Calendered PVC and TPEs: Teknor Apex Lays Down the Gauntlet

US thermoplastic polymer supplier Teknor Apex has announced that new technologies from three cooperating suppliers make possible film products that combine the advantages of thermoplastic elastomers (TPEs) over PVC, the quality benefits of calendering, and the sealing efficiency of radio frequency (RF) welding. The technologies will be highlighted at Teknor Apex's booth at MD&M East in Philadelphia on June 17-22, 2013.

In collaboration with film manufacturer O’Sullivan Films and welding company Genesis Plastics Welding (Booth 3137), both based in the USA, Teknor Apex says it has demonstrated that films produced from its Medalist MD-500 Series elastomers eliminate the traditional disadvantages of TPEs in such applications as fluid drainage and storage bags, cushioning bladders, and surgical pouches, exhibiting performance that is fully comparable to PVC in processing, bonding, assembly, and clinical handling.

Teknor Apex has performed tests with cooperating customers which show that Medalist MD-500 Series TPEs provide a number of property improvements over PVC, along with substantial savings in weight and cost, according to Elliott Pritikin, global medical market manager for the company's thermoplastic elastomer division.

While calendered PVC film is widely used in medical applications, traditional TPEs have not performed well in calendering, a process which typically provides better thickness uniformity, more consistent physical properties, and greater thermal stability than film extrusion. Working with Teknor Apex, O’Sullivan Films has demonstrated that Medalist MD-500 Series medical elastomers can be formulated for successful calendering.

“Our company has attempted to calender a wide range of plastics besides PVC and concluded that most are simply not calenderable,” noted Chuck Stronach, O’Sullivan Films commercial manager for healthcare products. “We were intrigued to discover that Medalist 500 Series compounds can be adapted for this process, and together with Teknor Apex we carried out a lot of R&D work to optimise the production and properties of Medalist calendered films.”

Film and bag applications for Medalist MD-500 Series TPEs include cushioning bladders (for mattresses, wheel chairs, and gurneys); IV and saline bags; medicine storage and delivery pouches; bags for enteral and parenteral nutrition storage and delivery; dialysis bags; and surgical pouches.

Medalist MD-500 Series TPEs Provide Range of Advantages over PVC

“While there is pressure on medical device companies to replace PVC in a number of applications, the track record and excellent cost-performance profile of PVC have in the past made it difficult to replace,” said Elliott Pritikin. “Recently, however, Medalist MD-500 Series elastomers have been commercially successful as alternatives to PVC in medical tubing, and now they are proving to offer clear-cut advantages over PVC in film products.”

Two of the greatest advantages cited by Mr Pritikin involve:

● Raw material economy. Film made from Medalist MD-500 Series TPEs exhibits the same degree of strength as PVC film that is twice as thick (see table).

● Weight savings. Because the Medalist compounds are 30% less dense than flexible PVC and can be down-gauged without compromising strength, finished products can be 66-70% lighter.

Other comparisons provided by Teknor Apex are as follows. Medalist elastomers are available at lower hardness ranges than flexible PVC, provide a broader processing window, exhibit greater elasticity and tear strength, have superior flexibility and impact strength at low temperatures, are less permeable to nitrogen and moisture, and have a wider range of service temperatures. Furthermore, these TPEs exhibit 25% less colour change upon exposure to gamma irradiation than standard (ie, not gamma-stable) grades of flexible PVC.

Making the Switch to TPEs

In developing Medalist 500 Series compounds for film products, Teknor Apex was guided by the concept of making the process of changing over to Medalist TPEs as simple as possible for the device manufacturer, according to Richard Faulkner, Teknor Apex medical market manager.

“Teknor Apex started off by listening to the voice of the customer, consulting with manufacturers of medical devices to identify all of the regulatory and performance considerations that may arise in film applications and to learn how traditional TPEs and PVC compare,” said Mr Faulkner. “As in our development of compounds for tubing, we partnered with companies that have longstanding expertise in the target applications.”

One key partner is O’Sullivan Films, whose healthcare products include both PVC and TPE. The company’s PVC products are manufactured by calendering. This process produces film by fusing compound in a mixer and then passing the material through a series of synchronised nip rolls. In its ISO 13485-certified operation for medical films, O’Sullivan Films has calendered Medalist MD-500 Series compounds into films with widths up to 76 inches (193 cm), using special vision monitoring systems for quality control and a dedicated “healthcare” slitter capable of producing widths down to 1 inch (25 mm).

Teknor Apex also collaborated with Genesis Plastics Welding, an ISO 13485:2003 certified medical device contract manufacturer. Genesis's proprietary radio frequency (RF) welding technology, ecoGenesis, enables sealing of polar and non-polar plastics, including film produced from a Medalist elastomer. While the alternative technique of heat sealing produces only a straight-line bond, RF welding with ecoGenesis makes it possible to form strong permanent bonds in complex geometric patterns; including sealing two mono-layered film to tubing producing traditional infusion bags.

For information on O’Sullivan Films visit www.osul.com. For information on Genesis Plastics Welding, visit www.genesisplasticswelding.com.

Editor's comment

Teknor Apex is in a good position to observe the behaviour of medical device makers switching from PVC to TPE alternatives as it manufactures both materials. Device manufacturers are considering alternatives to PVC for a variety of reasons with some going PVC-free. That said, these companies are still in the minority as PVC is an remains a safe material. There have been challenges as to the safety of the PVC plasticiser DEHP but the PVC industry has faced these challenges head on and developed a range of comparable alternatives. For more information about DEHP in PVC-based medical devices, see the link to the article on DEHP in the related articles links.