POLYURETHANE USAGE IN ARMORING SOLUTIONS
By Michael J. Babiarz, Vice President, Business Development, Line-X Protective Coatings
Jun 08. As the demand for different armoring solutions grows, the usage of polyurethanes and polyureas is becoming more and more common. In the world of weight versus cost, polyurethanes are allowing some of those gaps to be filled. The physical properties that can be achieved are allowing different composite armor solutions to be utilized.
Polyurea can be defined as the result of a chemical reaction between an isocyanate and an amine. In polyurea coating terms, this is generally a reaction between an MDI (methylene diisocyanate), IPDI (isophorone di isocyanate), HDI (hexamethylene diisocyanate), and/or TDI(toluene diisocyanate) pre-polymer with amine-terminated resins. Polyurea is generally used as an industrial coating where fast reactivity, high film built, and moisture insensitive characteristics are important. Polyuerea coatings are predominantly designed for severe environments with good chemical resistance, and most likely are formulated for a 1:1 mix ratio.
Polyurethane can be defined as the result of a chemical reaction between an isocyanate and a polyol. Polyurethane rate of reaction and cure rate can be adjusted with catalyst.. Polyurethanes are generally used in slow reacting products, self leveling such as as casting materials and pourable foams. They show good longevity, flexibility in end-product physical properties and are relatively inexpensive.
Polyurea/Polyurethane hybrid formulations can be defined as the result of a chemical reaction between an isocyanate and a mixture of polyol and amine co-reactants. These formulations generally provide an “intermediate” polyurea that displays many of the same properties of a polyurea. However, hybrid formulations can also be formulated to display the combined advantages of polyurea and polyurethane chemistries. Polyurea/polyurethane hybrids are normally associated with use in service environments items that generally do not require immersion or extreme temperature conditions for application. Some examples of these applications include sprayed-in truck bed linings and other automotive applications.
The vast majority of materials used in armoring applications will be hybrids due to their wide blend of polyurea and polyurethane physical properties. What is critical to note is that different physical properties will provide significantly different protection levels in armor applications. In simple terms, all polyurethanes are not equal.
Since the formulations can vary so dramatically, it is imperative that any supplier can provide independent certification of its physical properties. Also, the raw materials used in formulating can vary dramatically. While many of the products may look the same, the ability to perform in severe service environments can be dramatically different.
Currently, polyurethanes are being incorporated in three main areas: blast mitigation, spall protection, and simple impact/abrasion protection.
Blast mitigation on buildings using polyurethanes has been tested since 1999 when the USAF performed initial testing in Florida. The initial positive results led to a more formal test performed by Technical Support Working Group (TSWG) in 2004. Twenty seven companies submitted samples in that round of testing. Based on that testing, PAXCON has been awarded numerous contracts for applications to US Government buildings and private facilities as well.
Polyurethane hybrids have also been used by various defense contractors for simple abrasion and impact protection. These applications range from flooring on personnel carriers, dashboards, equipment racking, etc. These are all basically generic applications with minimal specification requirements.
In the last few years, the demands for blast mitigation protection on vehicles have increased. The ne