The use of polydopamine for improving polymer flame retardancy

Abstract

This thesis introduces a new method to utilize polydopamine (PDA) in flame retardancy.Three types of PDA are mentioned in this thesis: a) PDA nano-particles, b) PDA coating andc) PDA encapsulation.PDA nano-particle, a bio-flame retardant filler was synthesized through theself-polymerization of dopamine hydrochloride in alkaline solution, yielding nano-sizedpolydopamine (nano-PDA) particles ranging between 50 and 100 nm in diameters. Blendinga small amount (2 wt%) of the nano-PDA particles with epoxy can remarkably decrease thepeak heat release rate by 53.6%, exceeding the performance aluminum trihydroxide (ATH)particles at 10 wt%. The significant improvement in flame retardancy at a relatively lowloading of PDA has been found to originate from several key mechanisms including radicalscavenging, higher char yield, and production of CO2. Furthermore, the addition ofnano-PDA in the epoxy resin increased the tensile strength by ~ 6%. In contrast, the additionof common flame retardant, such as ATH, to achieve the same increase in flame retardancy ofepoxy would reduce the tensile strength by 28%. The enhancement of mechanical property ismainly due to the better bonding between PDA particles with epoxy than ATH with epoxy.PDA coating has proven to be a fire resistant layer on polyurethane (PU) foam outside. HNT& PDA hybrid coating was hypothesized to have synergetic effect between HNT and PDA inflame retardant applications. However, 10 wt% PDA coating on PU foam surface result in similar reduction of the peak heat release rate when compared to 20 wt% HNT & PDA hybridcoating, implying that there is no synergistic effect between the PDA coating and NHTparticles.PDA encapsulated ATH particles, synthesized via a self-polymerization of dopaminehydrochloride on ATH surface in alkaline condition, have been proved to improve the surfacemorphology of ATH particles which would improve the dispersibility of ATHs in polymer