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.

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.

No abstract

In this work, nickel-catalyzed high- cis 1,4-polybutadiene rubbers (PBR) with different molecular weight, molecular weight distribution, and Mooney relaxation time have been solution blended at different ratios and their rheological, thermal, and physical properties were characterized. PBR blend compositions showed similar processability as pristine rubber grades at higher temperature, but their Mooney relaxation time and rheological branching index (BI) are distinctly different from both pristine PBR grades at low temperature. In addition, Mooney relaxation time and BI of the blends were found to be independent of blend compositions; however, glass transition temperature ( Tg), cis%, volatile% of the compositions remain similar to the raw rubbers.