Study On The Spinnability Of Semi-Aromatic Polyamide

With the rapid development of science and technology, automobile need to be lighter, electronic products need to be smaller, smarter and cost fewer, cable and wires need higher weatherproof. Therefore, stricter requirements are essential for heat resistance, dimensional stability and precision molding of the organic materials, Polyamide has a wide range of applications in various fields. The PA fiber is also on research and development. In order to adapt to the demands for heat resistance, water absorption, dimensional stability and other aspects, aromatic rings with good thermal stability are introduced into the main chain when designing molecular structure and the aromatic acid or amide is used to replace the aliphatic acid or amide to synthesize semi-aromatic polyamide. This new type of polyamide possessing both the advantages of aromatic and aliphatic polyamide has become the hot research area.In this work, appropriate material was selected. Its thermal degradation mechanism and non-isothermal crystallization kinetics were analyzed to provide a reference for the spinning process. And suitable process parameters were adjusted for preparing semi-aromatic polyamide spun fiber by twin-screw extruder. After that, the fibers were heat treated as the follow-up process. The result indicated:1. Comparing test results of Melt Index (MI), DSC together with TG, the No.2 sample was selected to be the row material for spinning. The MI of the No.2 sample was 17.71g/min, the melting point was 290℃, and the heat decomposed temperature was up to 450℃which indicated that the raw material can maintain stable under high temperature.2. The thermal degradation of semi-aromatic polyamide was one-step reaction. The thermal degradation kinetics of semi-aromatic polyamide samples was studied using Kissinger method and Flynn-Wall-Ozawa method. Two possible mechanisms of degradation can be found. 3. Non-isothermal crystallization process and its dynamics of semi-aromatic polyamide were studied using DSC. The tends of the crystal peaks was moving to lower temperature and the width of the peaks became wider along with the increase of the cooling rate which suggested the cooling process was controlled by the nucleation. While the half-crystallization time t1/2 increased that showed that the crystallization rate increased with the increase of cooling rate. Under the non-isothermal condition, the semi-aromatic polyamide crystal might grow as lamella. When the cooling rate increased, the crystallization form might transfer into three-dimensional spherulite.4. The semi-aromatic polyamide pellets were spun by twin-screw extruder. A 40cm-long slow cooling device was attached under the spinneret to overcome difficulty of fiber forming with the temperature about 220℃. The spinning temperature was between 295-320℃. Appropriate mechanical properties had been found on the spun fibers. The semi-aromatic polyamide fibers were then heat treated and found that its elongation at break significantly decreased, while strength and modulus increased. Considering the impact on thermal and mechanical properties, heat treatment under 160℃,60 min was appropriate. And the melting point of post-treat semi-aromatic polyamide fibers was 300℃, elongation at break, Young's modulus and tensile strength was 6%, 12.3 GPa and 0.77GPa respectively, which shows that post-processing can greatly improve mechanical properties of semi-aromatic polyamide fibers.