Study On The Preparation Of Two Novel Flame Retardants And Their Application In Flame Retardant Coatings For Steel Structures

The flame retardant coatings of steel structure have become the best choice for fire protection of steel structures due to their excellent flame retardant properties.In which flame retardant has a crucial influence on the performance of fireproof coating.The intumescent flame retardant systems（IFR）which consists of ammonium polyphosphate（APP）,pentaerythritol（PER）and melamine（MEL）could serve as the flame retardant additives in traditional fireproof coating.However,the char residue formed by the IFR system is too poor and brittle to protect the steel structure.Therefore,it could be a good idea to develop many novel environmentally friendly flame retardants to enhance or replace the IFR system.The work in this paper starts from two routes of enhancing and replacing the traditional IFR system,designs and develops two novel efficient and environmentally friendly flame retardants.The flame retardants are added to the polymer binder through the method of liquid phase physical mixing to prepare environment-friendly water-based flame retardant coating.The properties of flame retardants and flame retardant composite coatings are analyzed and the following main conclusions are drawn:（1）Nano graphene oxide（GO）is an emerging flame retardant,but its special layer structure makes it easy to agglomerate in a polymer matrix.In this work,a new type of flame retardant GO/Mg Al Cr-LDHs was synthesized by in situ growth of layered double hydroxides（Mg Al Cr-LDHs）on GO surface by hydrothermal method,and the flame retardant GO/Mg Al Cr-LDHs is used together with IFR system to boost the flame retardancy of epoxy resin（EP）composite coating.Compared with the pure EP coating,the peak heat release rate（p HRR）and total heat release（THR）values of the EP coating which contains 5wt% GO/Mg Al Cr-LDHs decrease by 51.7% and 29.7%,respectively.Besides,thermogravimetric（TGA）results show that the carbon residue of the EP based composite coating reaches 34.6wt%.The improvement of its flame retardancy and char-forming ability is mainly attributed to the fact that GO/Mg Al Cr-LDHs is conducive to form an integral and stabilized char layer in the condensed phase,which could hinder the transfer of heat,oxygen and combustible gases to the interior of the coating,thereby improving the fire resistance of the coating.Therefore,the coating has an excellent fire protection effect on steel structures.（2）Multi-component flame retardants have attracted a lot of attention in recent years.In this work,a novel organic-inorganic hybrid flame retardant Ca（H2PO4）2@HCCP integrating phosphorus/nitrogen/silicon was successfully prepared by surface modification technology and applied in waterborne polyvinyl alcohol（PVA）coatings.The flame retardant Ca（H2PO4）2@HCCP has superior compatibility with PVA matrix and significantly enhances the thermal stability and carbon-forming properties of PVA composite coating.Furthermore,30wt%Ca（H2PO4）2@HCCP could reduce the p HRR and THR values of the PVA composite coating to 117.1W/g and 16.7k J/g,respectively.Which indicates that the flame retardant Ca（H2PO4）2@HCCP imparts PVA composite coating with excellent fire resistance.From the scanning electron microscope（SEM）and Fourier transform infrared spectra（FTIR）results,it may be discovered that the flame retardant mechanism of Ca（H2PO4）2@HCCP can be divided into gas phase and condensed phase.That is,it interrupts the combustion chain reaction and releases incombustible gas in the gas phase,and promotes the formation of a dense char layer structure in the condensed phase.Therefore,Ca（H2PO4）2@HCCP helps to improve the flame retardant properties of PVA composite coatings and expands the application range of PVA composite materials.Coating PVA flame retardant coating on the surface of the steel structure can effectively reduce the damage of fire to the steel structure.