Journal of Biomaterials and Nanobiotechnology, 2011, 2, 361-368 doi:10.4236/jbnb.2011.24045 Published Online October 2011 (http://www.SciRP.org/journal/jbnb) Copyright © 2011 SciRes. JBNB 361 The Influence of Different Sterilization Techniques on the Time-Dependent Behavior of Polyamides Galina Kubyshkina 1 , Barbara Zupančič 2* , Marina Štukelj 3 , Dušan Grošelj 4 , Ljubo Marion 4 , Igor Emri 2 1 Elektromaterial Lendava d.d., Lendava, Slovenia; 2 Center for Experimental Mechanics, Faculty of Mechanical Engineering, Univer- sity of Ljubljana, Ljubljana, Slovenia; 3 Veterinary Faculty, University of Ljubljana, Ljubljana, Slovenia; 4 Faculty of Medicine, Uni- versity of Ljubljana, Ljubljana, Slovenia. Email: * barbara.zupancic@fs.uni-lj.si Received July 18 th , 2011; revised August 22 nd , 2011; accepted September 27 th , 2011. ABSTRACT For this investigation conventional polyamide 6 with monomodal molecular mass distribution, and the newly developed bimodal one were used. Conventional polyamide 6 was used as a reference material in order to emphasize prospects of us- ing bimodal material for medical applications from the point of view of sterilization resistance and improved creep behavior. Time-dependent mechanical properties of testing samples were characterized by torsional creep measurements in non-ster- ilized state and after sterilization with three different techniques: with autoclave, ethylene oxide, and hydrogen peroxide plasma. Results show that the two materials exhibit pronounced difference in morphology and consequently, mechanical properties. Both of them were not significantly affected by any of used sterilization techniques. However, bimodal material, originally being noticeably more time-stable in comparison to monomodal one, retains these preferences also post steriliza- tion. Keywords: Sterilization, Polyamide, Creep, Time Stability 1. Introduction Polymers are often the materials of choice for medical devices, medical packaging, and food packaging, replac- ing traditional materials such as stainless steel and glass [1]. Polymers are beside non-dental applications exten- sively used in dentistry as composite (resin-ceramic) res- torative materials, implants, dental cements, and denture based teeth. Theoretically, they can be modified for maximum bio- compatibility and acceptable mechanical properties. Al- though all three groups of polymers (thermoplasts, ther- mosets, elastomers) are used for medical applications, the thermoplastics are most widely used [2]. They offer manufacturing cost savings, lighter weight, and performance characteristics that meet and exceed the demand in many highend applications. However, the pro- cess of sterilization can strongly affect the properties of the polymers [1,3]. Sterilization is the complete elimination of microbial viability, including the vegetative forms of bacteria and spores. Sterilization of surgical equipment, implants, linens, and attire is one aspect of a series of highly regimented steps constituting aseptic technique. The methods of ster- ilization can be divided into two general groups: physi cal and chemical. Although sterility can be achieved with certain chemicals, physical methods are generally more reliable. Heat, filtration, and radiation are the most com- monly used physical methods of sterilizing medical and surgical materials. Chemical sterilization is usually ac- complished with ethylene oxide or hydrogen peroxide, although formaldehyde and β-propiolactone are also used occasionally. The most commonly used techniques in ve- terinary medicine are steam, ethylene oxide, and hydro- gen peroxide gas plasma sterilization [4]. Sterilization has increasingly been a topic of discus- sion when comes to the implantology. There are several issues to be considered when sterilization methods are being selected for implantable medical devices [5]. The number of agents capable of sterilizing product or material without adversely or deleteriously affecting pro- duct quality or material integrity is few. There is no sin- gular sterilization method that is compatible with all healthcare products including drugs, polymers, devices, and materials, because of the severity of a process to meet the sterilization criteria and definition [6].