| Low melting point polyamide(LMPA) is a class of modified products with lower melting point than conventional polyamide. Its fiber has prominent characteristics such as low bonding temperature, easy manufacturing, high bonding strength and small influences on the materials, so the fiber has been used for composite yarns, sneakers surface and so on. Now, there are more reports on the synthesis and properties of LMPA, but for the 110℃ polyamide, which could be used for the fiber are few. Fiber-grade LMPA should not only has the certain melting point, but also has the appropriate crystallinity and better spinnability. Because the research is started later, the technology is relatively less mature in China, Fiber-grade LMPA is absent, and it mainly rely on imports, the cost is high. So, by the cooperation with domestic enterprises, we prepare two kinds of polyamides named A and B, the melting point of which is about 110±10℃.By analyzing the performance of LMPA, exploring fully drawn yarn(FDY) spinning process parameters, the LMPA fiber is received. This research also analyzes the adhesive property of the fiber.The structures and performances of LMPAs were analyzed by Differential scanning calorimeter(DSC), X ray diffraction(XRD), Fourier transform infrared spectrometer(FT-IR) and Thermogravimetric analysis(TG). FT-IR indicated that the two LMPAs had the same characteristic groups, their structures were similar. TG evidenced sample B had the better thermostability. DSC indicated the melting point of samples was about 110℃. The two melting peaks appeared in the isothermal crystallization processes. The lower melting peak moved towards higher temperature with increasing isothermal crystallization temperature or time, while the higher melting peek kept relatively constant. The greatest crystallinity appeared at 80℃, and the crystallinity increased with the expansion of the isothermal crystallization time at the same temperature. XRD also showed that the diffraction peaks became sharp,and the intensity gradually increased with the extension of crystallization temperature and time. The addition of the dicarboxylic acid and diamine with long carbon chain made the sample B had the better crystallization property than that of the sample A, and it was suitable for spinning.The melt index(MI) of LMPAs was investigated that MI was increasing with the enlargement of temperature. At low shear rate, two samples had close melt viscosity. The rheological properties showed that LMPA exhibited a pseudoplastic fluid. At the same temperature, non-newtonian index n of sample B was smaller than sample A. In the range of the temperature, the flow activation energy of LMPA decreased with the increase of the shear rate. And at the same shear rate, the flow activation energy of sample B was smaller than that of sample A. It was in favor of controlling the technological conditions in the process of spinning.The process of FDY and the properties of the fibers showed that the spinnability of sample B was better than that of sample A. Subsequently the discussion focused on sample B. With the increasing of spinning speed, the orientation and crystallinity was also increased, and the breaking strength of fibers was enlarged, when the elongation was reduced. With the increasing of draft ratio, the orientation, crystallinity and mechanical properties were somewhat improved. And when the draft ratio was between 2.6 and 2.9, the properties of fibers were better. The orientation was not obviously increased, and the crystallinity had a little raised with the increasing temperature of GR2. The temperature of GR2 should be settled at about 70℃.By using LMPA fiber and LMPET(low melting point polyester) fiber to be woven fabrics respectively with PA6, PP and PET draw texturing yarn(DTY), the adhesive property of the low melting point fiber was evaluated. The experimental results indicated that under the condition of the same fabrics basic parameters, low melting point fiber had played a good bonding effect. In the small deformation area, the tensile strength first increased and then decreased, at 140℃ reached the maximum with the increase of heat setting temperature. The sample 1(LMPET+PA6) had the greater strength, and the sample 5(LMPET+PET) next to it, so that LMPA and PA6 had the best consistency and better adhesive property. It also indicated that the same kind of fibers had the best adhesive property. The microscope tests showed when the heat treatment temperature was increasing, the low melting point fibers became melting gradually, then it depended on basis fibers. In a word, LMPA fiber has the better adhesive property. |
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