Ž . Applied Clay Science 17 2000 25–34 www.elsevier.nlrlocaterclay On the action of hydrotalcite-like clay materials as stabilizers in polyvinylchloride L. van der Ven, M.L.M. van Gemert, L.F. Batenburg, J.J. Keern, L.H. Gielgens, T.P.M. Koster, H.R. Fischer ) TNO-TPD, Materials DiÕision, Institute of Applied Physics, PO Box 595, 5600 AN EindhoÕen, Netherlands Received 8 October 1999; received in revised form 22 December 1999; accepted 10 January 2000 Abstract Hydrotalcites with different counterions were tested with respect to their ability to act as heat stabilizers in PVC. The stabilization activity results from the capacity of the layered double Ž . hydroxides LDHs to react with the HCl formed during degradation of PVC. The experiments described are heat stability tests and experiments for a determination of the capacity of the hydrotalcites to react with HCl gas. They show a linear relationship between HCl capacity of Ž . LDHs with different counterions and their action as heat stabilizer. The reaction between the Ž . LDHs and the HCl occurs in a two-step process, firstly if possible , the counterions between the LDH layers tend to react with the HCl gas, and, secondly, the LDHs themselves react with the HCl under complete destruction of the LDH structure and formation of metal chlorides. q 2000 Elsevier Science B.V. All rights reserved. Keywords: stabilization; PVC; hydrotalcite; HCl-scavenger 1. Introduction Chlorine containing polymers like PVC undergo an autocatalytic dehydro- chlorination reaction under the influence of temperatures and energy rich radiation such as UV-light. As a consequence, the material becomes brittle and ) Corresponding author. 0169-1317r00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S0169-1317 00 00002-8