Hi Stan,

Thank you for your comment!
Our local team will be in touch with you soon to discuss in detail. In a general level (and not yet knowing the full details of process conditions), Vaisala's process refractometers can be used if polyethylene can be dissolved in decalin (tetrahydronapthalene), if desired polyethylene amount is in %-level class, if the individual Refractive Index values of polyethylene are different than of decalin (tetrahydronapthalene).