Design, construction and application of bio-inspired flame retardant nanocoatings for fire protection and warning
Creators: name: Cao, Cheng-Fei
Publisher: name: University of Southern Queensland
Year: 2023
Subjects: graphene oxide
multifunctional nanocoating
flame retardant polymers
fire warning sensors
mechanical analysis
fire safety and protection

description: The development of human history is accompanied by the acquaintance, control, and utilization of fire. However, once fire is out of control, it may induce fire disasters and lead to massive casualties and irreparable property losses and negatively impact the global environment. Therefore, fire safety and prevention are of paramount importance in modern society. At present, constructing flame-retardant coating is regarded as one of the effective approaches for improving flame retardant performance of combustible materials and reducing fire hazards due to its numerous advantages. In the past few years, many efforts have been made to construct flame-retardant coatings on different types of flammable material substrates. However, it remains a huge challenge to fabricate desirable coating systems with excellent comprehensive performance. In addition, most flame-retardant coatings only have a single flame shielding function, which has limited their further application in fire safety and protection. Therefore, it is attractive and meaningful to design and construct multifunctional flame-retardant coatings and extend their application.

In this Ph.D. project, a series of high performance smart flame retardant hybrid networks with fire shielding and fire warning capacities were fabricated by combining t wo dimensional 2D ) nanomaterial i.e. e., graphene oxide ( GO ) nanosheets with functionalized fillers or molecules based on rational bionic design strategies. Based on characterizations and tests , t he mechanical, thermal, and flame retardant properties as well as fire shielding and fire alarm performance s of the achieved flame retardant coating s ystems were systematical ly studied . Therefore , th e related mechanisms were also investigat ed and clarified. The main research contents are as follows:

1) GO nanosheets is one of desirable candidate for constructing flame retardant nanocoating. However, GO coating network usually displays poor thermal /structural stability , mechanical and flame retardant properties when used alone. Herin, the bio mass derivatives i.e., 1D phosphorylated cellulose nanofibrils P CNFs ) and tannic acid ( TA ) molecules were employed to combine 2D GO nanosheets for fabricating the high performance GO based hybrid networks Benefiting from the multiple synergistic interactions in the GO/TA/P CNFs network, the optimized hybrid network exhibited improved mechanical properti es (tensile strength and Young’s modulus up to ~ 132 MPa and ~7 GPa), good structural stability in harsh aqueous environments and excellent fire shielding capacity for combustible PU foam materials In addition, by utilizing ii the flame/thermal the flame/thermal--induced electric transition induced electric transition behavior of GO networkbehavior of GO network, , it can endow the it can endow the hybrid hybrid networknetwork with with an an ultrasensitive fire alarm function (e.g., ultrafast flame alarm time of &lt; 1 s)ultrasensitive fire alarm function (e.g., ultrafast flame alarm time of &lt; 1 s).
2) To further improve the o further improve the mechanical strength, mechanical strength, fire shielding and fire alarming fire shielding and fire alarming performances of performances of GO networkGO network,, in this study, in this study, the multithe multi--amino molecule (HCPA) that can serve as tripleamino molecule (HCPA) that can serve as triple--roles i.e., roles i.e., crosslinker, fire retardant and reducing agent was utilized for decorating GO crosslinker, fire retardant and reducing agent was utilized for decorating GO nanonanosheets and sheets and obtaining the GO/HCPA hybrid networks. The achieved GO/HCPA network exhibits significant obtaining the GO/HCPA hybrid networks. The achieved GO/HCPA network exhibits significant increment in mechanical strength. More importantly, based on P and N doping and promoting increment in mechanical strength. More importantly, based on P and N doping and promoting thermal reduction effect on GO network, the thermal reduction effect on GO network, the outstandingoutstanding high temperature resistance high temperature resistance (withstanding ~1200 °C flame attack), ultra(withstanding ~1200 °C flame attack), ultra--fast fire alarm response time (~0.6 s) and ultrafast fire alarm response time (~0.6 s) and ultra--long long alarming period (&gt;600 s) are obtained, representing the best comprehensive performance of GOalarming period (&gt;600 s) are obtained, representing the best comprehensive performance of GO--based based fire alarm sensor fire alarm sensor counterparts. Furthermore, the fireproof GO/HCPA coating is constructed counterparts. Furthermore, the fireproof GO/HCPA coating is constructed and applied inand applied in polymer foam, and exhibited epolymer foam, and exhibited exceptionalxceptional fire shielding performancefire shielding performance.
3) On the basis of above researchOn the basis of above researcheses, the supermolecule melamine diborate (M·2B) was combined , the supermolecule melamine diborate (M·2B) was combined with GO nanosheets to form nacrewith GO nanosheets to form nacre--like supramolecular crosslinking nano systems (GO/MB). like supramolecular crosslinking nano systems (GO/MB). Compared to Compared to the aforementionedthe aforementioned GO/TA/PGO/TA/P--CNFsCNFs networks networks and GO/HCPA networks, besides and GO/HCPA networks, besides possessingpossessing enhanced mechanical properties, e.g., tensile strength and toughness up to enhanced mechanical properties, e.g., tensile strength and toughness up to ∼∼122 MPa 122 MPa and and ∼∼1.72 MJ/m1.72 MJ/m33, respectively,, respectively, highhigh--temperature resistance as well as fire shielding and alarming temperature resistance as well as fire shielding and alarming performances,performances, e.g.,e.g., sensitive fire alarm response (sensitive fire alarm response (∼∼0.70.72 s), and ultralong alarming time (&gt;1200 s)2 s), and ultralong alarming time (&gt;1200 s),, such GO/MB network also shows harsh environmentsuch GO/MB network also shows harsh environment--tolerance i.e., its structure can well maintain tolerance i.e., its structure can well maintain even under strong acid/alkaline solution immersion and water bath ultrasonication conditions, even under strong acid/alkaline solution immersion and water bath ultrasonication conditions, showing promising fire safety and protection application prospectshowing promising fire safety and protection application prospects as desirable s as desirable fire alarm sensor fire alarm sensor and fire shielding material in complicated and harsh environments.and fire shielding material in complicated and harsh environments.