Homogenization in mechanical mixing involving polyvinyl chloride. II. Effect of different types of polymers on breakdown of PVC particulate structure and mixing mechanism
Titel:
Homogenization in mechanical mixing involving polyvinyl chloride. II. Effect of different types of polymers on breakdown of PVC particulate structure and mixing mechanism
Auteur:
Kwak, S. Y. Nakajima, N.
Verschenen in:
Journal of macromolecular science. Part B, Physics
Paginering:
Jaargang 34 (1995) nr. 1-2 pagina's 153-170
Jaar:
1995-02-01
Inhoud:
The process of mixing PVC with other polymers, including an examination of how these polymers contribute to the breakdown of the particulate structure of PVC, is described. The polymers were an immiscible nitrile rubber containing 22% acrylonitrile (NBR-22) and two miscible polymers, poly-ε-caprolactone (PCL) and copolyester thermoplastic elastomer (trademark Hytrel). The mixing of PVC and NBR-30, as investigated in the previous paper (Part I), was also considered as a reference. The overall progress of mixing for the three systems (i.e., PVC/NBR-22, PVC/PCL, and PVC/Hytrel) was similar to that for PVC/NBR-30; the removal of skins was followed by breakdown of PVC particles. However, the rate of breakdown differed widely from system to system, depending on the inherent thermodynamic and viscoelastic nature of the individual polymers which served as the medium for stress transfer to the PVC particles. Molecular mixing, which provides a strong interfacial adhesion between PVC and the component polymer, was important in the breakdown process; the immiscible pair, PVC/NBR-22, gave the slowest mixing. The magnitude of the storage modulus, G' at the onset of mixing and at the mixing temperatures was also important. Among the three miscible polymers, the breakdown rate decreased with decreasing modulus, in the order Hytrel, NBR-30, and PCL. The higher temperatures in PVC/Hytrel mixing contributed to a faster rate of PVC breakdown, due to the more serious weakening of the interparticle bonds and more melting of PVC microcrystallites.
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