Nonconventional Wood Preservation Methods - ACS Publications

4 Nonconventional W o o d Preservation Methods

Downloaded by UNIV OF PITTSBURGH on March 10, 2016 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0043.ch004

ROGER M. ROWELL Forest Products Laboratory,P.O.Box 5130, Madison, Wis. 53705

A most effective way to extend the Nation's timber supply i s to use wood so that its service life i s increased. The service life of wood i n hazardous use conditions can be increased severalfold by the proper use of wood preservatives. I t i s e s t i mated that the preservative treatment of railway ties results i n an annual savings of 2.4 billion board feet of lumber and that, if utility poles were not treated, an additional 20 m i l l i o n mature trees of pole-stock quality softwoods would be needed each year simply as replacements for those destroyed by decay and termites. Some 275 m i l l i o n cubic feet of wood are treated annually for protection against decay fungi, insects, or marine borers. Nevertheless, losses to these agents are still large and may amount to between $1 and $2 billion in the United States annually. These losses may be attributed to either inadequate or no preservative treatment. Although conventional preservatives are generally effective, they are coming under increasing attack because of their t o x i c i t y , so information is urgently needed on newer, safer, more environmentally acceptable, effective preservatives. A l l of the commercial wood preservatives presently used i n the United States are effective i n preventing attack by microorganisms because of their toxic nature. Most of these preservatives are c l a s s i f i e d as broad spectrum preservatives, that i s , effective against several different types of l i v i n g systems. Because of the toxic hazards and environmental concerns and because prevention of wood decay i s needed i f we are to extend our timber resources by increasing i t s service l i f e , we have i n v e s t i gated alternative methods of wood preservation not based on t o x i c i t y for their effectiveness. This paper i s not meant to present finished data as much as i t i s to present ideas, concepts and research approaches i n the area of new methods for wood preservation. For this discussion, a nonconventional preservation method w i l l be defined simply as a concept or process not presently i n use but with future potential.

Goldstein; Wood Technology: Chemical Aspects ACS Symposium Series; American Chemical Society: Washington, DC, 1977.


48

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TECHNOLOGY:

CHEMICAL

ASPECTS

C o n t r o l l i n g micro-organisms by means other than p o i s o n i n g them can be i n v e s t i g a t e d by c o n s i d e r i n g the b a s i c needs o f the organism. I n order f o r wood-destroying micro-organisms to t h r i v e , they r e q u i r e : (1) oxygen, (2) water, (3) food, i n c l u d i n g a l l e s s e n t i a l t r a c e compounds, and (4) a f a v o r a b l e environment. To e l i m i n a t e any one of these w i l l e f f e c t i v e l y c o n t r o l the growth of the organism. I t i s very d i f f i c u l t to r e s t r i c t the oxygen from microorganisms so c o n t r o l measures based on t h i s approach would proba b l y be f r u i t l e s s . Wood below the f i b e r s a t u r a t i o n p o i n t does not decay. Therefore, by r e s t r i c t i n g the amount of water i n the wood c e l l w a l l below the f i b e r s a t u r a t i o n p o i n t , the microorganisms w i l l not t h r i v e . R e s t r i c t i n g or e l i m i n a t i n g an e s s e n t i a l component i n the micro-organism food chain such as m e t a l s , v i t a m i n s , e t c . , would cause the organisms t o look elsewhere f o r nourishment. M o d i f y i n g the wood so the organism d i d not r e c o g n i z e i t as food would a l s o p r o t e c t i t from a t t a c k . I n h i b i t i n g the enzyme systems such as the c e l l u l a s e s unique t o those organisms capable of b r e a k i n g wood down would a l s o p r o t e c t the wood without the treatment being harmful t o humans. The f i n a l c o n s i d e r a t i o n , a f a v o r a b l e environment, would c a p i t a l i z e on c r e a t i n g a h o s t i l e environment f o r the organism. For h i g h e r organisms that destroy wood, such as rodents, deer, b i r d s , e t c . , r e p e l l e n t s , which are not t o x i c to the organisms, but because of t h e i r s m e l l , t a s t e , or t e x t u r e , cause the pros p e c t i v e d i n e r to leave the t r e a t e d m a t e r i a l alone. Changing the pH of the wood o r m a i n t a i n i n g a temperature above or below that r e q u i r e d f o r organisms to t h r i v e w i l l e f f e c t i v e l y c o n t r o l t h e i r growth. The problem w i t h t h i s approach i s that some of the c o n d i t i o n s which are not f a v o r a b l e f o r the organisms a r e a l s o not f a v o r a b l e to m a i n t a i n the d e s i r a b l e p r o p e r t i e s of the wood. For example, a t a low pH, the wood components undergo h y d r o l y s i s causing severe s t r e n g t h l o s s e s . In d i s c u s s i n g concepts f o r p r e v e n t i n g a t t a c k by organisms not based on t o x i c i t y , the mechanism of e f f e c t i v e n e s s q u i t e l i k e l y i s not based on any s i n g l e mechanism, but a combination of s e v e r a l f a c t o r s . For example, i n the d i s c u s s i o n to f o l l o w on chemical m o d i f i c a t i o n of wood, the mechanism f o r the p r o t e c t i v e a c t i o n may be due t o : (a) b l o c k i n g conformational s i t e s r e q u i r e d f o r the h i g h l y s p e c i f i c enzyme-substrate r e a c t i o n s to take p l a c e , (b) p l u g g i n g h o l e s i n the l i g n i n - h e m i c e l l u l o s e s h i e l d p r o t e c t i n g the c e l l u l o s e , (c) s t a b i l i z i n g l a b i l e polymer u n i t s which may be the p o i n t of the fungus f i r s t a t t a c k , (d) removal of s o l u b l e chemicals i n the wood which a r e r e q u i r e d by the micro-organisms to s t a r t or s u s t a i n the a t t a c k , (e) changing the wood-water r e l a t i o n s h i p as to be i n i m i c a b l e t o m i c r o b i a l l i f e , and (f) combinations of these or other p o s s i b i l i t i e s . 1


4.

ROWELL

Research

Nonconventional

Wood

Preservation

49

Methods

Approaches

A. I r r a d i a t i o n . Ponderosa p i n e , red and white oak, sweetgum and D o u g l a s - f i r have been t r e a t e d w i t h h i g h l y p e n e t r a t i n g gamma r a d i a t i o n emitted by C o b a l t i n an attempt t o a l t e r the polymer s t r u c t u r e of the wood. A f t e r i r r a d i a t i o n of the wood, the decay r e s i s t a n c e was determined u s i n g : (a) the s o i l - b l o c k t e s t employing the fungus P o r i a m o n t i c o l a ( P o r i a p l a c e n t a ) (Madison 698) (1) o r agar-block t e s t s using L e n z i t e s trabea (Gloeophyllum trabeum) (Madison 617) ( 2 ) . R a d i a t i o n l e v e l s from 1 0 - 1 0 reps showed no change i n decay r e s i s t a n c e i n the i r r a d i a t e d wood over n o n i r r a d i a t e d c o n t r o l b l o c k s . I t has been found by s e v e r a l workers (3-5) that the primary e f f e c t s o f high-energy r a d i a t i o n on wood polymers are d e p o l y m e r i z a t i o n , d e c r y s t a l l i z a t i o n , and degradation. I t would be expected that the e f f e c t s o f i r r a d i a t i o n would cause a decrease i n the decay r e s i s t a n c e o f wood r a t h e r than an i n c r e a s e . B. Thiamine D e s t r u c t i o n . F a r r e r (6) showed that one o f the e s s e n t i a l m e t a b o l i t e s f o r f u n g a l growth, thiamine, was destroyed i n 2 hours a t 100°C a t pH 7. At the same temperature but a t pH 8, d e s t r u c t i o n was complete i n 1 hour and a t pH 9 i n 15 minutes. These r e s u l t s encouraged B a e c h l e r , et_ a l . (7_,8) t o t r e a t wood w i t h e i t h e r ammonia or sodium hydroxide to presumably destroy the thiamine, thus p r o t e c t i n g wood by removing an e s s e n t i a l t r a c e compound so long as o u t s i d e sources of thiamine were excluded. D o u g l a s - f i r , b i r c h , southern p i n e , and sweetgum b l o c k s were t r e a t e d w i t h 1% aqueous ammonia o r sodium hydroxide f o r v a r i o u s times, temperatures, and pressures ( 9 ) . These samples were subm i t t e d to s o i l - b l o c k t e s t s w i t h two brown-rot f u n g i P o r i a monticola (Madison 698) and L e n t i n u s l e p i d e u s (Madison 534) and two w h i t e - r o t f u n g i Polyporus v e r s i c o l o r ( C o r i o l u s v e r s i c o l o r ) (Madison 697) and _P. anceps (F 784-5) as w e l l as o u t s i d e exposure t e s t s (10). I n the s o i l - b l o c k t e s t s , the t r e a t e d wood was r e s i s t a n t to the two brown r o t t e r s , but was not r e s i s t a n t to the two white r o t t e r s . I n the outdoor stake t e s t s , the average l i f e time was 3.5 years w h i l e untreated c o n t r o l s had an average l i f e time o f 3.6 y e a r s . The outdoor t e s t s show that there i s no i n crease i n r o t r e s i s t a n c e by t h i s treatment. C. Heat Treatments. S e v e r a l woods have been heated under wet and dry h e a t i n g c o n d i t i o n s to determine the e f f e c t heat has on the decay r e s i s t a n c e of these woods. Alaska-cedar, A t l a n t i c white-cedar, b a l d cypress, D o u g l a s - f i r , mahogany, redwood, white oak, S i t k a spruce, and western redcedar were heated under dry c o n d i t i o n s o r wet c o n d i t i o n s a t temperatures of 80-180°C f o r v a r y i n g lengths o f time. Boyce (11) found that dry heat a t 100°C or steam heat a t 120°C f o r 20 minutes had no e f f e c t on the decay r e s i s t a n c e . S i m i l a r r e s u l t s were observed by Scheffer and E s l y n (12) i n s o i l - b l o c k t e s t s w i t h L e n z i t e s trabea f o r the heated softwoods and Polyporus v e r s i c o l o r f o r the heated hardwoods. Thus, heat treatments do not i n c r e a s e the decay r e s i s t a n c e of the 6 0


z


7


50

WOOD

TECHNOLOGY:

CHEMICAL

ASPECTS

h e a t - t r e a t e d wood. I n some cases, a s l i g h t l o s s i n decay r e s i s t a n c e was observed. D. P l a s t i c Composites. Many d i f f e r e n t woods have been t r e a t e d w i t h o r g a n i c monomers and the monomers c a t a l y t i c a l l y polymerized w i t h i n the wood s t r u c t u r e . The s u b j e c t of t r e a t i n g wood t o form p l a s t i c composites i s covered by Dr. John Meyer i n another s e c t i o n of t h i s p u b l i c a t i o n . For the most p a r t , these composites have been prepared and s t u d i e d f o r t h e i r use i n dimen s i o n a l - s t a b i l i z e d products ( f o r example, see 13-17). Southern p i n e , D o u g l a s - f i r , and y e l l o w p o p l a r stakes were impregnated w i t h p h e n o l i c r e s i n and cured (impreg) o r impregnated w i t h p h e n o l i c r e s i n , compressed, and cured (compreg). Separate samples were t r e a t e d w i t h urea-formaldehyde and cured. These samples were p l a c e d i n the ground and t h e i r average l i f e t i m e determined. The r e s u l t s a r e shown i n Table I ( 1 8 ) . Table I . Average L i f e t i m e of Resin-•Impregnated Wood i n Ground Contact Treatment

Retention Lb/ft

3

Average

Life

ΧΕ

—

Ι.8-2.7

Impreg-phenolic r e s i n

5

6.8-11.7

Impreg-phenolic r e s i n

10

12.4-19.5

Compreg-phenol r e s i n

10

19.5

6

9.1

Control

Urea-formaldehyde

Ε. R e p e l l e n t s . I t i s q u e s t i o n a b l e whether a r e p e l l e n t would have any e f f e c t on micro-organisms, but they have been s t u d i e d f o r a p p l i c a t i o n f o r p r o t e c t i n g wood a g a i n s t higher l i f e forms. The amount of damage to wooden s t r u c t u r e s each year by animals i s c o n s i d e r a b l e . The b a s i c approach here i s to r e p e l the p r o s p e c t i v e d i n e r , not to k i l l i t . Various r e p e l l e n t s have been t e s t e d f o r d i f f e r ent animals (19). S o l u t i o n s or s l u r r i e s of these compounds have been p a i n t e d on wooden s t r u c t u r e s . Since no bonding to the wood components takes p l a c e , these r e p e l l e n t s are leached, v o l a t i l i z e d , broken down, and weathered out of the wood. A new approach i n t h i s area i s to encapsulate the r e p e l l e n t i n a r e s i s t a n t or slow r e l e a s e s h e l l . This way there i s very l i t t l e , i f any, r e p e l l e n c y u n t i l the animal comes i n t o contact w i t h the wood. T h i s contact causes the s h e l l to be broken and r e l e a s e s the r e p e l l e n t . The slow r e l e a s e type would slowly break



4.

ROWELL

Nonconventional

Wood Preservation

Methods

51

down and r e l e a s e the r e p e l l e n t over a p e r i o d of time depending on the s t a b i l i t y or weathering c h a r a c t e r i s t i c s of the capsule. The encapsulated chemicals could be added to a d i s p e r s a n t or p a i n t and a p p l i e d to the wood s u r f a c e . I f the capsules could be made small enough, deep p e n e t r a t i o n by pressure impregnation might be possible. F. Bound Toxins. Another approach to more environmentally acceptable p r e s e r v a t i v e s i s to c h e m i c a l l y bond a t o x i c compound onto a wood component so that i t cannot be leached out. The compound, once r e a c t e d , would have to r e t a i n i t s t o x i c p r o p e r t i e s . Compounds now used as wood p r e s e r v a t i v e s are t o x i c to the organism because they are ingested by the organism. I f the t o x i c compound were bound to the wood, they may be t o x i c to the organism only when ingested. Because of t h i s , the approach of perman e n t l y bound t o x i n s may not be a f r u i t f u l research area. I t i s a l s o p o s s i b l e to r e a c t a c i d c h l o r i d e s (20) or anhyd r i d e - c o n t a i n i n g compounds so as to form e s t e r bonds w i t h hydroxy1 groups on one of the wood components. E s t e r bonds could s l o w l y hydrolyze and r e l e a s e the bound t o x i n . In t h i s case, the r e l e a s e of the p r e s e r v a t i v e s would be a f u n c t i o n of the r a t e of h y d r o l y s i s and not d i r e c t l y r e l a t e d to weathering e f f e c t s ( f o r example, water s o l u b i l i t y , vapor pressure, UV degradation, e t c . ) . C o n t r o l l e d r e l e a s e f u n g i c i d e s based e i t h e r on slow h y d r o l y s i s or capsule e r o s i o n could g r e a t l y decrease the q u a n t i t y of preservat i v e needed to adequately p r o t e c t a wooden s t r u c t u r e , s i n c e l e a c h i n g could be c o n t r o l l e d . G. M e t a b o l i c D i f f e r e n c e . Micro-organisms a t t a c k wood by s e c r e t i n g enzymes i n t o the immediate s t r u c t u r e which i n t u r n break down the wood components i n t o s m a l l , s o l u b l e u n i t s that become n u t r i e n t s f o r the organism. The main d e s t r u c t i v e enzyme system the wood-rotters c o n t a i n i s a c l a s s of p r o t e i n s known as c e l l u l a s e s . These enzymes break down *~he polymeric c e l l u l o s e , the strong backbone of wood, i n t o d i g e s t i b l e u n i t s . Humans do not possess t h i s enzyme system; consequently, we cannot degrade cellulose-containing materials. C a p i t a l i z i n g on t h i s metabolic d i f f e r e n c e between higher forms of l i f e and micro-organisms i s the b a s i s f o r t h i s research approach to wood p r o t e c t i o n . Compounds are a v a i l a b l e which i n h i b i t the c e l l u l a s e enzyme systems ; however, t h e i r s p e c i f i c i t y has not been determined. MandeIs and Reese (21,22) found that the e x t r a c t s from the immature f r u i t of persimmon or the e x t r a c t from leaves of bayberry were very e f f e c t i v e i n h i b i t o r s of the c e l l u l a s e system. At c o n c e n t r a t i o n l e v e l s of .00005 and .00018%, r e s p e c t i v e l y , these two e x t r a c t s i n h i b i t e d the c e l l u l a s e enzymes i s o l a t e d from Trichoderma v i r i d e . I t i s not known what the a c t i v e component(s) are i n these two e x t r a c t s . New m a t e r i a l s need to be i n v e s t i g a t e d as p o s s i b l e s p e c i f i c i n h i b i t o r s to the c e l l u l a s e enzymes. This research approach w i l l r e q u i r e the screening of chemicals a g a i n s t pure enzyme s o l u t i o n s of known a c t i v i t y . S p e c i f i c i t y must be determined using a



52

w o o d t e c h n o l o g y : c h e m i c a l aspects

v a r i e t y of human-type enzymes such as t r a n s f e r a s e s , phosphoryl a s e s , dehydrogenases, e t c . U l t i m a t e success w i l l depend on f i n d i n g compounds which are only i n h i b i t o r y to the c e l l u l a s e enzymes. A more b a s i c approach to t h i s area would be to study the c e l l u l a s e enzymes themselves. I f the a c t i v e s i t e s and t r u e nature of t h i s p r o t e i n were known, s e l e c t i v e i n h i b i t i o n could be d e t e r mined . H. Chemical M o d i f i c a t i o n . The chemical m o d i f i c a t i o n of wood i n v o l v e s a chemical r e a c t i o n between some r e a c t i v e p a r t of a wood component and a simple s i n g l e chemical reagent, w i t h or w i t h out c a t a l y s t , to form a covalent bond between the two. The wood component may be c e l l u l o s e , h e m i c e l l u l o s e , or l i g n i n . The o b j e c t i v e of the r e a c t i o n i s to render the wood decay r e s i s t a n t . The mechanism of the e f f e c t i v e n e s s i s not known, but some p o s s i b l e explanations were given e a r l i e r . By f a r the most abundant r e a c t i v e chemical s i t e s i n wood are the hydroxyl groups on c e l l u l o s e , h e m i c e l l u l o s e , and l i g n i n . The types of covalent chemical bonds of the carbon-oxygen-carbon type that are of major importance are e t h e r s , a c e t a l s , and e s t e r s . The ether bond i s s t a b l e to bases, but l a b i l e to a c i d s , and the e s t e r bond i s l a b i l e to both a c i d s and bases. The t r e a t e d wood must s t i l l possess the d e s i r a b l e p r o p e r t i e s of untreated wood; the s t r e n g t h must remain h i g h , l i t t l e or no c o l o r change (unless a c o l o r change i s d e s i r a b l e ) , good e l e c t r i c a l i n s u l a t o r , not dangerous to handle, g l u a b l e , p a i n t a b l e , e t c . For t h i s reason, the chemicals to be considered f o r the m o d i f i c a t i o n of wood must be capable of r e a c t i n g w i t h wood h y d r o x y l groups under n e u t r a l or m i l d l y a l k a l i n e v-onditions at temperatures below 120°C. The chemical system should be simple and capab l e of s w e l l i n g the wood s t r u c t u r e to f a c i l i t a t e p e n e t r a t i o n . The complete reagent molecules should r e a c t q u i c k l y w i t h the wood components y i e l d i n g s t a b l e chemical bonds that w i l l r e s i s t weathering (23,24). These chemicals, once r e a c t e d , are e f f e c t i v e i n preventing a t t a c k by micro-organisms, but they are not t o x i c to the decay organisms. The important f a c t o r i n preventing a t t a c k i s to a t t a i n a treatment l e v e l which i n h i b i t s the growth of the organisms. A recent review on t h i s subject (23) shows that r e a c t i o n w i t h a c e t i c anhydride, dimethyl s u l f a t e , a c r y l o n i t r i l e , butylène oxide, phenyl isocyanate, and β-propiolactone a l l give good r o t r e s i s t ance at 17-25 weight percent gain (WPG). The exception to t h i s i s formaldehyde where a 2-5 WPG gives decay r e s i s t a n c e . I n t h i s case, there may be c r o s s l i n k i n g of l a r g e r wood u n i t s which gives i t d i f f e r e n t p r o p e r t i e s (25). Figure 1 shows that the decay r e s i s t a n c e of a c e t y l a t e d wood i s d i r e c t l y p r o p o r t i o n a l to the WPG (26). The degree of dimen s i o n a l s t a b i l i t y i s a l s o p r o p o r t i o n a l to the WPG so the e x c l u s i o n of c e l l w a l l or b i o l o g i c a l water may be a very important f a c t o r i n the decay r e s i s t a n c e mechanism.


4.

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Nonconventional

Wood Preservation

Methods

53

The average s e r v i c e l i f e of a c e t y l a t e d y e l l o w b i r c h and cyanoethylated southern pine stakes i n ground contact i s shown i n Table I I ( 2 7 ) . Table I I . Average L i f e t i m e of Chemically Wood i n Ground Contact Treatment

--

Control Downloaded by UNIV OF PITTSBURGH on March 10, 2016 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0043.ch004

L e v e l (WPG)

Acetylation

19.2

—

Control

Modified

Average L i f e

(Years)

2.7 17.5 3.6

Cyanoethylation

11

3.9

Cyanoethylation

15

5.3

I n p r e l i m i n a r y t e s t s , a l k y l e n e o x i d e - t r e a t e d southern pine (28) was found to be r e s i s t a n t to t e r m i t e a t t a c k and a t t a c k from the marine b o r e r s , Teredo (shipworm) and Limnoria. I . B a s i c Mechanism of A t t a c k . The u l t i m a t e s o l u t i o n f o r p r e v e n t i n g a t t a c k by micro-organisms w i l l come once we know how an organism breaks wood down. How does the organism know wood i s something to eat? What does i t recognize f i r s t t o s t a r t the a t t a c k ? What enzymes are v i t a l i n the i n i t i a l and sustained attack? I s there a s p e c i f i c weak l i n k i n those important enzymes that can be used to develop s e l e c t i v e i n h i b i t o r s ? I t i s a l s o p o s s i b l e that enzymatic r e a c t i o n s are not the only degrading r e a c t i o n s i n the d e t e r i o r a t i o n of wood by organisms. F i g u r e 2 shows i n the l e f t hand graph that only a 10-15% weight l o s s occurs i n the f i r s t 2 weeks of a t t a c k by brown-rot f u n g i . The graph on the r i g h t , however, shows that w i t h only a 10% weight l o s s , there i s a drop i n the average degree of p o l y m e r i z a t i o n of the h o l o c e l l u l o s e from 1,600 to 400 (29). This represents a f o u r - f o l d decrease i n DP, which a f f e c t s the strength of the wood w i t h very l i t t l e t o t a l weight l o s s . These r e s u l t s would i n d i c a t e t h a t , a t l e a s t i n the i n i t i a l a t t a c k , h y d r o l y t i c chemical r e a c t i o n s p l a y an important p a r t . I t has been suggested that hydrogen peroxide and i r o n a r e the cause of t h i s r a p i d depolymerization (30). I t i s p o s s i b l e that the i n i t i a l a t t a c k by micro-organisms i s not enzymatic but hydrol y t i c and o x i d a t i v e i n nature. I f t h i s i s t r u e , then a preservat i v e system could be based on a n t i - o x i d a n t p r o p e r t i e s of the chemical. I f the i n i t i a l a t t a c k can be stopped, then the t o t a l a t t a c k has been stopped. I t i s a l s o p o s s i b l e t h a t the i n i t i a l and sustained a t t a c k s are caused by a combination of chemical


54

WOOD TECHNOLOGY: CHEMICAL ASPECTS


40

r

WEIGHT PERCENT GAIN Figure 1.

Figure 2.

Decay resistance of acetylated wood

Action of brown-rot fungi on pine


4.

ROWELL

Ν unconventional

Wood

Preservation

Methods

55

(hydrolytic, oxidative, etc.) and enzymatic reactions.


Conclusions The purpose of this paper was to plant seeds for thought in the area of new methods of wood preservation, which are not based on broad spectrum toxicity for their effectiveness. The present concern for our environment has created the opportunity for re search in this area to find alternative wood preservatives which are effective in preventing attack by organisms and, at the same time, not harmful to the environment or man. Chemical modification of wood does result in a treatment which is nontoxic, effective, and nonleachable. The high chemi cal treatment level required for effectiveness, however, results in a rather expensive treatment. Dimensional stability is also obtained at these high (17-25 WPG) substitution levels so, for those products where both rot resistance and dimensional stability are important, the present state of the technology is close to a viable industrial process. Toxic chemicals which are permanently bound to the wood com ponents may be an environmentally acceptable preservation method. The actual effectiveness of a bound toxicant, however, s t i l l needs to be investigated. The encapsulation of preservatives is another interesting area for research. Procedures for encapsulation, capsule properties, and capsule size are important factors to be deter mined. Slow release fungicides by means of hydrolyzable link ages is also an interesting possibility. Basic knowledge of the nature of the attack of micro organisms on wood, the enzymes involved which are unique to micro-organisms, the chemical reaction which takes place in the i n i t i a l and sustained attack, and an investigation of specific inhibitors for these reactions is the most promising long-range approach. Literature Cited 1. Scheffer, T. C., Forest Prod. J . (1963), 13(5): 208. 2. Kenaga, D. L., and Cowling, Ε. Β., Forest Prod. J . (1959), 9(3): 112-116. 3. Lawton, E. J., Bellamy, W. D., Hungate, R. Ε., Bryant, M.P., and Hall, Ε., Science (1951), 113: 380-382. 4. Saeman, J . F., Millett, M. A., and Lawton, E. J., Ind. Eng. Chem. (1952), 44: 2848-2852. 5. Mater, J., Forest Prod. J . (1957), 7(6): 208-209. 6. Farrer, K.T.H., J . Proc. Austral. Chem. Inst. (1941), 8: 113. 7. Baechler, R., Forest Prod. J . (1959), 9(5): 166-171. 8. Gjovik, L. R., and Baechler, R. Η., Forest Prod. J . (1968), 18(1): 25-27. 9. Highley, T. L . , Phytopathology (1970), 60(11): 1660-1661.


56 10. 11. 12. 13. 14.


15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30.

WOOD TECHNOLOGY: CHEMICAL ASPECTS Comparison of wood preservatives i n stake tests, USDA Forest Service Research Note FPL-02 (1975), 52. Boyce, J. S., Jr., J. of Forestry (1950), 48(1): 10. Scheffer, T. C . , and Eslyn, W. Ε., Forest Prod. J. (1961), 11(10): 485-490. Stamm, A. J., Forest Prod. J. (1959), 9(3): 107-110. Stamm, A. J., and V a l lier, Α. Ε., Forest Prod. J. (1954), 4(5): 305-312. Meyer, J. A., and Loos, W. Ε., Forest Prod. J. (1969), 19(12): 32-38. Loos, W. E., Wood Sci. & Tech. (1968), 2(4): 308-312. Choong, E. T., and Barnes, Η. Μ., Forest Prod. J. (1969), 19(6): 55-60. Ref. 10, 22: 13. Hampel, C. A., and Hawley, G. G., "The Encyclopedia of Chemistry," Van Nostrand Reinhold Co., 3rd ed., p. 968, 1973. A l l a n , G. G., Chopra, C. S., Neogi, Α. Ν., and Wilkins, R. M. Tappi (1971), 54(8): 1293-1294. Mandels, Μ., and Reese, E. T., Ann. Rev. of Phytopathology (1965), 3: 85-102. Mandels, Μ., and Reese, E. T., "Enzymic Hydrolysis of C e l l u lose and Related Materials," The MacMillan Co., New York, e d . , Ε. T. Reese, pp. 115-157, 1963. Rowell, R. M., Proc. Amer. Wood-Preservers Assoc. (1975), 71: 41-51. Rowell, R. M., Amer. Chem. Soc. Symp. Ser. No. 10 (1975), pp. 116-124. Stamm, A. J., and Baechler, R. Η., Forest Prod. J. (1960), 10(1): 22-26. Goldstein, I. S., Jeroski, E. G., Lund, Α. Ε., Nielson, J.F., and Weaver, J. W., Forest Prod. J. (1961), 11(8): 363-370. Ref. 10, 52: 26. Rowell, R. M., and Gutzmer, D. I., Wood Sci. (1975), 7(3): 240-246. Cowling, Ε. Β., "Comparative Biochemistry of the Decay of Sweetgum Sapwood by White-Rot and Brown-Rot Fungi," USDA Forest Service Tech. Bull. No. 1258, p. 50, 1961. Koenings, J. W., Wood & Fiber (1974), 6(1).


Nonconventional Wood Preservation Methods - ACS Publications

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