Gelation/fusion behavior of PVC plastisol with a cyclodextrin derivative and an anti-migration plasticizer in flexible PVC

We successfully evaluated the effects of 2,3,6-per-O-benzoyl-β-cyclodextrin (Bz-β-CD) on the rheological properties of PVC plastisols and the migration behavior of plasticizer from flexible PVC. Two types of plasticizer, di-isononyl phthalate (DINP) and diisononyl cyclohex-4-ene-1,2-dicarboxylate (Neocizer), along with Bz-β-CD as a migration inhibitor were mechanically mixed into an emulsion grade PVC resin to prepare plastisols. The presence of Bz-β-CD was expected to facilitate formation of stable complexes with DINP or Neocizer in the flexible PVC. It was necessary to determine whether changes in the processing conditions of the PVC plastisol were needed for use in this application. To this end, the viscoelastic properties of the plastisols, including the elastic modulus, G′, and the viscous modulus, G″, were continuously monitored as a function of temperature during the gelation and fusion processes using rheological analysis techniques. The results showed that complete gelation was slightly delayed and both moduli (G′ and G″) decreased upon addition of Bz-β-CD to the PVC matrix. FE-SEM images yielded insight into the gelation and fusion processes. The curing conditions and physical properties of the flexible PVCs containing Bz-β-CD were optimized, and the influence of Bz-β-CD on the migration of the plasticizers and the stability of the flexible PVC was studied. The results showed that Bz-β-CD reduced migration of DINP and Neocizer from the flexible PVC by almost 40% and 25%, respectively, thereby favorably restricting migration within the flexible PVC.