A study of polyethylene packaging films in presence of slip‐agent and anti‐block additives: A tale of surface and bulk crystallinities

Abstract Polyolefin films are widely used in flexible packaging industries. However, the processing, storage, and application of these polymers pose numerous difficulties due to their high coefficient of friction (COF) and high blocking. Slip‐agent and anti‐block additives are usually used to prevent films from being adhered to each other and to metal rollers. This work aims to study the surface morphology of blown polyethylene films in the presence of these two additives. To do this, various types and concentrations of additives were employed at different ratios of the polymer blend (LDPE/LLDPE). However, it was found that the polymer composition was not as effective as the presence of additives. COF and blocking force measurement, contact angle, haze evaluation, differential scanning calorimetry (DSC), grazing incident x‐ray diffraction (GI‐XRD), and atomic force microscopy (AFM), were utilized to investigate the surface and bulk properties of the films. It was found that the migration of additives leads to the formation of various surface structures thereby making the surface to be more crystalline. The result was a decrease in the COF from ca. 1–0.1 and lowering the blocking force of approximately 8–3 N, highlighting the impact of the optimal concentration of additives. Results showed that the surface energy of the films decreased (20–30 mJ/m 2 ) in the presence of additives due to the formation of a weak boundary layer at the surface. Comparison of DSC and GI‐XRD results showed that crystallinity values in the bulk phase changed from 20%–40% to 30%–50% at the surface for most samples. The lowest and highest of roughness was 22 and 90 nm, respectively, as revealed by AFM. Highlights Various slip‐agent and anti‐blocks were used in polyethylene‐blown films. Coefficient of friction and blocking force were tested at different conditions. Crystallinity of films and other investigations were correlated to obtained data. Experimental design revealed the impact of studied parameters.