Glues for use in aircraft


Material Information

Glues for use in aircraft
Series Title:
Report ;
Physical Description:
2, 1 p. : ; 26 cm.
University of Wisconsin
United States -- Forest Service
Forest Products Laboratory (U.S.)
U.S. Dept. of Agriculture, Forest Service, Forest Products Laboratory
Place of Publication:
Madison, Wis
Publication Date:


Subjects / Keywords:
Airplanes -- Materials   ( lcsh )
Glue   ( lcsh )
federal government publication   ( marcgt )
non-fiction   ( marcgt )


General Note:
Cover title.
General Note:
"October 1941"--Cover.
General Note:
"This report is one of a series issued to aid the nation's war program."
General Note:
"In cooperation with the University of Wisconsin."

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 029321604
oclc - 756002798
System ID:

Full Text


October 1941

I U S DEP-- 'T(- "Y

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No. 1337

Madison, Wisconsin
In Cooperation with the University of Wisconsin

I iii' jr


The glues that are adapted for gluinf wood in aircraft 7jV.
conveniently be divided into five classes, as follows: (1) srnthetic-
resin glues, (2) casein glues, (3) blood albumin Flues, (4) marine
glues, and (5) miscellaneous adhesives.

Synthetic-resin and casein glues are most important for nir-
craft. Blood-albumin glues were formerly of importance in producing
water-resistant plywood but they have been largely displaced by syn-
thetic-resin glues. Blood albumin may be encountered, however, as
filler or extender of synthetic-resin glues2. Synthetic-resin 'lues
are used chiefly in the production of plywood. In the fabrication of
other parts and in the assembly of the finished craft, casein rnd cold-
press resin glues will find use. Marine glues are used in wooden float
and hull construction but not for making joints where high strentrtn is

Synthetic-resin glues are based on resins synthesized from
various chemical compounds. Of the many t-pes of synthetic resins,
only two have found wide use as woodworking adhesives. Of the two, the
most highly resistant to moisture is the condensation product formed
by the reaction of an aldehyde (usually formaldehyde) and a phenol
(usually phenol or cresol). The product of the reaction between urea
and formaldehyde is not so highly resistant to all types of exposure
as the phenol-aldehyde product but, in a glue line, its resistance is
superior to that of casein glue and it is widely used in woodworking.
In preparing these products for use as adhesives, the reaction between
the chemicals is stopped at an intermediate stage in which the product
may be applied on the veneer, the plies assembled, and the reaction
completed under simultaneous application of heat and pressure (hot
pressing). Some are applied in the form of a film, some as aqueous
suspensions or solutions, and others in alcohol solution. A few are
available that can be anplied and pressed at room temperatures (cold
pressing). These depend on the addition of "catalyst" or "lhardmnr"
to cause the condensation reaction to proceed at room temperatures.

Casein glues are a mixture of casein and other materials
(usually lime and one or more sodium salts) combined in such propor-
tions as to dissolve the casein and produce a mixture of satisfactory
properties. The casein itself is a variable product, and the use of
different ingredients in varying proportions results in glues of widely

-This mimeograph is one of a series of progress reports issued by the
Forest Products Laboratory to aid the Nationts defense -ffort.

2Animal, vegetable, liquid, soybean, and flour-extended resin -lues,
which are extensively used in other wood-working industries, are not
suited for aircraft work.

Mimeo. NTo. 1337

differin- properties. A markc-d diff-rr,.:c., exists in "';ter --
a property of ve-ry re,,t .importance in aircraft, since only thr, nore
water-resistant .-lues shoul- 'e used for this purpose.

'-Ilo-), -1bimin -lucr_ m,'.ar'n with ar albuninous base obt-,in-d
fro-:m the blool I of nnirrals, combined 'ith chemicals, such as lime, crus-
tic 30.o:1, sodium nilicat-', paraformtal,--hy-.o, etc. Th' albumir. is
usually 'ou.-ht in dry form.

:tarino .-lue used in aircraft construction is solely for the
purnose of r.a'in. hulls !nd floats, constructed of '-oo- nlan-in,-, vat,-r-
proof. The F-lue, their fore, must havi- g-ood dIhnsive q-.iwlities, rL'.iin
tqiky in all climates, nn. be of such consist.-nc.' is to rc-r.ctrgte fabric
of high thr-ad coinrit. In -en.-ral, marine rlue should contain the follow-
ing ir.-rrelients: Rosin, noino tar, denaturedi -lcohol, ar.' a dryirn-; oil
(Tun, oil, rosin oil, or linseed oil), the proportions of which are
left entirely to the mrinufacturer.

:iscellpn-ous alhesives. Vef-etabl proteins, such as soy-
bepn 'and pe-nut, serve !.: bases for adhesives, which iin genral
properties r'2se-.ble casein liues. Sor.e of them have a -ooi degree of
-7ater resists-nce, moderate dry strength, and are rrlstively che,-,. in
their present st-,-3 of develonm-nt they do not quite equal thn strength
of the better-auz-lity casein flues. Other mrnterinls, incluiir1. cellu-
lose cements, asphalts, g, and rubber have b-'er: tr-e- as adhesives
for wood. In their present forms these materials are not suitable as
l.-ue for wood joints, although some of therm ma:" have ro-ibilities of
development, and an improvement in one or more re-,oects m?y :
use in aircraft desirable.

Properties of glues. A comparison of syr.tnetic resin, c-sein,
nnd blood ,Ilbiur.i: -lVies is m.nde in the acomrrn'in table. It should
be rcm.,:.berc.,, however, that there is a Vide variation anonr tne -:lucP
of any o.f these classes and that the comparison nrnlies ,-.eIv to th,
stror.--nt rnd most durable of each class.


Properties of glues used in aircraft

Property or Casein glue Blood albumin glue Synthetic resin glue

Strength (dry)2 :Very high to high :High to low :Very high to high
Strength (wet after soaking :About 25 to 50 percent of dry :About 50 to nearly 100 percent of :Very high; nearly 100 percent
in water 48 hours) : strength -- varies with glue: dry strength of dry strength

Durability in 100 percent
relative humidity or pro-
longed soaking in water

Rate of setting

Working life

Consistency of mixed glue

Temperature requirements

Mixing and application

Tendency to foam

Tendency to stain wood

Dulling effect on tools

Spreading capacity-
Extremes reportedA
Common range

:Deteriorates eventually --
rate varies with glue

:Rap id
:Few hours to a day

:Medium to thick; little
change with temperature
:Mixed cold with water;
: applied cold by hand or
: mechanical spreaders

:Slight if not mixed too
:Pronounced with certain wo

:Moderate to pronounced

55 to 80
:6 to 60

:Deteriorates slowly but usually
completely in time

:Very fast with heat

:Few to many hours

:Thin to thick; little change
with temperature
:Heat required to set most glues
;Usually mixed cold with water; ap-
: plied cold by hand or mechanical
: spreaders

:Slight to pronounced

ods :None, except dark glue may show
through thin veneers


30 to 100

:Very high If resin is un-
9 adulterated

:Very fast with heat

:Few to several hours for
: liquid forms; several weeks
: for films
:Medium for liquid forms

:Heat required for most glues
:Often applied as received or
: after addition of "catalyst";
: liquid forms best applied by
: rubber-covered rolls

:None, although glue may
penetrate through thin or
porous veneers


30 to 100
35 to 50

lGrades and quality only of glues that pass aircraft specifications.
2Based chiefly on Joint strength tests.
2Based on plywood strength tests.
tExpressed in square feet of single glue line per pound of dry glue for veneer work.
5Based on reports from manufacturers of various commercial products.

z A 37648 F

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