Mechanism And Technological Research On Micro-Crosslinking Method To Improve Anti-dripping Properties Of Melt Spinning Fibers Based On High Energy Irradiation

In order to solve the melt drip of thermo-plastic fiber and to improve the flame retardant and anti-dripping properties simultaneously,"the principle of changing the property of the material" in the TRIZ innovative theory was accepted to show that changing the linear macromolecular to three dimensional network is the effective method to hinder the melt dripping. Also, the patent reviews of irradiaiton crosslinking indicated that irradiation can lead to cross-links in the polymers which can be cross-linked, which is the best way to solve the melt-drip problem with the engieering and practical meaning. Keeping these in view, irradiation crosslinking was used for the first time to solve the dripping of the melt spinning synthetic fibers, such as polyamide and polyester in this paper. The use of irradiation crosslinking to reduce the melt drips effectively was verified; also the change of mechanical propertiey was in the acceptable range. Meanwhile, the regularity was got about the effect of sensitized irradiation crosslinking on the structure and property of polyamide and polyester fibers, which provide the fundamental data for textile material research. Further, the excellent flame retardant properties reflected in the high value of LOI30.1, the zero extinguished time and no-drip were achieved using irradiation crosslinking. The mechanisms of the flame retardant and anti-dripping were explained to provide the experiment foundation for preparing the thermo-plastic fibers with excellent flame retardant and anti-dripping properties.The main results are as the following:(1) The best sensitizer was chose as triallyl cyanurate (TAC) with the use level of5%from the view of reactivity, mixability and spinnability. The presence of TAC and the use of nitrogen atmosphere enhanced irradiation cross-linking and the gel content arrived at a higher level at100kGy where there were longer burning time from29.19s to35.67s, prolonged the first dripping from4.24s to18.43s and the drastic reduction in the total amount of drops during the burning time from thirteen to six. The breaking strength increased from3.0cN/dtex to3.61cN/dtex, elongation at break decreased from71.1%to52.9%. Irradiation of PA6fibers with sensitizer2.9%TMAIC and3.4%TMPTMA also resulted in an improved dripping-resistance at the dose of100kGy in nitrogen with the melt drop decreased from sixteen to eight. The appearance of first melt-drop changed from9.75s to23.58s, the burning time prolonged from33.26s to59.36s.The breaking strength increased from3.27cN/dtex to3.34cN/dtex, elongation at break decreased from87.04%to63.70%. Cross-linking has an enhanced effect on the breaking strength which increased first then decreased, while elongation at break decreased all the time with increasing the dose. Irradiation had not changed a crystal form of PA6fibers; it caused the crystalline damage to decrease the melting temperature and crystallinity. The onset temperature of degradation fell slightly and the amount of non-volatile residue at600℃increased after irradiation.(2) The dynamic rheology test showed that complex viscosity became larger after irradiation cross-linking which indicated that the melting polymer could not flow at the beginning of combustion to result in no melt drop in the early stage. Thermo-gravimetric analysis showed that the solid residue increased drastically after irradiation cross-linking. The curve of heat release rate and mass loss rate had the same shape which showed that irradiation cross-linking had the effect in the condense phase. The char formed after cone calorimetric test had the wrinkle structure to wrap the melt drops. Irradiation cross-linking had two aspects of effects on the combustion behavior of PA6fibers:improving the melt viscosity of polymer and promoting the char formation during combustion which attributed to the improvement of anti-dripping.(3) Irradiation cross-linking improved the flame retardant and anti-dripping properties of PA6with melamine drastically in the presence of sensitizer. The value of LOI grew with the increase the use level of melamine and the irradiation dose, also the vertical burning and anti-dripping properties were improved. The excellent flame retardant property with LOI value28.5and UL94V-0was achieved with no melt drop at the dose of60kGy with30%melamine. Thermo-gravimetric analysis showed that the solid residue got more after irradiation. Cone calorimetric test indicated that irradiation cross-linking extended the time to ignition, decreased the heat release rate and mass loss rate and increased the solid residue. Meanwhile, the total smoke release of flame-retardant samples decreased compared with the un-irradiated which indicated that irradiation cross-linking had the smoke suppression effect.(4) TG, SEM and XPS analysis were used to investigate the mechanism of flame retardant and anti-dripping after irradiation crosslinking.The char-forming mechanism in condense phase was confirmed. Irradiation cross-linking increased the amount of char and changed the structure of char layer from fluffy, rough and brittle to thicker, finer and harder. The existence of Si element fixed and reinforced the strength of char layer. All aboved conditions prevented the spread of heat and hindered the melting polymer transferring towards surface. So the better flame-retardant and anti-dripping properties were achieved.(5) The sensitizing effects of TAC, TAIC, TMAIC and TMPTMA were studied for polyester fiber which showed that TAC had the best performance. The spinning property was good with the dosage of5%.The highest cross-linking degree and density was achieved at the dose of1000kGy by electron-beam irradiation cross-linking in nitrogen atmosphere where the first drpping occurred later and there were longer combustion process. The drops decreased from fourteen to eight during the longer combustion process. Breaking strength decreased firstly then increased at the dose from200to1000kGy, whereas elongation at break had the contrary tendency. The melting temperature and crystallinity decreased as the dose increased. The onset temperature of degradation got higher slightly and the scope of weight loss temperature became wider, also the maximum weight loss rate was slower, the amount of non-volatile residue at600℃increased as the irradiation dose increased. Irradiation cross-linking increased the amount of carbon retained in the residue, also changed the structure of char to be continuous and with less hole. Irradiation cross-linking had different flame retardant and anti-dripping effects on different flame retardant systems. It improved the flame retardant and anti-dripping properties of diphenyl anilinophosphonate and mealmine with diphenyl anilinophosphonate.