The determination of 50 hydrochloric acid-insoluble material

Refluxing 2 g of polyamide 6 or 66 with 50 ml of 50% hydrochloric acid for 2 h readily dissolves the polyamide. Any impact modifier, any carbon black, together with any polymer such as EVA used as a pigment carrier, and the bulk of any glass filler are insoluble. 

The insoluble material is quantitatively separated by filtering, under suction, through a tared glass filter circle, and washing with 50% hydrochloric acid, water and finally ethanol. The oven-dried filter circle and insolubles are reweighed and the total percentage of insoluble material is calculated. 

If this material is only carbon black or only impact modifier, then the percentage of insolubles is taken as the percentage of that additive. A mixture 

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