Air Force Research Laboratory (AFMC) Edwards AFB United States
The effectiveness of an experimental, non-commercial diamine monomer as a replacement for methylene dianiline MDA inthe commercial polyimide PMR-15, was assessed in this SERDP research project. The monomer, designed and synthesized at AFRL, features a polyhedral oligomeric silsesquioxane POSS core with an aromatic periphery to maximize its thermal stability. MDA is a known irritant, causative agent for liver damage, and possible carcinogen to humans as it has been found to cause liver and thyroid cancer in mice. In response, OSHA has set a low permissible exposure limit and replacement efforts for materials containing MDA are ongoing. Unfortunately, many efforts spanning approximately 35 years seeking an alternative to MDA in PMR-15 have not produced a solution that affords an equivalent balance of properties. The POSS monomer was chosen based on speculation of non-toxicity based on its chemical structure and high molecular weight. Furthermore, premise for this work was in part because of the novelty of POSS and its chemical framework for this particular application. Due to the limited scope of this SEED project, the POSS diamine was not examined for any biological effects but could be the focus of future studies. The subject POSS monomer was used as a drop-in replacement for MDA in heritage PMR-15 chemistry and resultant oligoimide, cured polyimide, and carbon fiber reinforced composite properties were examined.