This Small Business Innovation Research (SBIR) Phase I project describes the development of an instrument that will quantitatively measure the dimensional change, i.e. swelling behavior, of crosslinked polymer samples as they are exposed to changing environments, such as solvent conditions, pH, and temperature. The wide prevalence of radiation and chemically-crosslinked polymers in industries including biomedical, wire and cable, and packaging has led to the need for a reliable measurement technique to quantify the degree of crosslinking, obtainable from swelling measurements, for process development and quality control. Additionally, end-users would like to know the environmental response of these materials a priori. Currently, researchers rely on weighing techniques to monitor the swell ratio as a sample is placed in a solvent. Solvent evaporation and technician procedure make this technique prone to error and transient measurements difficult to obtain. In the instrument proposed here, a micrometer system will monitor the change in one dimension of a sample as it swells or de-swells in controlled environment with a resolution far better than gravimetric means. These transient measurements will provide the steady state swell ratio, degree of crosslinking anisotropy, and the kinetics of swelling, the latter information valuable for drug release systems, hydrogels, and smart materials.
There are currently no commercial instruments designed specifically to measure the swell ratio of crosslinked polymers. The orthopedic industry, in conjunction with the ASTM, is developing a new guideline for these measurements that requires dimensional measurements made while the sample is in the swelling solvent. In addition to providing material parameter information, this instrument will allow quantitative prediction of material behavior when exposed to changing environments. This technology has applications to hydrogels, smart materials, films, granular material, and the wire and cable industry.
