The aim is to determine the effect of polymer density, correlated to the comonomer content, and nanosilica addition on the mechanical and Environmental Stress Cracking Resistance (ESCR) characteristics of high-density polyethylene (HDPE). In this regard, five HDPE samples with similar Melt Flow Index (MFI) and molar mass but various densities were acquired from a petrochemical plant. Two polymerization reactors work in series and differ only in the amount of 1-buene comonomer fed to the second reactor. To ascertain the microstructure of the studied samples, GPC and SSA (successive self-nucleation and annealing) analyses were accomplished. All samples resulted having similar characteristics but slightly various SCB/1000C=7.26-9.74 (SCB=Short Chain Branching). Consequently, meanwhile studied HDPEs reveal similar notched impact and stress at yield values, the tensile modulus, stress-at-break, and elongation-at-break tend to demonstrate different results with the SCB content. More significantly, ESCR characteristic varied considerably with SCB/1000C extent, so that higher amount of SCB acknowledged advanced ESCR. Notably, blending HDPE sample containing higher amount of SCB/1000C, with 3 wt.% of chemically modified nanosilica enhanced ESCR characteristic by 40%. DFT (Density Functional Theory) calculations unveiled the role of the comonomer, quantitatively by binding energies and qualitatively by Non Covalent Interaction (NCI) plots.

中文翻译：

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通过共聚单体添加和纳米复合材料方法提高高密度聚乙烯牌号的耐环境应力开裂性


目的是确定与共聚单体含量相关的聚合物密度以及纳米二氧化硅的添加对高密度聚乙烯 (HDPE) 机械和耐环境应力开裂 (ESCR) 特性的影响。在这方面，从石化厂获得了五个具有相似熔体流动指数 (MFI) 和摩尔质量但密度不同的 HDPE 样品。两个聚合反应器串联工作，仅在加入第二个反应器的1-丁烯共聚单体的量上有所不同。为了确定所研究样品的微观结构，完成了 GPC 和 SSA（连续自成核和退火）分析。所有样品均具有相似的特征，但略有不同 SCB/1000C=7.26-9.74（SCB=短链支化）。因此，同时研究的 HDPE 显示出相似的缺口冲击和屈服应力值，拉伸模量、断裂应力和断裂伸长率往往会随着 SCB 含量的变化而表现出不同的结果。更重要的是，ESCR特性随SCB/1000C程度变化很大，因此较高的SCB量表明先进的ESCR。值得注意的是，将含有较高量 SCB/1000C 的 HDPE 样品与 3 wt.% 的化学改性纳米二氧化硅混合，ESCR 特性提高了 40%。 DFT（密度泛函理论）计算通过结合能定量地揭示了共聚单体的作用，并通过非共价相互作用 (NCI) 图定性地揭示了共聚单体的作用。