Effects Of Ionic Liquid And Layered Double Hydroxide On The Intumescent Flame-retardant Thermoplastic Polyurethane Elastomer

Thermoplastic polyurethane elastomer(TPU)has been extensively used in numerous fields such as wires and cables,pipes,automotive accessories,medical equipment,etc.due to its excellent mechanical properties and thermoplastic molding characteristics.However,it is usually required to be modified in the processing and production process because of its poor flame retardancy,weather resistance,water resistance and melt flow.Intumescent flame-retardantss can effectively enhance the flame retardancy of TPU composites.However,the relative large loading usually also cause negative impacts on mechanical properties and other properties.Therefore,the preparation of intumescent flame-retardant TPU composites with excellent comprehensive properties is of great significance.This work mainly focus on the role of ionic liquid(IL)and layered double hydroxide(LDH)in the intumescent flame-retardant TPU composites.The flame-retardant properties,in association with the thermal stability,processing fluidity,mechanical properties,and light transmission properties of TPU composites are tested and characterized.The main research work is as follows:1.The phosphomolybdic acid doped layered double hydroxide(PMA-LDH)was prepared by a mechanical ball-milling method which combined phosphomolybdic acid and layered double hydroxide,and then was introduced to the intumescent flame-retardant TPU composites with ionic liquid(IL).The results showed that the LOI of the TPU composite was increased to 30.7%and the vertical burning passes UL-94 V-0 when 2.0wt%PMA-LDH and 0.2wt%IL were added.Compared with the control TPU,the total heat release(THR)and peak heat release rate(pHRR)was decreased by 17.08%and 69.63%,respectively.The TPU composites showed good processing fluidity in the presence of PMA-LDH and IL,while the mechanical properties had no significant changes compared with that with IFR only.2.The phosphomolybdic acid-based ionic liquid(PMAIL)was prepared by ion-exchange method,and then mixed with LDH to be introduced into intumescent flame-retardant TPU composites.The results show that the LOI of the TPU composites was increased 30.1%and the vertical burning passes the V-0 grade at the presence of 0.2wt%PMAIL and 1.Owt%LDH,and the THR and pHRR was decreased by 45.88%and 88.06%,respectively.The addition of PMAIL and LDH give the composites good thermal stability and processing fluidity,but its mechanical properties and light transmittance were seriously reduced.3.The layered double hydroxide and ionic liquid were combined to prepare the layered double hydroxide-loaded ionic liquid(IL@LDH)by ultrasonic method and was directly introduced into the intumescent flame-retardant TPU composites.The results showed that the LOI of TPU composites was 30.5%and the vertical burning reached UL-94 V-0 when 1.0wt%IL@LDH was introduced to replace IFR with the same amount,and the THR and pHRR was reduced by 26.12%and 80.82%,respectively,and the residual carbon rate at 800? reached 21.02%.The introduction of IL and LDH had little effect on the mechanical properties of the TPU composites,and it had good weather resistance and light transmittance at the same time.