| Polypropylene products have the characteristics of light quality, corrosion resistance. It has been widly used in construction industry and packing field. Compared with other general-purpose resins, the major drawbacks of polypropylene are poor low-temperature impact performance, poor anti-aging properties, etc. These shortcomings greatly limit the application of polypropylene. In the aim of improving the performance of polypropylene,reducing costs, broadening its applications, many scholars carried out extensive research. The way to modified polypropylene including filling, alloying, copolymering, cross linked,grafted and addition of nucleating agents. The addition of nucleating agents and copolymerization are concerned by its obvious effect. In this paper,we carry out our research on modification of polypropylene by those two methods. We intend to explore the theory and method of obtaining polypropylene with high performance. We try to establish foundation and evidence for the development of high performance Polypropylene products.Polypropylene is one of the semicrystalline polymers. The incorporation of nucleating agents with polypropylene can enhance the degree of crystallinity, improve the transparency and mechanical performance. So far, there are two kinds of commercial nucleating agents,?-phase and ?-phase. In which a-phase nucleating agents improves the stiffness of polypropylene, and ?-phase nucleating agents improves the toughness and heat distortion temperature of polypropylene. The first part of this article evaluate the performace of commercially available nucleating agent TMB-5, WBG and three homemade ? crystal nucleating agent by melt blending. The results show that those polypropylene addition with ?crystal nucleating agent show better mechanical properties than pure polypropylene. The homemade ? crystal nucleating agent NA3 show a clear effect in modifying the properties of polypropylene. NA3 have the equal effect with TMB-5 and WBG in improving distortion temperature and yield strength. At the same time, NA3 show a better performance in impact strength, elongation at break and the increasing content of ? crystal than TMB-5 and WBG.Thus, the homemade ? crystal nucleating agent has a high application value.Compared with addition of ? crystal nucleating agent by melt-blending method,polymerization of propylene involved crystal nucleating agent avoided the mixing process of powered polypropylene with ? crystal nucleating. It is also easier to achieve the dispersion result. The second part of this article introduced the method of improving polypropyleneproperties by addition of our homemade ? crystal nucleating agent NA3 in a 10 L polymerization reactor. We investigate the influence of nucleating agent amount to catalyst activity, impact strength, flexural modulus, tensile strength, elongation at break rate and the percentage of ? crystals. The results show that when the amount of nucleating agent is0~550ppm, the activity of catalyst have little fluctuation and show a stable performance.Comepared with pure polypropylene, when adding NA3 with the amount of 205 ppm, the impact strength increased 3.5kJ/m2, tensile strength improved with 5.6MPa, elongation at break increase 92%, the crystallinity increase 13%, flexural modulus improve a little at the same time.Polymer alloy is a mixture of partially compatible polymers made of multi-level structure of the polymer blend, the multiplicity of the structure and motion of the polymer alloy shows many features. Two polypropylene alloy products, which have almost the same properties in impact strength, flexural modulus but essentially different in elongation at break,prepared in one reactor were selected in the third part of the article select.. We study the cause of the difference. The results show that the content of the solvent phase, the ratio of the viscosity of the rubber phase and the matrix, the size of the rubber phase and the degree of uniform size are the main effect contribute to the difference of elongation at break. |
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