Unusual hierarchical distribution of β-crystals and improved mechanical properties of injection-molded bars of isotactic polypropylene

Abstract Isotactic polypropylene (iPP) was nucleated in-situ with calcium pimelate during melt compounding. Calcium pimelate is a highly effective β-nucleator for isotactic polypropylene (iPP). The β-nucleated iPP was characterized by wide angle x-ray diffraction (WAXD) and differential scanning calorimetry (DSC) for its crystallinity and crystal structure. In addition, the injection-molded samples were tested for thermo-mechanical properties. It is found that very low quantity (< 0.1 wt. %) of β-nucleator is required to produce sufficiently high β-crystal fraction (Kβ) in isotactic polypropylene. β-nucleated iPP shows increment of 11 to 14 °C in its heat deflection temperature (HDT). It was also observed that slow cooling rate of β-nucleated iPP promotes the formation of β-crystals and that tensile stretching leads to complete transformation of β crystals into a-crystals at room temperature. It was also revealed that the presence of maleic anhydride grafted polypropylene (PP-g-MA), a well-known coupling agent (or compatibilizer), may reduce the (Kβ) value to a marginal extent. It was also observed that the thermo-mechanical properties were not much affected by the presence of PP-g-MA. Therefore, calcium pimelate may be used as β-nucleator in case of neat as well as reinforced polypropylene containing maleic anhydride as coupling agent.

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The influences of a novel shear layer-spherulites layer alternated structure on the mechanical properties of injection-molded isotactic polypropylene

Polymer ◽

10.1016/j.polymer.2017.06.035 ◽

2017 ◽

Vol 122 ◽

pp. 12-21 ◽

Cited By ~ 14

Author(s):

FengYi Hou ◽

DaShan Mi ◽

Man Zhou ◽

Jie Zhang

Keyword(s):

Mechanical Properties ◽

Shear Layer ◽

Isotactic Polypropylene ◽

Injection Molded

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Melting, Crystallization Behaviors and Mechanical Properties of iPP Nucleated by β Nucleation Masterbatches

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.941-944.1229 ◽

2014 ◽

Vol 941-944 ◽

pp. 1229-1232

Author(s):

Guo Rui Dou ◽

Qiang Dou

Keyword(s):

Mechanical Properties ◽

Differential Scanning Calorimetry ◽

Impact Strength ◽

Isotactic Polypropylene ◽

Tensile Strain ◽

Mechanical Tests ◽

Crystalline Form ◽

Scanning Calorimetry ◽

Crystallization Behaviors ◽

Injection Molded

Injection-molded β-isotactic polypropylene (β-iPP) specimens were prepared by adding three β nucleation masterbatches, i.e., NT-MA, NT-MB and NT-MC, respectively. The melting, crystallization and mechanical properties of β-iPP specimens were investigated by means of differential scanning calorimetry (DSC) and mechanical tests. It is revealed that β crystalline form contents were enhanced by the β nucleation masterbatches, and the β contents of the cores were higher than those of the skins of injection molded specimens. The tensile strain at break and Izod notched impact strength of iPP were greatly improved by the β nucleation masterbatches. It was found that the β nucleation efficiency was in the order: NT-MC > NT-MA > NT-MB.

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