Surface Modification Of Para-Aramid Nanofiber And Its Flame Retardant Thermoplastic Polyurethane Elastomer

In this paper,aiming at the problems of high crystallinity,strong chemical inertness,difficult surface modification,and poor compatibility with polymers,aramid fibers(AF)were prepared by deprotonation method to prepare chemically modifiable para-aramid nanofibers(ANF),using the heat resistance,flame retardancy and high strength of ANF to prepare flame retardant and reinforced TPU composites.However,the alkaline environment of ANF itself deteriorates the mechanical properties of TPU composites.Therefore,in this paper,epichlorohydrin(HY),3-(chloropropyl)trimethoxysilane(Si),and 3-chloropropyne(PC)were further used to covalently modify the surface of ANF to prepare ANF-HY.,ANF-Si and ANF-PC three modified nanofibers,and used for flame retardant reinforcement of TPU composites.The combustion properties,thermal properties and mechanical properties of flame-retardant TPU composites were studied,and the flame-retardant enhancement mechanism of modified aramid nanofibers to TPU was discussed.The main research conclusions are as follows:1.The study found that the thermal stability of ANF-HY,ANF-Si and ANF-PC was improved,and the dispersion in TPU was not affected by surface grafting.2.When the addition amount of modified ANF fiber is 0.25wt%,the p HRR of TPU/ANF-Si0.250 is the lowest,its p HRR is 445.38 k W/m2,and the THR is 97.74MJ/m2;under the same addition amount,TPU/ANF-PC0.250 has the smallest CO release during the combustion process,only 1.00 g.3.The results of SEM,XPS and Raman spectroscopy show that the ID/IG of TPU/ANF-Si0.250 and TPU/ANF-PC0.250 are the highest,which are 0.72 and 0.76,respectively.The degree of graphitization of the carbon layer of the TPU composite was improved,and the morphology of the carbon layer was dense.Based on catalytic char formation,fibers and modified fibers can achieve high-efficiency flame retardancy,smoke suppression and detoxification of TPU.4.The modified ANF fiber can inhibit the thermal decomposition of TPU,reduce the volatilization of combustible substances and toxic substances,and make most substances stay in the condensed phase.Among them,the carbon residue rate of TPU/ANF-Si0.250 reaches 21.9%,and the material Has good thermal stability.5.The tensile test results show that ANF-HY and ANF-PC show obvious advantages in maintaining the mechanical properties of TPU composites,in which the tensile strength and elongation at break of TPU/ANF-PC0.250 only decrease compared with TPU 20.3 % and 33.5 %,83.4 MPa and 659.3 %,respectively,and far better than11.2 MPa and 102.5 % of TPU/ANF0.250.