Product/Service

PurSil and CarboSil Silicone Urethane Copolymers

Source: The Polymer Technology Group
Silicones have long been known to be biostable and biocompatible in most implants, and also frequently have the low hardness and low modulus useful for many device applications.
Silicones have long been known to be biostable and biocompatible in most implants, and also frequently have the low hardness and low modulus useful for many device applications. Conventional silicone elastomers can have very high ultimate elongations, but only low to moderate tensile strengths. Consequently, the toughness of most biomedical silicone elastomers is not particularly high. Another disadvantage of conventional silicone elastomers in device manufacturing is the need for cross-linking to develop useful properties. Once cross-linked, the resulting thermoset silicone cannot be redissolved or remelted.

In contrast, conventional polyurethane elastomers are generally thermoplastic with excellent physical properties. Thermoplastic urethane elastomers (TPUs) combine high elongation and high tensile strength to form tough, albeit fairly high-modulus elastomers. Aromatic polyether TPUs can have excellent flex life, tensile strength exceeding 5000 psi, and ultimate elongations greater than 700 percent. They are often used for continuously flexing, chronic implants such as ventricular-assist devices, intraaortic balloons, and artificial heart components. TPUs can easily be processed by melting or dissolving the polymer to fabricate it into useful shapes.

The prospect of combining the biocompatibility and biostability of conventional silicone elastomers with the processability and toughness of TPUs is an attractive approach to what would appear to be a nearly ideal biomaterial. For instance, it has been reported that silicone acts synergistically with both polycarbonate- and polyether-based polyurethanes to improve in vivo and in vitro stability. In polycarbonate-based polyurethanes, silicone copolymerization has been shown to reduce hydrolytic degradation of the carbonate linkage, whereas in polyether urethanes, the covalently bonded silicone seems to protect the polyether soft segment from oxidative degradation in vivo.

PTG synthesized and patented silicone-polyurethane copolymers by combining two previously reported methods: copolymerization of silicone (PSX) together with organic (non-silicone) soft segments into the polymer backbone, and the use of surface-modifying end groups to terminate the copolymer chains. Proprietary synthesis methods make high-volume manufacturing possible.

PurSil

  • Non-Adhesive Silicone Surface
  • Outstanding Hydrolytic Stability
  • Hydrophobic
  • High Tensile Strength
  • Optically Clear

CarboSil

  • Low-Energy Silicone Surface
  • Outstanding Oxidative Stability
  • Hydrophobic
  • High Tensile Strength
  • Optically Clear

The Polymer Technology Group, 2810 7th Street, Berkeley, CA 94710. Tel: 510-841-8800; Fax: 510-841-7800.