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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). [ABSTRACT FROM AUTHOR]

In the present study, trimodal high-density polyethylene (tri-HDPE) slurry phase samples from the polymerization reactors were subjected to high temperature gel permeation chromatography/size exclusion chromatography (HT-GPC/SEC) analysis. The molecular weight (Mw) and its distributions were evaluated using commercially available HT-GPC instruments equipped with different detection modes (DRI, IR5 MCT, and light scattering). The SEC studies reveal the fact that there is a considerable challenge in generating a repeatable and reproducible data for the reactor grade HDPE samples which could be attributed to different detection modes employed and instability of HDPE reactor grades which are susceptible to undergo thermo-oxidative degradation during HT-GPC analysis. Among various instrumentation and detection modes investigated, the HT-GPC with IR5 MCT detection showed reliable results (%Error <15) when compared with absolute Mw data obtained from MALS detection. Based on the findings, proposed suitable SEC mode to characterize the HDPE reactor grade polymer samples. [ABSTRACT FROM AUTHOR]

The structure property correlation of different commercial grades of high-impact polystyrene (HIPS) with varying polybutadiene rubber (PBR) content has been investigated. The average molecular weights of polystyrene, rubber content, gel content, swelling index, degree of grafting, morphology of rubber, and rubber particle size distribution were characterized and correlated with the mechanical properties of HIPS. The dynamic light scattering and transmission electron microscopy techniques were employed to characterize the loss of submicron tiny PBR gel particles. The obtained results reveal the fact that submicron tiny PBR gel particles that are lost during gel estimation by ultracentrifugation process lower the gel content and rubber efficiency, which significantly contribute to the overall impact performance evaluation of the final HIPS product. [ABSTRACT FROM AUTHOR]