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The morphology and thermal properties of PHBV/PHO/starch blends are investigated using polarized optical microscopy, differential scanning calorimetry, thermal gravimetric analysis, and X-ray diffraction. The crystallization behavior of the PHBV in PHBV/PHO was improved via the incorporation of a biodegradable nucleating agent, starch, as indicated by thermal analysis and polarized optical micrographs. The PHBV and PHO show phase separation in the blend. The XRD patterns of PHBV in blends are identical to those of neat PHBV. The Avrami exponents were not considerably impacted by the presence of PHO or starch. Furthermore, the nucleation constant, Kg, of the PHBV blends was evaluated using a modified Lauritzen–Hoffmann treatment. The Kg values indicated that the crystallization of PHBV in all blends occur in Regime III. PHO and starch have little impact on the maximum degradation temperature of PHBV. [ABSTRACT FROM AUTHOR]

The development of high-performance and low-cost composite nucleating agents has become a pioneering point in expanding the application of isotactic polypropylene (iPP). To this end, this article used a physical blending method to mix nucleating agent organic phosphate salt (LPN-9081) with inorganic fillers such as wollastonite and talc powder. Change the ratio of nucleated mineral-reinforced composition LPN-9081/wollastonite (L/WO) and LPN-9081/talc powder (L/Tac) to study their effects on the crystallization, melting behavior, and mechanical properties of iPP. And a preliminary exploration was conducted on its mechanism. The results suggest that the nucleated mineral-reinforced composition more significantly enhance the crystallization temperature, increasing it by up to 10 °C. Furthermore, it was observed that the mechanical properties of iPP were significantly improved via the synergistic effect of LPN-9081 and the inorganic fillers. In the iPP/L/WO system, the addition of the composite nucleating agent improved rigidity by 146% while maintaining toughness. Similarly, compared with iPP system, the iPP/L/Tac system has improved its rigidity by 107% and toughness by 50%. Using the nucleated mineral-reinforced compositions mentioned above can reduce industrial expenses, while increases the rigidity and toughness of iPP, expanding its potential of applications. [ABSTRACT FROM AUTHOR]

In this work, the applicability of a series of bisamide compounds (DCDC-R-n/R) with different structures as nucleating agents for isotactic polypropylene (iPP) was investigated. The effect of these nucleating agents on crystallization and melting behavior of iPP was analyzed using differential scanning calorimetry (DSC), results revealing a clear impact on the nucleus density in iPP. It is shown that the nucleation effect is better when the carbon number of the methylene chain in the intermediate structure is even rather than odd. In addition, the effect is stronger when the side substitution is a cyclic group rather than a branched group, while bisamide nucleating agents containing a cyclic intermediate group tends to form more β-crystals in iPP. The crystallization peak temperature ( T c) of iPP can be increased by more than 10 °C when the addition amount of DCDA-Cy-4, DCDA-Cy-6 and DCDA-Cp-6 is 0.3 mass%. The analysis of the iPP mechanical properties shows that DCDA-Cy-4 and DCDA-Cy-6 greatly improve its stiffness, while DCDA-Cy-Cy and DCDA-Cy-pPh have an excellent toughening effect on iPP as a result of β-phase. The structure-nucleation effect relationship of bisamide compounds was confirmed by further tests using wide-angle X-ray diffractometer (WAXD) and Materials Studio, showing good agreement with DSC data. Furthermore, the nucleation mechanism of these nucleating agents in iPP was investigated by using the lattice matching theory. The unit cell parameters of nucleating agents and iPP match well, indicating that these nucleating agents can induce epitaxial growth of iPP on their surface. [ABSTRACT FROM AUTHOR]

The low crystallization rate and long molding time of poly(ethylene terephthalate) (PET) restricts its application in the field of engineering plastics. PET/graphene oxide (GO) composites were synthesized through in situ polymerization method with dimethyl terephthalate (DMT), ethylene glycol (EG) as reactants and GO as filler in order to overcome the above shortcomings. Influence of GO on the crystallization performance of PET was investigated. It was revealed GO raised the crystallization temperature and crystallization rate of PET, demonstrating the excellent nucleation capability of GO. The mechanism of PET nucleation induced by GO was investigated by Avrami equation and Hoffman-Lauritzen theory. It was obvious the crystallization behavior of PET was improved by reducing the free energy of nucleation and the fold surface free energy of PET caused by GO. Moreover, the non-isothermal kinetics of thermal decomposition of PET and PET/GO composites were studied by Friedman method. It was obvious that all of PET and PET/GO composites exhibited a fine thermal stability with no significant mass loss observed up to 370 °C (< 0.5%). The addition of GO improved the thermal stability of PET through raising the apparent activation energy, inhibiting the escape of volatile products and absorbing the degradation products in PET thermal decomposition procedure. [ABSTRACT FROM AUTHOR]

TMB-5 of the aromatic diamides and WBG-II of the rare earth compound were employed as β-nucleating agents in conjunction with three commercially available α-nucleating agents MDBS, TMP-6 and HPN-68L, and the nucleating effects of compounded α/β-nucleating agents in isotactic polypropylene (iPP) were investigated. The crystallization and melting curves of iPP were measured by differential scanning calorimetry (DSC), mechanical properties were tested and the microstructure of nucleated iPP was explored via polarized optical microscope (POM). The action mechanism of the compounded nucleating agent in iPP was preliminarily discussed. The study revealed that the nucleating efficiency was in the order of HPN-68L > TMP-6 > TMB-5 > WBG-II > MDBS when the addition concentration was 0.10 mass%. The nucleating effect of compounded α/β-nucleating agents depends not only on the nucleating efficiency of individual α-nucleating agents or β-nucleating agents but also on the significant correlation with the difference in nucleating efficiency between the two kinds of nucleating agents. There is a competitive nucleation between α-nucleating agents and β-nucleating agents, and the nucleating agent with high nucleation efficiency can play a dominant role in the crystallization process of iPP even at low addition concentrations. TMB-5/TMP-6 can effectively balance the rigidity and toughness of iPP, with the optimal compounding ratio being 1:3. By using appropriate α- and β-nucleating agents in combination and adjusting the compound ratio, the modification effect of compounded nucleating agents on iPP can be controlled as expected. [ABSTRACT FROM AUTHOR]

Glass fiber-reinforced polyamide 66 composite with red phosphorus flame retardant (PA66-GF FR (RP)) has excellent strength and flame retardant properties, and is widely used in electrical engineering. In order to further improve the mechanical and crystallization properties of PA66 composites, post-treatment of the composites is necessary. In this paper, the crystallization behavior and melting behavior of PA66-GF25 FR (RP) untreated and treated by three different post-treatment routes were studied by differential scanning calorimetry. The Jeziorny-modified Avrami's model, Ozawa's model, and Mo's model were applied to analysis the non-isothermal kinetics, and Kissinger theory was used to calculate the activation energies of non-isothermal crystallization. The results showed that the Mo's model can successfully describe the non-isothermal crystallization kinetics of PA66-GF25 FR (RP) untreated and treated by three different post-treatment routes, while the other two models are not applicable. In addition, it is identified that post-treatment processes can improve the crystallinity and crystallization rates of PA66-GF25 FR (RP). [ABSTRACT FROM AUTHOR]

The effect of 1,2,3-triazolium-functionalized PCL-b-PEG block copolymer (PCL-b-PEG(IL)) on crystallization behavior and kinetics of PLA was systematically studied by DSC, POM and XRD. A small amount of micelle of aggregated PCL-b-PEG(IL) containing ionic clusters and a large number of disaggregated PCL-b-PEG(IL) can significantly improve the chain segment mobility of PLA. The glass transition temperature and cold crystallization temperature of PLA gradually decreased with the increase in PCL-b-PEG(IL) or PCL-b-PEG content. Compared with PCL-b-PEG, PCL-b-PEG(IL) decreases the Tg of PLA more obviously because of the strong plasticizing effect of PCL-b-PEG(IL). More importantly, the isothermal crystallization kinetics results manifested that the synergistic effect of heterogeneous nucleation agent of ionic clusters of PCL-b-PEG(IL) and chain mobility promoter of PEG chain segment can enhance the crystallization ability of PLA at all crystallization temperature. The 5 mass% PCL-b-PEG(IL) can induce high amount of stable α-form crystal of PLA after annealing treatment. [ABSTRACT FROM AUTHOR]

In this study, composites based on polypropylene (PP), basalt fiber (BF), polypropylene-graft-maleic anhydride (MAPP) and different elastomers were manufactured by extrusion compounding and injection molding. The main focus of this study was to comparatively investigate the effect of three kinds of elastomers (ethylene-propylene-diene monomer (EPDM), polyethylene-octene (POE) and ethylene-vinyl-acetate (EVA)) on non-isothermal crystallization and mechanical properties of the composites with various BF contents. The tensile test results showed that BF had a reinforcing effect on PP resin, and the addition of MAPP further improved the tensile properties by the enhancement of PP/BF interfacial bonding. Among the elastomers, EPDM was more effective in improving the tensile strength and tensile modulus, while POE significantly toughened the impact strength. Micrographs of scanning electron microscope on the impact fracture surfaces indicated a good dispersion by the addition of POE and EPDM, while some agglomerations were observed in the presence of EVA. The non-isothermal crystallization kinetics were investigated based on Avrami and Mo equations at six different cooling rates by using differential scanning calorimetry. Micrographic images of polarized optical microscopy showed that the spherulite size of PP reduced in the presence of EPDM and EVA. [ABSTRACT FROM AUTHOR]

The crystallization transformation kinetics of Ti20Zr20Hf20Be20(Cu50Ni50)20 high-entropy bulk metallic glass under non-isothermal conditions are investigated using differential scanning calorimetry. The alloy shows two distinct crystallization events. The activation energies of the crystallization events are determined using Kissinger, Ozawa and Augis-Bennett methodologies. Further, we observe that similar values are obtained using the three equations. The activation energy of the initial crystallization event is observed to be slightly small as compared to that of the second event. This implies that the initial crystallization event may have been easier to be occurred. The local activation energy (E(x)) maximizes in the initial stage of crystallization and keeps dropping in subsequent crystallization process. The non-isothermal crystallization kinetics are further analyzed using the modified Johnson-Mehl-Avrami (JMA) equation. Further, the Avrami exponent values are observed to be 1.5 < n(x) < 2.5 for approximately the entire period of the initial crystallization event and for most instances (0.1 < x < 0.6) of the second crystallization event, which implies that the mechanism of crystallization is significantly controlled by diffusion-controlled two- and three-dimensional growth along with a decreasing nucleation rate. [ABSTRACT FROM AUTHOR]

Isothermal crystallization behavior of isotactic polypropylene (iPP) nucleated with three cyclic carboxylate nucleating agents, namely, sodium bicyclic[2,2,1] heptane dicarboxylate (HPN-68), sodium benzoate (Be-Na), and sodium salt of hexahydrophthalic acid (HHPA-Na), was investigated by using differential scanning calorimetry. The classical Avarmi method was used to evaluate the isothermal crystallization behavior of iPP. The nucleus density was obtained by the calculation model of Lamberti based on the Avrami method of crystallization kinetics from calorimetric crystallization curves recorded under isothermal conditions. This method was able to measure nucleus density and growth rate of nucleated iPP, for which the nucleation phenomenon was substantially heterogeneous. The addition of nucleating agents shortened the crystallization halftime (t1/2) and increased the crystallization rate of iPP under isothermal crystallization, eventually increasing the nucleus density of iPP nucleated with nucleating agents for finishing crystallization under higher crystallization temperature, which was larger than that of virgin iPP. The results of polarized optical microscopy also showed that the nucleus density and crystallization rate were greatly increased with addition of nucleating agents. In these three nucleating agents, HPN-68 had the best nucleation effect, and iPP nucleated with HPN-68 had shorter crystallization halftime and higher nucleus density than iPP nucleated with Be-Na and HHPA-Na. [ABSTRACT FROM AUTHOR]

A recycled packaging material was found to be a PP copolymer after examinations with DSC, FTIR, and TG techniques. It produced 4.39% residue when heated to 800 °C. In addition, SEM microscopic observations revealed some particles dispersed in the recycled PP (recPP) matrix, resulting in a great source for promotion of recPP crystallization temperature. In the present work, NPG, TMB-5, and CaPA were used as β-nucleating agents to modify PP and recPP crystallization behaviors. The results imply that these three nucleating agents are effective for PP to form β crystal in which TMB-5 revealed the best induction and heterogeneous nucleation effects. However, the nucleating effect for NPG decreased when it was added to recPP. The effect of CaPA also weakened, whereas TMB-5 performed well with the optimum content of 0.1%. When CaPA was added together with PCB powder, the β-nucleating effect of CaPA was enhanced, making β crystal as the main form when using only 0.01% CaPA. [ABSTRACT FROM AUTHOR]

The crystallization behavior of partially melted poly(ether ether ketone) (PEEK) was investigated by differential scanning calorimetry. The influence of pre-crystallization conditions was studied in details. After partial melting, the maximum peak shifts to higher temperature by 8.4-11.8 °C during subsequent cooling, indicating that self-nucleation remarkably enhanced the overall crystallization rate of PEEK. An interesting finding is that the self-nucleation temperature domain of PEEK is way outside the melting curve, and its magnitude is greatly large (28-35 °C). Moreover, samples that were pre-crystallized nonisothermally or from the glassy state exhibit a larger self-nucleation effect, and a larger self-nucleation temperature domain. The isothermal crystallization data were analyzed by the Avrami model. The Avrami exponent is found to be remarkably different for melts with and without self-nucleation effects, indicating that self-nucleation changes the crystallization mechanism of PEEK. [ABSTRACT FROM AUTHOR]

Polyamide-6 (PA6)/carbon fiber (CF) composites were prepared by melt-extrusion via continuous fiber fed during extruding. The mechanical, thermal properties, and crystallization behavior of PA6/CF composites were investigated. It was found that the tensile modulus and strength of the composites were increased with the addition of CF, while their elongations at break were decreased. Scanning electron microscopy observation on the fracture surfaces showed the fine dispersion of CF and strong interfacial adhesion between fibers and matrix. Dynamic mechanical analysis results showed that the storage modulus of PA6/CF composites was improved with the addition of CF. Non-isothermal crystallization analysis showed that the CF plays a role as nucleating agent in PA6 matrix, and the α-form crystalline structure was favorable in the PA6/CF composites, as confirmed from the X-ray diffraction analysis. A trans-crystallization layer around CF could be observed by polarizing optical microscopy, which proved the nucleation effect of carbon fiber surface on the crystallization of PA6. The thermal stability of PA6/CF composites was also enhanced. [ABSTRACT FROM AUTHOR]