Biomedical Engineering Reference
In-Depth Information
molecular weight of 0.5-5 × 10
6
g.mol
−1
) with a low surface energy, an
excellent lubricity and a high chemical inertness conferring its long-
term stability. PTFE also possesses a low friction coefficient. In
biomedical applications, PTFE is used in its expanded form (e-PTFE)
since its microporous structure allows biointegration for fixation. Its
mechanical properties vary with the porosity and the microstructure.
As a consequence, e-PTFE is widely used for soft-tissue
reconstruction such as vascular grafts. The main drawback of PTFE is
its high density (2.2 g.cm
−3
) in comparison with polyester fabrics
(1.31-1.38 g.cm
-3
) and its low elastic modulus which limits its use in
structural components [PAR 07].
Poly(ethylene terephthalate) (PET) is a non-degradable polyester
with a high melting temperature, a moderate crystallinity degree (30-
40%), a high tensile strength and stiffness, and a good dimension
stability. The hydrolysis of PET is restricted because of the presence
of hydrophobic aromatic groups and its crystallinity. PET is mainly
used in fabric or fiber forms for vascular grafts, ligaments and sutures
[SUB 14].
Poly(etheretherketone) (PEEK) combines aromatic groups and
flexible ether segments. It is a semi-crystalline polymer with a
maximum crystallinity of 48%. PEEK possesses a good resistance to
environmental stress cracking, an excellent chemical resistance, as
well as high tensile and flexural strengths, a high fatigue limit, and
favorable wear properties. PEEK is a thermoplastic alternative for
replacing metal implant components, especially in orthopedic
applications [TEO 98].
Due to their good processability and machinability, polyacrylates
are used in a wide range of biomedical applications, such as
intraocular lenses, bone cements for joint prosthesis fixation, denture
and maxillofacial prostheses. Without any additives, poly(methyl
methacrylate) (PMMA) is an amorphous polymer with a high
transparency (92% transmission), a refractive index of 1.49, and a
good UV light resistance, which make it appropriate in lens
applications. The main advantage of PMMA as bone cement is
