The effect of accelerated ageing on performance properties of addition type silicone biomaterials K. Stathi • P. A. Tarantili • G. Polyzois Received: 1 July 2009 / Accepted: 5 January 2010 / Published online: 22 January 2010 Ó Springer Science+Business Media, LLC 2010 Abstract The UV-protection provided to addition type silicone elastomers by various colorants, such as conven- tional dry earth pigments, as well as the so called ‘‘func- tional or reactive’’ pigments, was investigated. Moreover, the effect of a UV light absorber and a silica filler was also explored. Under the experimental parameters of this work, the exposure of silicone to UV radiation resulted in some changes of the IR absorbance, thermal decomposition after 400°C, T g and tensile properties, whereas the storage modulus of samples was not affected. The obtained spec- troscopic data, as well as the results of TGA and storage modulus, were interpreted by assuming that chain scission takes place during aging, whereas the improvement of tensile strength allows the hypothesis of a post-curing process, initiated by UV radiation. Therefore, the increase of T g could partly be due to the above reason and, fur- thermore, to the contribution of a rearrangement of chain fragments within the free volume of the elastomeric material. Regarding the evaluation of various coloring agents used in this work, the obtained results show that dry pigments are more sensitive to accelerated ageing condi- tions in comparison with functional liquid pigments. Moreover, the hydrophobic character of silicone matrix is enhanced, with the addition of this type pigments because of the vinyl functional silanes groups present in their chemical structure. Finally, it should be noted that the incorporation of silica nanofiller did not seem to prevent the silicone elastomer from degradation upon UV irradia- tion, but showed a significant reinforcing effect. 1 Introduction Maxillofacial prostheses play an important role in rehabil- itation following ablative surgery, congenital deformity or trauma. Silicone biopolymers are today the material of choice for the fabrication of facial prostheses because of chemical inertness, strength, durability and ease of manip- ulation [1]. The longevity of a prosthesis is dependent on several factors, including the material from which it is constructed and behavioral factors of the wearer. Over the years there have been several studies on the longevity of facial prostheses and older ones report wearing time for 6–12 months [2–4]. A more recent study reported a mean life span of 14 months [5]. Despite this little improvement the life span of the prostheses still remains relatively short. Clinical experience has indicated the need for frequent replacement of facial prostheses because rapid discoloration in the service environment and/or degradation of the phys- ical and dynamic properties of silicone biopolymers [6, 7]. Studies have reported that color fading and deterioration of feathered edges (tear) were the most common for replace- ment of prostheses [3–5]. Discoloration may be the result of intrinsic or extrinsic colorations secondary to environmental factors. It is a combined multifactorial phenomenon and some of the factors involved are intrinsic characteristics of the material, type of colorants, cleaning habits, use of cosmetics or adhesives and environmental staining (e.g. climate, fungal, body secretions) [8–12]. Coloration of a facial prosthesis is typically achieved through the use of various colorants, such as inorganic dry K. Stathi  P. A. Tarantili (&) Polymer Technology Laboratory, School of Chemical Engineering, National Technical University of Athens, Heroon Polytechniou 9, Zographou, 15780 Athens, Greece e-mail: taran@chemeng.ntua.gr G. Polyzois Division of Removable Prosthodontics, Dental School, University of Athens, Thivon 2, Goudi, 11527 Athens, Greece 123 J Mater Sci: Mater Med (2010) 21:1403–1411 DOI 10.1007/s10856-010-3991-y