The term ‘Xylene Solubles’ refers to the percentage of soluble species in homo- and copolymers of polypropylene. Its value correlates to the R21 value and to the amorphous content of the polymer. For polypropylene homopolymers, R21 is a measure of tactility parameters like stiffness and hardness. Investigating copolymers, R21 additionally corresponds to comonomer related parameters such as transparency and gloss. Its measurement is widely used to control the polymerization process and to determine the physical properties of final products for Quality Control.
Historically the xylene soluble content (ISO 16152, ASTM 5492) has been measured by extraction.
With this time consuming method, a direct controlling of the polymerization process is not feasible. In contrast, the TD-NMR application is fast, operator independent and requires no harmful solvents or dedicated lab-space.
