New laser technique binds aluminum with plastic in injection molding

As developers in the automotive and airline industries push to make more efficient vehicles, they are turning their attention to designing sturdy, lightweight machines. Designing lightweight materials, however, requires carefully joining together different types of materials like metals and polymers, and these additional steps drive up manufacturing costs. New work in laser technology recently increased the adhesion strength of metal-plastic hybrid materials.

A group of German engineers recently demonstrated a technique for binding plastic to aluminum by pretreating sheets of aluminum with infrared lasers. In the Journal of Laser Applications, from AIP Publishing and the Laser Institute of America, the researchers found that roughening the surface of aluminum with continuous laser beams created a mechanical interlocking with thermoplastic polyamide and led to significantly strong adhesion.

"In other joining methods you have a plastic part you want to fit together with a metal part. In the injection molding process we generate a plastic part on top of the metal part in a cavity of the machine," said Jana Gebauer, an author on the paper. "As a consequence, it is very difficult compared to thermal pressing or other joining technologies because of the specific thermal conditions."

To tackle these issues, Gebauer and her colleagues used both a continuous laser and one pulsed for 20 picoseconds at a time to make the surface of aluminum sheets more adhesive for a polyamide layer to be molded over it. They then placed the sheets in an injection mold and overmolded them with thermoplastic polyamide, a polymer related to nylon that is used in mechanical parts like power tool casings, machine screws, and gears.

"Following that, we analyzed the surface topography and conducted mechanical tests of the bonding behavior to find out which parameters led to maximum bonding strength," Gebauer said.

Tests using optical 3D confocal microscopy and scanning electron microscopy revealed that the aluminum sheets treated with pulsed lasers enjoyed much smoother line patterns in the trenches on their surfaces than those pretreated with continuous laser radiation. Aluminum sheets treated with infrared lasers also exhibited stronger bonding, but these properties diminished in tests with increasing levels of moisture.

Despite the team's success, Gebauer said that much work lies ahead to understand how pretreatments of the metal's surface can be optimized to make the process more economical for manufacturers. Now, she and her colleagues look to take on studying how molded thermoplastics shrink when cooled.

"The thermal contraction leads to mechanical stresses and can separate both parts. The current challenge is to generate a structure that compensates for the stresses during shrinkage without softening the aluminum by the laser treatment," Gebauer said. "Now we want to produce a reliable bonding under usage of ultrashort pulsed laser to reduce thermal damage in the metal component."

The Fraunhofer Institute for Material and Beam Technology, Leibnitz Institute for Polymer Research, Technical University Dresden were involved in producing the findings in this paper.

Research Report: "Laser structured surfaces for metal-plastic hybrid joined by injection molding"

Related Links
American Institute of Physics
Space Technology News - Applications and Research

Tweet

Thanks for being there;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Monthly Supporter
$5+ Billed Monthly

paypal only

SpaceDaily Contributor
$5 Billed Once

credit card or paypal

Chemists make breakthrough on road to creating a rechargeable lithium-oxygen battery
Waterloo, Canada (SPX) Aug 30, 2018
Chemists from the University of Waterloo have successfully resolved two of the most challenging issues surrounding lithium-oxygen batteries, and in the process created a working battery with near 100 per cent coulombic efficiency. The new work, which appears this week in Science, proves that four-electron conversion for lithium-oxygen electrochemistry is highly reversible. The team is the first to achieve four-electron conversion, which doubles the electron storage of lithium-oxygen, also known as ... read more