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Dario Cavallo
Dipartimento di Chimica e Chimica Industriale, Università degli Studi di Genova, Via Dodecaneso 31, 16146 Genova, Italy

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Journal article
Published: 18 August 2021 in Polymers
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Poly(glycolic acid) (PGA) holds unique properties, including high gas barrier properties, high tensile strength, high resistance to common organic solvents, high heat distortion temperature, high stiffness, as well as fast biodegradability and compostability. Nevertheless, this polymer has not been exploited at a large scale due to its relatively high production cost. As such, the combination of PGA with other bioplastics on one hand could reduce the material final cost and on the other disclose new properties while maintaining its “green” features. With this in mind, in this work, PGA was combined with two of the most widely applied bioplastics, namely poly(l-lactide) (PLLA) and poycaprolactone (PCL), using the melt blending technique, which is an easily scalable method. FE-SEM measurements demonstrated the formation of PGA domains whose dimensions depended on the polymer matrix and which turned out to decrease by diminishing the PGA content in the mixture. Although there was scarce compatibility between the blend components, interestingly, PGA was found to affect both the thermal properties and the degradation behavior of the polymer matrices. In particular, concerning the latter property, the presence of PGA in the blends turned out to accelerate the hydrolysis process, particularly in the case of the PLLA-based systems.

ACS Style

Luca Magazzini; Sara Grilli; Seif Eddine Fenni; Alessandro Donetti; Dario Cavallo; Orietta Monticelli. The Blending of Poly(glycolic acid) with Polycaprolactone and Poly(l-lactide): Promising Combinations. Polymers 2021, 13, 2780 .

AMA Style

Luca Magazzini, Sara Grilli, Seif Eddine Fenni, Alessandro Donetti, Dario Cavallo, Orietta Monticelli. The Blending of Poly(glycolic acid) with Polycaprolactone and Poly(l-lactide): Promising Combinations. Polymers. 2021; 13 (16):2780.

Chicago/Turabian Style

Luca Magazzini; Sara Grilli; Seif Eddine Fenni; Alessandro Donetti; Dario Cavallo; Orietta Monticelli. 2021. "The Blending of Poly(glycolic acid) with Polycaprolactone and Poly(l-lactide): Promising Combinations." Polymers 13, no. 16: 2780.

Research article
Published: 31 July 2021 in POLYMER CRYSTALLIZATION
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The self-nucleation behavior of a polybutene-1/ethylene random copolymer, P(B1-ran-E), which undergoes a complex crystal-crystal transition behavior, has been studied in detail. Similar to PE random copolymers, this material shows a strong melt memory effect even above equilibrium melting point of PB-1 homopolymer. Different polymorphic forms can be obtained when P(B1-ran-E) is cooled from different self-nucleation domains. The trigonal form I′ could only be nucleated in the presence of remaining form I crystals via self-seeding, while the melt memory in Domain IIa could only act as self-nuclei for kinetically favored form II. Furthermore, observations from optical microscopy illustrated that melt memory is able to enhance nucleation density but it does not affect the spherulitic growth rate.

ACS Style

Zefan Wang; Xia Dong; Dario Cavallo; Dujin Wang; Alejandro J. Müller. Peculiar self‐nucleation behavior of a polybutene‐1/ethylene random copolymer. POLYMER CRYSTALLIZATION 2021, e10201 .

AMA Style

Zefan Wang, Xia Dong, Dario Cavallo, Dujin Wang, Alejandro J. Müller. Peculiar self‐nucleation behavior of a polybutene‐1/ethylene random copolymer. POLYMER CRYSTALLIZATION. 2021; ():e10201.

Chicago/Turabian Style

Zefan Wang; Xia Dong; Dario Cavallo; Dujin Wang; Alejandro J. Müller. 2021. "Peculiar self‐nucleation behavior of a polybutene‐1/ethylene random copolymer." POLYMER CRYSTALLIZATION , no. : e10201.

Research article
Published: 23 July 2021 in Macromolecules
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We investigate for the first time the morphology and crystallization of two novel tetrablock quarterpolymers of polyethylene (PE), poly(ethylene oxide) (PEO), poly(ε-caprolactone) (PCL), and poly(l-lactide) (PLLA) with four potentially crystallizable blocks: PE187.1-b-PEO3715.1-b-PCL2610.4-b-PLLA197.6 (Q1) and PE299.5-b-PEO268.8-b-PCL237.6-b-PLLA227.3 (Q2) (superscripts give number average molecular weights in kg/mol, and subscripts give the composition in wt %). Their synthesis was performed by a combination of polyhomologation (C1 polymerization) and ring-opening polymerization techniques using a ″catalyst-switch″ strategy, either ″organocatalyst/metal catalyst switch″ (Q1 sample, 96% isotactic tetrads) or ″organocatalyst/organocatalyst switch″ (Q2 sample, 84% isotactic tetrads). Their corresponding precursors—triblock terpolymers PE-b-PEO-b-PCL, diblock copolymers PE-b-PEO, and PE homopolymers—were also studied. Cooling and heating rates from the melt at 20 °C/min were employed for most experiments: differential scanning calorimetry (DSC), polarized light optical microscopy (PLOM), in situ small-angle X-ray scattering/wide-angle X-ray scattering (SAXS/WAXS), and atomic force microscopy (AFM). The direct comparison of the results obtained with these different techniques allows the precise identification of the crystallization sequence of the blocks upon cooling from the melt. SAXS indicated that Q1 is melt miscible, while Q2 is weakly segregated in the melt but breaks out during crystallization. According to WAXS and DSC results, the blocks follow a sequence as they crystallize: PLLA first, then PE, then PCL, and finally PEO in the case of the Q1 quarterpolymer; in Q2, the PLLA block is not able to crystallize due to its low isotacticity. Although the temperatures at which the PEO and PCL blocks and the PE and PLLA blocks crystallize overlap, the analysis of the intensity changes measured by WAXS and PLOM experiments allows identifying each of the crystallization processes. The quarterpolymer Q1 remarkably self-assembles during crystallization into tetracrystalline banded spherulites, where four types of different lamellae coexist. Nanostructural features arising upon sequential crystallization are found to have a relevant impact on the mechanical properties. Nanoindentation measurements show that storage modulus and hardness of the Q1 quarterpolymer significantly deviate from those of the stiff PE and PLLA blocks, approaching typical values of compliant PEO and PCL. Results are mainly attributed to the low crystallinity of the PE and PLLA blocks. Moreover, the Q2 copolymer exhibits inferior mechanical properties than Q1, and this can be related to the PE block within Q1 that has thinner crystal lamellae according to its much lower melting point.

ACS Style

Eider Matxinandiarena; Agurtzane Múgica; Agnieszka Tercjak; Viko Ladelta; George Zapsas; Nikos Hadjichristidis; Dario Cavallo; Araceli Flores; Alejandro J. Müller. Sequential Crystallization and Multicrystalline Morphology in PE-b-PEO-b-PCL-b-PLLA Tetrablock Quarterpolymers. Macromolecules 2021, 54, 7244 -7257.

AMA Style

Eider Matxinandiarena, Agurtzane Múgica, Agnieszka Tercjak, Viko Ladelta, George Zapsas, Nikos Hadjichristidis, Dario Cavallo, Araceli Flores, Alejandro J. Müller. Sequential Crystallization and Multicrystalline Morphology in PE-b-PEO-b-PCL-b-PLLA Tetrablock Quarterpolymers. Macromolecules. 2021; 54 (15):7244-7257.

Chicago/Turabian Style

Eider Matxinandiarena; Agurtzane Múgica; Agnieszka Tercjak; Viko Ladelta; George Zapsas; Nikos Hadjichristidis; Dario Cavallo; Araceli Flores; Alejandro J. Müller. 2021. "Sequential Crystallization and Multicrystalline Morphology in PE-b-PEO-b-PCL-b-PLLA Tetrablock Quarterpolymers." Macromolecules 54, no. 15: 7244-7257.

Research article
Published: 04 May 2021 in Macromolecules
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Crystallization kinetics under processing-relevant cooling conditions of polyethylene/isotactic-polypropylene (PE/PP) blends, with compositions similar to real recycled blends, was investigated through an in situ temperature monitoring technique. Continuous Cooling Curve (CCC) diagrams in a large crystallization temperature range were obtained for the two phases, thanks to a new apparatus allowing fast quenching of polymer samples. Using this technique, we found an “inversion point” in the crystallization order of the two polymers, which arises from the difference in crystallization rates between PP and PE with an increasing cooling rate. The order of crystallization of the two polymers at low cooling rates, that is, before the inversion point, can be tuned by employing non-nucleated or nucleated PP. In particular, non-nucleated PP crystallizes after PE above 0.5 °C/s, while nucleated PP solidifies before PE until 80 °C/s. Interestingly, mutual nucleating effects, previously shown only for ideal systems such as thin-layered films, were found at the interface between the phases, in correlation with the inversion point. During cooling, the phase which crystallizes first can enhance the onset of crystallization of the second lower crystallizing phase through nucleation at the interface. Ex situ morphological and wide-angle X-ray diffraction experiments confirmed the validity of the results shown by CCC diagrams. Our approach to characterize semicrystalline polymer blends with CCC diagrams facilitates tailoring their properties at cooling rates relevant for polymer processing. Moreover, the importance of knowing and controlling the type of components in blends obtained from recycling is demonstrated, given the variety of crystallization behaviors attainable.

ACS Style

Enrico Carmeli; Gottfried Kandioller; Markus Gahleitner; Alejandro J. Müller; Davide Tranchida; Dario Cavallo. Continuous Cooling Curve Diagrams of Isotactic-Polypropylene/Polyethylene Blends: Mutual Nucleating Effects under Fast Cooling Conditions. Macromolecules 2021, 54, 4834 -4846.

AMA Style

Enrico Carmeli, Gottfried Kandioller, Markus Gahleitner, Alejandro J. Müller, Davide Tranchida, Dario Cavallo. Continuous Cooling Curve Diagrams of Isotactic-Polypropylene/Polyethylene Blends: Mutual Nucleating Effects under Fast Cooling Conditions. Macromolecules. 2021; 54 (10):4834-4846.

Chicago/Turabian Style

Enrico Carmeli; Gottfried Kandioller; Markus Gahleitner; Alejandro J. Müller; Davide Tranchida; Dario Cavallo. 2021. "Continuous Cooling Curve Diagrams of Isotactic-Polypropylene/Polyethylene Blends: Mutual Nucleating Effects under Fast Cooling Conditions." Macromolecules 54, no. 10: 4834-4846.

Research article
Published: 04 May 2021 in POLYMER CRYSTALLIZATION
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Fused filament fabrication (FFF) is among the most accessible and rapidly developing additive manufacturing (AM) technologies. Even though amorphous thermoplastic polymers are the elected materials in FFF, semicrystalline polymers would enhance the strength and durability of 3D printed parts. The properties of the products depend on the crystalline structure and on the morphology, which develops during the printing process. However, to date, polymer crystallization during 3D printing is still largely unexplored. Then, fundamental knowledge of the crystallization process in realistic printing conditions is necessary to pave the way to semicrystalline polymers in FFF. This work focuses on the implementation of a simple optical setup to follow the crystallization process in situ. The new setup exploits light scattering generated during filament deposition and cooling. To this purpose, the beam scattered by a growing 3D printed wall geometry is collected on a semi‐transparent screen during the deposition for both amorphous polylactide and a semicrystalline polyamide copolymer. While the amorphous polymer scatters light anisotropically and generates a vertical scattering pattern, the semicrystalline polyamide produces isotropic scattering. Moreover, the kinetics of scattering intensity increase follows closely that of deposition in the case of polylactide. Instead, it strongly deviates from that for the semicrystalline polyamide. These pieces of evidence suggest that simple light scattering measurements, which are quickly and cost‐effectively implemented on a lab‐scale, can be further developed to allow a better understanding of polymer structuring phenomena in the highly non‐equilibrium conditions of 3D printing.

ACS Style

Andrea Costanzo; Roberto Spotorno; Paola Lova; Marco Smerieri; Giovanni Carraro; Dario Cavallo. Light scattering approach to the in situ measurement of polymer crystallization during 3D printing: A feasibility study. POLYMER CRYSTALLIZATION 2021, 4, e10182 .

AMA Style

Andrea Costanzo, Roberto Spotorno, Paola Lova, Marco Smerieri, Giovanni Carraro, Dario Cavallo. Light scattering approach to the in situ measurement of polymer crystallization during 3D printing: A feasibility study. POLYMER CRYSTALLIZATION. 2021; 4 (4):e10182.

Chicago/Turabian Style

Andrea Costanzo; Roberto Spotorno; Paola Lova; Marco Smerieri; Giovanni Carraro; Dario Cavallo. 2021. "Light scattering approach to the in situ measurement of polymer crystallization during 3D printing: A feasibility study." POLYMER CRYSTALLIZATION 4, no. 4: e10182.

Journal article
Published: 02 May 2021 in Polymer
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The origin of “annealing peaks” in semicrystalline polymers, obtained with aging thermal protocols at temperatures between the glass transition and the melting temperature, and revealed by calorimetry as small endotherms preceding the main melting peak, has been recently debated in the literature. On the one side it is claimed that these small endotherms are related to the melting of defective/thinner crystals, on the other side it is proposed that they can be associated to the enthalpy relaxation of the rigid amorphous fraction (RAF), i.e., that part of the amorphous region directly coupled to the crystalline stems. With this work we aim to contribute to the debate, by exploiting the different thermal properties of the RAF coupled with different crystal modifications of polymorphic poly (butene-1) (PB-1). In this polymer the RAF mobilizes at largely different temperatures when it is coupled with crystals of trigonal Form I, or tetragonal Form II. By exploiting this peculiarity, we performed isochronous aging experiments with differential scanning calorimetry (DSC) on both crystalline phases, in a wide temperature range between the glass transition of the mobile (bulk) amorphous fraction and the onset of crystal melting. An endothermic peak above the aging temperature was typically observed. The trend of the enthalpy of this annealing peak with temperature can be described by a bell-shaped curve, approaching zero recovered enthalpy at temperatures of 100–110 °C, and 40–50 °C for Form I and Form II, respectively. These temperatures coincide with previous literature report about mobilization of PB-1 RAF and are thus identified as the upper limit of the RAF glass transition for the two polymorphs. Isothermal aging experiments as a function of time suggest that the enthalpy recovery of Form I RAF show the typical signature of glassy dynamics, similarly to what occurs for Form II RAF after short aging times. At longer times, the superposition of the polymorphic phase transition and RAF aging changes the kinetics of the recovered enthalpy for the latter polymorph, possibly due to the increased stress at the crystal-amorphous interface and creation of additional RAF in parallel with Form II to Form I transformation. Overall, our results demonstrate that for PB-1, at least within the investigated temperature range, the annealing peaks can be related to the RAF strive to attain thermodynamic equilibrium in its glassy state.

ACS Style

Wei Wang; Seif Eddine Fenni; Zhe Ma; Maria Cristina Righetti; Daniele Cangialosi; Maria Laura Di Lorenzo; Dario Cavallo. Glass transition and aging of the rigid amorphous fraction in polymorphic poly(butene-1). Polymer 2021, 226, 123830 .

AMA Style

Wei Wang, Seif Eddine Fenni, Zhe Ma, Maria Cristina Righetti, Daniele Cangialosi, Maria Laura Di Lorenzo, Dario Cavallo. Glass transition and aging of the rigid amorphous fraction in polymorphic poly(butene-1). Polymer. 2021; 226 ():123830.

Chicago/Turabian Style

Wei Wang; Seif Eddine Fenni; Zhe Ma; Maria Cristina Righetti; Daniele Cangialosi; Maria Laura Di Lorenzo; Dario Cavallo. 2021. "Glass transition and aging of the rigid amorphous fraction in polymorphic poly(butene-1)." Polymer 226, no. : 123830.

Journal article
Published: 17 March 2021 in Polymer Testing
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The complete understanding of polymers crystallization kinetic in real industrial processes is fundamental for designing materials towards specific applications. Hereby, we propose a method for fast cooling preparation of polymers by means of air and water sprays, which presents several enhancements with respect to previous similar devices. The new device was built in order to fulfill safety and cleaning standards required in an industrial environment. Furthermore, the small dimensions and the limited costs enable its implementation in any laboratory. Moreover, preliminary results on selected isotactic-polypropylenes (iPP) were obtained in a cooling range from 0.01 to a few thousand °C/s, in order to validate the present method by comparison with previous literature results and to highlight the large range of studies that can be carried out with this set-up. Ex-situ analysis with WAXS, DSC and AFM techniques were performed to characterize such prepared samples.

ACS Style

Enrico Carmeli; Dario Cavallo; Davide Tranchida. Instrument for mimicking fast cooling conditions of polymers: Design and case studies on polypropylene. Polymer Testing 2021, 97, 107164 .

AMA Style

Enrico Carmeli, Dario Cavallo, Davide Tranchida. Instrument for mimicking fast cooling conditions of polymers: Design and case studies on polypropylene. Polymer Testing. 2021; 97 ():107164.

Chicago/Turabian Style

Enrico Carmeli; Dario Cavallo; Davide Tranchida. 2021. "Instrument for mimicking fast cooling conditions of polymers: Design and case studies on polypropylene." Polymer Testing 97, no. : 107164.

Review article
Published: 16 February 2021 in Progress in Polymer Science
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The crystallization of heterogeneously nucleated bulk polymers typically occurs in a single exothermic process, within a narrow temperature range, i.e., a single exothermic peak is detected by differential scanning calorimetry when the material is cooled from the melt. However, when a bulk semicrystalline polymer is subdivided or dispersed into a multitude of totally (or partially) isolated microdomains (e.g., droplets or cylinders), in number comparable to that of commonly available nucleating heterogeneities, several separated crystallization events are typically observed, i.e., fractionated crystallization. This situation is often found for the minor crystallizable component in immiscible blends. When the bulk polymer is dispersed into a number of microdomains that is several orders of magnitude higher than the available number of heterogeneities within it, most microdomains will be heterogeneity-free. In these clean microdomains the nucleation can occur by contact with the interfaces (i.e., surface nucleation) or by homogeneous nucleation inside the microdomain volume. These cases can be easily encountered in cylinders or spheres within strongly segregated block copolymers, or in infiltrated polymers within nanopores of alumina templates. In this work, a comprehensive review of the known cases of fractionated crystallization is provided. The changes upon decreasing microdomain sizes from a dominant single heterogeneous nucleation, through fractionated crystallization, to surface or homogeneous nucleation are critically reviewed. Emphasis is placed on the common features of the phenomenon across the different systems, and thus on the general conclusions that can be drawn from the analysis of representative semicrystalline polymers. The origin of the fractionated crystallization effects and their dramatic consequences on the nucleation and crystallization kinetics of semicrystalline polymers are also discussed.

ACS Style

Leire Sangroniz; Bao Wang; Yunlan Su; Guoming Liu; Dario Cavallo; Dujin Wang; Alejandro J. Müller. Fractionated crystallization in semicrystalline polymers. Progress in Polymer Science 2021, 115, 101376 .

AMA Style

Leire Sangroniz, Bao Wang, Yunlan Su, Guoming Liu, Dario Cavallo, Dujin Wang, Alejandro J. Müller. Fractionated crystallization in semicrystalline polymers. Progress in Polymer Science. 2021; 115 ():101376.

Chicago/Turabian Style

Leire Sangroniz; Bao Wang; Yunlan Su; Guoming Liu; Dario Cavallo; Dujin Wang; Alejandro J. Müller. 2021. "Fractionated crystallization in semicrystalline polymers." Progress in Polymer Science 115, no. : 101376.

Journal article
Published: 14 December 2020 in Polymers
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International newspapers and experts have called 3D printing the industrial revolution of this century. Among all its available variants, the fused deposition modeling (FDM) technique is of greater interest since its application is possible using simple desktop printers. FDM is a complex process, characterized by a large number of parameters that influence the quality and final properties of the product. In particular, in the case of semicrystalline polymers, which afford better mechanical properties than amorphous ones, it is necessary to understand the crystallization kinetics as the processing conditions vary, in order to be able to develop models that allow having a better control over the process and consequently on the final properties of the material. In this work it was proposed to study the crystallization kinetics of two different polyamides used for FDM 3D printing and to link it to the microstructure and properties obtained during FDM. The kinetics are studied both in isothermal and fast cooling conditions, thanks to a home-built device which allows mimicking the quenching experienced during filament deposition. The temperature history of a single filament is then determined by mean of a micro-thermocouple and the final crystallinity of the sample printed in a variety of conditions is assessed by differential scanning calorimetry. It is found that the applied processing conditions always allowed for the achievement of the maximum crystallinity, although in one condition the polyamide mesomorphic phase possibly develops. Despite the degree of crystallinity is not a strong function of printing variables, the weld strength of adjacent layers shows remarkable variations. In particular, a decrease of its value with printing speed is observed, linked to the probable development of molecular anisotropy under the more extreme printing conditions.

ACS Style

Andrea Costanzo; Umberto Croce; Roberto Spotorno; Seif Eddine Fenni; Dario Cavallo. Fused Deposition Modeling of Polyamides: Crystallization and Weld Formation. Polymers 2020, 12, 2980 .

AMA Style

Andrea Costanzo, Umberto Croce, Roberto Spotorno, Seif Eddine Fenni, Dario Cavallo. Fused Deposition Modeling of Polyamides: Crystallization and Weld Formation. Polymers. 2020; 12 (12):2980.

Chicago/Turabian Style

Andrea Costanzo; Umberto Croce; Roberto Spotorno; Seif Eddine Fenni; Dario Cavallo. 2020. "Fused Deposition Modeling of Polyamides: Crystallization and Weld Formation." Polymers 12, no. 12: 2980.

Journal article
Published: 26 November 2020 in Polymers
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It is widely accepted that melt memory effect on polymer crystallization depends on thermal history of the material, however a systematic study of the different parameters involved in the process has been neglected, so far. In this work, poly(butylene succinate) has been selected to analyze the effect of short times and high cooling/heating rates that are relevant from an industrial point of view by taking advantage of fast scanning calorimetry (FSC). The FSC experiments reveal that the width of melt memory temperature range is reduced with the time spent at the self-nucleation temperature (Ts), since annealing of crystals occurs at higher temperatures. The effectiveness of self-nuclei to crystallize the sample is addressed by increasing the cooling rate from Ts temperature. The effect of previous standard state on melt memory is analyzed by a) changing the cooling/heating rate and b) applying successive self-nucleation and annealing (SSA) technique, observing a strong correlation between melting enthalpy or crystallinity degree and the extent of melt memory. The acquired knowledge can be extended to other semicrystalline polymers to control accurately the melt memory effect and therefore, the time needed to process the material and its final performance.

ACS Style

Leire Sangroniz; Connie Ocando; Dario Cavallo; Alejandro J. Müller. Melt Memory Effects in Poly(Butylene Succinate) Studied by Differential Fast Scanning Calorimetry. Polymers 2020, 12, 2796 .

AMA Style

Leire Sangroniz, Connie Ocando, Dario Cavallo, Alejandro J. Müller. Melt Memory Effects in Poly(Butylene Succinate) Studied by Differential Fast Scanning Calorimetry. Polymers. 2020; 12 (12):2796.

Chicago/Turabian Style

Leire Sangroniz; Connie Ocando; Dario Cavallo; Alejandro J. Müller. 2020. "Melt Memory Effects in Poly(Butylene Succinate) Studied by Differential Fast Scanning Calorimetry." Polymers 12, no. 12: 2796.

Journal article
Published: 16 October 2020 in Macromolecules
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ACS Style

Wei Wang; Bao Wang; Agnieszka Tercjak; Alejandro J. Müller; Zhe Ma; Dario Cavallo. Origin of Transcrystallinity and Nucleation Kinetics in Polybutene-1/Fiber Composites. Macromolecules 2020, 53, 8940 -8950.

AMA Style

Wei Wang, Bao Wang, Agnieszka Tercjak, Alejandro J. Müller, Zhe Ma, Dario Cavallo. Origin of Transcrystallinity and Nucleation Kinetics in Polybutene-1/Fiber Composites. Macromolecules. 2020; 53 (20):8940-8950.

Chicago/Turabian Style

Wei Wang; Bao Wang; Agnieszka Tercjak; Alejandro J. Müller; Zhe Ma; Dario Cavallo. 2020. "Origin of Transcrystallinity and Nucleation Kinetics in Polybutene-1/Fiber Composites." Macromolecules 53, no. 20: 8940-8950.

Research article
Published: 08 October 2020 in ACS Omega
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Melt blending of homopolymers is an effective way to achieve an attractive combination of polymer properties. Dynamic vulcanization of fatty-acid-based polyester polyol with glycerol and poly(l-lactic acid) (PLLA) in the presence of hexamethylene diisocyanate (HDI) was performed with the aim of toughening PLLA. The dynamic vulcanization in an internal mixer led to the formation of a PLLA/PU biobased blend. Melt torque, Fourier transform infrared (FTIR), and gel fraction analysis demonstrated the successful formation of cross-linked polyurethane (PU) inside the PLLA matrix. Scanning electron microscopy (SEM) analysis showed that the PLLA/PU blends exhibit a sea-island morphology. Gel fraction analysis revealed that a rubbery phase was formed inside the PLLA matrix, which was insoluble in chloroform. FTIR analysis of the insoluble part shows the appearance of an absorption band centered at 1758 cm-1, related to the crystalline carbonyl vibration of the PLLA component, thus suggesting the partial involvement of PLLA chains in the cross-linking reaction. The overall content of the PU phase in the blends significantly affected the mechanical properties, thermal stability, and crystallization behavior of the materials. The overall crystallization rate of PLLA was noticeably decreased by the incorporation of PU. At the same time, polarized light optical microscopy (PLOM) analysis revealed that the presence of the PU rubbery phase inside the PLLA matrix promoted PLLA nucleation. With the formation of the PU network, the impact strength showed a remarkable increase while Young's modulus correspondingly decreased. The blends showed slightly reduced thermal stability compared to the neat PLLA.

ACS Style

Seif Eddine Fenni; Francesca Bertella; Orietta Monticelli; Alejandro J. Müller; Nacerddine Hadadoui; Dario Cavallo. Renewable and Tough Poly(l-lactic acid)/Polyurethane Blends Prepared by Dynamic Vulcanization. ACS Omega 2020, 5, 26421 -26430.

AMA Style

Seif Eddine Fenni, Francesca Bertella, Orietta Monticelli, Alejandro J. Müller, Nacerddine Hadadoui, Dario Cavallo. Renewable and Tough Poly(l-lactic acid)/Polyurethane Blends Prepared by Dynamic Vulcanization. ACS Omega. 2020; 5 (41):26421-26430.

Chicago/Turabian Style

Seif Eddine Fenni; Francesca Bertella; Orietta Monticelli; Alejandro J. Müller; Nacerddine Hadadoui; Dario Cavallo. 2020. "Renewable and Tough Poly(l-lactic acid)/Polyurethane Blends Prepared by Dynamic Vulcanization." ACS Omega 5, no. 41: 26421-26430.

Research article
Published: 23 September 2020 in Macromolecules
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The semicrystalline state of polymers implies the formation of a noncrystalline interphase beside lamellar crystals known as the rigid amorphous fraction (RAF). This devitrifies on heating at temperatures much higher than the one typical of the bulk-amorphous fraction. Its glass transition and physical aging in the glassy state have thus far remained elusive. Here, we study the RAF glassy dynamics in poly(l-lactic acid) (PLLA) applying recently developed aging thermal protocols based on fast scanning calorimetry (FSC). Specifically, semicrystalline samples are aged in different conditions between the glass transition of mobile amorphous fraction and the crystals’ melting temperature (TM). A distinct endothermic peak at temperatures above that of aging develops with time. We provide compelling evidence that in the initial part of aging the origin of this peak is due to the enthalpy recovery of glassy RAF. At longer aging times, the aging peak is at least partly associated with secondary crystallization. Isochronous experiments at different aging temperatures enable to obtain a fair estimate of the RAF glass transition temperature, whose upper limit is about 135 °C. The proposed method holds the promise of gaining new insights into the elusive glassy dynamics of the RAF of semicrystalline polymers.

ACS Style

Xavier Monnier; Dario Cavallo; Maria Cristina Righetti; Maria Laura Di Lorenzo; Sara Marina; Jaime Martin; Daniele Cangialosi. Physical Aging and Glass Transition of the Rigid Amorphous Fraction in Poly(l-lactic acid). Macromolecules 2020, 53, 8741 -8750.

AMA Style

Xavier Monnier, Dario Cavallo, Maria Cristina Righetti, Maria Laura Di Lorenzo, Sara Marina, Jaime Martin, Daniele Cangialosi. Physical Aging and Glass Transition of the Rigid Amorphous Fraction in Poly(l-lactic acid). Macromolecules. 2020; 53 (20):8741-8750.

Chicago/Turabian Style

Xavier Monnier; Dario Cavallo; Maria Cristina Righetti; Maria Laura Di Lorenzo; Sara Marina; Jaime Martin; Daniele Cangialosi. 2020. "Physical Aging and Glass Transition of the Rigid Amorphous Fraction in Poly(l-lactic acid)." Macromolecules 53, no. 20: 8741-8750.

Full paper
Published: 17 August 2020 in Polymer Crystallization
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Ternary biodegradable polymer blends of poly(lactic acid) (PLA), poly(butylene succinate) (PBS), and poly(ε‐caprolactone) (PCL) with the composition 45/10/45 wt% and exhibiting partial‐wetting morphology were prepared. In this morphology, the minor phase is present as self‐assembled droplets at the co‐continuous interface of the other two major phases. The crystallization of the components in the various blends was thoroughly investigated. Differential scanning calorimetry highlighted minor differences in the overall kinetics of a given component in the ternary blend, with respect to the neat polymer. On the other hand, several unusual nucleation mechanisms could be studied by polarized optical microscopy (PLOM). With reference to the major phases, PLA spherulites displayed surface‐induced nucleation from the interface with molten PBS or PCL droplets. On lowering the crystallization temperature, the PBS phase effectively nucleated at the interface with previously crystallized PLA domains, forming a transcrystalline morphology. Concerning the minor phase, weak partial‐wetting PBS droplets displayed a droplet‐to‐droplet percolation of the nucleation events. Strongly partial‐wetting PCL droplets were confined between previously crystallized PLA and PBS co‐continuous phases and, instead, solidified as isolated domains randomly in space. This work provides further insights in the relationship between morphology and crystallization in immiscible ternary blends.

ACS Style

Seif Eddine Fenni; Jun Wang; Nacerddine Haddaoui; Basil D. Favis; Alejandro J. Müller; Dario Cavallo. Nucleation modalities in poly(lactide), poly(butylene succinate), and poly(ε‐caprolactone) ternary blends with partial wetting morphology. Polymer Crystallization 2020, 3, 1 .

AMA Style

Seif Eddine Fenni, Jun Wang, Nacerddine Haddaoui, Basil D. Favis, Alejandro J. Müller, Dario Cavallo. Nucleation modalities in poly(lactide), poly(butylene succinate), and poly(ε‐caprolactone) ternary blends with partial wetting morphology. Polymer Crystallization. 2020; 3 (6):1.

Chicago/Turabian Style

Seif Eddine Fenni; Jun Wang; Nacerddine Haddaoui; Basil D. Favis; Alejandro J. Müller; Dario Cavallo. 2020. "Nucleation modalities in poly(lactide), poly(butylene succinate), and poly(ε‐caprolactone) ternary blends with partial wetting morphology." Polymer Crystallization 3, no. 6: 1.

Research article
Published: 31 July 2020 in Macromolecules
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The effect of confinement on the crystallization, crystal orientation, and polymorphic crystal transition of bulk and infiltrated polybutene-1 (PB-1) within anodic aluminum oxide (AAO) templates were studied. After cooling from the melt, PB-1 within AAO templates crystallized into tetragonal Form II directly. The nucleation process inside the AAO pores was probably homogeneous when pore diameters were below 200 nm. The crystal orientation of Form II was investigated by grazing incidence X-ray scattering. Form II to I transition was investigated as a function of time and modeled with the Avrami equation. The rate of Form II to I transition for infiltrated PB-1 within 400 nm AAO was unexpectedly higher than that of the bulk. The stress generated because of the mismatch of the thermal expansion coefficients between PB-1 and AAO greatly enhanced the nucleation of Form I within the Form II matrix. A slower Form II to I transition was observed when the pore diameter of AAO decreased. The transition degree decreased with the decreasing pore diameter and was completely inhibited for PB-1 infiltrated within the 30 nm AAO template. A stable Form II interfacial layer with a thickness of ∼12 nm was postulated to account for this phenomenon.

ACS Style

Guangyu Shi; Zefan Wang; Ming Wang; Guoming Liu; Dario Cavallo; Alejandro J. Müller; Dujin Wang. Crystallization, Orientation, and Solid–Solid Crystal Transition of Polybutene-1 Confined within Nanoporous Alumina. Macromolecules 2020, 53, 6510 -6518.

AMA Style

Guangyu Shi, Zefan Wang, Ming Wang, Guoming Liu, Dario Cavallo, Alejandro J. Müller, Dujin Wang. Crystallization, Orientation, and Solid–Solid Crystal Transition of Polybutene-1 Confined within Nanoporous Alumina. Macromolecules. 2020; 53 (15):6510-6518.

Chicago/Turabian Style

Guangyu Shi; Zefan Wang; Ming Wang; Guoming Liu; Dario Cavallo; Alejandro J. Müller; Dujin Wang. 2020. "Crystallization, Orientation, and Solid–Solid Crystal Transition of Polybutene-1 Confined within Nanoporous Alumina." Macromolecules 53, no. 15: 6510-6518.

Research article
Published: 16 July 2020 in Macromolecules
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Nucleating agents (NAs) are widely used for speeding up processing and tuning the final optical and mechanical properties. Despite their industrial importance, the search for highly efficient NAs is still mainly empirical. In this work, the heterogeneous nucleation process of isotactic polypropylene (i-PP) droplets containing nucleating agents (i.e., sodium benzoate (SB), (4,6-di-tert-butylphenyl)phosphate (NA-11), quinacridone quinone (QQ)) dispersed in an immiscible polystyrene matrix has been studied by differential scanning calorimetry (DSC) using an isothermal step crystallization protocol. When semicrystalline polymers are confined into isolated micro- or nanodomains, nucleation can kinetically control the overall crystallization. Differently, in a bulk polymer, the contributions of the nucleation and growth steps to the overall crystallization rate are commonly of similar importance. In the studied system, it is shown for the first time that the crystallization of nucleated i-PP droplets exhibits a first-order kinetics, with characteristic times much larger than those required for the crystals to grow and occupy the whole microdomain volume. Therefore, the kinetics of heterogeneous nucleation can be directly assessed. On the contrary, when neat i-PP droplets are self-nucleated, the crystallization kinetics shows a sigmoidal trend, with times comparable to those for the crystal space filling. This indicates the absence of any primary nucleation barrier for ideally self-nucleated PP melts, or at least that this nucleation barrier is negligible in comparison to the one for secondary nucleation/crystal growth. For the first time, it is evidenced that, as long as nucleation is the rate-determining step in the overall crystallization kinetics, a first-order kinetics can be obtained for both homo- or heterogeneously nucleated droplets in immiscible blends. A novel way to calculate an “intrinsic” nucleation efficiency, based on the derived free-energy barriers of the different NAs, is proposed. This fundamental knowledge of heterogeneous nucleation can serve as a tool for a more rational search for new nucleating agents and can provide a method to unambiguously identify the origin of multiple-crystallization exotherms in fractionated crystallization of immiscible blends.

ACS Style

Bao Wang; Roberto Utzeri; Maila Castellano; Paola Stagnaro; Alejandro J. Müller; Dario Cavallo. Heterogeneous Nucleation and Self-Nucleation of Isotactic Polypropylene Microdroplets in Immiscible Blends: From Nucleation to Growth-Dominated Crystallization. Macromolecules 2020, 53, 5980 -5991.

AMA Style

Bao Wang, Roberto Utzeri, Maila Castellano, Paola Stagnaro, Alejandro J. Müller, Dario Cavallo. Heterogeneous Nucleation and Self-Nucleation of Isotactic Polypropylene Microdroplets in Immiscible Blends: From Nucleation to Growth-Dominated Crystallization. Macromolecules. 2020; 53 (14):5980-5991.

Chicago/Turabian Style

Bao Wang; Roberto Utzeri; Maila Castellano; Paola Stagnaro; Alejandro J. Müller; Dario Cavallo. 2020. "Heterogeneous Nucleation and Self-Nucleation of Isotactic Polypropylene Microdroplets in Immiscible Blends: From Nucleation to Growth-Dominated Crystallization." Macromolecules 53, no. 14: 5980-5991.

Research article
Published: 14 July 2020 in Biomacromolecules
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Biomedical applications of polymers require precise control of the solid-state structure, which is of particular interest for biodegradable copolymers. In this work, we evaluated the influence of crystallization conditions on the comonomer exclusion/inclusion balance of biodegradable poly (butylene succinate-ran-butylene adipate) (PBSA) isodimorphic random copolymers. Regardless of the crystallization conditions, the copolymers retain their isodimorphic character displaying a pseudo-eutectic behavior with crystallization in the entire composition range. This illustrates the thermodynamic nature of the isodimorphic behavior for PBSA random copolymers. However, depending on the composition, the crystallization conditions affect the exclusion/inclusion balance of the comonomers. Fast cooling favors BA inclusion inside the PBS crystals, whereas isothermal crystallization strongly limits it. PBA rich compositions behave differently. Both fast and slow crystallization formed the β-phase, whereas BS unit inclusion is favored independently of the cooling conditions. During Successive Self-nucleation and Annealing (SSA), the BA inclusion is intermediate between non-isothermal and isothermal conditions, while the crystalline structure of the PBA phase changes from -phase to the more stable -phase. We propose a simple crystallographic model to explain the changes in the unit cell dimension of the copolymers.

ACS Style

Ricardo Arpad Pérez-Camargo; Guoming Liu; Dario Cavallo; Dujin Wang; Alejandro J. Müller. Effect of the Crystallization Conditions on the Exclusion/Inclusion Balance in Biodegradable Poly(butylene succinate-ran-butylene adipate) Copolymers. Biomacromolecules 2020, 21, 3420 -3435.

AMA Style

Ricardo Arpad Pérez-Camargo, Guoming Liu, Dario Cavallo, Dujin Wang, Alejandro J. Müller. Effect of the Crystallization Conditions on the Exclusion/Inclusion Balance in Biodegradable Poly(butylene succinate-ran-butylene adipate) Copolymers. Biomacromolecules. 2020; 21 (8):3420-3435.

Chicago/Turabian Style

Ricardo Arpad Pérez-Camargo; Guoming Liu; Dario Cavallo; Dujin Wang; Alejandro J. Müller. 2020. "Effect of the Crystallization Conditions on the Exclusion/Inclusion Balance in Biodegradable Poly(butylene succinate-ran-butylene adipate) Copolymers." Biomacromolecules 21, no. 8: 3420-3435.

Journal article
Published: 09 July 2020 in Polymer
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A fast and easy-to-implement technique able to investigate the complex chemical composition of polyethylene/polypropylene (PE/PP) blends derived from recycling is required. Thermal fractionation, in particular the Successive Self-nucleation and Annealing (SSA) method, proves to be suitable for this purpose. Therefore, a new tailor-made SSA protocol, able to fractionate both PE and PP in the same temperature program, was developed. Furthermore, the fractionation of model blends with known composition allowed the assessment of the temperature regions where co-crystallization among the blend components does not occur, enabling the development of a method for the quantitative evaluation of the amount of the high melting PE component and of the PP phase in a blend. Finally, the composition of two recycled blends was successfully assessed by means of the novel quantitative method and the results were compared with those achieved by a solution-based fractionation technique on the same materials.

ACS Style

Enrico Carmeli; Davide Tranchida; Andreas Albrecht; Alejandro J. Müller; Dario Cavallo. A tailor-made Successive Self-nucleation and Annealing protocol for the characterization of recycled polyolefin blends. Polymer 2020, 203, 122791 .

AMA Style

Enrico Carmeli, Davide Tranchida, Andreas Albrecht, Alejandro J. Müller, Dario Cavallo. A tailor-made Successive Self-nucleation and Annealing protocol for the characterization of recycled polyolefin blends. Polymer. 2020; 203 ():122791.

Chicago/Turabian Style

Enrico Carmeli; Davide Tranchida; Andreas Albrecht; Alejandro J. Müller; Dario Cavallo. 2020. "A tailor-made Successive Self-nucleation and Annealing protocol for the characterization of recycled polyolefin blends." Polymer 203, no. : 122791.

Journal article
Published: 30 June 2020 in Additive Manufacturing
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Gaining a molecular understanding of material extrusion (MatEx) 3D printing is crucial to predicting and controlling part properties. Here we report the direct observation of distinct birefringence localised to the weld regions between the printed filaments, indicating the presence of molecular orientation that is absent from the bulk of the filament. The value of birefringence at the weld increases at higher prints speeds and lower nozzle temperatures, and is found to be detrimental to the weld strength measured by tensile testing perpendicular to the print direction. We employ a molecularly-aware non-isothermal model of the MatEx flow and cooling process to predict the degree of alignment trapped in the weld at the glass transition. We find that the predicted residual alignment factor, A¯, is linearly related to the extent of birefringence, Δn. Thus, by combining experiments and molecular modelling, we show that weld strength is not limited by inter-diffusion, as commonly expected, but instead by the configuration of the entangled polymer network. We adapt the classic molecular interpretation of glassy polymer fracture to explain how the measured weld strength decreases with increasing print speed and decreasing nozzle temperature.

ACS Style

Andrea Costanzo; Roberto Spotorno; María Virginia Candal; María Mercedes Fernández; Alejandro Muller; Richard S. Graham; Dario Cavallo; Claire McIlroy. Residual alignment and its effect on weld strength in material-extrusion 3D-printing of polylactic acid. Additive Manufacturing 2020, 36, 101415 .

AMA Style

Andrea Costanzo, Roberto Spotorno, María Virginia Candal, María Mercedes Fernández, Alejandro Muller, Richard S. Graham, Dario Cavallo, Claire McIlroy. Residual alignment and its effect on weld strength in material-extrusion 3D-printing of polylactic acid. Additive Manufacturing. 2020; 36 ():101415.

Chicago/Turabian Style

Andrea Costanzo; Roberto Spotorno; María Virginia Candal; María Mercedes Fernández; Alejandro Muller; Richard S. Graham; Dario Cavallo; Claire McIlroy. 2020. "Residual alignment and its effect on weld strength in material-extrusion 3D-printing of polylactic acid." Additive Manufacturing 36, no. : 101415.

Research article
Published: 11 June 2020 in Macromolecules
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Although the study of melt memory has attracted much interest, the effect of polymer chemical structure on its origin has not been fully elucidated. In this work, we study the melt memory effects by differential scanning calorimetry employing a self-nucleation protocol. We use homologous series of homopolymers containing different polar groups and a different number of methylene groups in their repeating units: polycarbonate, polyesters, polyethers, and polyamides. We show that melt memory in homopolymers is generally controlled by the strength of the intermolecular interactions. The incorporation of methylene groups reduces the melt memory effects by decreasing the strength of segmental chain interactions, which is reflected by the decrease in dipolar moments and solubility parameters. This work presents for the first time a unified view of the melt memory effects in different homopolymers.

ACS Style

Leire Sangroniz; Ainara Sangroniz; Leire Meabe; Andere Basterretxea; Haritz Sardon; Dario Cavallo; Alejandro J. Müller. Chemical Structure Drives Memory Effects in the Crystallization of Homopolymers. Macromolecules 2020, 53, 4874 -4881.

AMA Style

Leire Sangroniz, Ainara Sangroniz, Leire Meabe, Andere Basterretxea, Haritz Sardon, Dario Cavallo, Alejandro J. Müller. Chemical Structure Drives Memory Effects in the Crystallization of Homopolymers. Macromolecules. 2020; 53 (12):4874-4881.

Chicago/Turabian Style

Leire Sangroniz; Ainara Sangroniz; Leire Meabe; Andere Basterretxea; Haritz Sardon; Dario Cavallo; Alejandro J. Müller. 2020. "Chemical Structure Drives Memory Effects in the Crystallization of Homopolymers." Macromolecules 53, no. 12: 4874-4881.