PC laser weld

A maker of weldable tubing says it can now join clear tubes without compromising strength. Sure Bond tubing is a three-layer coextruded tube with a polyethylene inner layer to prevent absorption, a proprietary middle layer for adhesion, and an outer elastomer layer for bonding.

The elastomer, Ecdel, from Eastman Chemical Company, (eastman.com/medical) is an orthophthalate-free copolyester said to offer the clarity, toughness, flexibility, and chemical and heat resistance needed in crucial medical applications. Ecdel elastomer also withstands EtO and gamma sterilization without the yellowing associated with PVC.

Sure Bond tubing is the creation of Natvar, a Tekni-Plex Co. and manufacturer of extruded products for the medical market, and Gentex Corp., (gentexcorp.com) developer of colorless laser welding technologies. The tubing uses Gentex's patented Clearweld additive for laser welding tubing to transparent medical components used in intravenous therapy, hemodialysis, cardiovascular, urinary drainage, catheterization, neonatal, and angioplasty applications.

In laser welding, the Clearweld additive compounded into the Ecdel layer creates a clear, aesthetically appealing, stable joint without unwanted gaseous inclusions. The additive eliminates the need for solvent or adhesive bonding, which often leaves behind residual bonding material. In addition, laser-welded medical tubing helps eradicate quality challenges that crop up when connecting a tube to a luer (connector), including leaking, occlusions, and crazing that might compromise a product's proper function. Laser welding also creates several processing efficiencies, including a faster cycle time and reduced consumables. For example, with less bond-surface area to weld, component manufacturers have the potential to reduce the amount of luer material needed in their applications.

Eastman says it worked with Natvar and Gentex to conduct material testing to determine the product most compatible with the Clearweld technology. The company's Ecdel elastomer was chosen because of its optimal laser welding characteristics — particularly its ability to remain crystal clear and rapidly form a strong bond.

“Other commonly used medical-bonding techniques often create stress on an IV set or other device that delivers unstable medication, which might create leaks or occlusions and negatively impact, for example, insulin delivery to a patient,” says Bob Donohue, Divisional Director of Technologies for Natvar.

The Clearweld additive is based on organic absorbers. The technology enables a clear tube-to-clear tube weld for the visibility medical personnel need to monitor fluids. Historically, welding medical polymers with lasers was limited to bonding a transparent part to an opaque, typically black or gray, substrate. Now the technology offers color flexibility for creating custom tubing.

The Clearweld additive technology is non-invasive to the fluid path and can be used effectively within the high-pressure injector tubing market. Sure Bond tubing withstands pressures better and helps avoids catastrophic bond failure during intense surgical procedures.

Sure Bond manufacturing uses near infrared-absorbing colorless additives compounded into a thermoplastic before it is extruded into medical tubing. These light-absorbing additives convert laser energy to heat at a wavelength of 808 to 1,090 nm. Localized heating at the interface of the luer and tube produce strong (60 to 70 lb), hermetically sealed welds with minimal thermal and mechanical stress or presence of particulates.

“Another plus for Clearweld is that it eliminates UV curing which may require up to 20 seconds of cure time,” says John Pullo, Vice President and General Manager, Performance Materials, Gentex Corp. What's more, the bond is reproducible, making it ideal for medical applications that need optimum product integrity and consistent quality.