Dynamic light scattering studies on poly(vinyl chloride) clusters and aggregates in tetrahydrofuran

A novel method to characterize the history of processing for poly(vinyl chl oride) (PVC) has been presented. This method consists of: (1) dissolving PV C in tetrahydrofuran; followed by (2) dynamic light scattering (DLS); and ( 3) cluster-size distribution analysis. It was found that the characteristic decay time distribution function G(tau) showed the history of sample treat ment, where tau is the characteristic decay time. In the case of dilute sol utions of virgin PVC resin, G(tau) was dominated by the fast mode at tau (f ) approximate to 30 mus. This is the first observation of the presence of P VC clusters of ca. 4.5-6.0 nm. On the other hand, those prepared from a mil led PVC film exhibited another peak at a larger characteristic time, tau (s ) approximate to 3 ms. This indicates that aggregates about 100 times large r than the clusters are formed during processing. The formation of the larg er clusters was also verified by atomic force microscopy. It is concluded t hat DLS is a sensitive means in characterizing gel structure and processing history for PVC films. (C) 2001 Elsevier Science Ltd. All rights reserved.