{"id":6069,"date":"2017-03-10T08:05:30","date_gmt":"2017-03-10T14:05:30","guid":{"rendered":"https:\/\/www.ulprospector.com\/knowledge\/?p=6069"},"modified":"2017-09-13T15:31:30","modified_gmt":"2017-09-13T21:31:30","slug":"get-a-reaction-with-1k-self-crosslinking-and-isocyanate-free-technology","status":"publish","type":"post","link":"https:\/\/ulprospector.ul.com\/6069\/get-a-reaction-with-1k-self-crosslinking-and-isocyanate-free-technology\/","title":{"rendered":"Get a Reaction with 1K Self-Crosslinking and Isocyanate-Free Technology"},"content":{"rendered":"
\"What
Copyright: buranatrakul \/ 123RF Stock Photo<\/a><\/figcaption><\/figure>\n

Previous UL Prospector articles have discussed typical crosslinking chemistries1,2,3,4<\/sup>. These were predominantly polyurethane-based, relying on the reaction between a polyisocyanate (PI) and a polyol in a two-part system. There are also chemistries that rely on heat to initiate a reaction, such as hydroxyl-functional acrylics that utilize melamine as the crosslinker, or ambient-cure using polyisocyanates.<\/p>\n

In the former, lower levels of \u2013OH are ideal for the formulation of hot melt adhesives, while at higher hydroxyl content, acrylic emulsions such as ROSHIELD\u2122 3275 react with polyisocyanates. This is helpful for wood coating applications where early hardness and sandability are important, as either an ambient-cure system or heat-cure to accelerate processing.<\/p>\n

A one- or two-part (or -component) system is also referred to as 1K or 2K. That means that the paint consists of one-component which may be self-reactive (crosslink) or non-reactive, or two components which are two\u00a0parts that are mixed together prior to application.<\/p>\n

There are many factors that are driving the industry to develop a 1K self-crosslinking system, as well as isocyanate-free chemistries. First and foremost, there is a high level of regulatory pressure to eliminate polyisocyanates, although only about 15 percent are used in coatings, adhesives, sealants, and elastomers (CASE) applications, with the rest in rigid and flexible foams.<\/p>\n

A second motivation is the 2K system somewhat limits applications, in that a \u201ckit\u201d consisting of typically a part-filled gallon and a quart, has to be well-mixed prior to the time of application. This requires the reaction of the entire gallon, unless the applicator blends less material, back-calculating based on weights obtained from the MSDS\u2019 density reporting.<\/p>\n

Unless from the coatings industry, it is unlikely someone can prepare less than the full kit. On-site mixing is an issue as well, as poorly homogenized coating will provide less-than-ideal performance and may affect dry and cure. Open time is also a concern, in that the pot life may not be sufficient to complete a project.<\/p>\n

Therefore, at the least, isocyanate-free crosslinking is desired. A recent article in Coatings Tech<\/em>; \u201cIsocyanate-Free\u2009Polyurethane Technology for Automotive Refinish Applications\u201d5<\/sup>, outlines such an approach to achieve that goal.<\/p>\n

Prospector\u00ae<\/sup> coatings material searches<\/h2>\n