Polydimethylsiloxane as a Modifier of the Processing, Surface and Mechanical Properties of the Linear Low-Density Polyethylene Recyclate.

This study investigated the effect of adding polydimethylsiloxane (PDMS) on the processing, surface and mechanical properties of linear low-density polyethylene (rLLDPE) recyclate generated as post-production waste in the rotational molding process. Polymer blends containing 0.1, 0.2, 0.4, 1.0 and 2.0 wt.% of polydimethylsiloxane were produced during twin-screw extrusion, followed by cold granulation. The addition of the modifier at the adopted concentration range lowered the water absorption of the recyclate and contributed to a slight increase in processing shrinkage; however, it did not significantly affect its processability (MFR~const). The modification carried out increased the hydrophobic character of the recyclate surface (the wetting angle for water was enhanced) and decreased the value of the dynamic friction coefficient. It also contributed to an improvement in surface gloss. The deterioration of point hardness and scratch hardness of the recyclate was noted with an increase in the PDMS content in the mixture. The addition of polydimethylsiloxane caused changes in the nature of resulting cracks (increased width and reduced longitudinal deformation), which led to surface smoothing and increased the sliding effects. There was no negative effect of PDMS addition on the mechanical properties (static tensile) of the recyclate. The impact strength of rLLDPE deteriorated slightly. The research conducted shows the high application potential of PDMS as a modifier of the surface properties of low-density polyethylene linear recyclate and of selected processing properties, which can contribute to the shortening of the production cycle, thus potentially increasing its attractiveness compared to the original raw materials.