Adhesives for LSE substrates
Joining Methods

Non structural (<1000 psi OLS)

Adhesives




Hot melts (3M Jet-meltTM 3731)
Spray adhesives (3M Hi-Tack 76 Spray
Adhesive)
PSA Tapes (3M 300LSE High Strength
Laminating Adhesive or Double-Coated Tape)
Re-closable fasteners

Hook & loop (3M ScotchmateTM SJ-3506 and
SJ-3507)
Joining Methods

Structural (>1000 psi OLS)

Adhesives



Traditionally, surface preparations (priming, etching,
flame treatment) that alter the surface energy are
necessary (3M Scotch-weldTM DP-420 after flame
treating)
3M Scotch-weldTM DP-80XX (other than light cleaning no surface prep necessary)
Mechanical joining


Machine screws ( nut and bolt or threaded insert)
Self threading screws/nuts
Other Joining Methods

Snap fit






Hook/beam,annular, ball and socket,
Press fit
Heat staking/ hot air cold staking
Radio frequency dielectric heating
Ultrasonic welding
Multi-shot molding
Adhesive & Cohesive Strength
Adhesion – Force between dissimilar surfaces
Cohesion – Internal strength of material
Substrate
Substrate
Adhesive
Adhesive
Substrate
Substrate
Stresses on a Joint That Can Lead to
Bond Failure
Shear
Tensile
Cleavage
Peel
Joint Design

Designing the joint to minimize peel or cleavage
stresses on the bond line and maximize tensile, shear
or compressive stresses is desirable
Improving joint design to accommodate applied stress
Bonding Process
Surface prep (cleaning)
Applying liquid adhesive
WGT
Closing up the bond
Apply pressure during cure (clamping)
Bonding Process
Adhesive Wetting
Zisman's Equation
cos  1  b( c   lv )
θ
Contact Angle Q
 c  criticalsurface energyof substrate
 lv  surface energyof liquid
c-lv
Surface Treatment
Effects of Surface Treatment on Polyethylene
Surface Energy
(mN/sq.m.)
42
40
38
36
34
32
30
Untreated
Exposed to UV
Light
Flame Treated
Treatment
Exposure to UV
Light in presence
of solvent
Etched in
chromic acid
Key Performance Characteristics of a
Structural Adhesive

Bond making properties

Usability in manufacturing process






Degree of surface preparation necessary
Open time (work-life)
Time to handling strength (50 psi OLS)
Cure conditions (temperature, pressure)
Viscosity (non sag, pump ability)
Delivery equipment
Key Performance Characteristics of a
Structural Adhesive

Cured bond properties

Environmental resistance




Thermal
Shock
Weathering
Chemical resistance


Solvents
Moisture
Substrate Processing Effects


Processing of substrate impacts the bulk
and interfacial properties of the
substrate
Adhesive performance is coupled not
only to the material type but also to the
process conditions used to make the
substrate
3M Scotch-weldTM DP-8005



2 part – 10:1(B:A) mix
 Base (B) - acrylic
 Accelerator (A) - amine
Density
 B = 8.2 lbs/gal
 A = 8.9 lbs/gal
Viscosity
 B = 23,000 cps nominal
 A = 45,000 cps nominal
3M Scotch-weldTM DP-8005

Open time (work life)


Time to handling
strength



2-3 minutes @ 23C
2-3 hrs @23C
15 minutes @ 80C
Full cure time


8 hrs @ 23C
1 hr @80C
3M Scotch-weldTM DP-8005

Mechanical properties




Shore D hardness = 55
Peak strain = 5.3 %
Peak stress = 1889 psi
Thermal properties


Tg = 34-38 C (DSC @
10c/min.)
CTE = 6.6 ppm/degC
3M Scotch-weldTM DP-8005
Overlap Shear 3M Scotch-weld TM DP-8005 On Various Substrates
3000
SY = Substrate yield
SF = Substrate failure
AF = Adhesive failure
CF = Cohesive failure
MM = Mixed failure
2000
CF
CF
SF
SF
1500
SY
1000
SF
SY
SF
SY
SY
AF
SY
MM
SY
SY
SY
500
PE
/
HD
Substrate
Translucent
Black
HD
G
S
O
ily
CR
PE
/
HD
an
ea
le
d
G
G
al
v
PE
/
HD
P
HD
G
-F
R
Ny
l
on
-6
,6
S
HI
P
C
Ri
g
id
PV
M
A
PM
ar
bo
na
te
PE
LD
AB
S
Po
lyc
UH
M
W
PE
PP
PE
0
HD
Strength (psi)
2500
3M Scotch-weldTM DP-8005
Environmental & Chemical Exposure of 3M Scotch-weldTM DP-8005
14 days exposure at 75 F (unless another temp is noted) on HDPE
1200
SY
Mix
SY
SY
SY
SY
Mix
SY
Mix
OLS (psi)
1000
800
600
CF
CF
400
200
SY = Substrate yield
CF = Cohesive failure
Mix = Some of both
Translucent
Black
ne
lu
e
To
el
ie
s
G
as
ol
Fu
el
in
e
ze
tif
re
e
Chemical
D
20
%
An
Bl
IP
A
ea
ch
l
C
H
%
16
aO
H
N
%
10
R
H
0F
/W
at
er
So
ak
16
16
0F
/1
C
00
%
on
t
ro
l
0
3M Scotch-weldTM DP-8010





Similar to 3M Scotch-weldTM DP8005 with regard to performance
characteristics on LSE substrates
Longer work life – 10 minutes
Slightly shorter time to handling
strength – Just under 2 hours
More flexible – better peel
performance
Less sensitive to process history
of substrate
3M Scotch-weldTM DP-80XX Applications
• Bonding
Polypropylene with
polyethylene
3M Scotch-weldTM DP-80XX Applications
• Dashboard
3M Scotch-weldTM DP-80XX Applications
• Building industry
Application:
House connectors
Bonding a flexible pipe (PE)
with a rigid one (stainless steel)
3M Scotch-weldTM DP-80XX Applications
• Electronics
3MTM Jet-MeltTM
Polyolefin Bonding Adhesive 3731

Description:
A 100% solids, high
heat resistant adhesive
that bonds to a variety
of substrates including
polyethylene,
polypropylene and many
other plastics.
3MTM Jet-MeltTM
Polyolefin Bonding Adhesive 3731

Features:
•
•
•
•
•
Solvent free, 100% solids
High temperature resistance
Bonds well to polyolefin based plastics
Light tan color
Fast setting
3MTM Jet-MeltTM
Polyolefin Bonding Adhesive 3731

Typical Physical Properties:






Color : Light Tan
Specific Gravity: 0.92
Flash Point (C.O.C.): 525°F (273°C)
Viscosity @ 375°F(1) (191°C): 12,000 cps
Bonding Range - 1/8" (Bead sec. (3) ): 25-30
seconds
Impact Resistance (Inch lbs @ 72°F): 80
3MTM Jet-MeltTM
Polyolefin Bonding Adhesive 3731

Heat resistance:
3MTM Jet-MeltTM
Polyolefin Bonding Adhesive 3731

Overlap Shear Strength:
Future R&D Directions


Longer open times
Faster cure times



Inherent in the product
External techniques for accelerating
Adhesive performance



Adhesive
Bonding process
Substrate (material and processing history)