Influence Of α/β-compounded Nucleating Agent On Crystalline Morphology And Mechanical Property Of Injection Molded Polypropylene

Isotactic polypropylene (iPP) is widely used in industrial production with manyexcellent properties such as smaller relative density, good resistance to solvents,non-toxic, insulation, easy processing, etc. The price cheaper compared with PLA、PS and other materials. However, some defect of iPP such as low toughness andstiffness. Many researchers employ nucleating agent to modify according to thedeficiency of iPP. In this paper, the effect of α-nucleating agent and α/β-compositenucleating agent on crystalline structures and mechanical properties of iPP is studied,including the change law of crystal morphology and mechanical properties of iPPmodified by nucleating agent varying in content and ratio.1、iPP, modified by α-nucleating agent with different content,standard testingspecimens was prepared by Demag injection molding machine. The change law ofcrystalline structure and mechanical properties of iPP products corresponding to thecontent of α-nucleating agent is explored. It is found that crystal morphologyremains unchanged, spherulite size decreases and the crystallinity of α-crystallineincreases with increasing of α-nucleating agent. In addition, the tensile strength andimpact strength of iPP products increases and decreases respectively.2、It is explored crystal morphology and the change rule of mechanicalproperties of the iPP modified by different ratio of α/β-composite nucleating agent.Itis found that(1) The structure of snowflake and acicular will be shown in the PLM ofisothermal crystallization. It is the reason that the β-crystal have been created and thecrystal morphology have been changed. With the increase of content of α-nucleatingagent in composite proportion, the crystalline of β-crystal has reduced and thecrystalline of α-crystal has increased.(2)The tensile strength and impact strength of iPP parts have been improved byadding the composite nucleating agent. With the increase of content of α-nucleatingagent in composite proportion, the tensile strength and impact strength will reduce. When the composite proportion of α-nucleating agent and β-nucleating agent is0.1%：0.2%, the tensile strength and impact strength will reach the maximizingpoint.3、Annealing treatment have been made for the iPP parts which containnucleating agent in different types and contents. Then we do some research about thechanges of crystal morphology and mechanical property of the nucleating agentmodified iPP after annealed. Research findings:(1) After annealed, the crystallinity, tensile strength and impact strength of theα-nucleating agent modified iPP will improve.(2)After annealed, the crystallinity, tensile strength and impact strength of theAlpha crystal and Beta crystal in α/β-composite nucleating agent modified iPP willimprove. The composite proportion of α-nucleating agent and β-nucleating agent is0.1%：0.2%, the crystalline of β-crystal and α-crystal have reduced. Changing thecomposite proportion of two nucleating agent, the crystalline of β-crystal hasreduced and the crystalline of α-crystal has increased.