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Friction can turn medical products into failures

By: Frank Esposito

June 4, 2014

CLEVELAND — Researchers at RTP Co. are working to make sure friction doesn’t burn up users of single-use drug delivery devices.

The use of such devices — including syringes and injection pens — is becoming more widespread as patients are being taught how to administer their own medication, often at home. This, in turn, has put pressure on medical device makers to ensure that parts don’t exhibit stick/slip — basically, that they don’t get stuck — when being used.

“If the device doesn’t deliver the full amount of the drug, it’s a failure,” RTP global healthcare manager Josh Blackmore said May 6 at Plastics in Medical Devices, a conference hosted by Plastics News in Cleveland.

To find the best way to eliminate friction in these devices, researchers with Winona, Minn.-based RTP — which ranks among North America’s 30 largest compounders and concentrate makers — tested numerous resin pairings combined with several different lubricants.

Parts made of varying plastics — including polycarbonate, acetal, PBT, high density polyethylene, ABS and PC/ABS — were tested against each other after being filled with internal lubricants, according to product development engineer Ben Gerjets.

Lubricants used in the testing included fluorinated PFPE and RTP’s own APWA (all-polymeric wear alloy) Plus-brand lubricant. APWA Plus was commercialized earlier this year in acetal-based compounds.

RTP’s tests also measured how various plastic parts exposed to friction were affected by sterilization, UV degradation and shelf life. Parts also were exposed to 100 hours of wear over time.

“Dissimilar pairs [of resin] showed improved low friction,” Gerjets said. “But they performed best when dissimilar pairs were combined with internal lubricants.”

“Internal plastic lubrication improved stick/slip,” he added.