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Development of a Heat-

Resistant Polyurethane

Adhesive

Martin Feng

Jinlan Ju

Xiang-Ming Wang

Outline

Background

Objective

Methodology

Development of HRA polyurethane adhesives

Comparison between PUR and PRF in plywood

“burn through” test

Standard fire test of HRA PUR adhesive

Summary

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Engineered Wood Products (EWP): Beautiful Housing Materials

90% of Residential Housing in North

America

Engineered Wood Products

Background

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Engineering Wood Products in a Fire

Burn slowly

Char Retain 80% of strength

Degrade and soften Lose most of strength

Burn

EWP Burns and Collapses

Construction damages

Injury and/or death

Wood Adhesive

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Fire-Resistance Test of Finger-Jointed Wall Assemblies (2006)

American Wood Council (AWC) Canadian Wood Council (CWC)

USDA Forest Products Laboratory FPinnovations - Forintek Division

Type of Finger Jointed Lumber

(Douglas fir)

Assembly Fire-Resistance

Loading hour

Phenol-Resorcinol-Formaldehyde (PRF) 1 hour

Polyurethane (PUR) adhesive 51 min

Polyvinyl acetate (PVAc) adhesive 49min

Wall Assembly: U.S. 2006 International Building Code Table 720.1(2)

ASTM E119: Fire Tests of Building and Construction Materials

Background

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Background

Finger-Jointed Lumber used interchangeably

with solid sawn lumber if passing

1-hr Standard Fire Resistance rating

Western Wood Products Association (WWPA)

Glued Lumber Policy, 2007

(American Lumber Standard Committee)

Required: Heat Resistant Adhesive (HRA)

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Background

Applications of HRA Finger-Jointed Lumber

Market of Finger-Jointed Lumber in North America, 2007

•Separation in multi-story and multi-family buildings •Common walls in commercial structures •Mid-rised buildings (5,6 storey)

Voulme Value

Total stud lumber

consumption

8, 000

MMBF

C$ 1.9 billion

Finger jointed lumber 900 MMBF C$ 215 million

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Background

Commercial HRAs:

PRF & MF (formaldehyde based resin)

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Background

HRA

• Formaldehyde-free

• Colorless or light color

• Easy application

Market potential for

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1-hr Fire Rating

ASTM E 119 : (Standard Test Methods for Fire Tests

of Building Construction and Materials)

ASTM D 7374: (Standard Practice for Evaluating

Elevated Temperature Performance of Adhesives

Used in End-Jointed Lumber)

Objective

To develop:

1C-HRA- polyurethane adhesive

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Requirements for HRA

1. Heat resistance Lose weight slowly

Does not soften at

elevated temperature

Maintain strength at high

temperatures under load

2. Flame retardancy Hinder ignition

Slow down fire growth

Produce substances as fire

barriers

Reduce heat of combustion

Form char layer

Objective

Mechanical properties

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FPI’s patent publication # WO/2011/113137

pMDI + polyols polyurethane prepolymer

Formulation of PUR adhesives

PUR prepolymer + additives PUR adhesives

Methodology

Preparation of polyurethane adhesives

heating

Dry N2

Dry N2

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Methodology

Scaled Temperature Tension Test (STTT)

Thermal couple

Switch

sensor

220oC

Oven

Tensile

loading

10 MPa

Specimen

Scaled Temperature Tension Test FPinnovations-Forintek Division

Determination of Sample Failure point

Higher temp-to-failure means higher heat resistance.

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Methodology

Scaled Temperature Tension Test (STTT)

Finger-Joint

ASTM D4688-99

Fabrication of Finger-Jointed Billets

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HRA PUR Adhesives

Adhesive

name

Solvent or dispersion

media

Temperature-to-

failure (°C)

Time-to-failure

(s)

PUR-A NMP

(N-Methylpyrrolidone)

141.6 290

FR-PUR-A NMP 166 641

PUR-B water 36 34

PUR-C Solvent free 200 1635 (27min)

Heat-Resistance of commercial wood adhesives tested in 220 oC Oven

Note: Testing load was 1000 psi.

Heat-Resistance of commercial PUR adhesives

tested with STTT

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HRA PUR Adhesives

Small Scale Tension Test of

the PUR Adhesives

220

0

50

100

150

200

250

0 500 1000 1500 2000 2500

time (s)

tem

pe

ratu

re (

oC

)

MA modified PUR

dark blue line

Control PUR

yellow line

MB modified PUR

sky blue line

best commercial PUR

FR-A

Purple line

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HRA PUR Adhesives

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HRA PUR Adhesives

SEM of Finger-Joint Glueline

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PRF Glued 5-layer Plywood

At 2 min 21 sec At 1 min 29 sec

Polyurethane

Glued 5-layer Plywood

Comparison of flammability between HRA-PUR and PRF

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At 6 min 28 sec

At 6 min 01 sec

PRF

Glued 5-layer Plywood

Polyurethane

Glued 5-layer Plywood

Comparison of flammability between HRA-PUR and PRF

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At 13 min 40 sec At 10 min 21 sec At 15 min 25 sec

PRF

Glued 5-layer Plywood

Polyurethane

Glued 5-layer Plywood

Comparison of flammability between HRA-PUR and PRF

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At 20 min 23 sec

At 20 min 10 sec

PRF

Glued 5-layer Plywood

Polyurethane

Glued 5-layer Plywood

Burned spot

Comparison of flammability between HRA-PUR and PRF

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At 25 min 57 sec At 25 min 19 sec

PRF

Glued 5-layer Plywood

Polyurethane

Glued 5-layer Plywood

Comparison of flammability between HRA-PUR and PRF

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At 27 min 59

sec At 35 min 17 sec

PRF

Glued 5-layer Plywood

Polyurethane

Glued 5-layer Plywood

Void

Comparison of flammability between HRA-PUR and PRF

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PUR-Glued 5-layer Plywood

At 37 min 21 sec

PUR panel burned through

at 37min 21 sec. PUR

panel lasts 10 mins longer

than PRF panel

Comparison of flammability between HRA-PUR and PRF

Standard Fire Test on HRA PUR

Wall Assembly (ASTM D 7374-08 & D7470-08)

9 pieces of 2*4 finger jointed studs

2 plates

mineral wool insulation between studs

Gypsum board

Standard Fire Test on HRA-PUR

Fire Test Conditions (ASTM E 119)

•Expose wall assembly in

fire for 1 hr.

•Control furnace

temperature

•23,100 lbs constant load

on wall assembly

throughout testing

Time-Temperature Curve

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ASTM E 119 Furnace (Front)

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Construction of Wall Assembly

1 2 3 4

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Construction of Wall Assembly

Stud attached with 5 thermal couples

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Ignition of Furnace

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Testing

Start testing Measure deflection of wall

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Testing

In the beginning of test, mud

sealing was intact

After ~25 min., mud fell off and

flame shot out from drywall gap

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Testing

At the very

moment that the

test passed 1-

hour fire rating,

where the wall

assembly was

still intact. The

test continued.

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Wall Assembly was removed from the furnace

Drywall was

deformed and

cracked. FJ

lumber studs

were burning.

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Completion of Testing

Studs were burned

more than 2/3 of original

width. Wood failed

under the stress load

(~450 psi). Wall

assembly bent towards

unexposed side.

FPInnovations’

polyurethane adhesive

reached 78 minutes

without failure

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Burnt Finger-Jointed Studs

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The Joints of the Burnt Studs

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Cross Section of Burnt Joints

Depth Change of Burnt Joints

orig

ina

l

Note: The original depth of stud was 3.50 inches

The depth remaining ratio is 49+-6%, except specimens 1 and 9,

which were located on the sides of wall assembly

Specimen 1 2 3 4 5 6 7 8 9

average

remaining

Depth

(inches)

2.93 1.72 1.94 1.84 1.68 1.80 1.56 1.55 3.04

remaining

origingal

%

84 49 55 53 48 51 45 44 87

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42

Tension test on burnt studs Finger Joint Clear Wood

Specimen Max Load Depth Width Stress Max Load Depth Width Stress

(pounds) (inches) (inches) (psi) (pounds) (inches) (inches) (psi)

1 12840 2.93 1.51 2896 52200 2.93 1.51 11775

2 9155 1.72 1.53 3479 18160 1.72 1.53 6901

3 7480 1.94 1.50 2574 20610 1.94 1.48 7198

4 9072 1.84 1.53 3216 22070 1.84 1.51 7949

5 7817 1.68 1.52 3055 19430 1.68 1.52 7594

average * 9273 3081 26494 7410

Specimen Max Load Depth Width Stress Max Load Depth Width Stress

(pounds) (inches) (inches) (psi) (pounds) (inches) (inches) (psi)

177 39450 3.50 1.50 7514 51560 3.50 1.50 9821

F97 28560 3.49 1.50 5451 35840 3.49 1.50 6840

average 34005 6483 43700 8331

Average * = average (2, 3, 4, 5). Stud 1 was located on the side, which was

burnt much less than the other studs and was not counted in calculations.

Remaining Strength

Finger Joints: 48% Clear Wood: 89%

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Summary

Feasible to produce one component, room temperature curing

HRA polyurethane adhesives.

Unexpectedly, it was shown that flammability of HRA PUR was

less than that of PRF.

Studs burnt to only half of the original depth, which requires

wood adhesive highly heat/fire-resistant.

FPI’s polyurethane adhesive passed requirements of

HRA according to ASTM D7374 and ASTM E119 and

reached 78 minutes without failure, exceeding the 1-

hour target by a large margin.