations via step- and chain-growth mechanisms, yielded the more practical of the two routes. Beginning in 1979, research on different oils was undertaken. Experimental oils from potential new oilseed crops, suggested by the USDA, were investigated. In pmticular, epoxy-bearing oils from Vernonia (1) as well as chemically epoxidized linseed, Crambe, Lunaria, and Lesquerella oils were used (1, 17-19). While this research is continuing at the time of writing, this paper presents an integrated review of the research done to date, including chemical properties, mechanical behavior, and potential applications.
Introduction In today’s lingo, the term “renewable resources” means sources of energy or products that can be used, grown, or replenished naturally, time after time, as opposed to mineral and petroleum products, which, once used up, are gone forever. Among the renewable resources available in the world, plant products rank very high. Examples include wood, cellulose, starch, rubber, and botanical oils. These oils are usually obtained by pressing or extracting various seeds. For industrial purposes, the oils may be classified according to the principal types of chemical reactivity. Classically, the presence of multiple double bonds has allowed for ready polymerization, providing the basis for paints, adhesives, and other industrial uses. Many of these oils are also edible. Among the large volume oils of botanical origin only castor oil contains another type of reactive site, a hydroxyl group. Oils containing hydroxyl groups or other reactive groups, as discussed below, are nonedible. However, because of their high reactivity, they offer special industrial advantages. Recently, the USDA has pointed out that new oilseed crops, originating from wild plants, bear oils containing various interesting chemical groups (1). Besides other hydroxy bearing oils, keto and epoxy fatty acids, long chain fatty acids, as well as new sources of oils bearing conjugated unsaturation are being researched (1). Lehigh’s Oils Research Program Beginning at the time of the 1974 petroleum crisis, the Polymer Laboratory at Lehigh University, in cooperation with the Universidad Industrial de Santander in Colombia, South America, undertook a study of the preparation of tough plastics and reinforced elastomers based on castor oil (2-13).The synthesis route involved making either the 0196-4321/81/1220-0163$01.00/0
Materials Castor oil is the triglyceride of ricinoleic acid (1). As 0 CH2-0-C
II
I n
OH
-(CHA7-CH
CH-O-C-(CH2)7-CH
I
K
=CH-CHz-
I
CH-(CH2)5-CH3 OH
I
=C H - C H ~ - C H - ( C H Z ) ~ - C H ~
CH2-O-C-(CH2)7-CH=CH-CH2-CH-(CH2)5-CH3
(1)
OH
I
discussed above, the interesting reactive sites are the three 0
1981 American Chemical Society
164
ind. Eng. Chem. Prod.
Res. Dev., Vol.
20, No. 1, 1981
Table I. Epoxidation of Natural Oils mol of epoxy/mol mol wt of % epoxiof oil, epoxidized oil oil theoret max exptl dation "av X" (approx) linseeda 10.0 8.7 9.5 84-92 5.5 980 84-90 4.5 1000 soy bean" 8.0 6.9 7.2 90-93 3.4 993 Crambe 5.9 5.3 5.5" Lesquerella 4.9 5.0" -.3.0 1008 __-- 4.0" 2.8 1073 Lunaria Vernonia gatamensis 4.45d 2.7 927 " Commercially available. Naturally occuring epoxidized oil. Two different methods. Natural state. % oxirane
---
___
Table 11. Gelation Time for Homopolymer Elastomeric Networks at 140 "C epoxidized oil
g of cross- gel time, polyester linker/g of oil min network
___
Other acids, such as dimer acid, were also employed. Dimer acid is actually a mixture of three compounds, each bearing two carboxylic groups (eq 5).
Cross-Linking Agent: Sebacic Acid (SA) linseed 0.26 45 ELOSAN Crambe 0.25 60 ELOSAN Lesquerella 0.24 60 ELqOSAN Lunaria 0.23 140 ELuOSAN Vernonia galamensis 0.29 420 VOSAN Cross-Linking Agent: Dimer Acid (DA) linseed 0.73 60 ELODAN Crambe 0.72 120 ECODAN Lesquerella 0.68 130 ELqODAN Lunaria 0.67 180 ELuODAN
hydroxyl groups. This compound is 90% pure in ordinary pressed castor oil. By contrast, Vernonia oil consists mainly of the triglyceride of 12,13-epoxyoleic acid (Vernonia galamemis, native of Kenya, Africa, collected by Dr. R. E. Perdue, USDA) (eq 2) (20).
The reaction between a dibasic acid, such as sebacic acid, and an epoxy bearing oil can be written as eq 6. The OH
I
COOH vw W C HN -o C\H
t
-CH
M C /o\ H
I I COOHurr.
(CH2)a
WCH-CH-
-
0 CH2-0-C
II- fCH2)7CH
I
B
I
K
=CH-C
,o\
H2-CH-CHtCH2j4C
OH
H3
I
I c=o I (CH218 I c=o I 0
(6)
I
wCH-CHvvv
0
/ \
(2)
CH-OO-C--~CH~)~CH=CH-CHZ-CH-CH~CH~~~CH~
0
CH2-O-C-fCH2.f$H=CH-CH2-CH-CHCHCH3
/ \
Ordinary double bond bearing oils can be epoxidized chemically, frequently producing structures with more than three epoxy groups. A typical structure for totally epoxidized linseed oil is shown in eq 3. The level of epO H-O-CJCH@-
I
0
/O\
/O\ , O\ CH-CHF CH- CH-CH-CH-CH-CH2
2
CH3
(3)
oxidation of several oils studied in this program is shown in Table I (17). The epoxy groups react to form cross-linked polyesters with dibasic acids. Sebacic acid, itself commercially obtained from castor oil (and hence constituting a renewable resource), serves as an excellent cross-linker. 0
0
II II H-O-CC+CH2$8C-OH
(4)
reader should note that a free hydroxy group forms in eq 6, a possible locus of further reactions. The eight methylene units in sebacic acid in eq 4 a~ well as the long aliphatic chains in dimer acid, eq 5, contribute to a low glass transition temperature, Tg,of the final product. This aspect attains importance in the development of novel elastomers for impact-resistant plastics. Kinetics of Gelation The reaction between epoxy and carboxylic acid groups is a step-growth reaction. The presence of three or more epoxy groups leads to network formation when reacted with a diacid. When the reaction has consumed more than two of the epoxy groups, the material undergoes gelation as described by Flory (21).The time to gelation at 140 "C for typical compositions of epoxy-containing oil and dibasic acid, is shown in Table I1 (17). Similar studies were carried out with castor oil. At 190 "C, castor oil and sebacic acid reached the gel point in 8-10 h, depending on the catalyat (10).Since water removal is difficult beyond the gel stage, f d network formation was improved by finishing the cross-linking with the formation of urethane bonds. The SINSwere formed by mixing the epoxy elastomer prepolymer with styrene containing 1% divinyl benzene, DVB. At 80 "C the styrene reacts faster than the oil. As shown in Figure 1, the mix is poured (pumped)into a mold before the gelation stage of either product. Then the temperature was raised and the reaction completed.
Ind.
m.chrm.Rod. Res. Dev.. Vd. 20. No. 1. I981
16s
Finre 1. SIN ayntheaia from natural o h including the eporidation aeP. VOSAN/PSN 50150
I-s
01
-m Figure 2. Vernonia oilaebacic acid network/polptyrene netrork, VOSAN/PSN. 50/50. Studiea ria transmiasion electron mi-py ahow that the oil phase ia continuous for thia material.
Mechanical Behavior Figures 4 and 5 illustrate the stms-strain behavior for castor oil-based SINS (11). Figure 4 shows the behavior of reinforced elastomeric materials, and Figure 5 shows the equivalent behavior of rubber-toughened plastics. It is of interest to compare samples 6 and 7 in Figure 4. Although their composition is nominally identical, sample 6 was made via the SIN route, and sample 7 by the sequential IPN route (2). The latter has the polystyrene (plastic)phase continuous and has a much higher modulus. In sample 6, the castor oil elastomer phase in continuous, and the sample is much softer. The impact strengths of several epoxidized linseed oil/polystyrene SINS are compared with castor oil-based
60 TEMP (C)
160
pbrue 3. Dynamic meehanieal apeamaeopy of the m e m a w iuustnrted in Figure 2. Two gLasa banaitiom am indicated, one near -45 *C for the oil p b and the other near 120 'C for the polys t y " phaae. Measurements at 110 Hz.
During the reaction, phase separation (sometimes followed by phase inversion) occurs, depending on composition. Characterization of SIN'S By inspection, most of the SINS made were opaque white and elastomeric, leathery, or hard depending on the weight ratio of oil to styrene. Mechanical deformation of the samples by hand indicated significant strength and toughness in many of the preparations. The morphology of a 50/50 Vernonia oil-sebacic acid network/polystyrene network, VOSAN/PSN, is shown in Figure 2 (19). Osmium tetroxide was used to stain the double bonds in the oil phase. Clearly, in Figure 2, the polymerized Vernonia oil forms the continuous phase. The dynamic mechanical behavior of this material is shown in Figure 3 (19). At 110 Hz,the Vernonia oil polymer is seen to have a Tgof about -40 OC and that of the polystyrene is slightly over 100 "C. A t room temperature, the product has a storage modulus of about 3-4 X lo* dyn/cm2, in the soft leathery range.
-60
I COIIN Y COPfM 4
6 4-
CWNIKN
42460cmwm
S42460CWfUNIKN
m
ao
60
STRAIN
X
FiKlJre4. s ' #ludieaon C&iu oil SIN'S, m b k matadah COPEN. castor oil polyester network COPEUN. eastor oil polyeater-urethane network COPUN, castor oil polyurethane network. Reprinted with permieaion from ref 11. Copyright 1979 Society of Plastica Engineers, Inc.
I:
I4
'3
I
a
16
IX
STRAIN
._ ;
zo
%
Figure 5. Strsss-strain studiea on castor oil SIN'S, tough plnstic materials. Reprinted with permhaion from ref 11. Copyright 1979 Society of Plastica Engineers, Inc.
polymera in Table 111. Unfortunately, the e p o x i d d linseed oil SINS contain a higher percentage of oil than
188 Ind. Eng. Chem. Prod. Res. Dev., Vol. 20, No. 1, 1981
Table 111. Notched Izod Impact Strengths of Botanical Oil-Based SIN’S sample no.
(I
specimen compn
Izod impact strength, J / m u
1
PSN (control)
21.4
2 3 4 5
Epoxidized Linseed Oil E L 0 SAN/PSN 15/85 E L 0 DAN/PSN 15/85 E L 0 SAN/PSN 25/75 E L 0 DAN/PSN 25/75
76 84 98.5 95.2
6 7 8
Castor Oil COPEN/PSN 10/90 COPEUN/PSN 10/90 COPUN/PSN 10/90
67.8 44.8 24.6
9
Butadiene Based HiPS
80.0
1J/m = 0.0187 ft-lb /in.
the castor oil-based materials, so that an exact numerical comparison is difficult. However, the castor oil-sebacic acid polyester-based SIN, sample 6, in Table In, is comparable to the epoxidized linseed oil-sebacic acid-based SIN, sample 2. Possible Applications The first question always raised is price. At the present time, castor oil and linseed oil are still more expensive than butadiene, the latter being the monomer of choice for rubber-toughened plastics and many general purpose elastomers. Vernonia oil is not yet commercial, although it may well be in a few years. However, this is an age where gasohol has suddenly appeared at the gas pumps and continuity of petroleum supplies is uncertain. At current rates of price change, it is easy to imagine a price inversion within 3-5 years, with botanical oils becoming the cheaper. Castor oil, Vernonia oil, epoxidized linseed oil, etc., can be used to make useful elastomeric materials. In combination with polystyrene, a range of rubber-toughened plastics, reinforced elastomers, and interesting leathery products seems likely. For example, one of the authors (L.H.S.) owns a pair of shoes with castor oil-based heels. The shoes have been worn all over America, and the heels are still in excellent shape. (See composition 5, Figure 4.) However, the botanical oil-based materials must not be required to behave exactly like butadiene materials. They have their own properties and promise to make outstanding but somewhat different products.
Conclusions The energy crisis has forced a renewed effort in the field of natural products. By applying the concepts of modern polymer science, novel plastics and elastomers of very high quality can be prepared from natural products. This review paper covers the use of oils with chemically active hydroxyl and epoxy groups. Materials equivalent (but not equal) to petrochemicdy based plastics and elastomers were made. This work is continuing, with the expectation of numerous applications becoming apparent as the price drops relative to petrochemical materials. Literature Cited (1) Princen, L. H. J. Coat. Techno/., 1977. 49(12), 88; J . Am. OilChem. SOC.,1979, 56(9), 845. (2) Yenwo, G. M.; Manson, J. A.; Pulldo, J.; Sperling, L. H.; Conde, A.; Devla, N. J . Appl. Pdym. Scl., 1977, 12, 1531. (3) Yenwo, G. M.; Sperllng, L. H.; Pulldo, J.; Manson, J. A. Polym. Eng. Scl., 1977, 77(4), 251. (4) Pulldo, J. E.; Yenwo, G. M.; Sperling, L. H.; Manson, J. A. Rev. UIS (Colombia) 1977, 7(7), 35. (5) Yenwo, 0. M.; Sperllng, L. H.; Manson, J. A.; Conde, A. “Chemlstty and Ropettles of Crosslinked Polymers”, Labana, S. S., Ed.; Academ IC Press: New York, 1977; p 257. (6) Sperhg, L. H.;Manson, J. A.; Yenwo, G. M.; Devla. N.; Pulldo, J. E.; Conde, A. “Polymec Alloys”, Klempner, D.; Frisch, K. C., Ed.; Plenum: New York, 1977. (7) DeVia, N.; Conde, A.; Sperllng, L. H.; Manson, J. A. Rev. UIS(c0lombia) 1977, 7(7), 19. (8) Devla-Menjanes, N.; conde,A.; Yenwo, G.; Pulldo, J.; Manson, J. A,; Sperllng, L. H. Polym. Eng. &I., 1977, 17(5), 294. (9) Devla, N.; Manson, J. A.; Sperllng, L. H.; Conde, A. Pdym. Eng. Scl., 1978. 18(3). 200. . i J. A.; Sperllng, L. H.; Conde, A. ~ s c r o m o l e c ~ l e ~ . ~ e v l a~ , knson, 1979, 72(3), 380. Devla, N.; Sperllng, L. H.; Manson, J. A.; Conde, A. Polym. €ng. Sci., 1979, 79(12). 870, 878. Devla, N.; SperUhg, L. H.; Manson, J. A.; Conde, A. J. Appl. Polym. Scl., 1979, 24, 587. Sperllng, L. H.; Devla, N.; Manson, J. A.; Conde, A. In “Modlflcation of Polymers”, Carraher, C. E.; Tsuda, M., Ed.; ACS Symposlum Series No. 121, Amerlcan Chemical Sodety: Waehlngton, D.C., 1980. (14) Kim, S. C.; Klempner, D.; Frlsch, K. C.; Radlgan, N.; Frlsch, H. L. Macromokules. 1978. 9. 258. (15) Llpetov, Y. S.; S e r h v a , L. M. R m . (2”. Rev., 1978, 45(1), 63. (18) Thomas, D. A.; SperRng, L. H. In “Polymer Blends”, Vol. 2, Paul, R.; Newman, S., Ed.; Academlc Press: New York, 1978. (17) Qweshl. S.; Manson,J. A.; Sperllng, L. H., Org. Coat. Plest. Chem. Prepr. 1980, 43, 7. (18) Qweshl, S.; Femandez, A. M.; Sperlng, L. H.; Manson, J. A., unpublished data. (19) Fernandez, A. M., unpublished results. (20) Carbon, K. D.; Schneider, W. J.; Chang, S. P.; Prlncen, L. H. Accepted for publlcatlon In “New Sources of Fats and Ons”, Pryde, E. H.; Prlncen, L. H., Ed.; Amerlcan Oil Chemlsts’ Soclety, 1981. (21) FiOry, P. J. “Principlesof Polymer Chemistry”, Cornell University Press, Ithaca, N.Y., 1953; Chapter 9.
Received for reuiew September 16, 1980 Resubmitted November 7, 1980 Accepted November 14, 1980 The authors wish to acknowledge financial support through National Science Foundation Grant No. PFR 7827336.
