| STUDY |
The PCPP polymer was the pulverized into particles 150-330 um in diameter and compression molded into this slabs whose dimensions varied from face surface areas of 0.2-3.0 3.0 aquare centimeters, a thickness of 0.05-0.10 centimeters, and had an average weight of 24 milligrams. The compression was conducted at 150.degree. C. and at 50 KPSI. These slabs were then placed in vials containing phosphate buffer at 37.degree. C. but whose pH ranged from 1.0-11.0. The in vitro erosion rates were then determined as in Example I. The results indicated that the rate of erosion for the PCPP matrix was approximately five times less than the erosion rate of PCPM in phosphate buffer at 7.4 pH held at 37.degree. C. However. the rate of erosion was accelerated with increases in pH. Each matrix under test maintained its physical integrity at each pH except at pH greater than 9 where some particles were found to separate from the matrix proper. At pH 1.0, however, the erosion rate was found to be almost negligible. Accordingly, the rate of erosion is thus demonstratably affected by the pH of the environment at the site of its intended use
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