| Polyamide has been found and commercialized since 1935.Early polyamide was mainly produced as raw material for polyamide (Nylon6) fiber, which is the earliest synthetic fiber in the word. For several decades, Nylon6 fiber was developing at the annual rate of 15% and have been applied in various industry fields of military, aerospace, vehicle and daily articles for its excellent mechanical properties such as high strength, excellent resistances to abrasion, chemicals and mildew, etc. Since 1950, Nylon6 has become one of the five most important engineering plastics due to the developments of nucleating agent and fiber reinforcement of plastics.However, it has some disadvantages, such as low Young's modulus, easy to deforming and poor thermal resistance, which seriously limit its further and wide applications in some special fields, such as high quality tire-cord, conveyer belt etc.On the other hand, hydro-open ring polymerization is a classical method for polymerization of ε -caprolactom with tedious production process and expensive equipments, and polymerization time will take more than 20 hours; it is difficult to prepare modified or differential products by this method; anion polymerization of ε -caprolactom can produce Nylon6 in a short time, such as several minutes, however, with very high molecular weight, wide molecular weight distribution and its product is difficult to be spun into fiber and can only be used as plastics.In situ polymerization of Nylon6/montmorillonite (PA6/MMT) composites was first introduced by professor Y. Fukushima in 1987 and since then great progress has been obtained in preparation, characterization and applications of PA6/MMT with high strength, high modulus and high thermal resistance. However, most of the studies are depended on hydro-open ring polymerization process and their products are on the forms of plastics or films and there is nothing concerned about the fiber grade PA6/MMT composite chip prepared by twin-screw extruder.The thesis focuses on the preparation and characterization of MMT modified PA chips and fibers. The results show that:1. At the first time to prepare MMT modified PA6 chips using twin-screw extruder as reactor, ε -caprolactom was in situ anion polymerized at the presence of MMTin a short time. By control polymerization parameter such as temperature, screw profile, fiber grade PA6/MMT nanocomposite chips was prepared continually in a quite shorter time compared with that by classical hydro-open ring polymerization method.2. The effect of screw profile on polymer properties was studied and a special combination of screw elements was designed in order to obtain a modified polyamide with suitable molecular weight (about 24000), narrow molecular weight distribution (about 1.8) for fiber making.3. The studies on crystallization kinetics and morphological studies show that the nanoMMT added in the system would react as nucleating agent. With the increase of MMT, Avrami index decreases. The spherulite develops rather in three dimensions when the amount of MMT is below l(wt)%, and show two dimensional propagation when the amount reaches 3%.4. The rheological studies on PA6/MMT system show that with the increase of shear rate and temperature, the apparent melt viscosity decreases. With the increase of MMT amount, melt apparent viscosity will increases.5. TGA was used to study PA6/MMT thermal property. The results show that its thermal stability is greatly improved compared with that of pure PA6 sample. The maximal degradation temperature for 3% MMT modified PA reaches 350℃. At same weight loss, such as 10%, pure PA6 was at temperature about 290 ℃, while modified one was 325 ℃.6. PA6/MMT composite chips with different MMT contents were spun and drawn into fibers. Fiber mechanical properties were tested and the results shown that the adding of nano-MMT could improve fiber mechanical properties. Compared with pure PA6 fiber, the tensile strengths of fibers with 1 and 2(wt)% MMT increased by 3% and 4%, while fiber Young's modulus increased by 10.7% a...
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