Engineering Insight

A disposable anti-needle-stick device is designed with a spring and two telescoping plastic components that must operate with minimal friction. Makrolon Rx1851, a polycarbonate (PC) from Bayer MaterialScience (Leverkusen, Germany; www.bayer

materialscience.com), is a low-viscosity resin with enhanced internal mould release technology, which also has a positive effect on the moulded part’s lubricity. This dynamic duo of properties is one of the primary reasons that Safety Syringes (Carlsbad, CA, USA; www.safetysyringes.com) selected the material for use in its safety syringe.

Designed for prefilled injectable syringes, the UltraSafe Passive Needle Guard device doesn’t push the needle guard forward into the user. On the contrary, it pulls away the syringe and needle from the patient and into the guard, thus preventing needlesticks. Needlestick injuries are reported every 30 seconds in the United States, according to the manufacturer. That should be cause for alarm, adds the company, when one considers that accidental needlesticks can lead to infections, illness and even death.

Minimising friction

Like materials don’t necessarily get along when they are supposed to slide against each other, says Kevin Dunay, Consumer and Medical Market Segment Leader, Polycarbonates, NAFTA, Bayer MaterialScience LLC. In fact, the close quarters may create some friction. That could have been an issue with the telescoping components, both of which are moulded from a PC resin, had it not been for the lubricity of Bayer MaterialScience’s Makrolon Rx1851. “That was a key attribute for this device, along with the material’s durability,” explains Dunay. “Furthermore, the resin’s strength and transparency facilitate visualisation of syringe markings, labels and contents while helping to maximise protection.”

The enhanced internal mould release technology enables design flexibility for complicated parts, adds Dunay. Components with shallow draft angles and multicavity moulds with long flow lengths are but two examples. The material’s easy flow properties make it suitable for thin-wall applications, as well.

From a production perspective, the release properties of Makrolon Rx1851 can lead to reduced cycle times, increased capacity and potential cost savings, according to Dunay. 

Dimensional stability

Dunay also touts the material’s dimensional stability properties even in extreme temperatures. “This is very important when you consider temperature variations that can exist during shipment in containers, for example,” says Dunay.

The medical-grade resin is supplied in pellet form for injection-moulded applications. It is available in a clear tint as well as in other Rx Medical colours from the company’s LEDA compounded colour technology.

The material meets the biocompatibility requirements as set forth in US FDA–modified ISO 10993, Part 1 “Biological Evaluation of Medical Devices” with human tissue contact time of 30 days or less.

In addition to the aforementioned syringe components, other applications for the polycarbonate include IV access systems and cardiovascular devices.