In situ generation of a self-dispersed β-nucleating agent with increased nucleation efficiency in isotactic polypropylene

β-Nucleated Polypropylene: Preparation, Nucleating Efficiency, Composite, and Future Prospects

The β-crystals of polypropylene have a metastable crystal form. The formation of β-crystals can improve the toughness and heat resistance of a material. The introduction of a β-nucleating agent, over many other methods, is undoubtedly the most reliable method through which to obtain β-PP. Furthermore, in this study, certain newly developed β-nucleating agents and their compounds in recent years are listed in detail, including the less-mentioned polymer β-nucleating agents and their nucleation characteristics. In addition, the various influencing factors of β-nucleation efficiency, including the polymer matrix and processing conditions, are analyzed in detail and the corresponding improvement measures are summarized. Finally, the composites and synergistic toughening effects are discussed, and three potential future research directions are speculated upon based on previous research.

Crystalline Characteristic Effect of In Situ Interaction between ZnO and Pht on Inducing β Nucleation of Isotactic Polypropylene

The β-nucleating agent (β-NA), zinc phthalate (ZnPht), was prepared from a mixture of zinc oxide (ZnO) and phthalic anhydride (Pht) during the extrusion of isotactic polypropylene (iPP). To establish the relationship between the crystalline characteristic of ZnO and the crystallization of iPP, single-crystalline ZnO (ZnO(S)) and polycrystalline ZnO (ZnO(P)) were selected and mixed with Pht, respectively, to in situ inducing the β-crystal form of iPP (β-iPP). Compared to ZnO(S)/Pht, ZnO(P)/Pht has the selectivity of β-crystal nucleation during the crystallization of iPP; indeed, the relative content of β-crystal ( $k_{\beta }$ ) improved from 18.0% for ZnO(S)/Pht/iPP to 84.6% for ZnO(P)/Pht/iPP. Moreover, the impact strength of the ZnO(P)/Pht/iPP was nearly 2.0 times greater than pure iPP; for ZnO(S)/Pht/iPP, it was approximately 1.4 times greater than pure iPP. To explain these phenomena, we propose a mechanism that the content of ZnPht generated by ZnO(P)/Pht is more than that of ZnO(S)/Pht during its in situ reaction; evidence from Fourier transform infrared spectroscopy, wide-angle X-ray diffraction, and thermogravimetric infrared spectroscope analysis was consistent with this mechanism. This study may provide a new perspective to control the crystal type of polymorphic polymer by adjusting the crystalline characteristic of the nucleating agent.

Fabrication of MgAl LDH@graphene oxide nanohybrids and their effect on the thermal stability and crystallization behavior of polypropylene

The co-precipitation method is used to fabricate layered double hydroxide (LDH) nanohybrids with surface engineering of graphene oxide (GO) by radially grafting borate-LDH (BLDH) to BLDH@GO nanosheets, aiming at improving the surface characteristics and compatibility of LDH with the polymer matrix. The results prove the successful fabrication of BLDH@GO and LDH@GO nanosheets. The nanosheets are mixed into polypropylene (PP) by melt blending to study the structure and properties of the composites. The PP composites with BLDH@GO and BLDH have both exfoliation structures and aggregation structures, and the two nanosheets show enhanced interfacial interactions with the PP matrix compared with LDH and LDH@GO. The initial decomposition temperatures of the PP composites are lower than those of the neat PP, but the thermal degradation temperatures of the PP composites are higher. Compared with the other samples, BLDH@GO provides a higher nucleation density, reflected in a smaller spherulite size and a higher crystallization temperature confirmed by the differential scanning calorimetry (DSC) results. BLDH@GO shifts the crystallization temperature of PP to higher values (compared to the neat PP) due to the nucleation effect, which is in line with the increase in the nucleation density detected by polarized optical microscopy (POM).

Influence of Organo-Sepiolite on the Morphological, Mechanical, and Rheological Properties of PP/ABS Blends

To improve the poor impact toughness of polypropylene (PP), organo-sepiolite (O-Sep) filled 80/20 (w/w) polypropylene/poly(acrylonitrile-butadiene-styrene) (PP/ABS) nanocomposites were fabricated. The contents of O-Sep were correlated with the morphological, mechanical, and rheological behavior of PP/ABS/O-Sep blends. Scanning electron microscopy (SEM) was applied to study the morphology and thermogravimetric analysis (TGA) was applied to study the thermal stability. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) were applied to study the crystallinity. The obtained results show that O-Sep enhanced the dispersion of ABS in the PP matrix and increased the crystallinity of blends. The rheological results show that O-Sep could increase the viscosity, storage modulus, and loss modulus of blends. Moreover, the mechanical behavior shows that O-Sep (at proper content) simultaneously increased the tensile modulus, flexural modulus, and impact strength of PP/ABS/O-Sep blends.