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Abstract：
Understanding and characterizing semi-crystalline models with crystalline and amorphous segments is crucial for industrial applications. A coarse-grained molecular dynamics (CGMD) simulations study probed the crystal network formation in high-density polyethylene (HDPE) from melt, and shed light on tensile properties for microstructure analysis. Modified Paul-Yoon-Smith (PYS/R) forcefield parameters are used to compute the interatomic forces among the PE chains. The isothermal crystallization at 300 K and 1 atm predicts the multi-nucleus crystal growth; moreover, the lamellar crystal stems and amorphous region are alternatively oriented. A one-dimensional density distribution along the alternative lamellar stems further confirms the ordering of the lamellar-stack orientation. Using this plastic model preparation approach, the semi-crystalline model density (ρcr) of ca. 0.913 g·cm-3 and amorphous model density (ρam) of ca. 0.856 g·cm-3 are obtained. Furthermore, the ratio of ρcr/ρam ≈ 1.06 is in good agreement with computational (≈1.096) and experimental (≈1.14) data, ensuring the reliability of the simulations. The degree of crystallinity (χc) of the model is ca. 52% at 300 K. Nevertheless, there is a gradual increase in crystallinity over the specified time, indicating the alignment of the lamellar stems during crystallization. The characteristic stress-strain curve mimicking tensile tests along the z-axis orientation exhibits a reversible sharp elastic regime, tensile strength at yield ca. 100 MPa, and a non-reversible tensile strength at break of 350%. The cavitation mechanism embraces the alignment of lamellar stems along the deformation axis. The study highlights an explanatory model of crystal network formation for the PE model using a PYS/R forcefield, and it produces a microstructure with ordered lamellar and amorphous segments with robust mechanical properties, which aids in predicting the microstructure-mechanical property relationships in plastics under applied forces.
摘要：
理解和表征具有结晶和无定形片段的半结晶模型对于工业应用至关重要。粗粒分子动力学（CGMD）模拟研究了熔体在高密度聚乙烯（HDPE）中形成的晶体网络，并对拉伸性能进行微观结构分析。修改后的Paul-Yoon-Smith（PYS/R）力场参数用于计算PE链之间的原子间力。在300K和1atm下的等温结晶预测了多核晶体生长；此外，层状晶体茎和无定形区域交替取向。沿替代层状茎的一维密度分布进一步证实了层状堆叠取向的有序。使用这种塑料模型的制备方法，大约的半结晶模型密度(ρcr)。0.913g·cm-3和约的无定形模型密度（ρam）。得到0.856g·cm-3。此外，ρcr/ρam≈1.06的比值与计算(≈1.096)和实验(≈1.14)数据非常吻合，确保模拟的可靠性。模型的结晶度（χc）约为。在300K时为52%。尽管如此，结晶度在指定时间内逐渐增加，表明结晶过程中层状茎的排列。沿z轴方向模拟拉伸试验的特征应力-应变曲线表现出可逆的尖锐弹性状态，屈服抗拉强度约为。100MPa,和350％的不可逆断裂拉伸强度。空化机制包括层状茎沿变形轴的排列。该研究强调了使用PYS/R力场的PE模型的晶体网络形成的解释性模型，它产生了具有有序层状和无定形段的微观结构，具有强大的机械性能，这有助于预测塑料在外加力作用下的微观结构-力学性能关系。
