Daniel Schmidt, Plastics Engineering
According to the Vinyl Institute, 25 percent of all medical products containing plastic are made with PVC. Flexible PVC (FPVC) can be found in everything from examination gloves and tubing to blood bags and dialysis equipment. In many of these applications, improved barrier properties would be of potential benefit, both in terms of keeping air and moisture out and keeping plasticizers and additives in.
With that in mind, we have undertaken a study to determine the optimal nanoclay type and compounding conditions for the preparation of medical grade PVC nanocomposites, using a commercially available FPVC resin. Optimized, optically transparent systems were injection molded and sheet extruded and their structure, thermal mechanical, and barrier properties measured.
X-ray diffraction indicates polymer intercalation with the possibility of some exfoliation and the presence of highly oriented clay in the sheet-extruded samples especially. In spite of the presence of alkylammonium modifiers capable of catalyzing PVC degradation in the form of free salts, the study observed no reduction in the thermal stability of these materials in air or in their mechanical performance. The researchers found that the FPVC nanocomposites may be processed with little or no adjustment of the extrusion and injection conditions vs. the virgin FPVC resin. Finally, they demonstrated a substantial increase in barrier properties at optimized clay loadings.