A computer scanning procedure for the determination of total double-bond concentration resulting from PVC degradation is described. It is fast, fully automated, and has a very high sensitivity (5 ppm of degraded monomer units). This high sensitivity makes possible the monitoring of discoloration on a very small surface and generates very large amounts of experimental data allowing corrections for inhomogeneities and surface irregularities. The measured extinctions (Ergb) correlate with the concentrations of double bonds and allow the estimation of degradation rates.The measuring of stabilization times and the reaction rates of stabilizers with allylic chlorides and HCl offers the capability to optimize the W C stabilization.
Capillary rheometry allows monitoring of PVC thermal and shear stress degradations separately. Based on testing of PVC compounds with a capillary rheometer, stabilizers can be efficiently optimized to reduce both degradation processes. Capillary rheometry is an important tool for further improving productivity of PVC processing at high shear rates.
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