Are there different types of commercial purging compounds?
There are three main types of commercial purging compounds, and also hybrids** of these types. • Chemical types: Liquid & solids — these are often concentrates that need to be let down into your own next resin or are supplied as pre–blended in a carrier. This type of purging compound requires that the purge compound be added to the machine and the purging compound be allowed to soak in the barrel for a specific length of time and with adjusted heats without the screw turning to allow the chemical reaction to occur. Heat will activate the chemical reaction — this chemical reaction modifies the molecular chain of the polymers that need to be purged, making it easier for the next material to flush it out. Chemical purges can be effective but costly from a cost per lb. and also a “cost to purge” basis, as purging takes longer because of the soak time. Some of the chemical type purging compounds also release ammonia or others fumes which may be harmful to machine operators. Also the need to
