Example 7
Injection molded implants of succinic acid-1,4-butanediol-malic acid copolyester (Tepha lot 180333) with weight average molecular weight of 184 kDa, Tm=115° C., were prepared using an Arburg model 221 injection molder using the following conditions. The barrel temperature of the molder was increased from 70° C. at the feed zone to 170° C. at the end of the barrel. The mold temperature was maintained at 32° C. After molding, the implants were dried in a vacuum oven at room temperature for 48 hours, and tensile properties determined using an MTS test machine with a 2 inch/min cross head speed. Representative tensile properties of the implants were as follows: Young's Modulus 0.66 GPa (96,600 psi), Yield Strength 49.2 MPa (7,140 psi) and Break Stress of 71.7 MPa (10,400 psi).
Example 8
Interference screws with a diameter of 7 mm and length of 20 mm were injection molded from succinic acid-1,4-butanediol-malic acid copolyester (Tepha lot 180333), and from the same copolyester after blending with 50 wt. % beta-TCP (tri-calcium phosphate). The screws were formed using a similar procedure to that described in Example 7. After injection molding of the screws, the intrinsic viscosity of the compositions was essentially identical to that of the starting materials, indicating little loss of weight average molecular weight during injection molding occurred. The torsional strength of the screws was determined by embedding the tip of the molded screws in epoxy resin and measuring the maximum torque achieved by the screwdriver before failure of the screws. The average of three screws tested for the copolyester alone gave a value for torsional strength of 15.0 Ncm. The testing was repeated for the screws prepared from the blend, and the average value was 18.2 Ncm. For comparison, a commercial Arthrex Biointerference screw for implantation composed of PLLA (poly-L-lactic acid) was also tested. The Arthrex Biointerference screw has an average failure torque of 12.1 Ncm.
