Thermorheological analysis of PVC blends

The effect of temperature on dynamic viscoelastic measurements of miscible poly (vinyl chloride) (PVC)/ethylene-vinyl acetate-carbon monoxide terpolym er (EVA-CO) and immiscible PVC/high-density polyethylene (HDPE) and PVC/chl orinated polyethylene (CPE) molten blends is discussed. PVC plasticized wit h di(2 ethylhexyl) phthalate (PVC/DOP) and CaCO3 filled HDPE (HDPE/CaCO3) a re also considered for comparison purposes. Thermorheological complexity is analyzed using two time-temperature superposition methods: double logarith mic plots of storage modulus, G', vs. loss modulus, G ", and loss tangent, tan delta, vs, complex modulus, G*, plots. Both methods reveal that miscibl e PVC/EVA-CO and PVC/DOP systems are thermorheologically complex, which is explained by the capacity of PVC to form microdomains or crystallites durin g mixing and following cooling of the blends. For immiscible PVC/ HDPE and PVC/CPE blends the results of log G' vs. log G " show temperature independe nce. However, when tan delta vs, log G* plots are used, the immiscible blen ds are shown to be thermorheologically complex, indicating that the morphol ogy observed by microscopy and constitued by a PVC phase dispersed in a HDP E or CPE matrix, is reflected by this rheological. technique. (C) 2000 John Wiley & Sons, Inc.