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• Effect of β-nucleating agent on crystallization of post-consumer PP is studied. • Post-consumer PP with relative β-phase content higher than 0.80 is able to prepare. • It is possible to apply polymorphic modification in post-consumer PP recycling. The effect of two kinds of β-nucleating agents, an aryl amide derivative β-nucleating agent (TMB-5) and a rare earth complex (WBG), on crystallization of post-consumer polypropylene (PCW-PP) were investigated by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (XRD) and polarized-light optical microscopy (POM). The results indicate that introduction of TMB-5 and WBG is able to increase the crystallization temperature of PCW-PP and to induce a large amount of β-crystals. TMB-5 has stronger β-nucleating effect than WBG at low content, while the β-nucleating effect of WBG exceeds that of TMB-5 at a content of about 0.7 wt%, referring to the calculated relative content of β-phase and the concentration of nuclei in PCW-PP. Through adding 0.3 wt% TMB-5 or 0.7 wt% WBG, PCW-PP with β-phase content higher than 0.80 can be prepared, which provides a promising method to realize high-value added recycling of PCW-PP. [ABSTRACT FROM AUTHOR]

In order to prepare polypropylene (PP) composites with balanceable stiffness and toughness, hybrid wollastonite with different nucleation and morphology as fillers were added into PP matrix. Nucleation efficiency (NE), crystallization behavior and melting characteristics, as well as the mechanical properties of hybrid wollastonite‐filled PP composites were systematically investigated using differential scanning calorimetry, wide‐angle X‐ray diffraction, mechanical testing, and scanning electron microscopy, respectively. The results indicated that the NE of wollastonite with β‐nucleation is much higher than that of acicular wollastonite and ultrafine wollastonite with α‐nucleation, and eventually hybrid wollastonite‐filled PP composites mainly form β‐phase PP. Furthermore, there exists cooperative effect between the reinforcement of wollastonite of different morphology and the toughening of β‐phase, which can be effectively controlled through regulating the nucleating ability, morphology, and mass ration of hybrid wollastonite. POLYM. COMPOS., 40:E638–E646, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The morphology of partially crystalline/ordered poly(butylene naphthalate) (PBN) forming on cooling the melt has been analyzed by polarized-light optical microscopy (POM) and microfocus-beam X-ray diffraction (XRD). Crystallization at rather low supercooling of the melt, at temperatures higher than about 200 °C, leads to slow and irregular spherulitic growth of β′-crystals, with spherulites not showing a distinct Maltese cross in POM. At temperatures between approximately 200 and 160 °C, the melt partially converts directly to α-crystals, and the obtained spherulitic superstructure reveals an increasing nuclei density with decreasing crystallization temperature. At even lower temperature, a liquid crystalline (LC) phase develops. This mesophase may subsequently convert to α-crystals according to Ostwald’s rule of stages. The transition of the LC-phase into α-crystals is suppressed at temperatures lower than about 120 °C or on cooling faster than about 200–500 K/s. X-ray analysis of PBN liquid crystals formed at well-defined cooling conditions in a fast scanning chip calorimeter revealed smectic periodicity while there is simultaneously observed a distinct Schlieren texture in POM. [ABSTRACT FROM AUTHOR]

To obtain isotactic polypropylene (iPP) nanocomposites with high β-crystal content, TMB5, calcium pimelate and calcium pimelate supported on the surface of nano-CaCO3 were used as β-nucleating agent and MWCNT filled β-nucleated iPP nanocomposites were prepared. The effect of different β-nucleating agent and MWCNT on the crystallization behavior and morphology, melting characteristic and β-crystal content of β-nucleated iPP nanocomposites were investigated by DSC, XRD and POM. The results indicated that addition of MWCNT increased the crystallization temperature of iPP and MWCNT filled iPP nanocomposites mainly formed α-crystal. The β-nucleating agent can induce the formation of β-crystal in MWCNT filled iPP nanocomposites. The β-nucleating ability and β-crystal content in MWCNT filled β-nucleated iPP nanocomposites decreased with increasing MWCNT content and increased with increasing β-nucleating agent content due to the nucleation competition between MWCNT and β-nucleating agents. It is found that the calcium pimelate supported on the surface of inorganic particles as β-nucleating agent has stronger heterogeneous β-nucleation than calcium pimelate and TMB5. The MWCNT filled iPP nanocomposites with high β-crystal content can be obtained by supported β-nucleating agent. POLYM. COMPOS., 36:635-643, 2015. © 2014 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

To transform α-nucleation into β-nucleation of wollastonite surface for isotactic polypropylene (iPP), the wollastonite with a β-nucleating surface was prepared through the chemical reaction between wollastonite and pimelic acid in both liquid mixing (method A) and powder mixing (method B). The wollastonite with a β-nucleating surface was confirmed using differential scanning calorimetry (DSC), X-ray photoelectron spectroscopy analysis, wide-angle X-ray diffraction under different temperatures, thermogravimetry coupled with Fourier transform infrared spectrometry, and scanning electron microscopy. The crystallization and melting behavior and the crystalline morphology of iPP composites filled by wollastonite with a β-nucleating surface were investigated by DSC and optical microscopy. The results indicated that wollastonite filled iPP composites predominantly crystallize in the α-phase iPP and iPP composites filled by wollastonite with a β-nucleating surface mainly form β-phase iPP. It is proved that heterogeneous nucleating mechanism has been changed from α-nucleation into β-nucleation of wollastonite surface for iPP crystallization. What deserves to be mentioned is that the nucleation density of flat surface in the end of needle-like wollastonite is higher than that of curved surface of wollastonite. [ABSTRACT FROM AUTHOR]

In order to obtain wollastonite filled β-iPP composites, wollastonite treated with pimelic acid (W*) were prepared with various mass ratios of wollastonite/pimelic acid (W/PA). The crystallization behavior, melting characteristics and β-nucleating ability of iPP composites filled with wollastonite (W) and W* were investigated by DSC and XRD. The results indicated that addition of wollastonite increased the crystallization temperatures of iPP, but the crystallization temperatures of iPP in iPP/W* composites were higher than those of iPP/W composites, which proved that the β-nucleation of W* is stronger than untreated wollastonite. Although iPP/wollastonite composites mainly form α-phase iPP, modification of wollastonite by PA significantly enhanced nucleation of β-phase iPP. The β-nucleating ability of W* depend on the amount of formed calcium pimelate, therefore the β-phase contents of β-iPP/W* composites increased with increasing W* content and decreasing mass ratio of W/PA. Moreover, there exist different critical mass ratios of W/PA for preparation of β-iPP composites filled with different W* contents with highest β-phase content and low cost. [ABSTRACT FROM AUTHOR]

Poly(butylene 2,6-naphthalate) (PBN) is a crystallizable aromatic polyester and develops different crystal polymorphs as a function of the crystallization conditions. High-temperature crystallization above about 200 °C yields β′-crystals while α-crystals develop between about 160 and 200 °C, both forming directly from the melt. At lower temperature, crystallization follows Ostwald's rule of stages, with the melt first transforming into a smectic liquid crystalline structure, which then converts into α-crystals. Information about the morphology of the liquid crystalline mesophase at the nanometer-length scale and of α-crystals, formed directly from the melt or from the liquid crystalline mesophase, are not available yet, and is therefore analyzed in the present study using atomic force microscopy (AFM). Direct transformation of the melt into α-crystals proceeds via spherulitic crystal growth. AFM reveals formation of laterally extended lamellae with a thickness of 10–15 nm. The smectic liquid crystalline mesophase, isolated by quenching before its transformation into α-crystals, appears as a close arrangement of clusters with a characteristic spacing of around 10 nm. The overall morphology is preserved on transformation of the mesophase into α-crystals supporting the notion that the mesophase converts directly, that is, within a solid-solid phase transition into α-crystals without intermediate melting, confirming a crystallization pathway according Ostwald's rule of stages. Image 1 • Direct melt-crystallization at low supercooling of the melt leads to formation of lamellae. • Crystallization at high supercooling of the melt proceeds via Ostwald's rule of stages. • At high melt-supercooling, first liquid crystals (LC) form which then convert to α-crystals. • The LC-phase appears as a close arrangement of clusters with a characteristic spacing of 10–15 nm. • The transition of the LC-phase into α-crystals is not connected with a change of the morphology. [ABSTRACT FROM AUTHOR]

The effect of presence of up to 30 mol% diethylene 2,6‐naphthalate (DEN) constitutional defects on the crystallization kinetics and morphology of poly(butylene 2,6‐naphthalate) (PBN) was investigated by differential scanning calorimetry, fast scanning chip calorimetry, polarized‐light optical microscopy, and wide‐angle X‐ray scattering (WAXS). The results indicate that the crystallization behavior of butylene/DEN random copolymers [P(BxDEyN)] is analogous to the PBN homopolymer: at low supercooling direct crystallization from the melt occurs, while at lower crystallization temperature/higher cooling rates, the formation of a liquid crystalline phase precedes the development of the ultimately stable crystal, confirming the validity of Ostwald's rule of stages also for random copolymers. However, the incorporation of DEN counits into the polymer chains retards both crystal and liquid‐crystal formation proportionally to the DEN content. WAXS analysis suggests the exclusion of DEN counits from PBN crystals. Thus, the lower crystallization rate in the copolymers can be associated, with the filtering of crystallizable chain segments at the crystal growth front. [ABSTRACT FROM AUTHOR]

Abstract: In order to investigate the effect of crystallinity of second polymers on β-crystallization of β-nucleated isotactic polypropylene (β-iPP), a series of β-iPP blends with different poly(ethylene terephthalate) (PET) contents were prepared by using twin-screw extruder, and the β-iPP blends with different crystallinity PET were obtained by controlling the cooling rate, crystallization temperature and time, and melting temperature. The crystallization and melting behavior, crystalline morphology and β-crystal content have been investigated by DSC, WAXD and POM. The relationship between β-crystal content in the blends and the crystallinity of PET was discussed. Based on the effect of cooling rate, crystallization temperature and time, and melting temperature on β-crystallization of iPP in the β-iPP blend, it is considered that the crystallinity of PET is an important factor to the β-crystallization of β-iPP. The decreased crystallinity of PET would help the β-crystallization of β-iPP. [Copyright &y& Elsevier]

Abstract: In order to increase the antimicrobial properties and ultraviolet resistance of isotactic polypropylene (iPP), ZnO-supported zeolite particles were prepared and used as multifunctional filler for iPP composites. The ZnO-supported zeolites with different ZnO contents were obtained by treating the mixture of zeolite and zinc acetate by different methods. Atomic absorption spectroscopy, scanning electron microscope and wide-angle X-ray diffraction experiment indicated that the ZnO was formed on the surface of zeolite particles. UV-irradiation results showed that the ultraviolet resistance of ZnO-supported zeolite filled iPP composites is higher than that of iPP composite filled by the same content of micro ZnO. The ZnO-supported zeolite filed iPP composites exhibit higher antimicrobial abilities than ZnO filled iPP composites prepared by directly adding micro ZnO into iPP matrix for the Staphylococcus aureus and Escherichia coli. Incorporation of ZnO and zeolite increases the crystallization temperatures of iPP due to the heterogeneous nucleation of ZnO and zeolite particles. The prepared ZnO-supported zeolite particles have no influence on the crystallization and melting behavior of zeolite filled iPP composites. The ZnO-supported zeolite particles are an effective filler to prepare iPP composites with antimicrobial ability and ultraviolet resistance. [Copyright &y& Elsevier]

Abstract: Neat montmorillonite (MMT) causes strong heterogeneous nucleation of α-phase crystallites in isotactic polypropylene (iPP). By surface modification of MMT with pimelic acid (PA) MMT with tailored β-nucleation capacity (β-MMT) has been prepared and nanocomposites with β-iPP have been made. The polymorphism of the iPP in the nanocomposites, the effect of β-MMT on the morphology and its crystallization and melting behavior of iPP has been investigated by POM, DSC and XRD. β-MMT raises the crystallization temperature to a higher value than neat MMT. The β-nucleation ability of β-MMT depends both on the MMT/PA ratio and on the β-MMT content in the composite. The fraction of β-crystals with respect to the total amount of crystals increases with increasing β-MMT content and decreasing MMT/PA ratio. It can be adjusted between 0% and 98%. The accomplished surface modification of the MMT provides a simple and efficient way to prepare β-iPP nanocomposites. [Copyright &y& Elsevier]

Abstract: In order to prepare the zeolite filled β-iPP composites, the calcium pimelate as β-nucleator supported on the surface of zeolite (β-zeolite) was prepared by the interaction between calcified zeolite and pimelic acid. The β-nucleation, crystallization behavior and melting characteristic of zeolite, calcified zeolite and β-zeolite filled iPP composites were investigated by differential scanning calorimetry and wide-angle X-ray diffractometer. The results indicated that addition of the zeolite and calcified zeolite as well as β-zeolite increased the crystallization temperature of iPP. The zeolite and calcified zeolite filled iPP composites mainly crystallized in the α-crystal form and the strong β-heterogeneous nucleation of β-zeolite results in the formation of only β-crystal in β-zeolite filled iPP composites. The zeolite filled β-iPP composites with high β-crystal contents (above 0.90) can be easily obtained by adding β-zeolite into iPP matrix. [Copyright &y& Elsevier]