| At present, there are a few studies on polyamide 6/polyethtylene/non-metal minerals. This thesis has studied the effects of polyamide 6 modified by polyethylene and non-metal mineral particles, and the synergistil effects of polyethylene combined with kaolin reinforcing and toughening polyamide 6.The studying of polyamide 6/polyethylene/non-metal minerals is of great significance to improving the mechanical properties of composites and decreasing the cost of engineering plastics. Meanwhile, it can exploiting the application of non-metal minerals in polymer.In this thesis , methacryloxypropyl trimethoxy silane and isopropyle tri-(dioctylpyrophosphate)titanate were used to modify the surface of kaolin, and PE-MAH was used as compatibilizer, PA6/LDPE/Kaolin composite is prepared by blending modification of polyamide 6 adopted kaolin and low density PE. The best modification technics and formula have been confirmed through the studying of mechanical properties,thermal properties and water absorbability. Through above studies, some meaningful results were achieved.1. Compared the results of pre-evaluation of surface modification of kaolin and the results of kaolin modified by different modification agent filled in polyamide 6. Isopropyle tri-(dioctylpyrophosphate)titanate has better modification effect on kaolin and worse effect of combination with matrix, however, methacryloxypropyl trimethoxy silane has worse modification effect on kaolin and better effect of combination with matrix.2. In the preparation of composite using one-step process, PE-MAH has great compatibility on the blend of Kaolin/PE/PA6, the size of scattered is fine, the mechanical properties of blend are well. when the compounding ratio of PA6/LDPE/Kaolin modified by methacryloxypropyl trimethoxy silane/PE-MAH was 100/7/15/7, comparing with pure polyamide6, notched impact strength increased by 6.7%, yield strength increased by 21.1%, modulus of elasticity increased by 36.3%, water absorption decreased by 32.5%, tensile strength decreased by 18.2%, rockwell hardness decreased by 9.4%, the PA6/LDPE/Kaolin ternary composite which have been prepared has better properties.3. In the preparation of PA6/LDPE/Kaolin ternary composite using two-step process, there is the phenomenon of particle agglomerate because of Kaolin has been filled abundantly, the mechanical and thermal properties of prepared composite declined to some extent. when the compounding ratio of PA6/LDPE/Kaolin modified by methacryloxypropyl trimethoxy silane/PE-MAH was 100/20/30/10, comparing with pure polyamide 6, notched impact strength decreased by 4.56%, modulus of elasticity decreased by 4.58%, tensile strength decreased by 36.42%, rockwell hardness decreased by 28.37%, yield strength increased by 7.77%, nevertheless, water absorption decreased by 47.0%, melt flow rate much lower, the properties of composite become worse.4. Analysis from SEM micrographs of composite's tensile fractured surface, kaolin particles which was modified by isopropyle tri-(dioctylpyrophosphate)titanate combined with matrix worse than that of kaolin particles modified by methacryloxypropyl trimethoxy silane. When the content of modified kaolin particles was excessive, the dispersion of modified kaolin particles became worse, and the combination of particles with matrix was also decrease, so the mechanical properties of composite decreased, have the consistency with the test results of experiment.5. The DSC analysis of composite materials, the addition of LDPE has achieved better toughening in the composite of PA6/LDPE; The modified kaolin filled in composite can play the role of heterogeneous nucleating agent, the addition of nucleating agent to accelerate the crystallization rate, facilitate the nucleation and crystallization of polyamide, the spherocrystal particles are more fineness, it can increase the tensile-strength,modulus of elasticity in static bending and heat resistance of PA6/LDPE/Kaolin ternary composite.6. The course of forming interface of the filler and polymer includes the course of contacting and invading of the polymer and fillers and the solidification course that the chemical bond combines. And the integrality of interface is directly influence the properties of the composite. However, the integrality of interface is relevant with the geometry form of the fillers,chemical reaction activation,flexibility of polymer and chemical constitution.7. Kaolin filled in polyamide 6 has an advantage of filled with a higher proportion to reducing the cost, and compared with pure polyamide 6, its rigidity,wearability,heat resistance,water absorbability and chemical inactivity can be maintained or improved in different degrees. Consequently, the application of PA6/LDPE/Kaolin ternary composite in some fields can avoid causing the performance surplus, and also can reduce the cost, increase economic efficiency.
|
PDF Full Text Request