Assembly in Action: Adhesive Bonds Steel and Composite Auto Parts
The two-component urethane adhesive Casalini had been using to bond the steel-reinforcing frame to the glass-reinforced plastic cabin interior of these vehicles was not performing well.
Casalini’s performance requirements for the new adhesive were extensive. First, the adhesive had to have short working and fixture times and be capable of bonding substrates with little or no surface preparation. These capabilities would allow Casalini to minimize processing time.
Also, the adhesive had to provide high strength and good flexibility, as well as excellent fatigue resistance and the ability to withstand stress. Finally, the adhesive had to have excellent gap-filling properties and present no health and safety issues for Casalini workers.
Adhesive supplier ITW Plexus met with Casalini and recommended the manufacturer use MA422, a two-part methacrylate adhesive designed for structural bonding of thermoplastic, metal and composite assemblies. Production trials performed in the Casalini plant confirmed that the adhesive met all these rigorous requirements. ITW’s local supplier Vaber supplies the adhesive in ready-to-use 380-mililiter cartridges.
During assembly, the adhesive is machine-applied to the cabin wall. The frame is then positioned in place and held there while the adhesive rapidly sets.
“The methacrylate adhesive increases throughput and reduces our manufacturing costs,” says Sandro Fermi, Casalini production manager.
“Our material costs were also reduced by using an adhesive dispenser. Plus, the technical advice and assistance given to us throughout the production trials and since that time has been exceptional.”
Combined at a 10-to-1 ratio, the adhesive has a working time of 17 to 24 minutes and achieves approximately 75 percent of ultimate strength in 35 to 40 minutes at 74 F. The operating temperature of MA422 is -40 to 250 F.
The material is blue when mixed and dispenses as a non-sagging gel. It can fill gaps from 0.03 to 0.375 inch. MA422 has a flash point of 50 F.
When cured, the adhesive has a strength of 2,000 to 2,500 psi and a modulus from 70,000 to 90,000 psi. The adhesive’s strain-to-failure ratio is 75 to 100 percent.
MA422 offers excellent resistance to hydrocarbons, mild acids and bases (3 to 10 pH), and salt solutions. However, it is susceptible to polar solvents, and strong acids and bases.
For more information on methacrylate adhesives, call 800-851-6692 or visit www.itwplexus.com.