Thermal, mechanical, and rheological comparison of stereoblock ¯exible polypropylenes Atul R. Khare * , Samuel Y. Ding, Michael T.K. Ling, Chuan Qin, Lecon Woo Corporate Research and Technical Services, Baxter International, Route 120 and Wilson Road, Round Lake, IL 60073, USA Received 10 November 1999; accepted 20 July 2000 Abstract For medical ¯uid delivery applications, clear materials with both low modulus and high temperature resistance are highly sought after. Many of the currently available materials are either optically opaque, or far too expensive to be suited for the majority of applications. The recently available stereoblock homo-polypropylene polymers, where atactic and isotactic sequences are placed on the main-chain, present an attractive opportunity. We have examined some of these commercial as well as experimental polymers by thermal analysis, rheology and mechanical analysis for their potential suitability in medical applications. # 2001 Elsevier Science B.V. All rights reserved. Keywords: Polypropylenes; Polymers; Thermal analysis; Rheology; Mechanical analysis 1. Introduction The medical device and packaging industries require that a material provide unimpeded light trans- mission to allow visual inspection for particulate matter contamination or the completion of dissolution of mixed or compounded medications in order to safeguard patients. Also, the need for sterile delivery of therapies makes compatibility with steam autoclav- ing (the preferred method of sterilization) a must. But this seriously challenges a material's properties due to the high temperature of 1218C (2508F) and pressure. In the last few years, we have witnessed a funda- mental material revolution not seen in the last half century of polymer history. The single site catalysts, many of which are metallocene compounds, are creat- ing novel compositions with properties unheard of only a few years ago. In the medical plastics and packaging markets, the achievement of cost perfor- mance similar to that of ¯exible PVC has always been a technological challenge. With the metallocene cat- alysts, unprecedented co-monomer incorporation can be achieved with high homogeneity. However, with the steady reduction in crystallinity and modulus, the melting point also decreases monotonically. Thus, materials with both the ¯exibility and high tempera- ture capabilities are still rare. More recently, several developments on propylene based elastomers have been discussed. Combining the high melting point of isotactic polypropylene with a suitable elastomeric block structure appears to be promising in achieving these properties [1±3]. Researchers at E.I. DuPont discovered a catalyst with moderate productivity, which could produce elastomeric products with interesting properties. Thermochimica Acta 367±368 (2001) 119±124 * Corresponding author. Tel.: 1-847-270-3423; fax: 1-847-270-4361. E-mail address: atul_khare@baxter.com (A.R. Khare). 0040-6031/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved. PII:S0040-6031(00)00681-X