Wood and paper-base plastics

MISSING IMAGE

Material Information

Title:
Wood and paper-base plastics
Series Title:
Report ;
Physical Description:
9, 5 p. : ill. ; 26 cm.
Language:
English
Creator:
Stamm, Alfred J ( Alfred Joaquim ), b. 1897
Forest Products Laboratory (U.S.)
University of Wisconsin
Publisher:
U.S. Dept. of Agriculture, Forest Service, Forest Products Laboratory
Place of Publication:
Madison, Wis
Publication Date:

Subjects

Subjects / Keywords:
Wood   ( lcsh )
Paper, Plastic   ( lcsh )
Strength of materials   ( lcsh )
Genre:
federal government publication   ( marcgt )
non-fiction   ( marcgt )

Notes

Statement of Responsibility:
by Alfred J. Stamm.
General Note:
Caption title.
General Note:
"November 1943"--Cover.
General Note:
"In cooperation with the University of Wisconsin"--Cover.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 029318374
oclc - 755904630
System ID:
AA00020583:00001

Full Text
/l}\0


W UID ANLD PAIEI-EPASE PLASTICS
November 1943


No. IP1438






UNITED STATES DEPARTMENT OF AGRICULTURE
FOREST SERVICE
FOREST PRODUCTS LABORATORY
Madison, Wisconsin
In Cooperation with the University of Wisconsin






















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Impreg


A number of desirable pror.rties can be imparted to wood the for7-
ing of ".'thetic resins throu,:' out the structure from rrsin-formin;
constituents of low molecular weight that have an affinity for wood. Alt u;
the hardness and cn.ressive strer.rth properties of wood can be ..... "oved
by mechanically depositing any solid material within the structure,. -rmanent
dimensional stability and related properties have been successfully imparted
to the wood only with a few specific resinoids under sro'ific treating con-
ditions. This is due to the fact that materials such as fats, waxes,
natural resins, and orrrrciably pre-formed synthetic resins, because of :he1r
lar-'e molecular size an8 their lac1l- of polarity, under normal treatin- co--
diti -ns show no tendency to r-netrate the cell-wall structure of wood and,
no ter..ency to bond to the wood. Forest Products Laboratory tests have
shown that any water resistance these materials -ive to wood is entirely
mechanical in nature, Thev cut down the rate at which water can traverse
the structure but they do not change the final amount taken up and, conse-
quently, do not reduce the equilibrium swelling. Their failure to ace lish
this is cr in-rilv due to their lac'r of affinity for woed. O0e slight flaw
in an internal coating will allow water to work its wav between the fibrous
!.rtrjcture and thle coating and disperse itself throughout the continuous
structure. It thus becomes apparent that a treating material with an
affinity for the wood Treater than that of wood for water should be used.
Unfortunately, all such materials in themselves have a high affinity for
water. 71I s difficulty has been solved with treating a" -ts that are
selectively adsorbed within the intimate cell-wall structure of wood and
can subsequently be converted to water-insoluble resins wthin the w,'oc
structure while remaininT' permanently bonded to -che structure.

The most effective treating agent thus far found is a phenol-
for1malehde, water-soluble resinoid that is not advanced beyond the p, n ol-
alcohol s4-.,e. Resorcinol can be substituted for the phenol or furfrral for
the formal-o.r.yde without loss of effectiveness. All urea-formaldehyde
resinoids tried have proved to be too highly prepollv.erized to penetrate the
structure adequately, with the exception of demethylol urea. ven this
material when r -)lymerized within thie s ructure reduced the swellin" an!
shrin'" ir. on an m'uilibrium basis to only SO percent of -ormal in contrast
to reductions to 30 percent of normal effected b phenol-form,-l dehye resin.
None of the thermoplastic resins or thermoplastic resin-formin' systems thus
far tried have effectively reduced the swelling and sinin of wood
presumably because none of them have the desired affini'.' for the wood.

It was shown that the, chemical affinity' of wood for a resin-forrin
system can be 7au- by the de-ree to which the rs..-formin, solutn
swells r"','- -""ond the swelling caused by, water alone. A 40 percent
aqueous solution of a r! enol-foraaldiehyve resinold will swell wood about
20 percent more than dces water. '.nn this hiIhlYv swollen wood is dried
and the resin is formed within the structure by the a-.rltcation of heat,
considerably less than normal shrinkage occurs. .. ocen-dry treated wood
.. a volume about e,'.,i to that of the green untre ted o-:. .n an


R1438


-2-








am'"tj resin equivalent to 30 rrr.'.t of ".. r'., weig' of the '-'.I,. .
*"...,-' Io nt w ici. ca ses practically .. 1, -r .."'.-. r.. ct--+' on of .i.'.,llir:
:-, is rmed in the structure, ... s"cific graviiv i.
i ncrerseo m" a "'..t 18 percent rather r'' r p rent.

"i f 'ic' L '*"'." .. enric "' '. i or -"erly disr''l,., 'U r.-
5 'rmiur chemicals tr>- '..ut .- structure treatment a *. rs practical only for veneer. T..o value of anti-r-.r':.
r tmerts f '-. -'r w.icc is normally r :ilt into plr."-,-- r-) ,.. '-
uTj ic n +'*t". basis that, in cross-b~r.I',, p1l,-,vc''7, the ?-.^r dirbion
f one ply restraK-. the acr-.r -the-f"1ber di :,e ion :"}. -s of -'. '- . ..
ly, thus mechanicallv reducir. such c-.-r. ,..lli a.n:.-
ca nr ere y 'x es the direct ion of swell':*s .-. shrirn i: ,., the .-,.- ..
revte :.'orr swell ,- normally in the sheet directions it will ..-1l i.-
u tnckness direction or internally into the fi'-r cavities. "2.;-
JJ rma! Jlyoo" toKes up and then loses moisture, the plies are.c- .....-.11-.
xw r inr nd, as a result of the unevenly de,,elc:- sses, face o."- *"i:..~
is mFr serious than in solid boards. T.sin treatment, which -- .-'s "'.e
swe ]'- :nd shrirli. to about S ;s'rcent '.f normal, reduces o- --ses
t c sch an e;tnt that checrinr is ir-ctical el'y irn '., 7'." :'-e
ch ec'inr of fancy crotch veneer for use in f'.niture and rne]K".r ''a
.*?ila rv reduced treatment wit a '>-"- olic resin.

treatment of wood with stab lizin r'-si'.- also :-;'ts
arprecia"] e d'cay ana ter' cf roiu as-fir pl}wood with treate faces ." an untrea.-'' core, .:
srec mer was immersed for 6 months to a deart of half Its l-.-th in -
field where' ecay and termite action on wood are sB--,re, "*.-r*?r was lit>,
si'- of deeay, but plenty of termite action, .2. termites in a frontal
attack found the resin-treated >,ces not to their li'inr, so -...."ri a
:_' n" attack and, as a result, "r'."-tically cleaned out the untrea-'3 c r.?.
S2"i ay s.: irr.ens that were *' e coated w.'th resin '" those in which 11
he p1ies were treated were still sound after a 2-"-="r e.:- -urn. .*a
n.r'^e r'- cticr in decav and terrrite action, it a pears, is -.* rat.-r i-
.e fact that t"; treated wo-, will not take up enor wter wi" in -.
c e-, 1 ....1 struct.re to .... ort decay than to the toxicit of res"...

-rcatment of wo with sta1iliz"" resins increases its el,-c-
'ric'l rei st' c? rel 7 the r'du'>. A -ity ry is
an pxcel. e" electrical i sulator, but it loses its rest' e ;-" :"rties
r 7ly w tir increase in. os7 ,rp content, f.t .' -=rcent relati-e
nu-'itv e ectr cal resistance of the treated w. is about C tines
thIt of i trcla'rd w" whe ".t -rcent relati-e :dit' it ? about
1,'" *t +i:-es as' r^ sr
Re:in tr0 +t a7io ir>creeses "t' a*ci re of wco ''t it


rhi +re't-''t of wn with --rcent o- its we., -' of resin may
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S".'t sr' .- h is th one r ...'rtv that r- 4versey af' t. A
the resin content of wood is increased, it becomes more brittl4 I 2 ',
more uniform distribution of the resin also increases tt]on Unfortunetem,,, the best treatment 'trom the s tandn'o~in 0 of t+ ;*)'i za++ on i.-;
the p forest 'rom +the standnoint oO brittleness. rhra1 tir a
'.:a~t value of to 0 foot-pounds '.r inch '- ntch btt :en t-ret-id
with a stabilizinoR resin this value Irops to'-onl 2 to ft-no r
inch of note'

To surmmarize, impr'- has the +'ol owi.- advant.r.s oer or.a w"od
(s) redue swelinr-; (2) reduced chec^ina and surface dep"ra-;
resistance to dPcay and ter ites; (4) i..roved clec rica] r-wi sti ce;
(5) i :,roved cid resistance; nd () improved co 7-'essive s.rc:1t atr
hardness These ir rover'nts are secured at the r- --nse of Inc.rea
touf'hnes s.

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Compreg is re in-treated wood that is c r formed'within its structure. Altou,:1 a number of iffere. t rsns ove
been tried in mnakin, this materiall, none has proved as successful as n.. -
formaldehyde. There are two types of compreg; (l) teo older form.,
devel. -' in Eurc,-e, wlich is +reat'' with a spirit-soluble :nrlic 1 -es
prepol" Prized to the staae thit it does not tend to penetrrte the celi-
wall structure and bond to the polar groups o r the woo: nd, as F. resut,
does not stabilize wood arnreciablvy; () the form deve.o on'd the FYr
Frr'icts laboratory ch is treated with a water-sol1ble, phensl-
formalde&.,e resinoid, as in the case of ifpreg, so as to form the resin
throwhout the cell-waill, structure ?f the wood an ond it to t-e ac i -e
r-lar -roups of the wood. letter form of c-mpr(p is uch eore t'e
than the former 'ut tens to be nore brittle; i i'spee, i '.' 1o
decay and terl'ite resistance nd -cod elecrical res: sti ce.

orest rduts Irbrorrv comp-ee cas b c -t--ssed to -rtna-tv
the ultimate compression (specific -ravity of 15.3 to 14) ner a resure
of I,'' pounds per sqr ich, 'in pract'cal an-" species of woodr
The unstable form of cocpne on the cther hand, re'-nires prepssres :
2, -DO to 3,0.P( pounds nr square "nch to c t'e woo t 0 sa
A'-ree. There is 3 still I reader difference I n the prressres req i rer to
c '-17ss the wood of the stable anrd unstab-le forms to irtr drie t eres
of cPrression, Pra-ctical1v al the softwoods acl'iferous woods) ?nd the
softer hardwoods (dciduous woods) s' ch as cottor:7oo', basswo-, n -aspe,
can, when treated with a stab'c ]izi resin, be c aoprssed, to about ne-h. f:
their or+ -tial t. ickness under pressures as '' as 0 onds s u re
:nch, This Takres possible the coo resiion of o: re- facs r-n t- r
simultaneous assime.l- with an untreated o'r `ro r recur"d cor
rAut sli it com resosion of t;e core. "is t'/ne of *tria, i. s ws
..'r-.-.t rr i.-e for sestwar uses, cannot e a'e in one o--ration wen tie
Ses are treated with an opprecia"ly ol.' orize resin, s -hre is
little differential c, "r-:ssibiity between such treated rlius aad th e
Untreated plies.

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**"*.*,~o t- '. t ;K r". f'r1 ^f o "- ryg '" rely o'. '*i a*. b.:;.
:4"1 F tentia] finih 'L xists t. r utout the str cture.".1



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t -rnds to make the productt ,pore brittle. Under carefully cnnrol' oon-
iitions, the stable form of c--t-:4ep cin be made from birch with an Jz'.
i''"-.ct value of 5 to 7 fot-poun's per of notch, -. unsta.] m-
pr"g, on the other hand, will have an !zod nlue of 6 to 9 ft- nds
r..'-r inch of notch,

An -ortant feature of c ".m-.reg is that it can be made nfrn 'ro
varint. of woods, including such normally inferior species as cttonw:od,
and obtain a product with properties which approach the e timu. var ues
T. only species to be avoided are the naturally resinous woods, su&h as
southern pine, and those that are extremely difficult to treat, suc- as .

Compreg can be machined easily with metal-wor' ':.C: toI:s :ut "ot
with woodworki.- tools Because cf this, it is desirable to reogh ut
the shape of objects prior to compression, using woodworking t ols, and
then compress them to!the final -hr.pe- in some form of mold. A techni-...
for doinr. this has been developed at the Forest Products Laboratory.
*r.- ted, uncompressed plies are glued up into a blank of the correct siz
with a phenolic glue under conditions such that the treating resin is not
Scored and the bonding resin is but slightly cured. shearinp str neth
of such a block is not great but it is sufficiently strong so that it car
be carved or turned in such a manner that the final dimensions are obtained
in one plane but the thickness at ri-It andles to this lane is 1.1 to 3
Times the final dimensions. The carved blan-I is then nresserld in a s)lit
mold in the thickness direction. A Yichi,' company is using this method
to mold propellers for the ercund testin.r airplan -motors 'fir. 2)
and airplane aerial masts. An airplane tail wheel has been successfully
molded in this way so as to pass all static tests retirements (fig. 3,
lef-). 7- technique could be readily applied in the molding of pulley
and 7ear wheels by st-.-'ina out the correct sections in the plane of the
wheels from the individual plies and rotating these with respect to :ach
other in the assembly as desired, Although wood is not moldable in the
sense that a moldirii powder is, it is surprisior.-ly subject to molding
under pro'-r conditions.

A recently developed process of which nothing can at present be
divul.-d makes possible the production of a highly stable form of com-
pressed wood wi thout the use of any impregnating resin.


'' 11"."]i..



Lignin is "ature's plastic which cements the cellulose fibers of
wood t--ether, A mild hydrolysis treatment breaks the ellules-Ii".'
bond of ,wood, freeing the Irnin so that it can be ui-" to rep ond the
cellulose fibers together. '",cod waste, preferably hardwood sa"."-st or
mill waste, can re hylrolyzed *several different methodsT. *- rocJdure
which has received the -reatest atterntion at the Forest products Laboratoiry
is a hydrolysis with dilute sulfuric acid in a rotary di est-r at a steam
pressure of 135 to 2C(r pounds per su" re inch for 10 to 30 minutes.


P1438








,I l" "" -'"- I.his -rly.-,! r lroat-vnfn -,n
pi~les '--.,-L' "-,.-.. '.,- 41- rs7lulo.,e-li .: r,-i, .,.,_
-c"- the hcrreice ulo.-s to r-u,-.rs, ".-se su-. r; t.'-e-'rr ", '-. *'- 'icr ,
are v *. ....! out of the i.v,'rolz,:d wsrr and r, be t for-ertel to -rair r iec---.1
t .us *ivinr a valuable hypr..".-, .'7.. reos -. constit c. -?* o r' ierc,:-.t
f ^ weiAht f '-'" ori-i. -.l -.*.:--'. As result o the r.-'--Trl. -- of
t. c4llulose1 the li.-.:.i:? c,:-.t Ant is int re' .: to to 4a p rc',-.

,,>'ter drvi'.-, the iy ro '.'- ,d wood s ,'ite brash ," .. '"- rn: e Iv
rounr to a ,.','; er, -r'forsbly of .. o 100 nesh. Al4-.r '. the li--' -'
"'ro :'..- wood can e -'e to !"low suffici '-l', for the nold. o)f s--.e
st" Ie obh','ts Cerel', a-1inc small amounts c" water aoO -r. ss'-.- at
3" F, the ,how i, not aflc'.ate to -5've a 'Produrt th't is suffici'-]v.'
coherent to sta0-' lor.r water imersion. ",-r' similar re"2ts v.-.'r.? obt"tt.
w.1 nonresi0ous nl -ticizers eor lisnin were usedi- pce of .--ter, re
t ourh they did reduce the moldr1nr ..... eroture. It was hence f"w;.-
nercessary io use yuxiliKar"' rp.stics or nuastic-forpinph constituents,
t^et er with a o 'ticizer 1'or !i-rin, wvhet the r plastic -t -r' r1 -i'.-
not 'lso serve as such, "'*-*most suitable miterH;..) founO in the earl~.r
'vor1' tliat served both -u.* 3ti -r..- is a mixture of 8 ''--.eot aniline 9
renft f ,'f-ura], tore ,?r with '* "'ro nt ' co ..--. gI
amount of mold_ lubricant such as zinc stearate, .'ld products with oi
- I defi-,iti'n, water resistance, acid resistance, avd electrical ..
ochajnica' pr"--rties can be obta-,r.-' by r-ssr n t for 3 .',^P"
(in the cese of small objects) at 3,' to 4,i' '' "."- s "or si'," re ,.; e
Because the uro.)uct is semither ,- astic, it ust be cdoled .- *-*"*..>t ir.
the mold.

e flow of this mod'.- ",':-4'or is not so Freat as tht of not
- ner'l-rurpose co'snercial moldinp ....ers. {.s, tr -ther with 4 .or
that + ae roduct cannot 1e drawn hot from the ":-ess, led to '"r -,*r r*.serrcl.
or h ariciz of h'volz wood 'et -. ow oro'erties so I'- r
obt ined 'rave been with a m'-ollrf:"- noer coetain:- [ percent :' --.lli
r rsin and ".-.*rcoet ofV uyrrol-"'*. wood. "Vth this coo +Mion, the ]:'"
o -rti~es ayy1 the "-,---..rties of the rro uct ".re cr~roarab]e ,with th ose' &f
ner'1 -rc rose !oKI> .. copooi .'s cortain--. 0 o rcent of n-erno rc rr-ir,
Sndc of woo flour. f':.. ct tr''t o ].', .; f as r rue;. phenoli"
resin is : *uired with t-e hv'v.'" ed wood '< wt. wood our i
tha.t te li.r.in of the :'rol"-' wood '-'* "s hastic .r 'rties to
-" r o c t r


The :'"olv' w eood-r'..- olio '"osin "-oldi'i ora "or ve loyde'
,rodu' s with >lmri str"'.-l.s rar-' ''"3, C rounrs >3r
s-: r- irch, wa ..er K,'so- iors of onlv 0.2 to C.7 .-rcent ".'--r ,-. hours'
:1 "Tier ?on. i:r wat r, snr extr "'ly ":-.. acid resistance. It -rv rs to v'
l to "oil t'is z'.p er' 1 >nto t icer 'v r ^s ci
wie of nerp]-' "p ce con.ercia.l 'oh'i,- ... 'ers .: these
attributes, the t'-.terip', is now 'eel-- test in the 'oldin of .'zeabi.;
ob *+s o^ in^'.stri _] "rt .... -1,

If c i- ra+-her t.an j ':t",.:,. are '. -" 1 a" thc raw --' 'rial :l .-' ,.-
h '.rl" roduct i' ahradeo to f'.:,r ratiier t2r.r -rou1nd to a ':' 'or, i1








c..; "' formed into a sheet on the -riper machine. These sheets, i'h nIly
,.' .11 amount of r'i -nolic resin, can be c -"'ress- 1 tc. -ther into thick
Zp.n?].., Th,- panels have considerably hi -1 er flexural str .-ths tha pa+e:
m.i e t rom the molding powder because of the reinforcing acting of the r fc
icn-r-r cellulose fiber.


FPa preg


Paper laminates treated with r.Tenolic resins have been made for
",.rs r1. have been used chiefly for electrical insulating panel nd
for other nonstructural uses which do not require exceptional mechanic
pr-.erties. I'., manufacturers, in developing these materials, have
L T. ro:ached the problem primarily from the resin standpoint. It was hence
felt at the Forest Products Laborat'rv that further development of paer-
base laminates, from the standpoint of finding the most suitable *'..er for
the purpose, was a promising field of research. This proved to %e ti. c .*,
'"-thin 6 months after the research was started, a paper-base laminate was
developed that "-sses:.-3 several properties double those of the former
laminates.

The types of paper and modifications in nrocessin- cannot be piven
hero. It can be stated, however, that suitable papers are now beli' -
produced by several different paper mills*

Table 2 eives the readily obtainable properties of parallel-
laminated papreg as of november 1942, T-,-. term "parall l lam inated"
indicates that in all the sheets '-in- up the panel the machine direction
of the paper runs the same way. peor Tmade on a per machine is always
stronger in the machine direction than across the machine direction. -
difference may be as mich as twofold. "T,'n isotropic properties re
sou-1-i,, in the laminate, alternate sheets are crossed as in plvwood. Cross-
banded r proe' differs from pl.o.od and impreg nd conmpreg with plynwood
c- struction in that the strength properties ar" not so seriously re 'uced
below the values for parallel-laminated mraterial. Due to the fact that
veneer is from 20 to 40 times as strr -,- in tension in The fiber direct on
as across the fiber direction, the tensile strength of plwood depends
almost entirely on the lon-itudinal plies. Cross-banded papreg has
strength properties raniiir- from two-thirds to throe-fourths of th ose fir
the "- r'allel-l'.minated material, in contrast to the strength properties
of cross-banded c r 'z, which are only about one-half as a -h as its
parallel-laminated values. "any strength nr-'" rties of pVrallel-a inated
c--, reg and mrege are much the same. Cross-banded paprerpe is superior in
almost all stren't, properties to cross-banded compreg.

-.preg has sr': in properties adequ. te for 1 lar;e number of
semistructural uses and some structural uses. Ps structural ma-teri'l,
its brittleness seems to be its most serious n ricap. Co'pared to ori-
nary plastics, it has quite -:od Izod vlues, 'ut it is definitely`" er-,
ior in t.is res' --.t to fabric and 'class facric la- in r.--tes. It is, .er,
superior to fabric laminates in practicaIly all other strength properties,


R1438


-8-








se of s low elo--tion,". rr..-. Y rot easily '-.s]'r, d to
-: lp cur-v'aures Sre T brio laminates. It -"- been -j cc. .-":1'd,
1 ; ver, in "'old". of ,, i',- intricate ,*' .'*: ts with hut P. 1 i{ '- a oun
r-rirr rr ta 1tori'.r.

".r' is now underwsy o *ncornor t:-' other resi"-, both n"' r .I
n, .svnttiotic, ir .' r--" nlstics r"-imporily .'ren h stte"' int -,"
C! "-*..* t!:e product rnd Is wit *' obT "- ti ,e of huild ..- the
..- 'ves3 witho t too "r ..... scrifice in wrter resi' .'e 'nd their
m's1ch .ic.]" *''" ". .rti s. t, .il on tfhs :'1 se of the work c. nnot be ,-
't present,


Conclusi':;3


It is obvious from this 'rrai of products tht wood is .' n
'rt nt T1 oe for itself in* the plastics "e3.d, A4. wood :.its
costite ts ser mostly s the structural or filler irt : tese P>'--
rics, wod n w roducts s'. w promise of ir vad..- the resin "e"
Li nin .nd nsel (a rosin-..;rifictti on residue) show romise a s res In
diluents, I i aso of interest that "- -.-ls, furf.ral, and o-:. r "in-
'or '. ca sti ents "rr obt inble fror wooi' destructi'e distilltion
ald h..' ro nato n rocesses. It does not *' 'ire freo't "' ination to
isuli e asli:r-cont'i -" woo4 in.ustrv that uses wood almost i*llusivel.'
in thT "C iuf re of vwod r !la sties,


R14:38









S*ble 1, -*- or'". "'.-. i str ,.. -r- f

;* r T '1-1' .K.r: ; M r' r.; ,-" .... "^.


specific gravity of 1.351



Property : Talue

I. -r sq. in.

Tension:
Stress .t proportional l-it......: 22,000
t'xi s'. t: re'-- .. .. .. . ...... s 32,' -D
T'.r-dulus of e sticity. ............: 3,500,000

Flexure:
Stress at prorFrtional limit.......: 21,00'
odulus of rupture........... .. .; 36,000
!,:lus of elasticity.............. 3,[ *00

Compression parallel to -rain:
Stress -t proportional limit.. ..... 16,000
K aximur strength.0., 0.....,.. 24, )00
"'1 lus of elasticity....... "... ..: 3,5 ,

Johnson double sheor, parallel to
gra.in .nd r :r--ndicular to
laminations 7 )

:Ft.-lb. per in.
Izod ..,ct:2.
F notches 3 to
Edre-notched .... .................. 2 to 7


1-,
-7- rr perties ei^en, with the e"-ce' ion of i'oact
srreneth, are about the same for both stab,]ized
".nd unst ,bilized coiMprp7 -nd do not vary -ppre-
c....ly between species.
ITlhree to 7 foot-pounds per irch of notch for
st bilized comprer (face notched). Six to 9
foot-pounds -r'r inch of notch Por nnsthbilized
corprep (f ce-rotched).


R1438










~ble 2,-~-A-' ':-x *, r rt'o! r ".lle -l i.t

;r" ;Tr7


S'r-I'orty lue
-- - - - - - -- - - - -w- 4 -- - -


S"- **i e *r .vir ty. ,, ,....** *** .. **:

e

7,,! s ii o)'1; *


Nodulus of l u] tio *ty......4.......


Sexure-
'*'odulus Of o1" sticirev......,.... ... s


C .... ion:
r le to -r in. .. . ... .. :
FitV.se nerpenriculr to arin...:
S'1pewise perpendioulhr to T-ryin,...

Johns:on double shc.nr, --ralio' to :
r" in, ]:irv--" ]icul> r to
1''.mi n **t ions.



Iiz :['ct;
nce-notcned...... ., * * 9



Sr re-notere,. (24. .. n.... :
} c.rdne ss (K oc k'c 11),,..,. *.* .,,.,,:

". t er ''"s o r *i on (24 ;:*ou r s ).... ..:


I1 3.


* '- n'r *., -* i^.3,

1 "-' -




T t --,



-
3 ,! - ,' -





17,"; ".
r,0r:
1 r- (",


,** '
.92. *


5 9*"'


"" 1 ,


r .c ent


P143




r





























*1'











A ..'S
:0





















































Figure l.--Action of termites on 3-ply resin-bonded Douglas-
fir plywood with faces treated with 30 percent by weight of
synthetic resin (on the basis of the dry weight of the un-
treated wood) and an untreated core that was immersed to half
its length in a termite infested field. The core has been
2 M 51062 P almost completely eaten out up to the ground line while the
faces are perfectly sound.























* '- *! .5i





' 7'

. /. t
J "-^
:4'...i


z t: 51063 -


Figure 2.--A molded compreg propeller for testing airplane
motors that is being commercially produced by a Michigan com-
pany using the process developed at the FCrestI Products
laboratory.




I,


A


Figure 3.--Left to right, half of an airplane tail wheel
molded of compreg; a compreg specimen varying in specific
gravity from end to end (1.3 to 0.6); a model airplane pro-
peller molded of compreg; a cut panel of birch compreg
sanded and buffed to show that the finish exists throughout
the structure.


Z M 51064 1




UNIVERStTY OF FLORIDA
Iti2I 20892i5439nIII
3 1262 08925 4329



.1