Structural damages of maxillofacial biopolymers under solar aging P. N. Eleni Æ M. K. Krokida Æ M. J. Frangou Æ G. L. Polyzois Æ Z. B. Maroulis Æ D. Marinos-Kouris Received: 3 November 2005 / Accepted: 1 May 2006 / Published online: 5 May 2007 Ó Springer Science+Business Media, LLC 2007 Abstract Additional types of silicone biopolymers are widely used in maxillofacial prosthetics. Therefore, the knowledge of the solar radiation’s effect on their structural stability is highly important. Four different industrially synthesized biomaterials were examined, called Episil Europe 1, Europe 2, Europe 3 and Africa 3, which were exposed to solar radiation (UVA, UVB) for eight different time periods (from 8 to 168 h). Structural damages due to irradiation exposure were investigated by mechanical tests (compression) and dif- ferential scanning calorimetry (DSC) methods. Simple mathematical models were developed, containing parameters with physical meaning such as maximum stress (r max ), maximum strain (e), elasticity parameter (E), and viscoelastic parameter (p), for the compression test, and melting temperature (T m ) and Enthalpy in melting point (Heat) for DSC. With increasing irradia- tion time their maximum stress and strain decreased significantly, and the materials lost their elasticity and molecular stability. A decrement in their melting points and heats was observed as irradiation time was increasing. Finally, experimental results demonstrated that solar radiation has a severe effect on the structural stability of the examined biomaterials. Introduction Maxillofacial materials are used to replace missing facial parts which have been lost through disease or trauma [1]. The examined materials consist of siloxane. Silicone rubbers have in general the following advan- tageous characteristics: a wide service temperature range, non-adhesive properties, low toxicity, possible optical transparency, low chemical reactivity, and excellent resistance to attack by oxygen, ozone and sunlight [2]. Although they are widely used, these materials are far from ideal. Due to their exposure to several temperatures and forces, the knowledge of their thermal and mechanical properties as well as the effect of various factors on them are highly important. The quality of these materials depends greatly on their structural stability [3]. The most injurious factor for their structural stability, which also affects their mechanical and thermal properties, is solar radiation that causes disruption in polymers namely aging [4]. The effects of solar exposure are usually examined through differential scanning calorimetry (DSC), com- pression, and other thermal and mechanical methods [5, 6]. The effect of c-radiation has already been examined on the thermal, mechanical, and segmental dynamics of polydimethyl-siloxane (PDMS), using thermal, mechanical, chemical, and segmental methods. Each of these analytical methods identifies different aspects of the degradation mechanism [2]. It has been proved that dental materials provide an increase in their hardness after accelerated aging [7]. Tensile properties of the irradiated polymer after accelerated aging reproduce successfully the behaviour of the naturally aged com- ponents. The effect of microwave on thermal and P. N. Eleni (&)  M. K. Krokida  Z. B. Maroulis  D. Marinos-Kouris Department of Chemical Engineering, National Technical University of Athens, Zografou Campus, 15780 Athens, Greece e-mail: peleni@central.ntua.gr M. J. Frangou  G. L. Polyzois Division of Removable Prosthodontics, University of Athens, Dental School, 2 Thivon Str., 11527 Athens, Greece 123 J Mater Sci: Mater Med (2007) 18:1675–1681 DOI 10.1007/s10856-007-3027-4