Polymerisation of flame retardant organophosphorus and organo-inorganic hybrid coatings on polymeric surfaces

• Main Author: Williams, Kathrine
• Published: University of Bolton 2017
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.732048

Polymers are widely used across the globe in applications ranging from construction to biomedical, with increasing usage as time progresses. However, despite their prevalence polymers can be highly flammable materials, and though this may be combatted with the use of flame retardant additives, the additives themselves may have a detrimental effect on other properties of a polymeric material such as its aesthetics or structural integrity. One solution to this is the use of flame retardant coatings which are applied to the surface of a polymer, instead of additives which are incorporated into the polymer structure. Due to their surface application, flame retardant coatings will not affect the structure and thus the properties of the underlying polymer. In this PhD, a novel poly(vinyl phosphonic acid) (PVPA) based flame retardant coating was synthesised and characterised using Fourier Transform Infra-Red spectroscopy (FTIR), then tested as a flame retardant coating for both glass fibre reinforced epoxy (GRE) and poly(methylmethacrylate) (PMMA) under a cone calorimeter. The PVPA based flame retardant coating showed an impressive degree of flame retardance, lowering the peak heat release from 692 kW/m2 to 233 kW/m2 on GRE with significant intumescence of the coating. The coating was further tested for the adhesion to the surface of the substrate using a tape pull test, and for its durability in water using a water soak test. Whilst the coating showed good flame retardance and adhesion to the surface of the polymer substrate, the performance during water soak testing was poor due to the hydrophilicity of the poly(vinyl phosphonic acid). Further modifications were then made to the coating in order to improve its performance during the water soak test, the modifications made to the coating included the addition of additives and co monomers as well as the application of a secondary protective coating over the flame retardant (PVPA) to prevent attack from water. All synthesised coatings were tested using cone calorimetry, tape pull and water soak testing, as well as thermogravimetric analysis (TGA) and FTIR in order to provide further characterisation. The monomers, additives and top coatings tested were; dimethylvinylphosphonate, dibromostyrene, acrylonitrile, polydimethylsiloxane, magnesium oxide, zinc chloride, calcium silicate, chitosan, hexamethyldisiloxane, tetraethylorthosilicate, calixarene, vinyl acetate emulsion, commercial waterproofing spray, cellulose nitrate and cellulose acetate. While some improvements were made to the performance of the PVPA flame retardant coating through the use of additives, co monomers and top coatings there was no significant overall improvement which would render the PVPA coating suitable as a flame retardant coating with reasonable durability, with many of the improvements in water resistance resulting in a significant decrease in flame retardance. However this still leaves the path open to further research, with further possible modifications and combinations of already tested methods.