How are chemical purging compounds different?
With other types of purging compounds, you usually just run the material through the system until you think that everything is more or less clean. With chemical purging compounds, you typically flush the system with some stiff resin to remove the bulk of the production material, then you fill the system with one system volume of the purging compound and then slow or stop the screw for a period of time known as the “heat soak” period. This is when the chemistry does its job. So, in a nutshell, if you use a low-performance physical or abrasive purging compound the cost per pound will be low but you’ll use a whole lot of pounds to get good results – if you can get them at all! With a high performance chemical purging compound you will pay somewhat more per pound but you’ll use far less – only about one system volume – so the cost per purge will be very competitive, especially if you get good results!
