Flame Retardant Finishing Of Polypropylene Nonwoven Fabric

Polypropylene(PP)nonwoven fabric is a kind of cloth-like material which is made of oriented or disorderly polypropylene fibers.It is widely applicated in daily life because of its rich source,low cost,easy processing and non-pollution.However,its inflammability and burning with melt dripping could cause flame spread which limit its further application.Therefore,it is significant to improve the flame retardancy and fire safety of PP fabric in order to expand the application range.In this paper,flame retardants were introduced into PP fabric by traditional pad-dry finishing process.The surface hydrophilic treatment of PP fabric with surfactant was carried out to improve the add on amount of flame retardants on its surface.The flame retardancy,thermal stability and microstructure of modified PP fabric were tested and analyzed.The thermal degradation process of treated PP fabric was also investigated.This paper includes three parts:1.Chlorinated paraffin(CP)was dissolved in ethanol to prepare flame retardant solution.PP fabric was treated with the solution through two-dips and two-nips process.The flammability was tested and evaluated by limiting oxygen index(LOI)test and vertical burning test.The result showed that high chlorine content(CP60)leaded to high flame retardant efficiency.The LOI value increased from 18.2%to 28.7%.Antimony trichloride(SbC13)was compounded with CP60 before being applied in PP fabric by a pad-dry process,and the LOI was further improved to 32.2%.The damaged length and damaged area reduced significantly according to vertical burning test.The melt drippings also reduced.In CONE test,peak heat release rate(pHRR),total heat release rate(THR)were decreased significantly,however,the peak smoke release rate(pSPR)was increased slightly.The CP60/SbCl3 system had negative impact on thermal stability of PP fabric,so that it started to decompose at a lower temperature.There was no significant increase in the amount of char residue.The results indicated that CP60 and SbCl3 played an important role in gas phase in improving the flame retardancy of PP fabric.However,this formulation can reduce the tensile strength of PP fabric,and cause negative impact on environment.2.The surfactant hexadecyltrimethylammoniumchloride(CTAC)was introduced onto the surface of PP fabric by dipping and ultrasonic treatment.According to water contact angle test,the surface hydrophilicity of PP fabric was improved significantly.Then,water-soluble ammonium polyphosphate(APP)and pentaerythritol(PER)were used as intumescent flame retardant system(IFR).IFR was introduced into PP fabric through pad-dry process after hydrophilic treatment.The combustion performance of treated PP fabric was characterized by LOI test and vertical burning test.The thermal stability investigation was carried out by thermogravimetric analysis(TGA).The micro-structure of treated PP fabric and its char residue after combustion were observed through scanning electron microscope(SEM).The structure of char residues ealcined at high temperature in a muffle furnace was characterized and analyzed by infrared spectroscopy.When the concentration of IFR was 40%and the APP and PER ratio was 5:1,the modified PP fabric exhibited best flame retardant effect.The LOI was increased to 23.6%,and melt drippings was eliminated during the flammability test.NH3 and NZ were released during the combustion process.IFR could also promote the formation of char residue,as a result,its amount could increase from 7.1%to 22.0%.The pHRR and THR were also decreased.It is indicated that IFR plays an important role in both condensed phase and gas phase during the combustion.3.APP-DEA,a water-soluble three-source IFR,was prepared by combining diethanolamine(DEA)with APP by ion exchange method.PP nonwoven fabric was treated by two-dips and two-nips process.The test results showed that APP-DEA with 1:1 molar ratio can achieve good flame retardancy.When the add on was 50.3%,LOI could be increased to 24.7%.pHRR and THR decreased significantly during cone calorimeter test.PP fabric treated with APP-DEA can also produce NH3 during combustion.The char residue could be increased from 7.1%to 19.3%.After combustion,the external surface of char layer was continuous and compact,but the internal char residue was loose and porous,which is beneficial to hinder the exchange of heat,oxygen and gas,thus delaying or terminating the fire spread process.