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Blown film samples of 70/30 w/w low-density polyethylene (LDPE)/linear low-density polyethylene (LLDPE) are prepared and recycled by shredding, washing, and extrusion to produce recycled pellets and then are blended with virgin LDPE and LLDPE at various loadings and undergo the process of blow molding to form blown films with intrinsic LDPE/LLDPE composition of 70/30 w/w. Differential scanning calorimetry results show a decrease in the melting and crystallization temperatures along with crystallinity percentage due to the presence of crosslinks. The presence of crosslink networks is confirmed by the complex viscosity curve, storage and loss modulus curves, and the interception point of the storage and loss modulus curves. Cole-Cole, Han, and Van Gurp Palman curves confirm miscibility in all samples at all compositions. Stress and strain at yield and break of the samples display an increase due to the affirmative effect of the crosslinks. Light refraction caused by the presence of the crosslinks causes an increase and decrease in the haze and gloss of the films, respectively.

In this paper, using a comprehensive study, we have investigated the effect of various polymerization parameters during the synthesis of bimodal polyethylene resins on their rheological and mechanical properties. Bimodal polyethylene resins were synthesized in two subsequent stages in a lab-scale reactor by manipulating a set of parameters such as C 2 /H 2 ratios in the first and second stages, the split value, and the comonomer type. The results showed that the comonomer type and C 2 /H 2 ratio of the second stage of the polymerization are the most critical parameters that control the final resins' slow crack growth resistance properties. On the other hand, the shear-thinning behavior of the resins is mainly controlled by the first-stage polymers. Although the C 2 /H 2 ratio of the first stage results in a moderate effect on the rheological properties of the final resins, its split value governs the flow characteristics of the final molten polymers under high shear rates.

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Due to the important role of cocatalyst in the polymerization process employing industrially favored Ziegler–Natta catalysts, its effect on kinetic behavior, catalyst activity, and polymer properties is discussed. In this paper, triethyl aluminum (TEA) and triisobutyl aluminum (TIBA) have been used as the main cocatalyst ingredient with 10–20 mol percent of diethyl aluminum chloride (DEAC) and ethyl aluminum dichloride (EADC) cocatalysts, being neat TEA the cocatalysts with the highest activity. Moreover, TEA-DEAC and TEA-EADC cocatalysts revealed a built-up kinetic profile, while TIBA-DEAC and TIBA-EADC show a decay-type kinetic curve. According to melt flow index results, no considerable change in flowability was detected in the synthesized polyethylenes (PE). On the other hand, the ethylene insertion and chain termination mechanisms were investigated by means of density functional calculations using Ti active center located in (110) and (104) facets of the MgCl2 surface. To shed light on the bulkiness level of employed cocatalysts, buried volume (VBur) together with the two-dimensional map of cocatalyst systems were considered. Higher VBur of TIBA complex can explain its lower activity and decay type kinetic profile obtained by experimental studies.

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