INNOVATION | MEDICAL
fibre reinforcement. But even without fillers, PC will never flow like LCP.” For medical components such as injection pens and autoinjectors, which do not present major filling issues, but where lubricity and wear resist- ance are important because of their moving parts, acetal resins (POM) are often used. Vos points to another original Celanese thermoplastic, acetal copolymer, branded Hostaform, citing advantages over rival acetal homopolymer. “Hostaform POM copolymerdelivers a combination of outstanding wear resistance, long-term fatigue resistance, creep resistance, and toughness,” he says. “It is also resistant to moisture, solvents, and strong alkalis.” He continues: “In a recent in-house study comparing injection moulding processing, we found that Hostaform POM copolymer compared favourably to POM homopolymer because of its wider processing window and reduced effort for mould deposit and cleaning.” The company also has a strong position in thermoplastic elastomers of various types, thanks in good part to acquisitions in recent months of the Santoprene TPV business from ExxonMobil and Hytrel from DuPont, as well as the So.F.Ter com- pounding operations. The Santoprene portfolio includes medical grades, and Vos points to several important characteristics of TPVs for medical applications, including sealing performance, durability, low density and dimensional stability. “Of all TPEs, TPV is the one that comes closest to the compression set performance of thermoset rubber,” he says. “We compared TPV with liquid silicone rubber as it is one of the most widely used thermoset rubbers in the medical industry. Santoprene can be processed on standard thermoplastics equipment with rapid cycle times. Overmoulding onto other engineered thermoplas- tics is also an option. Notably, it is fully recyclable within the manufacturing process. Liquid silicone rubber requires a high cost of tooling, materials, and processing and can be over-engineered in applications that do not require high temperature resistance.” Celanese is not the only TPE supplier with a
strong and growing interest in medical applica- tions. Hexpol TPE has expanded its Mediprene range of thermoplastic elastomers for multi-com- ponent medical applications. The Mediprene A2 series offers bonding to thermoplastics that include ABS, PC, PETG and SMMA in two-component injection moulding and coextrusion. The Mediprene range was until recently avail- able in hardnesses ranging from 35 to 65 Shore A. “However, it was difficult to achieve decent chemi-
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cal bonding to polar substrates for medical devices incorporating even softer TPE design features and functionality,” says the company. The new Medi- prene A2 TPEs, which have hardnesses starting at 25 Shore A, have been developed to overcome these challenges. Fellow TPE major Kraiburg TPE, meanwhile, has just debuted medical and healthcare products at the Medical Manufacturing Asia and Medical Fair Asia in Singapore at the beginning of September. It too highlights multi-component injection mould- ing, with products that have high adhesion to polyolefins (COCs, as well as PP and PE) and engineering thermoplastics. “These low-friction, high-elastic, and translucent compounds also have high compression set and superior resealing properties,” the company says. Kraiburg’s Thermolast H product line is designed
exclusively for healthcare and medical device applications in the Asia Pacific market. Grades can be sterilised with an autoclave at 121°C and with EtO. There are two series: HC/AP and HC/RS/AP, the latter being for medical resealing applications. HC/RS/AP shows good adhesion with PP and PE. The Thermolast M series, available globally, is
produced in translucent, transparent, and natural colours, with high transparency and pre-colouring options.
CLICK ON THE LINKS FOR MORE INFORMATION: �
www.sumitomo-shi-demag.eu �
www.arburg.com �
www.engelglobal.com �
www.elix-polymers.com �
www.polyplastics.com �
www.celanese.com �
www.hexpol.com �
www.kraiburg-tpe.com �
www.sabic.com
September 2022 | INJECTION WORLD 59
Above: Testing for adhesion in two-component moulding at Hexpol TPE
IMAGE: HEXPOL TPE
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