Physico-mechanical properties of degradable polymers used in medical applications: a comparative study.

The physico-mechanical properties of degradable polymers used for medical applications have been characterized. The following polymers were included in this study: three samples of poly(ortho esters) derived from 3,9-bis(ethylidene 2,4,8,10-tetraoxaspiro[5,5]undecane) and various ratios of 1,6-hexanediol and trans-cyclohexane dimethanol, poly(glycolic acid), six samples of poly(L-lactic acid) and poly(D,L-lactic acid) with mol wt from 21,000 to 550,000, poly(epsilon-caprolactone), poly(beta-hydroxybutyrate) and three copolymers of beta-hydroxybutyric acid and various amounts of hydroxyvaleric acid, one sample each of two different types of poly(anhydrides), poly(trimethylene carbonate) and two different poly(imino-carbonates). For each polymer, the thermal properties (glass transition temperature, crystallization, melting and decomposition points) were determined by differential scanning calorimetry and by thermogravimetric analysis. The tensile properties (Young's modulus, tensile strength and elongation at yield and break) were determined by tensile testing on an Instron stress-strain tester. The flexural storage modulus as a function of temperature was determined by dynamic mechanical analysis.