The medical world is full of challenges, and Avantor's NuSil unit is ready to tackle them with an array of liquid silicone rubbers.
The firm boasts a deep product portfolio of self-lubricating LSRs, which, according to Brian Reilly — the business development director for biomaterials at NuSil — help original equipment medical device designers minimize friction to enhance the performance of their devices. The firm currently has six commercialized formulations that can be utilized for medical device applications, and Reilly said the firm can customize each to accommodate specific lubricity or elastomeric properties.
"Although primarily dependent on the device design or its intended function, friction may be an issue that nearly all device designers face at some point in their career," Reilly said in an email. "The idea that a device may experience friction during its use can certainly limit its ideal performance or intended functionality."
He added that the traditional solution to friction challenges requires manufacturers to apply a silicone lubricant to the molded part, adding a step in the manufacturing process. But self-lubricating LSRs help eliminate that step, enhancing efficiency. Lubricity is built into the silicone elastomer, yielding a lubricious surface onto the molded component over time after vulcanization.
NuSil said self-lubricating LSRs are ideal for uses in medical balloons, valves, stoppers, O-rings, silicone devices with moving or sliding parts and parts that require assembly.
"When using a self-lubricating LSR, the lubricant is built into the elastomer system, so when a molded part is created, the lubrication elutes to the surface," Reilly said. "This removes the need for a secondary processing step of adding a lubricant after the part is molded."
Surface tack and blocking is another challenge medical device OEMs face when working with silicone elastomers. Reilly said that the surface of cured silicones sometimes present challenges thanks to an inherent surface tack, sometimes characterized by a high coefficient of friction, tackiness and a tendency for blocking (or sticking to itself).
He added that the blocking is particularly evident in slit valves, where two sides of the silicone part touch one another and close the slit.
Silicone coatings help reduce the coefficient of friction on the surface of silicone parts, eliminating concerns about migration, leaking or rubbing off that Reilly said are commonly associated with traditional lubricants like oils and greases.
Coating options differ depending on how the silicone is designed to cure, Reilly said. While coatings can be applied by dipping, NuSil recommends spraying because it results in a smoother finish with more than a 50 percent decrease in the coefficient of friction when compared to a non-coated silicone.
Reilly said NuSil currently offers dozens of unique formulations intended to provide lubricity, including fluids, greases, curable coatings and self-lubricating elastomers.
"A majority of our lubricious silicone systems were designed to provide a solution to an unmet need," Reilly said. "For example, some lubricious coatings are required to cure at room temperature due to the heat limitations of the substrates they were intended to be applied to."
Both lubrication options provide advantages for the health care industry. Reilly said that low coefficient of friction coatings are ideal not only because of friction reduction and regulatory concerns, but because they achieve critical performance goals with negligible impact on the mechanical properties of the silicone substrates they coat.
In other words, a silicone device that is required to bend, twist or elongate can handle this movement without cracking, flaking or peeling.
"Not every design requires the same solution," Reilly said. "There is a tremendous amount of innovation taking place within the device industry. As device designers face new challenges, they often require multiple options to overcome those challenges."