Multiscale Simulation of Semi-Crystalline Polymers to Predict Mechanical Properties

Horn, Tobias Daniel; Heidrich, Dario; Wulf, Hans; Gehde, Michael; Ihlemann, Jörn

doi:10.3390/polym13193233

Cited by 10 publications

(3 citation statements)

References 30 publications

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“…14 It is well-established that the macroscopic mechanical properties of injection molded products primarily rely on the geometrical arrangement and stacking state (i.e., crystallinity) of microscopic molecules during the cooling stage in mold cavity. 15 A well-arranged molecular structure leads to a more ordered crystal structure and enhances crystallinity, typically associated with superior mechanical properties. Moreover, the internal molecular arrangement and stacking state of molded product depend on the mobility of the polymer micro molecules during injection molding.…”

Section: Introductionmentioning

confidence: 99%

Crystallinity and mechanical properties of polypropylene products foamed by microcellular injection molding process

Yu,

Song,

Gao

et al. 2024

J of Applied Polymer Sci

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Microcellular injection molding (MIM) is a pivotal technique for lightweight molding. Polypropylene (PP) is widely used in MIM due to light weight and easy processing. The crystallinity of foamed PP products influences the load‐bearing structures and consequently mechanical properties. To address the deterioration of mechanical properties caused by internal porous structure, a novel method is proposed to regulate the crystallinity by optimizing process parameters, thereby improving mechanical properties. Wide‐angle x‐ray diffraction, mechanical testing, and melt flow simulation are applied to investigate the influence of process parameters on crystallinity and mechanical properties. Parameters are further optimized by establishing a multivariate nonlinear regression model for process parameters and crystallinity. The results show that increasing melt temperature, injection rate, mold temperature, and cooling time stimulate crystallization, enhancing strength and decreasing elongation at break. Conversely, high injection ratio of supercritical fluid obstructs crystallization, reducing strength, and increasing elongation at break. The crystallinity increases by 20.81%; the corresponding tensile, flexural, and shear strength and corresponding modulus increases by 5.39% and 10.28%, 7.60% and 18.50%, 5.00% and 11.37%, and elongation at break decreased by 5.19% through the optimization of regression model. The proposed method is feasible to upgrade the mechanical properties of foamed PP products.

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Section: Introductionmentioning

confidence: 99%

Crystallinity and mechanical properties of polypropylene products foamed by microcellular injection molding process

Yu,

Song,

Gao

et al. 2024

J of Applied Polymer Sci

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show abstract

“…The properties of semicrystalline polymers depend on the unique internal structure with both crystalline and amorphous phases. The semicrystalline structures are intrinsically inhomogeneous and involve different length scales, ranging from molecules to nano-sized chain lamellae and micron-sized spherulites [ 2 , 3 ]. A fundamental understanding of the complex polymer crystallization affected by intrinsic and extrinsic factors can help to improve control over the properties of semicrystalline polymers and lead to novel inverse designs of polymer materials.…”

Section: Introductionmentioning

confidence: 99%

Unveiling the Nanoconfinement Effect on Crystallization of Semicrystalline Polymers Using Coarse-Grained Molecular Dynamics Simulations

Yang,

Chen,

Yang

et al. 2024

Polymers

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Semicrystalline polymers under nanoconfinement show distinct structural and thermomechanical properties compared to their bulk counterparts. Despite extensive research on semicrystalline polymers under nanoconfinement, the nanoconfinement effect on the local crystallization process and the unique structural evolution of such polymers have not been fully understood. In this study, we unveil such effects by using coarse-grained molecular dynamics simulations to study the crystallization process of a model semicrystalline polymer—polyvinyl alcohol (PVA)—under different levels of nanoconfinement induced by nanoparticles that are represented implicitly. We quantify in detail the evolution of the degree of crystallinity (XC) of PVA and examine distinct crystalline regions from simulation results. The results show that nanoconfinement can promote the crystallization process, especially at the early stage, and the interfaces between nanoparticles and polymer can function as crystallite nucleation sites. In general, the final XC of PVA increases with the levels of nanoconfinement. Further, nanoconfined cases show region-dependent XC with higher and earlier increase of XC in regions closer to the interfaces. By tracking region-dependent XC evolution, our results indicate that nanoconfinement can lead to a heterogenous crystallization process with a second-stage crystallite nucleation in regions further away from the interfaces. In addition, our results show that even under very high cooling rates, the nanoconfinement still promotes the crystallization of PVA. This study provides important insights into the underlying mechanisms for the intricate interplay between nanoconfinement and the crystallization behaviors of semicrystalline polymer, with the potential to guide the design and characterization of semicrystalline polymer-based nanocomposites.

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“…Several micromechanical models and multiscale simulations have been developed and applied to predict elastic properties of semicrystalline polymers [19][20][21][22][23][24]. In different models the semi-crystalline morphology is approached by holding different assumptions.…”

Section: Introductionmentioning

confidence: 99%

Robustness Study of a Tensile Modulus Prediction Model for Semicrystalline Polymers

Zarbali

Pinke

Menyhárd

2023

Period. Polytech. Chem. Eng.

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This work presents a robustness study of a previously developed empirical model that links Young's modulus to two key parameters of crystalline structure; crystallinity and lamellae thickness. The reliability of this modulus prediction model was tested by using different calorimeters and different polypropylene grades as well. Small samples were fabricated from injection-molded bars from different locations of the specimens in order to check the effect of structural inhomogeneity originated by the dynamic processing conditions. In addition, the standard deviation and consequently the accuracy of the prediction was tested by repeated calorimetric measurements. The crystalline structure and melting characteristics were measured by differential scanning calorimetry (DSC). The tensile properties of studied specimens were evaluated by standardized tensile tests. Although, the accuracy and reliability of the prediction model is dependent on the instrument used for thermal analysis, reasonably good agreement was found between the predicted and measured values in most cases. However, we may note that only well-calibrated calorimeters are suitable for reliable prediction of the modulus.

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Multiscale Simulation of Semi-Crystalline Polymers to Predict Mechanical Properties

Cited by 10 publications

References 30 publications

Crystallinity and mechanical properties of polypropylene products foamed by microcellular injection molding process

Crystallinity and mechanical properties of polypropylene products foamed by microcellular injection molding process

Unveiling the Nanoconfinement Effect on Crystallization of Semicrystalline Polymers Using Coarse-Grained Molecular Dynamics Simulations

Robustness Study of a Tensile Modulus Prediction Model for Semicrystalline Polymers

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