β Nucleating Agent To Influence The Performance Of Isotactic Polypropylene

It has become the important means of optimization of isotactic polypropylene (iPP) which is using beta nucleating agent to change the crystallization and to improve the performance of the iPP. In this article, we adopt CHB-5acting as beta nucleating agent to modified iPP (F401). The crystal properties and the mechanical properties of modified iPP are investigated by wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), polarizing microscope photos (POM), impact properties test, tensile performance test and bending performance test. At the same time, the dispersibility of CHB-5of modified iPP causing by the PE wax is studied by electronic scanning electron micrograph (SEM). And it further investigates the influences of crystal properties and mechanical properties of modified iPP with the action of CHB-5and PE wax. These aims are to making the modification iPP materials to meet the needs of outdoor applications.To this end, this thesis mainly does the following several aspects work, and gets the phased research results:(1)The effects on crystal morphology, crystallographic and melting behaviours, mechanical properties of iPP which are caused by CHB-5and its contents are studied. The results show that the addition of CHB-5into iPP plays the role of heterogeneous nucleation. It can induce iPP to generate β crystal effectively, raise the crystallization temperature of iPP and accelerate crystallization rate of iPP. The relative contents of beta crystal of sample increase gradually with the increase of concentration of CHB-5in the rangeof0.1%to0.6%. The impact strength also increases gradually, there are many small white areas in the impact cross section, and these areas connect each other together. All of the phenomenons show the characteristic of ductile fracture obviously.(2)The effects on crystal structure, crystallographic and melting behaviours of modified iPP which are caused by cooling rate are studied. The results show that the slower cooling rate is beneficial to improve the relative contents of beta crystal of iPP and to increase the melting point of beta crystal of iPP. As the cooling rate decreases from25℃/min to5℃/min, the relative contents of beta crystal increase from75.61%to78.45%and the melting temperature of beta crystal elevate from150.85℃to152.40℃。 In addition, the modified iPP is more crystallizer than pure iPP under the same cooling rate.(3)The effects on crystal structure, crystallographic and melting behaviours of modified iPP which are caused by crystallization temperature are studied. The results show that the optimum temperature range of forming the beta crystal is120℃～125℃ The relative contents of beta crystal and the crystallization rate of beta crystal arrive at the best state in this temperature range.(4)The effects on dispersibility of CHB-5in the modified iPP which are caused by the PE wax are studied. The results show that the PE wax reduces the reunion of CHB-5and improves the dispersibility of CHB-5in the modified iPP matrix.(5)The effects on crystal properties and mechanical properties of iPP which are caused by using the CHB-5and PE wax are studied. The results show that the PE wax makes the CHB-5better playing the role of heterogeneous nucleation in iPP. There is significant synergistic effect when using both CHB-5and PE wax. The relative contents of beta crystal increase by11.05%and the impact strength increase by37.78%than use alone CHB-5.