Flame Retardant Composite Finishing Of Cotton Fabric Based On Hyperbranched Polyester Derivatives

Cotton,as a natural textile fibre,is widely used in the world due to its softness,breathability,comfort and other good properties.However,the limit oxygen index value of cotton is only approximately 18%,and it ignites easily.Once cotton fabric ignites,the flames will spread rapidly,and fire accidents caused by cotton fabric lead to substantial losses of life and property,which restrict its application fields.Therefore,it is very important to study the application of flame retardants on cotton fabrics.Proban(?)and Pyrovatex(?)are two of the most important commercial flame retardants.However,the treated samples will release carcinogenic formaldehyde during the finishing and service processes,so researchers have been focused on developing formaldehyde-free,halogen-free,and durable flame retardants for cotton textiles.In addition,with the improvement of living standards,multifunctional cotton fabrics are becoming more and more popular.Flame-retardant cotton fabric with other functions such as UV-protection,aroma and mosquito repellent properties is of practical significance to expand the application fields.Therefore,it is necessary to study the multifunctional cotton fabric.Hyperbranched polyester has attracted much attention because of its non-toxic and a large number of hydroxyl end groups,which can be easily modified.In addition,the endogenous cavity of hyperbranched polyester can load functional particles.In this study,flame retardants containing reactive groups based on hyperbranched polyester derivative were synthesized.The flame retardancy and durability of treated cotton fabrics were systematically analyzed.The grafting mechanism,flame retardant mechanism of flame retardants,and thermal stability of flame-retardant cotton fabrics were studied.The effect of flame retardant on physical properties of cotton fabrics were also studied.In addition,on the basis of flame-retardant cotton fabrics,the UV-protection,aroma or mosquito repellent flame-retardant cotton fabrics were prepared.The main results were outlined as follows:(1)A novel flame retardant(FR),HBPOPN,was synthesized without formaldehyde and halogen.The finished cotton fabrics had excellent flame retardancy and durability.The results of Fourier transform infrared spectroscopy(FT-IR)demonstrated that the reactive groups of FR could react with cellulose to form P-O-C covalent bonds.The results of scanning electron microscopy(SEM)and X-ray diffraction(XRD)displayed that HBPOPN hardly influenced the structure of cellulose.The limit oxygen index(LOI)value of 160 g/L HBPOPN-treated fabric was42.0%.After 50 laundering cycles(LCs),the LOI value was maintained in 29.3%.Vertical flammability test suggested no after-flame or after-glow time.Furthermore,the cone calorimetry results showed that HBPOPN-treated fabrics displayed an obvious decrease in the peak heat release rate(PHRR)by 85.1%and the total heat release(THR)by 54.2%.The results of thermogravimetric analysis(TGA),TG-FTIR,and Py-GC-MS declared that HBPOPN changed the thermal decomposition process of cotton.The flame retardant mechanism of HBPOPN is mainly condensed phase flame retardant.HBPOPN decomposed to polyphosphate,which promoted the dehydration of cotton fiber into carbon,forming a dense and stable carbon layer on the surface of cotton fiber and reducing the generation of combustible substances.In addition,the effects of HBPOPN on tensile breaking strength and bending stiffness of fabrics were analyzed.The results showed that HBPOPN could reduce tensile breaking strength and increase bending stiffness.(2)A series of hyperbranched polyphosphate ammonium salts(HBPOPNs)with various generation numbers was successfully prepared by modifying different generations of hydroxyl-terminated hyperbranched polymers(HBPs).The influence of the generation number on flame resistant properties of treated samples was studied.The chemical structure of the samples was studied by FT-IR,which revealed the presence of a P–O–C covalent bond between cellulose and HBPOPNs.The thermal decomposition behavior of the samples was characterized by thermogravimetric analysis,which indicated that the thermal stability of HBPOPNs-treated fabric improved with higher generation number.The results of vertical combustion test,LOI and cone calorimeter showed that the finished cotton fabric had high flame retardancy and durability.In the vertical flammability test,all samples treated with the different generations of HBPOPNs were immediately extinguished after removing the igniter.Values of the limit oxygen index of 42.0%,42.7%and 43.0%were observed with the increase in the generation number(2,3 and 4)at a concentration of 160 g/L.After 50 LCs,the LOI values were remained at 29.3%,29.7%and29.6%.With increasing of generation number,the PHRR and THR of the treated samples decreased slightly.(3)A two-step method of preparing cotton fabrics with flame retardancy and UV-blocking properties was investigated.This method involved the in-situ deposition of Zn O nanoparticles(NPs)and the synthesis of a phosphorus ammonium salt.The application of Zn O NPs on cotton fabrics was achieved by an in-situ ammonia-smoking method with zinc acetate and ammonia.A hyperbranched polyphosphate ammonium salt(FHPOPN)was synthesized for application to the cotton fabrics after the ammonia-smoked finish was applied.The cotton fabric with excellent flame retardancy and high UV-resistance had been prepared.The Fourier transform infrared(FTIR)spectroscopy results showed that Zn O NPs were successfully deposited in the fabric and that FHPOPN was bound to the fabric by covalent bonds.The treated cotton fabrics were observed by SEM,and the results showed that the finishing process had little damage to cotton fibers.The flame retardancy properties of the FHPOPN-treated cotton fabrics were investigated.The effect of the zinc acetate concentration on the fire resistance and UV-blocking performance of the fabrics was investigated.The results of vertical combustion test,LOI and cone calorimeter demonstrated that the FHPOPN-and Zn O/FHPOPN-finished cotton fabric had excellent flame retardancy and durability.The cotton fabrics treated with 70 g/L zinc acetate and 160 g/L FHPOPN obtained excellent flame retardancy with a char length of 57mm,and had neither after-flame nor after-glow.The LOI value was 36.4%,after 50 LCs,the LOI remained at 26.0%.The PHRR and the THR of the Zn O/FHPOPN-treated samples were 26 k W/m~2 and 4.4 MJ/m~2,respectively,which were slightly lower than those of the FHPOPN-treated samples and much lower than those of the untreated cotton fabric sample.Furthermore,the thermogravimetric analyses of Zn O/FHPOPN-treated cotton fabric showed a char yield of 33.3%at 800°C,whereas FHPOPN-treated cotton fabrics had a 29.7%char yield.The Zn O/FHPOPN-treated cotton fabric mainly played an important role in condensed phase,and Zn O had a synergistic flame retardant role in the FHPOPN-treated fabric.The Zn O/FHPOPN-treated cotton fabric exhibited effective UV-protection properties with a UPF value of 224.80,which was higher than that of control and FHPOPN-treated cotton fabric.The result demonstrated that the Zn O/FHPOPN-treated fabric had excellent UV-protection performance.In addition,the breaking strength and bending rigidity of the finished cotton fabric remained well.(4)In order to prepare multi-functional cotton fabrics,HBPOPNs-cotton fabrics were finished with perfume or repellent.The flame-retardant cotton fabrics with aromatic or mosquito repellent property were prepared by coating lavender or permethrin with endogenous cavity of hyperbranched polymer.The effects of hyperbranched polymer algebra,temperature,stirring time and bath ratio on the content of lavender or permethrin in HBPOPNs cotton fabric were discussed.The sustained release properties of cotton fabrics before and after coating were studied.The optimum preparation process of HBPOPNs aromatic fabrics were as follows:the coating rate reached 12.95%when the fourth generation derivative HBPOPN4 was used at 40°C,stirring time was 20 min and bath ratio was 1:10.The optimum preparation process of HBPOPNs-mosquito repellant fabric was as follows:the temperature was 40°C,stirring time was 30 min,bath ratio1:10,and generation number was 4.Under the conditions,the inclusion rate was 13.68%.After coated with hyperbranched polyester derivatives,the sustained release properties of cotton fabric were significantly enhanced.In addition,aromatic or mosquito repellant treatment had little influence on the flame retardancy property.