Adhesives for LSE substrates
Joining Methods Non structural (<1000 psi OLS) Adhesives Hot melts (3M Jet-melt TM 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 Scotchmate TM 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-weld TM DP-420 after flame treating) 3M Scotch-weld TM 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
Stresses on a Joint That Can Lead to Bond Failure Shear Tensile Peel Cleavage
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 WGT Surface prep (cleaning)Applying liquid adhesive Closing up the bondApply pressure during cure (clamping)
Bonding Process
Adhesive Wetting
Surface Treatment
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-weld TM DP 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
Open time (work life) C Time to handling strength C Full cure time 8 23C 1 3M Scotch-weld TM DP-8005
Mechanical properties Shore D hardness = 55 Peak strain = 5.3 % Peak stress = 1889 psi Thermal properties Tg = C 10c/min.) CTE = 6.6 ppm/degC 3M Scotch-weld TM DP-8005
Similar to 3M Scotch-weld TM DP 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-weld TM DP-8010
Bonding Polypropylene with polyethylene 3M Scotch-weldTM DP-80XX Applications
Dashboard
Building industry Application: House connectors Bonding a flexible pipe (PE) with a rigid one (stainless steel) 3M Scotch-weldTM DP-80XX Applications
Electronics 3M Scotch-weldTM DP-80XX Applications
Description : A 100% solids, high heat resistant adhesive that bonds to a variety of substrates including polyethylene, polypropylene and many other plastics. 3M TM Jet-Melt TM Polyolefin Bonding Adhesive 3731
Features: Solvent free, 100% solids High temperature resistance Bonds well to polyolefin based plastics Light tan color Fast setting
3M TM Jet-Melt TM Polyolefin Bonding Adhesive 3731 Typical Physical Properties: Color : Light Tan Specific Gravity: 0.92 Flash Point (C.O.C.): 525°F (273°C) 375°F(1) (191°C): 12,000 cps Bonding Range - 1/8" (Bead sec. (3) ): seconds Impact Resistance (Inch 72°F): 80
3M TM Jet-Melt TM Polyolefin Bonding Adhesive 3731 Heat resistance:
3M TM Jet-Melt TM 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)