In this study, three commercially available low-density polyethylene (LDPE) polymers produced via a tubular reactor process, with varying melt flow rates at 190°C/2.16 kg (4.0, 1.9, and 0.75 g/10 min), have been selected and subjected to high temperature-size exclusion chromatography (SEC) analysis coupled with an infrared-5 (IR-5), viscometer (VISCO), and multiangle laser light-scattering detectors. The molecular weight (MW), MW distribution, short-chain branching (SCB), and long-chain branching parameters were investigated. It was found that MW obtained by the universal technique (∼1.57–1.7 times) and multiangle laser light-scattering detection technique is (∼1.43–1.55 times) higher than that of the conventional calibration technique, which could be attributed to structural complexity associated with LDPEs which is not clearly understood by conventional SEC mode alone. The bulk SCB per 1000 total carbon atoms estimated by IR-5 detection was found to range from 16.50 to 17.80. On the other hand, long chain branching frequency per 1000 total carbon atoms obtained by online VISCO and multiangle laser light-scattering detection ranged from 0.46 to 0.54 and 0.65 to 0.94, respectively. Further, the significance of long chain branching parameters on the polymer processing behavior was studied in correlation with rheological property (Die swell ratio).

中文翻译：

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采用三重检测的高温尺寸排阻色谱法评估低密度聚乙烯的分子结构：深入了解支化和加工性能的相关性

在本研究中，选择了通过管式反应器工艺生产的三种市售低密度聚乙烯 (LDPE) 聚合物，它们在 190°C/2.16 kg（4.0、1.9 和 0.75 g/10 分钟）下具有不同的熔体流动速率并结合红外 5 (IR-5)、粘度计 (VISCO) 和多角度激光光散射检测器进行高温尺寸排阻色谱 (SEC) 分析。研究了分子量 (MW)、MW 分布、短链支化 (SCB) 和长链支化参数。研究发现，通用技术（∼1.57–1.7倍）和多角度激光光散射检测技术获得的MW比传统校准技术高（∼1.43–1.55倍），这可能归因于相关的结构复杂性。与 LDPE 相比，单独使用传统 SEC 模式并不能清楚地理解这一点。通过 IR-5 检测估计，每 1000 个总碳原子的大量 SCB 范围为 16.50 至 17.80。另一方面，通过在线VISCO和多角度激光光散射检测获得的每1000个总碳原子的长链支化频率分别为0.46至0.54和0.65至0.94。此外，还研究了长链支化参数对聚合物加工行为与流变性能（离模膨胀比）的关系的重要性。