Structure and rheological properties of PVC melts

Abstract

The rheological properties of PVC compounds reflect the state of the flow units. The steady state structure which may be found in PVC melts is predicted to depend on the interaction of stresses in simple flow and temperatures for transition from rubberlike solid to liquid state and transition from a liquid state containing crystallite aggregates to a liquid state without d crystallite aggregates, called the gel destruction temperature T and the dynamic melting temperature Ttp. respectively. The model predictions for Td and T2w are compared with experimental data.

Thermorheological analysis of PVC blends

“…We remark the thermorheological heterogeneity of pure PVC and PVC/EVA-CO and PVC/DOP miscible systems, with respect to the other pure polymers and filled HDPE and PVC/ HDPE and PVC/CPE blends. Considering that the rheological response of PVC is due to the existence of ordered microdomains or randomly dispersed microcrystallites below 200°C, [23][24][25][26] we have to admit that microcrystallinity appears as the most probably cause of the lack of superposition displayed also by miscible PVC/EVA-CO blends and PVC/DOP systems ( Figs. 5 and 6).…”

“…Actually molten PVC blends are complex systems, because the peculiar rheological behavior observed in PVC at processing temperatures (170 -190°C), is due to the presence of ordered domains or microcrystallites. [23][24][25][26] The thermorheological complexity of pure PVC, which has been probed by dynamic viscoelastic results, 27,28 constitutes a difficulty in addition to the analysis of molten blends. However, in this article we show that temperature dependence analysis of dynamic viscoelastic functions in the molten state represents a useful technique to investigate structural and morphological aspects, related to final properties, of miscible and immiscible PVC-based blends.…”

The effect of crystallites on the rheological properties of microphase‐separated PVC‐PBA‐PVC triblock copolymers obtained by single electron transfer‐degenerative chain transfer living radical polymerization

“…4 and Table 2, which allows us to find resemblances between the rheological response of our triblock copolymers and the well-studied extrusion rheology of PVC samples. It is known [34][35][36][37][38][39] that PVC behaves rather like a filled polymer, owed to the systematic presence of crystallites at the test temperatures. A significant difference, in favor of the copolymers, is that, owing to the viscosity reduction associated with the copolymerization with PBA, temperatures considerably lower than with PVC can be used in capillary extrusion experiments.…”

“…The crossing of the lines is close to T 5 127 C, which coincides with the lower melting temperature, T m1 5 127 6 0.8 C, defined through DSC measurements. In the literature [37,39], two flow zones are defined for PVC, respectively, above and below the highest melting temperature of crystallites, T m2 . However, with our copolymers, we can define a new low temperature flow region that accounts for the presence of both crystallites that melt at T m1 and crystallites that melt at T m2 and is a particular feature of the triblock copolymers studied in this work, because, in the case of PVC, rheological measurements at such low temperatures are not possible.…”