Structural defects in poly(vinyl chloride)

Abstract

This article describes, in narrative style, the research of the author and his associates, performed over a period of 30 years, that led to the identification and quantification of the anomalous structures in poly(vinyl chloride) (PVC) and to detailed descriptions of their mechanisms of formation. Also examined here are the implications of this work for the thermal stability of PVC, for the overall chemical mechanism of vinyl chloride polymerization, and for other relevant aspects of the chemistry and technology of vinyl chloride homopolymers and copolymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2451–2467, 2005

Thermal characterization of poly(vinyl chloride) samples prepared by living radical polymerization: Comparison with poly(vinyl chloride) prepared by free radical polymerization

“…The mechanisms involved in the formation of the structural defects during the free radical polymerization of VCM were extensively studied over the last decades. 15,16 On the other hand, due to the absence of side reactions, in the LRP approach the molecular weight is completely controlled by the ratio monomer/initiator. Previous experiences had shown that in the range of 21-428C, the polymer is free of structural defects.…”

“…13,14 Because of its technological relevance and scientific importance, the thermal degradation and stabilization mechanism of PVC has been the subject of various studies and reviews. 15,16 The internal allylic chloride and tertiary chloride structural defects that are formed during the polymerization are identified as being structures responsible for the beginning of the dehydrochlorination process. Despite the low concentration in the PVC chains (allyl chloride concentration of 0.9 per molecule 17 ), the structural defects are responsible for the thermal dehydrochlorination process.…”

Ab Initio Study of Poly(vinyl chloride) Propagation Kinetics: Head‐to‐Head versus Head‐to‐Tail Additions

“…[3] Instead of further propagation after the Cl-shift, the chlorine attached to the third carbon atom can be abstracted by a monomer unit, producing an 1-chloro-2-alkene end group (EA, end allylic structure). [9] The eliminated chlorine radical initiates a new polymer chain that differs from other chains by the typical 1,2-dichloroalkane end group. This reaction is also referred to as chain transfer to monomer, and it is of great practical importance, as already mentioned.…”

“…These ÀCH 2 Cl branches are the most frequent short chain branches in PVC (approximately 4/1000 VC units), as is shown by 1 H and 13 C NMR measurements. [8][9][10][11] It is accepted that this well-known type of defect structure is mainly introduced in the chain by the mechanism described above. [9,12] The methyl branch is not thermally unstable since there are no chlorine atoms bonded to the tertiary carbon.…”

“…[8][9][10][11] It is accepted that this well-known type of defect structure is mainly introduced in the chain by the mechanism described above. [9,12] The methyl branch is not thermally unstable since there are no chlorine atoms bonded to the tertiary carbon. [3] Instead of further propagation after the Cl-shift, the chlorine attached to the third carbon atom can be abstracted by a monomer unit, producing an 1-chloro-2-alkene end group (EA, end allylic structure).…”