Effects Of Trivalent Metal Ions On The Flame Retardancy Of Carrageenan Fibers

Polysaccharides have been widely favored by scholars in recent years as a widely used bio-based material.Carrageenan is a kind of water-soluble polysaccharide extracted from red algae.Carrageenan fiber is a new type of seaweed fiber prepared by wet spinning process,which has natural flame retardancy and no pollution.In this paper,we introduced different trivalent metal ions to prepare trivalent ionic carrageenan fiber through wet spinning process,and the effects of different trivalent metal ions on the flame retardancy and mechanical properties of carrageenan fiber were studied.The main results and details are as follows:(1)The potassium aluminum carrageenan fiber(CAF-K,Al)was prepared by wet spinning process.For the first time,we used trivalent metal ions-aluminum ions(AlCl₃)were used as stretching bath,and potassium ions(KCl)as coagulation bath.The CAF-K,Al was characterized and analyzed by tensile test,EDS,FTIR,XRD,SEM,LOI,TGA,cone calorimetry.Pyrolysis products were analyzed by Py-GC-MS.The results show that the breaking strength of CAF-K,Al is 1.25 c N/dtex,and the breaking strength is 9.25 c N,which is close to three times of CAF-K,Ca in the control group;XRD also shows that CAF-K,Al have higher crystallinity than other carrageenan fibers;FTIR shows that the functional group structure of CAF-K,Al is different from other carrageenan fibers due to the effect of Al³⁺;through the LOI and TGA test of the fiber,it can be proved that CAF-K,Al have outstanding flame retardancy and high temperature resistance,the end temperature of TGA is 900?and the residual mass of TGA is about30%;SEM shows that CAF-K,Al still have complete and good fiber morphology after combustion at 800?;in cone calorimetry,CAF-K,Al have no obvious flame and smoke from beginning to end,and maintain a low HRR,the peak HRR is only 20.30 kw/m²;according to the characterize and analyse,the flame retardancy mechanism of CAF-K,Al is finally obtained.The fiber has excellent mechanical properties and flame retardancy,and is the best carrageenan fiber in comprehensive properties as far as we all know.(2)In order to explore the effect of trivalent metal ions on carrageenan fiber,we further used potassium ions(KCl)as coagulation bath and transition metal ions-trivalent iron ions(FeCl₃)as stretching bath to prepare potassium-iron carrageenan fiber(CAF-K,Fe).Accidentally,the mechanical strength of CAF-K,Fe is extremely fragile and easy to fracture,but the LOI of CAF-K,Fe is up to 32,and CAF-K,Fe still have good flame retardance.Through the TGA,FTIR and XRD characterizes of its combustion products at different temperatures,it is deduced that a large amount of Fe₂O₃ will be produced in the fiber at about 600?.The protective film formed during the combustion process will protect the fiber surface from oxygen and avoid high temperature and flame combustion.Therefore,Fe₂O₃ plays an important role in protecting fibers during combustion.