Study on the Rheological, Thermal, Mechanical, and Optical Properties of LDPE/LLDPE Blown Films Containing Recycled LDPE/LLDPE Pellets For Circular Economy

Abstract

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.

Correlation of structure, rheological, thermal, mechanical, and optical properties in Low Density Polyethylene/Linear Low Density Polyethylene blends in the presence of recycled Low Density Polyethylene and Linear Low Density Polyethylene

“…So, in this study, with the concentration of recycled LDPE being more than recycled LLDPE, it is logical to observe an increase in the storage and loss modulus of the blends as the loading of the recycled material rises. 3,43 The slopes of the lgG 0 versus lgω plots of the virgin/ recycled samples further provide proof of the presence of crosslinked structure in the blends. The slopes decrease due to crosslinked networks in the low-frequency region, with increased recycled material content.…”

“…These remarks align with the conclusions drawn from earlier work that suggest the presence of a new topological structure (in the present case, a crosslinking network). 3,6,14,22,23,29 During the industrial processing procedure, the shear rates are usually in the 100 and 1000 s À1 range, which, according to the Cox-Merz law, covers the 100-1000 rad/s range, meaning that under regular processing conditions, the addition of the recycled material to the blend does not lead to unusual or unmanageable viscosity and extrusion pressure or torque. 3,22,29 Figures 7 and 8 display the storage modulus, G 0 , and loss modulus, G 00 curves for the blends of virgin and recycled LDPE and LLDPE.…”

“…Some previous studies have noted a difference between the structural changes that happen during the first and second extrusion process of LDPE: during the first extrusion, the breakage of the polymer chains is, to an extent, more assertive than the emergence of networks, while following the subsequent extrusion cycles, the crosslinking of the chains is the prominent phenomenon during the extrusion process. 3,14,22 The scissioned blocks of polymer face fewer restrictions in their response to the shear flow and their movement. On the other hand, the presence of a crosslinked structure dramatically hinders the movement of polymer chains under identical conditions, resulting in enhancement in the solid-like elastic response.…”

“…For better visualization of the gel point, Figure 9 depicts the G 0 and G 00 curves as a function of frequency for the blends made from 100% virgin granules and 100% recycled material at 160 C. The plots for the blend made from recycled LDPE and LLDPE show that the gel point has moved farther to the left and over to lower frequencies compared to the gel point of the virgin blend, indicating that the chains' relaxation time has escalated due to the presence of crosslinked networks in the recycled LDPE. 3,45 Cole-Cole plots, which are described as the imaginary part of the complex viscosity, η 00 , plotted in response to its real segment, η 0 , were plotted for the blown film samples at 160 C and were used to study the miscibility of the sample components and the variations in the sample's structure as the recycled material loading increases. The plots are shown in Figure 10.…”

“…Just in 2019, it was reported that the global plastic market had stretched to 368 million tons, and it is projected to rise to 417 million tons by 2030 and double by 2050. [1][2][3][4][5][6][7] The linear global plastics economy, with its "take, make, use, and waste" approach, is responsible for the majority of plastic products being discarded without repurposing after reaching the end of their life. Also, it is worth mentioning the production leftovers, which take up a notable amount of total plastic waste.…”