Polymeric adhesives are used in a variety of joining applications in both military and civilian sectors. These adhesives often require toxic volatile organic compounds (VOC) to polymerize and, therefore, pose a significant health hazard. Based on the Toxic Release Inventory information, it is estimated that greater than 1.6 million pounds of VOCs are released annually through the use of solvent-based adhesives.
The objective of this project is to develop innovative polymers that will serve as a viable alternative to current high VOC, non-structural adhesives.
Cell-to-cell or cell-to-surface adhesion is a common feature among multi-cellular and communal organisms. Adhesive polymers are produced by microorganisms inhabiting extreme environments such as hot springs and microbial mats. Microbial adhesives release no VOCs and are cost competitive. The diversity amongst microorganisms provides compounds with a diversity of adhesive properties.
A two-phased approach is being used for the analysis and development of novel polymer adhesives. First, new polymers are being screened using standard physical performance tests for adhesive properties. Then, detailed analysis will lead to the formation of derivative compounds with expanded capabilities. The analytical techniques to be utilized will include Attenuated Total Reflectance Fourier Transformed Infrared (ATR-FTIR) and Time of Flight Secondary Ion Mass spectrometry.
Five promising adhesive-producing microorganisms have been identified out of the 250 microbial cultures subjected to preliminary screening for adhesive properties. Tensile strength of these adhesives extends to 1500 pounds per square inch (psi) on bare aluminum. In lap shear mode, anodized aluminum and various plastics showed adhesive strength up to 200 psi with some exhibiting elastic properties. The failure mode varied among the five adhesive preparations from cohesive to adhesive to mixed. ATR-FTIR indicates that the adhesives are largely polysaccharides with a protein element in some cases.
The amount of VOCs being released into the environment will be substantially reduced through the development of environmentally safe, thermostable, and water tolerant adhesives. Because the Army, Navy and Air Force use non-structural adhesives for gaskets, instrument panels, textiles, packaging and labeling, the Department of Defense (DoD) will realize significant cost savings from compliance with environmental regulations and the decrease in medical costs associated with the use of VOCs while continuing to meet physical property performance requirements for numerous DoD applications.