TABLE OF CONTENTS Christopher J. Howick
Chapter 6 of this handbook gives a detailed description of the formulations and techniques involved in the production of rigid polyvinyl chloride (PVC) foams. As far as the end product is concerned, the only difference between a rigid PVC foam and a flexible one is the presence of a plasticising species in the latter. However, this simple chemical difference hides a major difference in the production technologies available to produce flexible foams. The majority of flexible PVC foams are produced via a plastisol route, that is, the products are spread as a liquid dispersion of a speciality PVC resin in liquid plasticiser and gelled and fused in ovens rather than produced via the rigid foam route of extrusion and injection moulding. Additionally there is a large range of plasticising species available on the open market, each with the potential of altering the foaming characteristics of the formulation. All of these will be discussed in detail in this review.
In order to differentiate further, it should be stated that flexible foams can be formed from PVC resins produced by two distinct technologies. Suspension PVC resins (S-PVC), as used in rigid foams, can be used to form both rigid and flexible articles. For flexible articles, a plasticiser, usually a liquid (see next Section), is added in the dry blend stage of production and this remains in the final product to give flexibility to...
