Cellulose Models for Formaldehyde Storage in Wood: Carbon-13

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Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on May 14, 2016 | http://pubs.acs.org Publication Date: August 8, 1986 | doi: 10.1021/bk-1986-0316.ch006

Cellulose Models for Formaldehyde Storage in Wood: Carbon-13 Nuclear Magnetic Resonance Studies B. Meyer, K. Hermanns, and V. Baker Chemistry Department, University of Washington, Seattle, WA 98195 13C-NMR spectra of water soluble cellulose model compounds indicate that formaldehyde is capable of reacting with wood cellulose functions under hot press conditions as well as at room temperature yielding hemiacetals. The formation of hemiacetals is reversible, and thus constitutes a reservoir for formaldehyde storage. Due to its affinity for water, formaldehyde released during the manufacture of UF-resin bonded products will be retained in the aqueous phase of wood. Wood contains about 9 wt% of moisture. Most of this is in the S-2 secondary cell walls that consist mainly of wood cellulose. Even though formaldehyde release from UF-bonded wood products has been studied for more than 25 years, only very little is known about how formaldehyde is stored in UF-bonded wood products. In fact, it is not even known whether storage of formaldehyde is a physical or a chemical process. Formaldehyde is gaseous at room temperature, but it can polymerize forming para-formaldehyde, and it readily dissolves in water forming methyIenegIycoI (2)_. The most likely physical =storage process is absorption by moisture. Water is present in wood in two forms (1^: free water in the cell cavities in form of liquid and vapor, and bound water absorbed on cellulose in the S-2 layer of the secondary cell walls. Under standard conditions of 25UC and 50% RH wood contains a total of 9.2 wt% water. The most likely chemical process is the reaction of methyIenegIycoI with wood cellulose at the interphase on the secondary cell surface in the S-2 layer. There have been contradictory reports about the reaction of wood with formaldehyde from UF-resins. At room temperature, and up to the boiling point of water, wood absorbs only very little formaldehyde. Thus, gine chips treated with 35 wt% formaldehyde solution for 30 min at 160 C retain less than 0.01 wt% formaldehyde (3). Forest products scientists generally assume that UF resins do not bond to wood (4). However, at higher temperatures, wood absorbs formaldehyde and irreversibly changes its physical properties. Thus, after 15 hrs of exposure at 120 C, 7 wt% formaldehyde is retained by solid oak and causes a 50% reduction in swelling (5-8). Since wood cellulose i s 0097-6156/ 86/ 0316-0067$06.00/ 0 © 1986 A m e r i c a n C h e m i c a l Society

Meyer et al.; Formaldehyde Release from Wood Products ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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r e l a t e d t o c o t t o n c e l l u l o s e , i t i s r e l e v a n t t o note t h a t t e x t i l e c h e m i s t s have e s t a b l i s h e d e x t e n s i v e p r o o f t h a t formaldehyde can r e a c t w i t h c o t t o n c e l l u l o s e (9^10) and c a n c r o s s - 1 ink c e l l u l o s e under t e x t i l e f i n i s h i n g c o n d i t i o n s , i . e . d u r i n g 3-5 min exposure a t 150 C. These c o n d i t i o n s a r e s i m i l a r t o plywood and p a r t i c l e b o a r d p r e s s i n g conditions. The purpose o f t h i s c h a p t e r i s t o d e s c r i b e e x p l o r a t o r y 13C-NMR s t u d i e s o f f o r m a l d e h y d e - c e l l u l o s e r e a c t i o n model systems. S o l i d s t a t e NMR s p e c t r a a r e s t i l l c o m p a r a t i v e l y broad and do n o t r e v e a l a s much d e t a i l a s s o l u t i o n s p e c t r a ( 1 1 ) . F u r t h e r m o r e , s o l i d s t a t e NMR s t u d i e s a r e s t i l l cumbersome, and s i n c e no r e f e r e n c e s a r e a v a i l a b l e on s o l i d s t a t e s t u d i e s o f c e l l u l o s e - f o r m a l d e h y d e i n t e r a c t i o n s , we conducted an a n a l y s i s o f model systems f o r c e l l u l o s e t h a t a r e water s o l u b l e . T h i s paper r e p o r t s r e a c t i o n s o f formaldehyde w i t h methanol, e t h y l e n e g I y c o I , some s e l e c t s u g a r s , and e e l l o b i o s e . Aqueous

Formaldehyde

Formaldehyde i s q u a n t i t a t i v e l y absorbed i n water and h y d r o l y z e s t o y i e l d methyIenegIycoI: CH =0 + H 0 2

2

=

H0-CH -0H

(1)

2

Depending upon c o n c e n t r a t i o n methyIenegIycoI p o l y m e r i z e s a t room t e m p e r a t u r e i n aqueous s o l u t i o n (2) f o r m i n g polymethoxy methyIenegIycoI: H0-CH -0H * H0-CH -0H = H 0 - ( C H - 0 ) - 0 H * 2

2

2

(2)

n

The NMR spectrum o f t h i s system i s now w e l l e s t a b l i s h e d ( 1 3 ) . The most prominent 13C-NMR peaks a r e l i s t e d i n T a b l e I .

T a b l e I . 13C-NMR Peaks o f Methanol-FormaIdehyde Compound

HO- (trL-0) -OH Z

n

1

n

2 3 4 5 6 7 CH 0-(CH 0) -OH 1 1 22 3 Q

3

o

2

Derivatives

n

Methano I-Forma Idehyde

SO 86.6 88.9

91.6 89.2 92.3

92.1 92.5 92.7 92.9

90.7 94.5 94.5 95.2

83.7

Reaction

By f a r t h e s i m p l e s t p o s s i b l e model system f o r c e l l u l o s e i s t h e r e a c t i o n o f monovalent a l c o h o l s such a s methanol w i t h formaldehyde. T h i s system i s p r e s e n t i n aqueous phase i n commercial f o r m a l i n s o l u t i o n s t h a t a r e made by p a r t i a l o x i d a t i o n o f methanol. These


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s o l u t i o n s c o n t a i n about 37 wtX formaldehyde and 10-12 wt% methanol ( 2 ) . The formaldehyde i s p r e s e n t i n form o f a m i x t u r e o f methylene g l y c o l and p o l y m e t h o x y m e t h y l e n e g l y c o l , H0-(CH -0) "0H, and methoxypo I ymethoxymethy I eneg I y c o I, C H - 0 - ( C H - 0 ) - 0 H , o r even dimethoxy poIymethoxymethyIenegIyco I, CH3-0-(CH2-0)"-0-CH . These methoxy compounds a r e formed by c o n d e n s a t i o n : 2

3

2

n

n

3

CH 0H * H0-CH -0H = CH -0-CH -0H + H 0


3

2

3

2

(3)

2

Methoxy compounds can a l s o be c o n s i d e r e d a s h e m i a c e t a l s o f t h e t y p e R-0-CH -0H. The f o r m a t i o n and even t h e h y d r o l y s i s k i n e t i c s o f t h e s e compounds was s t u d i e d a s e a r l y as 1937 ( 1 2 ) . T h e i r presence enhances t h e s o l u b i l i t y o f formaldehyde i n water/ The c o r r e s p o n d i n g 13C-NMR s p e c t r a (13) a r e shown i n F i g u r e 1 and t h e s h i f t s a r e l i s t e d i n T a b l e I. S i m i l a r spectra are obtained f o r higher a l i p h a t i c alcohols. 2

E t h y l e n e GIycoI-FormaIdehyde R e a c t i o n The 13C-NMR spectrum o f t h e r e a c t i o n o f e t h y l e n e g l y c o l , i . e . e t h a n e d i o l , w i t h m e t h y l e n e g l y c o l i s shown i n F i g u r e 2. 13C-NMR s h i f t s a r e included i n Table I I . I t i s known t h a t , upon h e a t i n g , t h i s system can y i e l d methylene e t h e r b r i d g e d r i n g s . T h i s r e a c t i o n i s c a t a l y z e d by a c i d s o r bases. The p r o d u c t , d i o x o l a n e , b o i l s a t 76 C. A l t e r n a t i v e l y , p o l y a c e t a l s a r e formed ( 1 4 ) . However, s t u d y i n g t h e s e m i x t u r e s under room t e m p e r a t u r e c o n d i t i o n s we f i n d t h a t i n n e u t r a l s o l u t i o n and under our c o n d i t i o n s t h e main p r o d u c t s a r e hem i a c e t a I s : H0-CH -CH -0H • H0-CH -0H = H0-CH -CH -0-CH -0H • HgO 2

2

2

2

2

(4)

2

These compounds form r a p i d l y a t room t e m p e r a t u r e w i t h an e q u i l i b r i u m c o n c e n t r a t i o n depending on t o t a l and r e l a t i v e c o n c e n t r a t i o n o f a l l r e a g e n t s . The r e a c t i o n i s r e v e r s i b l e and r e l e a s e s formaldehyde upon d i l u t i o n . The r e s u l t i n g 13C-NMR s h i f t s a r e shown i n F i g u r e 2 and a r e included i n Table I I .

Table I I .

Compound

C

H0-CH -CH -0H Glycerol Erythritrol Mannito 1 Glucitol EG-0-CH--0H CH 0-(Cr1 0) -0H 2

3

2

2

13C-NMR Peaks o f Aqueous E t h a n e d i o l - F o r m a I d e h y d e D e r i v a t i ves

2

l

63.84 64.0 64.0 64.6 63.8 50.0 55.6

C

2

73..5 73..3 72..2 74..3

C

3

64.0 73.3 70.7 71.0

C

4

64. 0 70..7 72..6

C

5

72.2 72.5

90..5


C

6

64.4 64.2


MG


H O - C H

HA

90

MG

2

- 0 - C H

3

HA

9

70

ppm

ROH

50

F i g u r e 1. 13C-NMR spectrum o f 1 wt% formaldehyde and methoxy f o r m a l d e h y d e w i t h 0.5 w t % methanol. MG = m e t h y l e n e g l y c o l ; HA h e m i a c e t a l s ; ROH = methanol; 67.4 = p-dioxane s t a n d a r d .

70

ppm

F i g u r e 2. 13C-NMR spectrum o f e t h a n e d i o l - m e t h y l e n e g l y c o l m i x t u r e s . EG = e t h y l e n e g l y c o l ; MG = methyIenegIycoI; peaks a t 61.5, 69.6, and 89.5 ppm a r e h e m i a c e t a l s .


6.

M E Y E R ET

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Sugar-FormaIdehyde P e n t a e r y t h r i t r o l , m a n n i t o l , and s o r b i t o l r e a c t r e a d i l y w i t h formaldehyde i n t h e presence o f z i n c c h l o r i d e c a t a l y s t y i e l d i n g 1,2; 2,4, and 5,6 a c e t a l b r i d g e s . A c c o r d i n g l y , sugar can absorb up t o 5 moles of f o r m a l d e h y d e , but a p p a r e n t l y not a l l i s c h e m i c a l l y bonded (2). A s e r i e s of a u t h o r s have long n o t i c e d t h a t e v a p o r a t i o n of an aqueous sugar s o l u t i o n c o n t a i n i n g formaldehyde y i e l d s odor f r e e p r o d u c t s . I t was proposed t h a t t h e p r o d u c t s m i g h t be h e m i a c e t a l s (15) , but no e x p e r i m e n t a l e v i d e n c e was produced. The s t u d y of i n t e r a c t i o n between s u g a r s and formaldehyde i s c o m p l i c a t e d by t h e many t y p e s o f p r o d u c t s t h a t can be formed. The l i t e r a t u r e abounds w i t h r e p o r t s of such p r o d u c t s , but none of t h e s e p r o d u c t s has y e t been i s o l a t e d and c h a r a c t e r i z e d . We have conducted e x p l o r a t o r y e x p e r i m e n t s w i t h hexose compounds t h a t were r e a c t e d w i t h formaldehyde (16) . The 13C-NMR s p e c t r a c l e a r l y show t h a t t h e p r o d u c t s c o n t a i n h e m i a c e t a l s and e t h e r b r i d g e s , but t h e r e s u l t s a r e not y e t c o n c l u s i v e s i n c e t h e a s s i g n m e n t s of 13C s p e c t r a a r e not y e t unambiguous (16,17). CeI Iob i ose-FormaIdehyde The s t r u c t u r e of e e l l o b i o s e and i t s 13C-NMR spectrum a r e shown i n F i g u r e 3a. The s p e c t r a have been i d e n t i f i e d (18-20). C e I l o b i o s e i s water s o l u b l e . F i g u r e 3b shows t h e spectrum of r e a c t i o n p r o d u c t s w i t h formaldehyde a t d i f f e r e n t molar r a t i o s o b t a i n e d by 15 min r e a c t i o n a t 150 C, i . e . under c o n d i t i o n s t h a t c o r r e s p o n d t o t h o s e d u r i n g t h e manufacture of UF-bonded wood p r o d u c t s . As e x p e c t e d , formaldehyde can r e a c t w i t h s e v e r a l d i f f e r e n t f u n c t i o n a l groups. T h e r e f o r e , complex m i x t u r e s of p r o d u c t s a r e formed. I n t e r p r e t a t i o n of Model Compound R e a c t i o n s In wood, as i n a l l of t h e above model compounds, t h e formaldehyde a b s o r p t i o n and subsequent r e a c t i o n depends on t h e presence of an aqueous phase. T h i s phase may be a monomolecu Iar l a y e r of water on the c e l l s u r f a c e , o r water on t h e c u r e d U F - r e s i n f i l m , but t h e l a r g e s t r e s e r v o i r of water i s w i t h i n t h e wood c e l l . As i n d i c a t e d , wood may c o n t a i n two t y p e s of water: (a) f r e e o r c a p i l l a r y water, and (b) bound water ( 1 ) . The bound water i s l o c a t e d i n t h e S-2 l a y e r o f the secondary c e l l w a l l s t h a t expand and s h r i n k as water i s absorbed or r e l e a s e d . The thermodynamics o f t h e water a b s o r p t i o n a r e w e l l e s t a b l i s h e d and a r e summarized i n F i g u r e 4. The water a b s o r p t i o n mechanism can be e x p l a i n e d by two t y p e s of models. One assumes t h a t water forms a s o l u t i o n on t h e c e l l u l o s e l a y e r . T h i s t y p e o f model i s e x e m p l i f i e d by t h e HaiIwood-Horrobin t h e o r y ( 1 2 ) . The o t h e r assumes water a b s o r p t i o n on i n t e r n a l s u r f a c e s . T h i s model i s a m o d i f i c a t i o n of t h e Brunauer, Emmett and T e l l e r (BET) t h e o r y (21) t h a t has been expanded by Dent. Water i n wood can be o b s e r v e d and a n a l y z e d w i t h p r o t o n NMR (23-25). When formaldehyde i s r e l e a s e d from UF r e s i n d u r i n g hot p r e s s i n g a t 150-190 C and e l e v a t e d p r e s s u r e , t h e vapor p r e s s u r e i s s u f f i c i e n t l y l a r g e t o produce formaldehyde vapor t h a t m i g r a t e s from the hot p r e s s p l a t t e n towards t h e c o r e of t h e p r o d u c t as t h e t e m p e r a t u r e g r a d i e n t t r a v e l s t o t h e c o r e of t h e p r o d u c t ( 2 5 ) . Thus, formaldehyde permeates t h e p r o d u c t and some o f i t emanates from t h e p r o d u c t edges j o i n t l y w i t h t h e steam t h a t i s produced a t t h e same



72

1

0.2CB + 0.6F

^

F


J 0.I5M

C-B 6b,a

11"100

80

PPM

60

F i g u r e 3. 13-NMR spectrum o f e e l l o b i o s e , (a) 0.15 M s o l u t i o n , and (b) 0.2 M s o l u t i o n c o n t a i n i n g 0.6 M methyIenegIycoI. D o t t e d peaks a r e due t o r e a c t i o n p r o d u c t s .

100

300

cal /g

200-

100

2 0 % Moisture F i g u r e 4. Thermodynamics o f water a b s o r p t i o n on wood c e l l u l o s e . Q = h e a t o f s o r p t i o n ; G = f r e e energy; TS = e n t r o p y term; M i s t h e e x p e r i m e n t a l l y o b s e r v e d water s o r p t i o n i s o t h e r m ( a f t e r r e f e r e n c e 32).



6.

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t i m e . D u r i n g t h i s p r o c e s s formaldehyde vapor w i l l p e n e t r a t e wood c e l l s p r i m a r i l y t h r o u g h c e l l c a v i t i e s , even though i t i s f e a s i b l e f o r i t t o p e n e t r a t e t h e c e l l w a l l by d i f f u s i o n ( 3 2 ) . D u r i n g t h e c o o l i n g of t h e p r o d u c t t h e water c o n t e n t o f wood may be s u f f i c i e n t l y h i g h t o l e a v e t e m p o r a r i l y some l i q u i d water i n t h e c e l l c a v i t i e s , even though c e l l c a v i t i e s a r e n o r m a l l y d r y i n a l l e x c e p t green wood. I n t h i s c a s e , f o r m a l d e h y d e , due t o i t s p r o p e n s i t y f o r water a b s o r p t i o n , would c o l l e c t i n t h e c e l l c a v i t i e s . I n any c a s e , whenever formaldehyde r e a c h e s t h e i n t e r i o r o f t h e wood c e l l i t w i l l be s t r o n g l y a t t r a c t e d and p r e f e r e n t i a l l y bound i n t h e water l a y e r on t h e s u r f a c e o f t h e S-2 c e l l u l o s e l a y e r o f t h e secondary c e l l w a l l s . T h i s t r a n s p o r t o f formaldehyde from U F - r e s i n t o t h e c e l l u l o s e l a y e r w i l l c o n t i n u e d u r i n g coo I-down o f t h e p r o d u c t which n o r m a l l y t a k e s more than a day. Once formaldehyde reaches t h e bound water l a y e r i n t h e S-2 c e l l w a l l s i t i s a v a i l a b l e f o r r e a c t i o n w i t h t h e c e l l u l o s e s u r f a c e . Our e x p l o r a t o r y e x p e r i m e n t s i n d i c a t e t h a t such r e a c t i o n i s indeed e x p e c t e d , t h a t i t causes f o r m a t i o n o f h e m i a c e t a l s , r e a d i l y reaches e q u i l i b r i u m , and i s r e v e r s i b l e . The c o n c e n t r a t i o n o f formaldehyde bound i n form o f h e m i a c e t a l w i l l depend on t h e c o n c e n t r a t i o n o f water as we I I as t h a t o f formaldehyde. S i n c e t h e water c o n c e n t r a t i o n depends on r e l a t i v e h u m i d i t y o f t h e s u r r o u n d i n g a i r , t h e c o n c e n t r a t i o n o f water i n t h e S-2 l a y e r , and, i n t u r n , t h e c o n c e n t r a t i o n o f t h e formaldehyde s o l u t i o n and t h e h e m i a c e t a l l a y e r w i l l change as a f u n c t i o n o f s u r r o u n d i n g a i r h u m i d i t y . The mechanism and k i n e t i c s o f t h i s r e a c t i o n f o l l o w t h o s e f o r o t h e r a c e t a l s (26) and are i n c o m p e t i t i o n w i t h t h o s e o f U F - r e s i n f o r m a t i o n (27-29) s t e p s . The h y d r o l y s i s o f t h e former i s p r o b a b l y e a s i e r t h a n t h a t o f t h e l a t t e r ( 3 0 ) , and comparable t o t h e h y d o l y s i s o f poIyoxymethyIene compounds ( 3 1 ) . The k i n e t i c s a r e s t r o n g l y pH dependent. The pH depends on t h e wood s p e c i e s , t h e b u f f e r c a p a c i t y o f t h e r e s i n , and the n a t u r e o f t h e c a t a l y s t used ( 2 7 ) . I f we c o n s i d e r a s an example a r e l a t i v e a i r h u m i d i t y o f 50% and a t e m p e r a t u r e o f 25°C, t h e wood m o i s t u r e c o n t e n t would be 9.2 wt% (33) . I f we f u r t h e r c o n s i d e r t h a t t h e p r o d u c t m a n u f a c t u r i n g p r o c e s s leaves about 1 wt% o f t h e formaldehyde c o n t e n t o f t h e UF r e s i n a s u n r e a c t e d f o r m a l d e h y d e , we o b t a i n f o r p a r t i c l e b o a r d o r medium d e n s i t y f i b e r b o a r d (MDF), where U F - r e s i n makes up 6-10 wt%, an approximate formaldehyde c o n c e n t r a t i o n o f 0.2 M i n t h e S-2 c e l l o f t h e wood. This i s s u f f i c i e n t f o r p a r t i a l conversion t o eel Iulose-hemiacetal, w i t h a r e s i d u a l formaldehyde c o n c e n t r a t i o n o f l e s s than 0.1 wt% i n the c e l l water. T h i s formaldehyde c o n c e n t r a t i o n i s enough t o produce an e q u i l i b r i u m vapor p r e s s u r e o f 20 T o r r o f formaldehyde (34) i n t h e wood c e l l . The k i n e t i c s o f t h e formaldehyde r e l e a s e from water a r e a I so pH dependent ( 3 5 ) . T h i s vapor a c t s a s a d r i v i n g f o r c e f o r formaldehyde d i f f u s i o n from t h e wood c e l l towards t h e p r o d u c t s u r f a c e , and f o r e m i s s i o n from the f i n i s h e d wood p r o d u c t . An i n t e r n a l vapor p r e s s u r e o f 20 T o r r would a p p r o x i m a t e l y c o r r e s p o n d t o a formaldehyde a i r c o n c e n t r a t i o n of about 1 ppm a t 25 C, a load f a c t o r of I m and a v e n t i I a t i o n r a t e o f 1 a c h . However, as e m i s s i o n c o n t i n u e s and d e p l e t e s t h e methylene g l y c o l c o n c e n t r a t i o n i n t h e wood m o i s t u r e , t h e d i s s o c i a t i o n o f h e m i a c e t a l s w i l l s e t i n and add t o t h e formaldehyde s o u r c e . The b o t t l e n e c k i n t h e formaldehyde t r a n s p o r t w i l l be d i f f u s i o n through the p r o d u c t towards t h e p r o d u c t s u r f a c e . T h i s p r o c e s s depends on t h e p e r m e a b i l i t y o f t h e p r o d u c t w h i c h , i n t u r n , depends on d i f f u s i o n



74

FORMALDEHYDE RELEASE FROM WOOD PRODUCTS

through the wood, and diffusion through the air gaps between wood chips or wood layers that make up the product. Under normal product use conditions, the air humidity and product temperature will constantly fluctuate and pass through daily and seasonal cycles. This will cause changes and reversals of formaldehyde concentration gradients and formaldehyde transport within the product. The limiting kinetic step is likely the moisture diffusion through wood. It is well established that conditioning of wood for reaching moisture equilibrium may take several days to a week. Thus, real-life formaldehyde emission is not always strictly an equilibrium process and real-life conditions are determined by formaldehyde following water transport. An extreme example for such a process may occur in buildings that contain particIeboard, hardwood plywood or urea-formaldehyde insulation foam (UFFI) in contact with a wall cavity that contains improper moisture barriers. Under such conditions sunshine can heat the wall sufficiently to cause moisture to migrate in a daily cycle through the walls, starting in the morning in the east and ending in the evening in the west, while carrying formaldehyde vapor along. Summa ry Due to its affinity for water, formaldehyde will concentrate in wood products in their water reservoirs. Since wood collects water in its S-2 secondary wall on the surface of wood cellulose, formaldehyde will come into contact with wood cellulose. This work shows that formaldehyde can be expected to react with wood cellulose forming hemiacetals. Since this reaction is reversible, these hemiacetals constitute a temporary reservoir for formaldehyde within wood. This fact may explain the complex formaldehyde release and absorption properties of UF-bonded wood products. Literature Cited 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

Skaar, C. "Wood-Water Relationships"; Adv. Chem. 1984, 207, 127172. Walker, J. F. "Formaldehyde"; ACS Monograph Series 159, 1964. Ginzel, W. Holz Roh-Werkstoff, 1973, 31, 18-24. Johns, W. ACS Symp. Proc. 1986, ___, Chapter Stevens, M.; Schalk, J.; van Raemdonck, J. Int. J. Wood Preservation, 1979, 1,(2), 57-68. Burmester, A. Holz Roh-Werkstoff, 1971, 29(3) 97-102, and (5) 184-188. Stamm, A. J. Tappi 1959, 1, 39-44. Schürch, C. Forest Prod. J. 1968, 18(3), 47-53. Steele, R.; Giddings, Jr., L. E. Ind Eng., 1956, 48, 110-114. Cooke, T. F.; Dusenbury, J. H.; Kienle, R. H.; Linekin, E. E. Textile Res.J. 1954, 24(12), 1015-1035. Kottes-Andrews, B., ACS Symp. Proc. 1986, , Chapter Haw, J. F.; Maciel, G. Holzforschung 1984, 38, 327-331. Löbering, J.; Fleischmann, A. Ber. 1937, 70, 1680-1683, and 1713-1719. Dankelman, W.; Daemen, J. M. H. Anal. Chem., 1976, 48, 401. Dankelman, W.; Daemen, J. M. H.; de Breet, J. J. Angew. Makromol. Chem, 1976, 54, 187.


6.

14. 15. 16. 17.


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MEYER ET AL.

Cellulose Models for Formaldehyde Storage in Wood 75

Petryaev, E. P.; Gergalov, V. I.; Kalyazin, E. P.; Glushonok, G. K. Ukr. Khim. Zh., 1979, 45(9), 868-871 (C.A. 1980, 92, 40961). Contardi, A.; Ciocca, B. Rend. Inst. Lombard. Sci, 1936, 69, 1057. Gagnaire, D.; Mancier, D.; Vincedon, M. Org. Magnetic Resonance 1978, 11(7), 344-349. De Bruyn, A.; Anteunis, M.; Verhegge, G. Bull. Soc. Chim. Belg. 1975, 84(7), 721-734. Hall, L. D.; Morris, G. A.; Sukumar, S. J. Am. Chem. Soc. 1980, 102, 1745-1747. Angyal, S. J.; Le Fur, R., Carbohydrate Research, 1980, 84, 201209 and 137-146. Hall, L. D.; Morris, G. A.; Sukumar, S. J. Am. Chem. Soc. 1980, 102, 1745-1747. Brunauer, S.; Emmett, P. H.; Teller, E. J. Am. Chem. Soc. 1938, 60, 309-319. Dent, R. W. Textile Res. J. 1977, 47(2), 145-152 and (3), 188199. Nanassy, A. J., Wood Sci, 1973, 5, 187-193. Sharp, A. R.; Riggin, M. T.; Kaiser, R.; Schneider, M. H. Wood and Fiber, 1971 10(2), 74-81. Hsi, E; Vogt, J; Bryant, R. G. J. Coll. Interface Science 1979, 70(2), 338-345. Cordes, E. H.; Bull, H. G. Chem. Rev., 1974, 74, 581-603. Glutz, B. R.; Zollinger, H. Helv. Chim. Acta. 1969, 25, 19761984. Petersen, H. In "Chemical Processing of Fibers and Fabrics"; Marcel Dekker: New York, 1982. O'Connor, C. Quart Rev. 1970, 24(4), 553-564. Vail, S. L. Text. Res. J. 1969, 39(8), 774-780. Stanonis, D. J.; King, W. D.; Vail, S. L. J. Appl. Polym. Sci. 1972, 16, 1447.32. Siau, J. F. "Transport Processes in Wood"; Springer-Verlag: New York, 1984. "Wood Handbook," U.S. Forest Products Laboratory, Agriculture Handbook No. 72, U.S. Department of Agriculture, 1974. Meyer, B. "Urea-Formaldehyde Resins"; Addison-Wesley Publishers: Reading, MA, 1979; p. 31. Bell, R. P.; Evans, P. G. Proc. Royal Soc. 1966, 291A, 297-329.

RECEIVED January 14, 1986


Cellulose Models for Formaldehyde Storage in Wood: Carbon-13

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