Clariant displays polymers intended to improve laser-welding performance

Specialty chemicals company Clariant is showcasing medical devices and components made of Mevopur polymer materials at MD&M West, with the materials intended to improve laser-welding performance.

In 2016 Clariant began using additives in Mevopur masterbatches and compounds used in laser-marking applications. Welding presents additional challenges because laser marking involves only one polymer, while laser welding involves two ― one that is transparent to the laser energy and the other absorbing energy to create the weld. The process is further complicated by any pigments or fillers, which can change the way the plastic reacts to the laser.

Speaking before the show, Eric Rohr, medical & pharmaceutical segment manager, North America, said: "Laser welding is increasingly preferred in production of medical devices because it provides speed, and reliability, can handle complex structures and avoids some of the downsides of other methods, such as solvent residues. However, because medical devices are frequently made of transparent or translucent materials, the polymer’s ability to absorb the laser energy often needs to be enhanced using additives."

“For that reason, we take a ‘systems approach’ in our laser welding solutions. At MD&M West we will be displaying welded products that appear to involve two parts made of identical materials. In fact, we developed two different formulations to achieve laser transmission in one and absorption in the other so that they can be reliably welded together. Clariant’s formulation experience and skills are the real key to success.”

Another important factor in achieving a good weld is the even distribution of the additive throughout the polymer matrix of the final part. In some cases, a concentrate or masterbatch can be dosed at the injection-moulding machine, which than mixes it sufficiently into the polymer melt before moulding. Injection-moulding machines, however, are not always ideal for dispersing the concentrate into the host polymer. In some applications, the machine, the material or the part design may cause inconsistent distribution and lead to unreliable welding.

Like all Mevopur masterbatch concentrates and finished compounds, the new laser-friendly materials are manufactured at a dedicated facility in Lewiston Maine, and at two other sites in Malmo, Sweden, and Singapore. All three plants have been certified compliant with ISO13485-2016, the latest quality management system for medical devices.