High-density poly(ethylene) (HDPE) is an important class of polymer used extensively in plastic packaging as well as numerous other applications. HDPE has a structure that consists of crystalline (monoclinic and orthorhombic) and amorphous domains. Here, we exploit a range of approaches focusing on magic angle spinning (MAS) nuclear magnetic resonance (NMR) aimed at comparing the effect of the HDPE sample formulation (cutting, shaving and cryomilling), from the commercially available manufactured pellets, into these domains and their quantification. ¹³C cross polarisation (CP) experiments reveal that these formulated HDPEs are qualitatively different and ¹³C CP build-up curves and ¹³C direct excitation experiments enable the content of each domain to be obtained, pointing to an increase of monoclinic domain at the expense of the orthorhombic one upon increased processing. The crystallinity contents obtained compared, in some cases, favourably with those obtained by differential scanning calorimetry (DSC) data. These results provide evidence that the manner of preparation of HDPE pellets modifies the concentration of the various domains and suggest that care should be taken during processing.

中文翻译：

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通过魔角旋转核磁共振表征配制的高密度聚乙烯

高密度聚乙烯 (HDPE) 是一类重要的聚合物，广泛用于塑料包装以及许多其他应用。HDPE 的结构由结晶域（单斜晶系和斜方晶系）和无定形域组成。在这里，我们开发了一系列专注于魔角旋转 (MAS) 核磁共振 (NMR) 的方法，旨在比较 HDPE 样品配方（切割、剃须和冷冻研磨）、商用制造颗粒在这些领域的效果及其量化。¹³ C交叉极化（CP）实验表明，这些配制的HDPE在质量上有所不同，并且¹³ C CP建立曲线和¹³ C直接激发实验能够获得每个域的含量，这表明单斜域的增加是以牺牲为代价的。增加加工后的斜方晶系。在某些情况下，所获得的结晶度含量与通过差示扫描量热法（DSC）数据获得的结晶度含量相比更为有利。这些结果证明 HDPE 颗粒的制备方式会改变各个区域的浓度，并表明在加工过程中应小心谨慎。