Influences of molecular weight and particle morphology on film processing properties of polyvinyl fluoride

To select a suitable kind of resin for preparing films, the melting point (T), thermal decomposition temperature (T-d), and stretch property of polyvinyl fluoride (PVF) as a function of the viscosity-average molecular weight (M,) were investigated. The results showed that Td and maximal stretch ratio of extrusion-cast PVF films gradually increase with the increase of M, T,,, also increases when M-eta is below 400,000, but keeps invariable when M, is beyond 400,000. Six different kinds of PVF resin samples in this article were classified into three types, according to their particle morphologies: (1) loose-structured PVF (PVFA and G); (2) tight-structured PVF (PVF-F); and (3) intermediate-structured PVF (PVF-B, E, and H). The effects of the morphology on the solvent absorbability of PVF were studied. The results indicated that the loose-structured PVF has better absorption capacity to solvent than does tight-structured PVF. The processing temperature can be considerably reduced when N,N-dimethylformamide (DMF) as a plasticizer was mixed with PVF, and the diminished magnitude depends on the absorption capacity of PVF to DMF. The evaporation of DMF is influenced by both molecular weight and particle morphology of PVF, and the final residue of DMF in the PVF/DMF mixture is dependent on the molecular weight of PVF. (c) 2006 Wiley Periodicals, Inc.