Delamination Resistant Coating System for Zinc Sulfide Domes and Windows, Utilizing a Compliant Layer.

Zinc Sulfide (ZnS) is the most practical material for infrared transparent domes and windows operating at long wave infrared wavelength. Hard outer coatings have been applied to ZnS to protect it from rain and sand erosion. Theoretical analysis of multi-layer coatings suggests that a compliant layer between the hard outer coating and the ZnS surface may improve resistance to rain impact damage. In this program, a bonded ZnS window is proposed and an innovative nano-composite polymer material is developed as the compliant layer in addition to index matching for the hard coating. This novel compliant layer will absorb the energy created by the impact of rain and sand, and subsequent crack propagation, thereby protecting the ZnS dome from damage and preventing delamination of the coating system. Once the hard outer coating is severely damaged, it can be removed and replaced leading to life-cycle cost savings. The nano-composite polymer material itself has strong adhesion ability and can be used from – 70 oC to + 100 oC. It has high transparency (>90%) to long wave and mid wave infrared radiation. It is even transparent in the 0.6 – 2 micron region when its thickness is about 100 microns. In Phase I, we will develop the nano-composite polymer and bonded ZnS windows for the Whirling Arm Rain Rig test.BENEFITS: Delamination of hard outer coatings on ZnS domes and windows may be damaged by the impact of rain and sand. This degrades performance and may lead to excessive replacement of windows. For missile domes, the possibility of catastrophic failure is a serious concern. The proposed novel nano-composite polymer materials can bond hard protective coatings to infrared domes and windows to improve their resistance to rain impact damage. There are numerous commercial applications for the material. The proposed nano-composite polymer can also be used to bond zinc selenide domes and windows. It can be used as an immersion materials and glue to bond infrared optics and fibers in infrared imaging for the applications of fire fighting, industrial control, driver’s aids, traffic monitoring, biomedical imaging, pollution detection, and security systems.