The Preparation?Structure And Properties Of Flame Retardant Polyester And Its Blend With PET

Polyethylene terephthalate(PET)has been widely used in the fields of fiber,plastic and film because of its good mechanical property,thermal stability and ageing resistance.However,as the limiting oxygen index of PET is only 21%,it is consider as a combustible material.Therefore,improving the flame retardant property of PET has attracted considerable attention.Two methods can be used for this purpose including copolymerizing with a reactive flame retardant monomer and blending with an additive flame retardant.At present,many reports focus on the fabrication of flame retardant PET fibers by copolymerization modification,and the technology is becoming more and more stable.However,the preparation of flame retardant PET fibers by blending modification still faces a big challenge.The main reason is poor compatibility between flame retardants and PET,which not only affects the forming and mechanical property,but also brings the fibers nonuniform flame retardant performance.Nevertheless,there is still demand for flame retardant PET by blending method because it can meet the requirement of flexible production better.In this thesis,flame retardant polyesters with high phosphorus content were synthesized via condensation polymerization reaction by using 3-hydroxyphenylphosphinyl-propanoic acid(CEPPA)as the third monomer.The sequence composition and crystallization property of the flame retardant polyester were characterized by means of IR,NMR and DSC.The flame retardant polyester/PET blends were prepared by blending method.The effects of chain extender2,2,-(1,3-Phenylene)bis(2-oxazoline)(PBO)on the intrinsic viscosity of the blend were also investigated.In addition,the flame retardant polyester/PET blends were used to spinning to obtain flame retardant PET fibers and the structure and property of the fibers were studied.The main results obtained are as follows:1.The effect of flame retardant CEPPA on the polymerization reaction was studied.It can be found that introduction of flame retardant increased the reaction time of both esterification and polycondensation.The sequence composition and crystallization property of flame retardant polyester were characterized by means of elemental analysis,IR,NMR and DSC.The results showed that most of CEPPA units were copolymerized into the polyester chains in a form of short block distribution.With the increase of CEPPA content,the random coefficient of the copolyester decreased.Moreover,the high CEPPA content broke the regularity of the polyester chain,which led to the decrease of both glass transition temperature(T_g)and crystal ability of the flame retardant polyester.2.Flame retardant polyester/PET blends were prepared via blending method and their structures,morphologies and flame retardant properties were characterized by means of DSC,SEM,EDS,elemental analysis and limiting oxygen index test.The results showed that there is a good compatibility between PET and flame retardant polyester,and the flame retardant polyester dispersed uniformly in PET matrix.When the phosphorus content of the blend is about 6 mg/g,the material showed good flame retardant performance with the limit oxygen index above 28%.The higher the phosphorus content,the better the flame retardant performance.3.In order to prevent the degradation of polyester and the reduce of molecular weight in the process of blending,the effect of PBO on the flame retardant polyester/PET blend was investigated.The results showed that when the content of PBO is 1.6%,the intrinsic viscosity of the flame retardant polyester/PET blend obtained by mixing in twin-screw extruder at 250?increased about 0.12 d L/g.The addition of PBO did not affect the compatibility and dispersibility of the blends.4.The spinnability of the flame retardant polyester/PET blends was investigated.The results showed that the blends have good spinnability,and no broken filaments and breakage appeared when the spinning velocity was about 500 m/min.The crystal behavior,orientation structure,mechanical property and dyeing property of the fibers obtained at different flame retardant polyester content and different draw ratio were investigated,respectively.The results showed that with increasing the content of the flame retardant polyester,the degrees of crystallinity and orientation of the fiber decreased,while the dye-uptake increased.With the increasing of drawing ratio,the breaking strength,degrees of crystallinity and orientation enhanced,while the dye-uptake decreased.