Ind. Eng. Chem. Res. 1987, 26, 1735-1737 Greek Symbols
a, = acidity correlation parameters an,o,a,,, = parameters which describe the influence of the
acetic acid in the acidity function correlation p = parameter, which describe the influence of the zinc chloride in the acidity function correlation = nondimensional proton activities, h / h R = nondimensional paraformaldehyde concentration, CFo/
+
CFOR
7
= nondimensional toluene concentration, CTo/CToR
Registry NO.T, 108-88-3;CMT, 26519-66-4; AMT, 23786-13-2; DTM, 1335-47-3; F, 30525-89-4; HC1, 7647-01-0.
Supplementary Material Available: Analytical method for the gas chromatographic evaluation of toluene, chloromethyltoluene, methyl tolueneacetate, ditolylmethane, and chloromethylated ditolylmethane (8 pages). Ordering information is given on any current masthead page. L i t e r a t u r e Cited Brown, H. C.; Nelson, K. L. J . Am. Chem. SOC.1953, 75, 6292. Belen’kii, L. I.; Vol’kenshtein, Yu. B.; Karmanova, I. B. Russ. Chem. Reu. 1977, 46, 9. Cox, R. A.; Yates, K. Can. J . Chem. 1981, 59, 2116. Courtier, M. Method. Phys. Anal. 1966, 222. Dalmonte, D.; Sandri, E.; Brizzi, C. Ann. Chim.(Rome) 1963, 53(7), 918.
1735
Dvorak, F. Tech. Publ., Stredisko Tech. I n f . Potrauin. Prum. 1962, 161, 56. Fuson, R. C.; McKeever, C. M. Organic Reactions; Wiley: New York, 1942; Vol. 1. Handrick, K. Erdoel Kohle 1966, 19(3), 172. Himmelblau, D. M.; Jones, C. R.; Bischoff, K. B. Ind. Eng. Chem. Process Des. Dev. 1967, 6 , 536. Ionescu, M. Rev. Fiz. Chim. 1977, 7(14), 147, Irabien, J. A.; Ortiz, M. I.; Romero, A. Anal. Fis. Qulm. 1983, 79, 576. Kontsova, L. V.; Yukel’son, I. I. Kinet. Katal. 1970, 12(5), 1334. Mironov, G. S.;Budnii, I. V.; Farberov, M. I.; Shein. U. D. Zh. Org. Khim. 1970, 6(6), 1224. Nazarov, I. N.; Semenovskii, A. V. Bull. Acad. Sci. USSR, Diu. Chem. Sci. (Engl. Transl.) 1956, 1529. Ogata, Y.; Okano, M. J. Am. Chem. SOC.1956, 78, 5423. Olah, G. A. Friedel-Cratts and Related Reactions; Interscience: New York, 1963; Vol. 1. Olah, G. A.; Beal, D. A,; Olah, J. J . Org. Chem. 1976, 41(9), 1627. Olah, G. A,; Yu, S. J . J . Am. Chem. SOC.1975, 97(8), 2293. Pesin, V. G.; D’Yachenko, E. K.; Khatetskii, A. M. Zh. Obsch. Khim. 1964, 34(4), 1258. Rey, M. I.; Ortiz, M. I.; Irabien, A. J . Mol. Catal. 1987, 39(1), 105. Ripple, D. U S . Patent 4 194 886, 1980. Szmant, H. H.; Dudek, J. J . Am. Chem. SOC.1949, 71, 3763. Uphadye, R. S. Comput. Chem. Eng. 1983, 7(2), 87. Wei, S.; Prater, D. C. Adv. Catal. 1962, 13, 203.
Received for review February 27, 1985 Revised manuscript received December 2, 1986 Accepted May I, 1987
Particle Boards from Undebarked Natural Rubber Wood and Lignocellulose Byproducts T. 0. Odozi Department of Applied Chemistry, University of Port Harcourt, Port Harcourt, Nigeria
Particle boards (0.5 in. thick) were prepared from the combination of undebarked rubber wood, wood shavings, mangrove bark, corn cobs, and sugar cane bagasse, by treatment with adhesives based on vegetable tannins. Results from mechanical and various physical tests showed, on a n average, that the bending strengths of boards made of 25% undebarked rubber chips were about 30% higher than those of t h e commercial grade boards of other lignocellulose materials. Additionally, t h e specific gravity, weight to strength ratio (specific strength), and water resistance of t h e wood-based board were found t o be better. Although no nail fastness test was carried out, all boards showed evidence of nailability. Owing to the anticipated expansion of the population among the people living in cities of the less developed countries such as Nigeria, a major increase in housing and associated services is inevitable. Consequently, this will generate a large demand for building materials and components. In looking ahead, it is, therefore, in the interest of all concerned to consider ways of making the greatest use of their local materials for building. The most widespread construction materials in this part of the world are wood and wood-based products such as particle board. However, despite the large area of tropical forests available in Nigeria, their potential as commerical sources of forest products is limited in the long term. For example, the proportion of inaccessible and unproductive forests is already significant and is increasing, so that many demands are placed on the remaining forest products. Particle board is one of the commonly used wood-based products, which was orginally made from waste wood (i.e., wood shavings, saw dust, etc.). In recent times, however, there has been a shift toward the use of a hybrid of lignocellulose materials, and a leading candidate in achieving this is the use of agricultural waste. Agricultural wastes O888-5885/ 8712626-1735$01,50/0
such as sugar cane bagasse, corn cobs, mangrove bark, etc., represent a few of the potential and readily available lignocellulose materials which might be useful for particle board production. Although many studies on the use of agricultural byproducts (Mobarak et. al., 1975;Back and Lundqvist, 1975; Chawla and Shanker, 1973; Pizzi, 1978; Coppens et. al., 1980) in particle boards are available in the open literature, as yet information regarding the use of corn cobs, mangrove bark, and undebarked rubber wood chips is lacking. It is the object of the present paper to investigate the utilization of these materials for particle panel production. To further render the boards panels less expensive, systems based on urea and resorcinol modified natural tannins (red onion skin and mangrove bark) and formaldehyde condensates (Odozi et. al., 1986) were tried as adhesive resins. Experimental Section Materials. The raw materials (mangrove bark, corn cobs, sugar cane bagasse, undebarked rubber wood, and wood shavings) employed for the production of the paticle panels were disintegrated by using a laboratory mill 0 1987 American Chemical Society
1736
Ind. Eng. Chem. Res., Vol. 26, No. 9, 1987
Table I. Properties of Particle Boards Made by Using Different Lignocellulose Materials
board material used 1 undebarked rubber wood (20%), mangrove bark (80%) 2 undebarked rubber wood ( 2 5 % ) , wood shavings (25%), mangrove bark (50%) 3 mongrove bark (25%), corn cobs ( 2 5 % ) , sugar cane bagasse (25%), wood shavings (25%) 4 wood shavings (50%),sugar cane bagasse (25%), corn cobs (25%) 5 same as board 4 wood shavings (50%), mangrove bark 6 (50%) mangrove bark (50%), sugar cane 7 bagasse (50%) 8
bending specific specific strength," strength,* gravity psi psi312 1.08 197.6 2471.40
binder composition 9% onion skin tannin-urea-formaldehyde resin, 5% CMS (cassava based), 0.5% paraformaldehyde 9% onion skin tannin-urea-formaldehyde resin, 5% CMS (cassava based), 0.5% paraformaldehyde
1.13
295.2
4233.55
20% resorcinol fortified onion skin tannin resin, 2% paraformaldehyde, 5% CMS (cassava based)
1.10
224.7
2939.56
15% mangrove bark tannin-urea-formaldehyde resin, 5% CMS, and 2% paraformaldehyde same as board 4 20% mangrove bark/onion skin tannin-ureaformaldehyde resin, 2% paraformaldehyde 10% resorcinol fortified onion skin resin + 10% mangrove tannin-urea-formaldehyde resin, 5% CMS 2% paraformaldehyde
1.07
185.2
2258.10
0.98 1.07
80 184.7
737.56 2252.10
1.09
204.7
2570.03
1.08
157.2
1756.07
commercial grade board
+
Generally the low bending strength or MOR of boards is due to very low ratio of span to board thickness. *Specific strength = (bending strength/specific
(corona, Landers and CIA, SA), sieved to remove the powdery materials and other fines by passing them through a 60-mesh sieve. The size distributions (1-5 mm) were oven dried to a moisture content of 12%. Adhesive Resins. The methods employed in the preparation of tannin-formaldehyde adhesives have been described elsewhere (Odozi et. al., 1986). Production of Particle Boards. Particle boards (panels) of about 0.5 in. thick were made as follows. A food-type vertical blade mixer was used for mixing, and during mixing binders and lignocellulose materials were added manually and as evenly as possible, for an average time of 5 min. Thereafter, a known weight of treated material was then put in an open iron mold for pressing, demolded, and allowed to air dry overnight. The temperature during the pressing operations ranged between ambient temperature to 120 "C for an average press time of 20 min and press pressure of 250-400 psi. Particle boards 1-3 and 6 were obtained by cold pressing, while 4, 5, and 7 were by hot pressing. Testing the Particle Board. Static bending strength was measured on dry and wet panels according to ASTM Method D1037-60T (1977), using an Avery Dension Universal Testing machine, but a very small ratio of span to board thickness was used in order to save materials (boards). Specific gravity was determined by the drop weight method, and all board samples were tested for affinity for water (water absorption) by the method described by Chawla and Shanker (1973).
Results and Discussion The characteristics of particle boards prepared from undebarked rubber wood and some lignocellulose wastes combinations are recorded in Tables I and 11. The boards obtained had a specific gravity of 0.98-1.13 and an average thickness of 0.5 in. Bending Strength. The most commonly encountered force by boards during service is the bending force. Thus, particle board, like other material, needs to be clearly defined in its specification and engineering properties (i.e., strength, stiffness, and stability) to be acceptable to designers. All boards were tested for bending strength. It is evident (Tables I and 11) that a number of boards have greater than 180 psi (more) and water absorption ( 2 h) of less than 6%.
Table 11. Water Absorption and Changes in Bending Strength of Boards on Immersion in Water b e n m strength (psi) after water absorption ( % ) for water a l m q t i o n for board 2h 5h 24 h 2h 5h 24 h 174.0 158.0 63.0 4.2 8.9 30.7 272.0 267.0 154.3 2.4 3.2 12.5 211.0 199.0 122.6 2.7 1.4 18.6 165.0 149.6 21.14 5.6 9.0 33.8 Cr Cr 40.0 60.0 35 154.4 26.7 5.8 9.7 34.5 167.0 8.2 29.0 174.0 88.4 3.1 191.0 145.2 58.9 "Cr = crumbled.
It may be seen also from Table I that the combination of undebarked rubber chips (%TO), wood shavings (25%), and mangrove bark (50%) gave boards with the highest bending strength. The combination of undebarked rubber chips (20%) and mangrove bark (80%)boards showed a somewhat lower bending strength. The reason for this difference is quite clear if the chemical and anatomical differences in the materials are taken into consideration. In this connection, Back and Lundqvist (1975) have reported that tree bark usually has a much lower content of cellulose, which is the most oriented and stiffest component of lignocellulose materials. Similarly, Stewart et. al. (1953) have in their report indicated a higher percent of phenolic acids and suberin for bark than wood. These factors may have been responsible for the lower strength values shown by board 1. By use of another binder (Table I), the combination of mangrove bark (25%), corn cobs (25%), wood shavings (25%),and bagasse (25%) gave values as high as 224 psi for bending strength. The relatively high strength values found for this combination (board 3) are to a large extent due to the amount and type of binder employed and to a lesser degree to the nature and presence of the bagasse. The case of binder type is made more evident by the lower strength values exhibited by boards 4 and 6, which were made by using tannin-urea-formal resins. To the contrary, board o formed by using tannin-resorcinol resin gave higher values. This result shows the effect of resin type to be much more important than it may be expected and suggests that it may be an essential factor in explaining the differences in
Ind. Eng. Chem. Res., Vol. 26, No. 9, 1987 1737 strength values between the boards. Furthermore, it has been reported that bagasse fiber, which is similar to cotton fiber, is highly hydrogen bonding, is crystalline, and therefore ought to offer greater resistance to mechanical forces. Specific Gravity and Weight to Strength Ratio. The specific gravity of lignocellulose material, because it is a measure of the relative amount of solid cellulose, is the best index that exists for predicting the strength properties. Table I shows the relationship of bending strength of boards with the specific gravity. From the table, it is clear that the bending strength varies in a direct proportional but not linear relationship to the specific gravity. A measure of the efficiency of wood-based material to resist stress is given by an index called the specific strength, which is the ratio of bending strength to specific gravity to the 1.5 power (Panshin and De Zeeum, 1970). The index referred to as weight to strength ratio is a useful parameter for the comparison of materials of differing specific gravity, employed to determine whether the differences are due to factors other than specific gravity. It may be seen in Table I that the specific strength values of the boards do not necessarily reflect the differences in specific gravity. It is of interest to note (Table I) that boards 4 and 6 having the same specific gravity values showed specific strength values of 2258.10 and 2252.10 psi, respectively. Similarly, boards 1 and 8 showed a wide variation in their specific strength values. The results obtained demonstrate that factors other than specific gravity account for the difference in the specific strength values. In the case of board 1,the additional strength may be due to high content of polymerizable tannin and lignin. Back and Lundqvist (1975) have reported similar observation. Taken together, the results show that board 2 based on 25% rubber chips possessed the highest strength to weight ratio. Wet Strength. Table I1 illustrates the change in bending strength of the various boards on immersion in water and shows a continuous loss of strength. Considering all the boards, board 2 appears to be better in strength retention. However, its ability to retain strength on continued immersion in water up to 24 h is marginally worse than board 3. As may be seen, the commercial grade board exhibited about 37% strength retention after 5 h of water immersion, while board 5 (formed without paraformaldehyde) crumbled within 5 h of water immersion. The results in Table I1 demonstrate the effect of increased
moisture content on board strength, and despite some scatter, it shows that a high water absorption leads to a high loss in strength. Water Absorption. The experimental data of the water absorption for the various boards tested after 2,5, and 24 h of water immersion are summarized in Table 11. Results indicate high water resistance for most boards, with board 2 showing the least absorption of only 12.5% after 24 h of immersion. Boards 1,4, and 6 appear to have high water absorption. This may be due to the fact that urea-formaldehyde adhesives are prone to deterioration by water, as reported by Pizzi and Scharfetter (1978). It is also seen in Table I1 that the percent water absorptions of board 5, prepared in the absence of paraformaldehyde, are very high, and the board even crumbled on continued immersion in water. In addition to the reason previously stated, the presence of compounds having greater affinity for water effectively contributes to the observed behaviors. I t is then obvious that the addition of paraformaldehyde is essential if the board is to be manufactured from these lignocellulose materials.
Conclusion Although too few data are available to make a complete statement about the performance of boards based on rubber wood chips, it however appears that increasing content of rubber wood in a given combination increases the bending strength value. Literature Cited Annual Handbook of ASTM, ASTM: Washington, DC, 1977; ASTM D1037-60T. Back, E. L.; Lundqvist, K. E. Suen. Papperstidn. 1975, 78, 157. Chawla, J. S.; Shanker, G. Chem. Ind. 1973, 19, 53-54. Coppens, H. A.; Santana, M. A. E.; Pastore, F. J. For. Prod. J . 1980, 30(4),38-42. Mobarak, F.; Nada, A. M.; Fahmy, Y. J. Appl. Chem. Bcotechnol. 1975,25,653-658. Odozi, T. 0.; Akaranta, 0.; Ejike, P. N. Agrzc. Wastes 1986, 16, 237-240. Pizzi, A. For. Prod. J. 1978, 28(12), 43-47. Panshin, A. J.; De Zeeum, C. Textbook of Wood Technology, 3rd ed.; McGraw Hill: New York, 1970; Vol. I, p 220. Pizzi, A.; Scharfetter, H. 0. J. Appl. Polym. Sci. 1978,22, 1745-1761. Stewart, C. M.; Ames, G. L.; Harvey, L. J. Aust. J . Bzol. Scz. 1953, 6, 21-47. Recezued for review February 10, 1986 Accepted April 30, 1987
