The objective of this project is to develop a new visual technique to examine the interfacial structure of total resorbable fiber-reinforced composites. It is well-known that interfacial structure of a composite is the weakest link in composites and is also one of the most important parameters for determining its success or failure. For a total resorbable composite, this interfacial region would also be the first to degrade and fail. Unfortunately, there is no good visual technique to examine this critical region of composites.
We have recently developed a visual technique to examine this critical region of total resorbable composites. The technique is based on laser confocal microscope and its capability to conduct "optical thin section", i.e., non-destructive. We have shown that the interfacial gap width has a close relationship to interfacial shear strength of a variety of biodegradable composites. We believe that this new characterization technique could be use to screen a wide range of fiber/matrix combinations for specific end uses.
We have also extended this new characterization technique
to measure the pH of the interior of biodegradable biomaterials
without physically breaking the biomaterials apart.
Our data demonstrate experimentally the long speculated belief
that, due to the heterogeneous nature of hydrolytic degradation
of bulk biodegradable biomaterials like polyglycolide, polylactide,
their interior pHs are lower than their surface or the degradation
media. This differential pH values as a function of depth of the
biodegradable biomaterials are due to the acidic degradation
products that accumulate within the interior of biomaterials
during hydrolytic degradation.