Green Synthesis Of Tin-based MOF And Its Flame Retardant Study In Epoxy Resin

Epoxy resin(EP),an important thermosetting resin,has excellent chemical and mechanical properties.However,EP generates a large amount of heat and smoke during combustion,which severely limits its application scope.Therefore,it is necessary and important to conduct flame and smoke suppression studies on EP.In this paper,a tin-based metal organic skeleton(SnBDC)flame retardant was prepared,and two types of composite flame retardants were simply prepared using this as a substratum.The effects on the flame retardancy,combustion and mechanical properties of the EP samples were investigated using limiting oxygen index(LOI),cone calorimeter(Cone)and universal testing machine;and the flame retardancy mechanism was preliminarily analyzed by means of thermogravimetric analysis(TGA),Cone and scanning electron microscopy(SEM)tests.The details of the study are as follows.Part Ⅰ,rosette-like and cauliflower-like tin-based metal organic skeletons(SnBDC)with micro-and nano-structures,denoted as R-SnBDC and C-SnBDC,were successfully synthesized in aqueous solutions at room temperature without using any organic solvents using stannous sulfate and terephthalic acid as raw materials.The products were investigated by Xray diffractometry(XRD),infrared spectroscopy(FTIR)SEM and TGA were performed to characterize the products.The results showed that both have good thermal stability and meet the processing temperature of most polymers.When SnBDC was added at 3 wt%,the oxygen index values of the EP composites could meet the requirements for flame-retardant materials with a slight decrease in mechanical properties and unfortunately no rating in the UL-94 test.Part Ⅱ,a simple saturated aqueous solution method was used to modify SnBDC with β-CD surface to obtain a new hybrid SnBDC@β-CD.The hybrid material was applied to EP for flame retardant studies.C-SnBDC@β-CD increased the residual carbon rate although it promoted the pre-decomposition of EP composites.C-SnBDC@β-CD has excellent smoke suppression and flame retardant properties SEM and X-ray photoelectron spectroscopy(XPS)analyses showed that C-SnBDC@ β-CD promoted the formation of denser,continuous carbon layers with strong resistance to thermal oxidation.The thermal gravimetric infrared coupling test under nitrogen atmosphere showed that the addition of flame retardants promoted the early release of organic products such as aromatics and esters with high release intensity,but for the whole pyrolysis process its total release did not increase.Part III: The SnBDC and ammonium polyphosphate(APP)were mainly mixed and applied to the EP matrix.Mechanical and LOI data show that the EP/3.9APP/0.1SnBDC system can pass the UL-94 vertical combustion test with a V-0 rating.And EP/3.9APP/0.1C-SnBDC has the best overall performance with improved tensile strength and elongation at break compared to EP/4APP.both APP and SnBDC promote the pre-decomposition of EP and increase the amount of carbon residue.However,a small amount of SnBDC improves the thermal stability of EP/APP composites.tapered calorimetric data for EP/3.9APP/0.1SnBDC showed little difference in effect compared to EP/4APP.However,XPS and macroscopic photo analysis showed that EP/3.9APP/0.1C-SnBDC had the largest expansion height,high densities,and high resistance to thermal oxidation compared to EP/4APP.