Clariant has launched new medical-grade polymer compounds and concentrates supported by formulation expertise that can help medical-device manufacturers take a ‘Quality by Design’ (QbD) approach to laser-welding of plastic components.
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The compounds and concentrates, are marketed under the Mevopur brand name covering Clariant’s ‘medical grade’ materials and are among several innovations being presented at MD&M West 2020.
Laser-welding offers numerous advantages in medical and diagnostic applications in terms of speed and reliability, according to Steve Duckworth, global head of marketing & business development. Yet, if the combination of polymer, colorants, part design and processing techniques are not considered in the earliest stages of product development, weld consistency can suffer, and the risk of product failure may become unacceptable.
Compared to other methods of assembly, laser welding can develop a high-strength bond, without many of the disadvantages of other methods. Surfaces do not require pre-treatment and the risk of creating potential leachables from solvent residues or adhesive is eliminated.
Colour choices play a critical role in the ability of one part to transmit laser energy, and the other to absorb laser energy and melt at the bond line. In many applications, colour decisions are taken only in the latter stages of the development cycle by the marketing team or others not involved in the functional design process. When laser welding is involved, this introduces considerable and unnecessary risk and complexity.
Duckworth said: “Traditional approaches to coloration may not work. For example, having a visually opaque black or very dark colour that typically uses carbon black would not perform in the laser-transmitting component. Neither would a white component, where a typical pigment used is titanium dioxide.
“Our team of experts has a thorough knowledge of pigment and additive options for absorbing and transmitting parts, so we can give different colour options in a wide range of polymers including polypropylene, ABS, polycarbonate, PC/ABS blends and more. In collaboration with laser equipment suppliers, we’ve developed analytical techniques that can be used to screen different solutions to find the best one.”
Once an optimal colour has been selected, the distribution of pigments and additives in the plastic component and part-to-part consistency become important. Although masterbatch concentrates added to the host polymer during processing may be convenient for introducing colour, the processing equipment, and the flow-path in the tool, may only allow for poor or inconsistent distribution of the pigments at the targeted weld-line. Using a fully compounded ready to use material may help solve this distribution problem.
This is why the Mevopur laser-welding solutions are available in both a concentrated masterbatch form, and as a ready-to-use compound. The Mevopur products have been manufactured in one of three global Clariant facilities certified to EN: ISO13485-2016 quality standards.