A Generalized Avrami Equation for Crystallization Kinetics of Polymers with Concomitant Double Crystallization Processes

Wang, Ruiyang; Zou, Shufen; Jiang, Baiyu; Fan, Bin; Hou, Meng-Fei; Zuo, Biao; Wang, Xin Ping; Xu, Jun‐Ting; Fan, Zhiqiang

doi:10.1021/acs.cgd.7b01016

Cited by 35 publications

(17 citation statements)

References 61 publications

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“…Moreover, it is warranted to mention a recent study of the crystallization kinetics of polymers by differential scanning calorimetry that applied an Avrami analysis. [21] It is certainly remarkable that the time-temperature-transformations of this study proceed on a time scale of minutes that compare well with our dose related experiments. Indeed, the solid lines of Figure 3a approximate our data by an Avrami Equation (S9), Supporting Information, where time is given by t = d/d r (d: total dose, d r : dose rate).…”

Section: Resultssupporting

confidence: 78%

Exploring Functional Materials by Understanding Beam‐Sample Interactions

Kisielowski

Specht

Rozeveld

et al. 2022

Adv Funct Materials

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Ultra-low-dose electron diffraction is performed with a double metal cyanide catalyst (DMC) to understand how electron irradiation stimulates structural alterations in functional materials. The commonly fading diffraction patterns with dose accumulation depend on the irradiated area and the beam current even when below 50 femto Amperes. Heat generation is observed and modeled by statistical, inelastic scattering events to describe how phonon excitations modulate radiation hardness. Specifically, the characteristic 1/e-decay of Bragg intensities from DMC is delayed from 6 to 30 eÅ −2 at room temperature, which is comparable to the effect of embedding radiation soft matter in ice. DMC's radiation hardness is enhanced by a latency dose that forms during a phase transformation. This unifying model predicts that a critical dose rate exists for any material that varies between 0.1 and 10 4 eÅ −2 s −1 because of a material dependent competition of heat generation and spread. It shows that Brillouin scattering causes time dependent perturbations in electron irradiated solids that trigger time-temperature-transformations on a time scale of nanoseconds to microseconds at room temperature, which is not included in traditional models describing the decay of Bragg intensities by radiolysis.

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Section: Resultssupporting

confidence: 78%

Exploring Functional Materials by Understanding Beam‐Sample Interactions

Kisielowski

Specht

Rozeveld

et al. 2022

Adv Funct Materials

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“…On the other hand, t 1/2 basically became smaller as OH-BNNS loading increased, showing that the addition of OH-BNNS can accelerate PLLA crystallization, especially at higher T a s. This can be attributed to more heterogeneous nuclei formed by OH-BNNS at higher loading of OH-BNNS. However, we noticed that PLLA-0.5 exhibited values of t 1/2 even larger than PLLA-0 at higher T a s. This could be explained by the fact that two crystallization processes may occur in PLLA-0.5 with a low OH-BNNS loading [50]. The PLLA chains contacting OH-BNNS crystallized faster due to heterogeneous nucleation, while the PLLA chains far from OH-BNNS crystallized at a much slower rate and may have been spatially trapped into and/or among the crystals formed via heterogeneous nucleation.…”

Section: Resultsmentioning

confidence: 99%

Functionalized Boron Nitride Nanosheets/Poly(l-lactide) Nanocomposites and Their Crystallization Behavior

et al. 2019

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In this work, hydroxyl-functionalized boron nitride nanosheet (OH-BNNS) was prepared and was blended with poly(l-lactide) (PLLA) to yield PLLA/OH-BNNS nanocomposites with excellent dispersion of OH-BNNS via the interaction of carbonyl in PLLA and hydroxyl in OH-BNNS. The effects of OH-BNNS on the crystallization and melting behaviors, isothermal crystallization kinetics, macroscopic crystal morphology and crystal structure of PLLA were studied by means of various techniques. The addition of OH-BNNS nanofillers can effectively accelerate the crystallization of PLLA and enhance the nucleation density, leading to a smaller spherulite size, increased crystallinity, a more obvious crystallization peak upon cooling but weakened cold crystallization behavior upon heating. Low OH-BNNS loading can increase the relative content of α-crystal, but the relative content of less perfect α′-crystal is increased at high OH-BNNS loading due to the strong interaction between PLLA and OH-BNNS.

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“…Avrami equation log[‐ln(1 ‐X t )] = log k+n log t was used to analyze isothermal crystallization kinetics and quantitatively described the macroscopic evolution of X c during primary crystallization of PLA and composite . Usually crystallization process has two stages; namely the primary crystallization stage and the secondary crystallization stage.…”

Section: Resultsmentioning

confidence: 99%

Evaluation of Relationship Between Crystallization Structure and Thermal‐Mechanical Performance of PLA with MCC Addition

Wen

Wang

et al. 2019

ChemistrySelect

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Poly(lactic acid) (PLA) biocomposite with 1 wt % microcrystalline cellulose (MCC) addition were prepared by melt-mixed method using torque rheometer and annealed under different isothermal conditions. The morphology, crystallization behaviors, thermal and dynamic-mechanical properties were evaluated by techniques of polarized optical microscopy (POM), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and dynamic mechanical analysis (DMA). Nucleus density, crystallization rate and crystallinity (X c ) of PLA matrix were significantly increased by addition of MCC. It was found that MCC could improve the activity of PLA segments at low crystallization temperature (T c ), and the stability of segments in crystal lattice was also enhanced at high T c . DSC and XRD analysis supported that MCC contributed to the transformation of α' form into α form in PLA during annealing. The temperature range in which α crystal form appeared for pure PLA was 125 to 135°C and it was enlarged from 105 to 145°C for PLA with MCC addition. The Avrami exponent (n) and crystallization rate constant (k) for MCC/PLA decreased and increased respectively, supporting that the time dimension in nucleation mode was inhibited and crystallization kinetics was improved. MCC/PLA showed an increased stiffness and the highest value of storage modulus (E') was 52 GPa at T c of 125°C, which is basically consistent with the condition of maximum X c . DMA analysis supported that at high T c , the addition of MCC greatly increased the crystallization ability of PLA and the elasticity and toughness were also improved.[a] Dr.

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A Generalized Avrami Equation for Crystallization Kinetics of Polymers with Concomitant Double Crystallization Processes

Cited by 35 publications

References 61 publications

Exploring Functional Materials by Understanding Beam‐Sample Interactions

Exploring Functional Materials by Understanding Beam‐Sample Interactions

Functionalized Boron Nitride Nanosheets/Poly(l-lactide) Nanocomposites and Their Crystallization Behavior

Evaluation of Relationship Between Crystallization Structure and Thermal‐Mechanical Performance of PLA with MCC Addition

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