The Modification of Polypropylene by Melt Grafting and Blending and Its Fatigue Resistance
|Course||Materials Processing Engineering|
|Keywords||Isotactic polypropylene Graft Blends Polymorphs Melt strength Fatigue resistance|
In recent years, the strong development momentum of China's paper industry. At present, many foreign domestic paper-making enterprises are mainly imported plastic paper core pipe, some domestic companies are also stepping up the development of high rigidity and high toughness plastic paper core tube. Our early research on the performance of polypropylene pipes: α crystalline β-crystal transition phenomenon Ziegler-Natta isotactic polypropylene pipes after use, to make the material easy to fracture; metallocene isotactic polypropylene does not form a new beta. crystal. This may be related to the distribution of the three-dimensional structure with polypropylene. As the metallocene catalyst is expensive, the domestic production of polypropylene Ziegler-Natta isotactic polypropylene. If inhibition of crystal transition of the Ziegler-Natta isotactic polypropylene used in the process, the material life can be extended. The topic selection of the Ziegler-Natta isotactic polypropylene as the basic raw material, the use of the multi-functional monomer melt grafting polymer nylon 6 melt blending and add α crystal nucleating agents modified to change the polypropylene crystallization behavior and aggregation structure, and thus inhibit the transformation of the two crystal forms in order to improve the fatigue resistance of polypropylene. Using differential scanning calorimetry method, X-ray diffraction, infrared spectroscopy, polarizing microscope, a simple dynamic fatigue test and other mechanical properties of test methods to characterize the microstructure and properties of the sample. Draw the following conclusions: (1) modified polypropylene melt grafting its fatigue resistance: (a) pentaerythritol triacrylate (PETA) modified by melt grafting successfully grafted onto polypropylene skeleton. This not only improves the mechanical properties of the blends of polypropylene / glass fiber (PP / GF), polypropylene / glass fiber interface between the binding force, but also increase the melt strength of the blends, the melting point of the blend, The crystallization temperature and the crystallization rate. Meanwhile, the graft polymer can be suppressed the formation of the β polymorph in the fatigue process. (B) pentaerythritol tetraacrylate (PETeA) will not only improve the melting point and crystallization temperature of the polypropylene, so that the ball Jingjing grain refinement, but also increases the melt strength of the polypropylene. Pentaerythritol tetra-acrylate graft copolymer of polypropylene can be suppressed the formation of the β polymorph. Similarly, in the circulating mechanical fatigue, the graft-modified polypropylene does not produce the β crystal, significantly inhibited the transformation of the crystalline form, to improve the fatigue resistance of the material to increase its useful life. (2) Polypropylene modified and its fatigue resistance: (a) nylon 6 (PA6) serves as polypropylene of a nucleating agent, to improve the processing properties of the polypropylene melt. Nylon 6 significantly inhibited the generation of the β crystal in the molding process, and, in the role of cyclic fatigue, and there is no new β crystal generates, i.e. having a role in inhibiting the formation of β crystal. (B) α nucleating agent refined polypropylene ball Jingjing particle size, and promote the formation of α crystal type. After cyclic fatigue, polypropylene is no new beta crystal. This shows that α nucleating agent also has a role in the formation of the β crystal in the inhibition fatigue process. Features and innovations of the topics: (1) The topic selection of multifunctional monomer melt grafting modified polypropylene, enhance its melt strength. Dynamic fatigue tests showed that: this chemical graft modified polypropylene polymorph transformation is suppressed, improving its fatigue resistance. (2) dynamic fatigue testing: selection of high crystallization temperature of the polymer (nylon 6) or α nucleating agent added to the PP significantly inhibited β-crystal formation in polypropylene molding process and dynamic fatigue process. (3) using a simple dynamic fatigue test methods can simulate polypropylene material fatigue process in the actual application process.