Preparation And Characterization Of Environmental Friendly Flame Retardant Polyethylene Terephthalate Transparent Films

Polyethylene terephthalate(PET)is the third most common synthetic polymer,accounting for about 18%of world polymer production.The flammability of PET has attracted widespread attention.Its LOI value is only 18.2%,and there is a very serious droplet during the combustion process.In recent years,a variety of flame retardants have been used to improve the fire performance of PET materials.Among them,only a few is related to the formulation of green,environment-friendly,high-efficiency and flame-retardant transparent PET film.In this paper,three kinds of environmental friendly transparent PET films are prepared.The main tasks as follows:(1)The three bio-based flame retardants,including chitosan(CH),sodium alginate(SA)and phytic acid(PA),are deposited on the surface of PET film through layer-by-layer self-assembly electrostatic interactions with different concentrations and different layers to obtain PET(CH/SA/CH/PA)composite materials.The results show that the control PET film cannot achieve any UL-94 grade with a LOI of only 18.2%.When the concentration of the three substances was 0.3%and the weight gain was 7.98%,the light transmittance of the PET composite film falls within an acceptable range,which passed the UL-94 V-0 rating,and the LOI was increased to 27.5%,and the carbon residual value in the atmosphere was increased from 7.90%to 14.78%under nitrogen.SEM observation revealed that the PET film with bio-based flame retardant layer had a relatively dense carbon layer after combustion,which improved the flame retardancy of the film.(2)Sodium polyborate(SPB)was prepared by the reaction of boric acid and borax,and then blended with CH to obtain PET@(SPB/CH)composite.The results showed that borax boric acid generated sodium polyborate(SPB)through the change of crystal form and chemical reactions.With the presence of SPB and CH(6%and 1%respectively),the LOI of PET composite film was increased from 18.2%of pure PET film to 30.5%,UL-94 grade reached V-0 level,and the peak of heat release rate(pHRR)was decreased from 679.8 kW/m2 to 473.6 kW/m2.(3)Polyvinyl alcohol(PVA),two-dimensional inorganic nanosheets such as montmorillonite(MMT)and laponite(LAP)are deposited on the surface of PET film under the effect of gravity orientation in order to obtain PET(MMT/LAP/PVA)composite materials.The results show that the presence of four deposited layers with a weight gain of 5.20%,the PET film achieved the UL-94 V-0 rate.The pHRR was reduced from 679.8 kW/m2 to 406.3 kW/m2 and the total heat release was reduced from 36.2 KJ/m2 to 23.6 KJ/m2.The light transmittance of the film was decreased by less than 5%.The oxygen transmission rate of the PET film was reduced from 20.0 cc/m2/day to close to 0 cc/m2/day.