Reactive Extrusion of Injection-Grade Polypropylene Toward Controlled-Rheology Materials for Spunbond Manufacturing

Abstract

The spunbond process is one of the main technologies for producing polypropylene (PP)-based nonwoven fabrics, widely used in industrial applications and in the automotive sector. In this work, an injection-molding-grade polypropylene was modified through the addition of 0.5 wt% Nexamite R202, a concentration representative of the levels typically employed in commercial controlled-rheology grades for spunbond applications. The effects of controlled degradation on the material’s properties were then evaluated, together with its potential suitability to produce nonwoven fabrics intended for car cover coatings. Characterization included mechanical tests (tensile and impact), thermal analysis (DSC, VICAT) and rheological measurements. The results show that peroxide addition increases melt flow rate (MFR) from 12.5 to 33.3 g/10 min (+167%), reduces capillary viscosity, lowers the maximum tensile stress from 25.5 to 22.7 MPa, keeps the strain at break statistically comparable (18.9% to 18.6%) and reduces the impact energy from 139.6 to 102.2 kJ/m2. In the regrading stage, formulation SB#4, containing a regrading additive, antioxidants, and a virgin fraction, showed the best compromise between processability and toughness, although without fully restoring the properties of the virgin material. These results indicate that a combined regrading strategy represents an effective route for valorizing reprocessed PP within a circular economy framework.