Recent developments in macro-defect-free (MDF) cements

During the early 1980s macro-defect-free (MDF) cements were developed which had properties complimentary to those of conventional ceramics, plastics and metals. The research completed on MDF cements, and particularly the polyvinyl-alcohol/calcium aluminate cement (PVA/CAC) system has been reviewed and the advantages, limitations and potential applications of MDF cements are outlined. The microstructural features of the PVA–CAC MDF systems and the influence this has on physical properties such as flexural strength and moisture resistance are discussed. Possible solutions to the poor moisture resistance of MDF cements are examined critically and alternatives to PVA–CAC described. The recent development of calcium aluminate phenol resin (CAPR) MDF cements that have particularly promising properties is presented. MDF cement technology has the potential to produce more sustainable materials that can compete with ceramics, plastics and metals in a range of applications and key research issues that need to be addressed if MDF cements are to become commercially viable are highlighted.