Effect of boiling for various periods of time on the strength of joints in birch plywood bonded with urea glue fortified...

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Material Information

Title:
Effect of boiling for various periods of time on the strength of joints in birch plywood bonded with urea glue fortified with varying amounts of melamine and resorcinol
Series Title:
Report ;
Physical Description:
2, 2 p. : ; 26 cm.
Language:
English
Creator:
Lecher, Sylvia M
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:
Adhesive joints   ( lcsh )
Plywood   ( lcsh )
Genre:
federal government publication   ( marcgt )
non-fiction   ( marcgt )

Notes

Statement of Responsibility:
by Sylvia M. Lecher.
General Note:
Caption title.
General Note:
"December 1946"--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 - 029314965
oclc - 236087607
System ID:
AA00020577:00001

Full Text

I)Dcmber 194(













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No. 1549


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


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Iitl &ull' -


FrrrcT OF ICOILING rcP VAIICUS IpEIIoIDS or TIM(
ON TIlE STIPENTII OF JOINTS IN PIICEI PLYWOOD
IBONDED WITIJ UP A CItI FOITIFI]D WITH VAPYINe
AMOUNTS OF MELAMINI AND PtSOlPCINOL


4 u


i 7 -







EFFECT OF BOILING FOR VARIOUS PERIODS OF TIME ON TEE SRENGTH OF JOINTS

IN BIRCH PLYWOOD BONDED WITH UREA GLUE FORTIFIED WITH
1
VARYING AMOUNTS OF ALAMINE AN1D RESORCINOL-


By SYLVIA M1 LECHER, Technologist





Boiling tests are commonly made on glued Joints as & means of distinguishing
urea glues, which are weakened by boiling, from glues, such as phenol, mela-
mine, and resorcinol, that are not so affected. Because glues are on the
market that are mixtures of urea resins and either melarine or resorcinol
resins (cornmonly referred to as "fortified ureas"), information was desired
on the effect of boiling on the strength of joints made with uro glues con-
taining varying amounts of these fortifiers.

The purpose of the work here reported was to ascertain the effect of boiling
for various periods of time on the strength of joints in birch plywood bonded
with urea glues fortified with varying amounts of melamine or resorcinol.

The procedure was to prepare plywood panels with urea-formaldehyde glues
containing vaiouis nroportions of mnelardne-resin and resorcinol fortifiers,
to boil 3r spcmens cut from these panels for various periods of time,
and to dotarmi'ne the joint strengths of the boiled specimens by the standard
ply.nvood shear tests.


Resorcinol-fortified Urea-formaldehyde Glues


The urea-formaldehyde glue employed in this phase of the work was a liquid
urea-resin solution containing 70 percent nonvolatile* To this solution was
added various amounts of a resorcinol fortifier and appropriate amounts of a
catalyst. The relative parts by weight of urea resin and resorcinol in the
six glues tested (all formulated to produce hot-setting glues) are given
in table 1.

The panels were made of three plies of 1/16-inch yellow birch heartwood
veneer conditioned in an atmosphere of 80 F. and 65 percent relative
humidity. A 4-hour closed-assembly time -,ms allowed, and the panels were
pressed for 4 minutes at 280 F. under a pressure of 250 pounds per square

1
-This study was made during the war period at the request of the Air Tech-
nical Service Conmand of the Army Air Forces with funds provided by them
for the purpose.


Report No. 1549


-i-







inch. One 24- by 2)I-inch panel was made with each glue. The specimuns cut
therefrom were selected so that spocimcns ma~c&ed as nearly as possible were
subjected to each of six exposure conditions. The specimens were condi-
tioned for 1 week at S0 F. and 65 percent relative humidity before boiling
and testing.

The results of the shear tests on these specirrm:ns before and after boilinr,
are presented in table 1.


Melamine-resin-fortified Urea-formaldehyde Glues


The urea-for7Qldohyde glue employed in this phase of the work was a powdered
urea-formanldohydo resin. To this resin wore added various proportions of
molamine rosin and appropriate quantities of water. The relative propor-
tions by weight of urea resin and of melamine resin in the nine glues tested
are given in table 2.

The plyurood panels were made in the same mnner as described for the experi-
ment with rosorcinol-fortified urea glue, except that a 16-hour closed-
assembly period was allov.'ed anid the panels were held under pressure at
2U0 F. for 8 minutes.

The results of the shear tests on these specimens before and after boiling
are presented in table 2.


Conclusions


From the results of these experiments it appears that, except for rather
laoi concentrations of fortifiers, periods of boiling in excess of 12 hours
would be required to reduce the joint strengths of fortified urea glues
below acceptable values. Ib would, therefore, be necessary to boil for
periods longer than 12 hours in order to differentiate between such forti-
fied urea glues and low-temperature phenol, melamine, or resorcinol glue.


Report No. 15r49


-2-







Table 1.--Average results of shear tests on three-ply 3/16-inch birch plwood
specimens, glued with a urea-formaldehyde resin glue fortified
with resorcinol, before and after boiling in water

Glue; Relative parts :Number: :
num-: by weight : of : Dry- : Wet- Boilin period2.
br : --------.-------: speci-: -----------------------------
:Uroa-:Resorcinol: mnns :3 hours:6 hours:9 hours :12 hours
:resin: :tested:

:4 .4 4 :4 34 :
1 :100 0 120 -477-91 :573-96 :.150-1 "54-i1 "442-1 23-0
2 93 : 7 ; 120 504-92 : 635-99 344-0 :271-1 208-1 : 204-0
:-2 42 8m 32 $:
3 : 57 : 13 : 120 523-8 : 671.00O: 453-42: 42-32 394-11 391-7
4 80 : 20 : 120 : 536-j : 671-100oo: 499-77: 481-95: 4,-65. 465-65
4 0 2010 536-0 48
5 : 73.5: 26.5 : 120 :16-94 : 601-100: 536-91 s 491-49 492-S4 : 469-69
6 62 : 3 : 120 : 443-99 : 576-100- 549-J5& 50O-S5 515-72 : 495-23




1
-Tested dry after conditioning at SO* F9 and 65 percent r31ative humidity.
2
--Tested wet after soaking in water 4,5 hours.
ITested wet after boiling for the period designated.
4
-The first figure is the shear strength in pounds per square inch; the
second figure is the .vood failure in percent.


Report "o, 159







Table 2.--Avjoere results of shear tests on throe-ply 3/16-inch birch ply.iood
specimens, gluod with a urca-formaldohyde rosin lue fortified
iith mlaminoe rosin before and after boiling in water


Glue: Relative parts :Number:
num-: by weight : of
bor :-----.----------.: speci-:
:Uroa-: Molaminc-: mens :
:resin: rosin :tested:
-----------:----------


100
95
90

85
80
6o

4o
20
0


156
36
36

36
120
120

120
120
120


15
20
40

6o
80
100


1 2 :------ po d-z
Dry- Wot- : Boiling poriodl
I ----------"W----.-_------_------
:3 hours:6 hours:9 hours l12 hours
S S S
.
-:--------------- -w^ ^_^__ ^___<^^


:4 :IL :
433-9 :-480-99 :-'113-3 :
: 462-97 : 396-100: 183-5 :
: 428-95 : 484-94 : 302-5 :
*
: 589-9S : 495-95 : 382-42:
: 454-100: 518-100: 421-78:
: 438-100: 454-99 : 425-96:

: 472-95 : 498-100: 431-89:
: 455-54 : 13-91 :l 474-93:
419-57 : 95-97 : 51S-95:


4 :

133-3 :
212-0 :

276-17:
339-30:
392-$85:

408-78:
447-56:
449-87:


4
-0-0
83-0
196-0

225-6
302-21
370-68

41o-8o
440-60
445-86


4
20-0
160-0

215-1
330-32
363-75

409-73
430-62
434-92


1
-Tested dry after conditioning at 80 F. and 65 percent relative humidity.
2
Tested wet after soaking in water 40 hours.
Tested wet after boiling for the period designated.
4 ,strrrngth
The first figure is the shear/In-pounds per square inch; the second figure
is the wood failure in percent.


Report No. 1549






UNIVERSITY OF FLORIDA
3 1262 08924 6606


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