Boron-neutron-capture radiation treatment of polymers for application in laminated glass window interlayer material
Authors:   , Philipps Joseph Caleb 
Published: September 2022

[EMBARGOED UNTIL 5/1/2024] Critical infrastructure that is either vulnerable to attack or that is located within a high threat area will require increased protection. United States government facilities worldwide have seen ongoing disruption and destruction due to a lack of sufficient capabilities or technology to fully resist attack. Increased efforts to strengthen the building structure, particularly with regards to the explosion-resistant window and building envelope systems, can improve the life-safety and continued operability of critical infrastructure under adverse circumstances. The exterior envelope is the most vulnerable component of a building to an exterior hazard because it is the part of the building closest to the source of the hazard. Among all the exterior envelope components, light elements such as the glass windows are critical points of vulnerability. Polymer interlayer materials are utilized in laminated glass systems to provide increased resilience from blast incidents. The polymer chains within the interlayer material can benefit from material modifications that increase cross-linking between adjacent chains. One theorized method of targeted cross-linking is made possible through a boron-neutron-capture process. This process utilizes neutron radiation that bombards boron-containing material, thus producing emissions of highly energetic particles into the polymer material. Those particles are the catalyst to cross-linking between polymer chains. Previous theoretical work suggested this methods for bulk treatment of polymeric materials. This method has been experimentally utilized for bulk material processing as well as surface treatment during the course of this research. The technique was proposed to alter polymer characteristics such as hardness and elasticity. This document describes initial experiments to evaluate the validity of the technique and to suggest alternative approaches. Commercially available borated polymers have been treated and evaluated with varied neutron flux rates and with varied total neutron dose amounts to determine effective techniques for future application. Custom blended polymers were also irradiated and tested to determine the effects of varying amounts of boron inclusion. A new surface treatment approach using the boron-neutron-capture process is described to improve additional material characteristics such as Toughness. Early results have shown promising material behavior change in tensile tests. The surface treatment process has been extensively investigated in this study to manipulate polymers commonly used as laminated glass window interlayer material. Comparison evaluation tests have been completed to show the treated material behavior change through static tensile loading, dynamic tensile loading, indentation testing, and scratch resistance testing. Results indicate the specific material behavior changes, effects on different interlayer material, and optimizations for the treatment processes. Data resulting from these tests will expand the understanding of the material behavior changes from treatment techniques and show evidence of the expected crosslinking. This understanding will lead to quantifiable application of system capacities to improve the future designs of the window and building systems and lead to safer, more secure, and resilient infrastructure.